Added islandora_advanced_search module.

.gitignore

@@ -1,2 +1,3 @@
 vendor
 /.idea/
+/.vscode

modules/islandora_advanced_search/CONTRIBUTING.md

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+# Welcome!
+
+If you are reading this document then you are interested in contributing to Islandora 8. All contributions are welcome: use-cases, documentation, code, patches, bug reports, feature requests, etc. You do not need to be a programmer to speak up!
+
+We also have an IRC channel -- #islandora -- on freenode.net. Feel free to hang out there, ask questions, and help others out if you can.
+
+Please note that this project operates under the [Islandora Community Code of Conduct](http://islandora.ca/codeofconduct). By participating in this project you agree to abide by its terms.
+
+## Workflows
+
+The group meets each Wednesday at 1:00 PM Eastern. Meeting notes and announcements are posted to the [Islandora community list](https://groups.google.com/forum/#!forum/islandora) and the [Islandora developers list](https://groups.google.com/forum/#!forum/islandora-dev). You can view meeting agendas, notes, and call-in information [here](https://github.com/Islandora/documentation/wiki#islandora-8-tech-calls). Anybody is welcome to join the calls, and add items to the agenda.
+
+### Use cases
+
+If you would like to submit a use case to the Islandora 8 project, please submit an issue [here](https://github.com/Islandora/documentation/issues/new) using the [Use Case template](https://github.com/Islandora/documentation/wiki/Use-Case-template), prepending "Use Case:" to the title of the issue.
+
+### Documentation
+
+You can contribute documentation in two different ways. One way is to create an issue [here](https://github.com/Islandora/documentation/issues/new), prepending "Documentation:" to the title of the issue. Another way is by pull request, which is the same process as [Contribute Code](https://github.com/Islandora/documentation/blob/master/CONTRIBUTING.md#contribute-code). All documentation resides in [`docs`](https://github.com/Islandora/documentation/tree/master/docs).
+
+### Request a new feature
+
+To request a new feature you should [open an issue in the Islandora 8 repository](https://github.com/Islandora/documentation/issues/new) or create a use case (see the _Use cases_ section above), and summarize the desired functionality. Prepend "Enhancement:" if creating an issue on the project repo, and "Use Case:" if creating a use case.
+
+### Report a bug
+
+To report a bug you should [open an issue in the Islandora 8 repository](https://github.com/Islandora/documentation/issues/new) that summarizes the bug. Prepend the label "Bug:" to the title of the issue.
+
+In order to help us understand and fix the bug it would be great if you could provide us with:
+
+1. The steps to reproduce the bug. This includes information about e.g. the Islandora version you were using along with the versions of stack components.
+2. The expected behavior.
+3. The actual, incorrect behavior.
+
+Feel free to search the issue queue for existing issues (aka tickets) that already describe the problem; if there is such a ticket please add your information as a comment.
+
+**If you want to provide a pull along with your bug report:**
+
+That is great! In this case please send us a pull request as described in the section _Create a pull request_  below.
+
+### Contribute code
+
+Before you set out to contribute code you will need to have completed a [Contributor License Agreement](http://islandora.ca/sites/default/files/islandora_cla.pdf) or be covered by a [Corporate Contributor License Agreement](http://islandora.ca/sites/default/files/islandora_ccla.pdf). The signed copy of the license agreement should be sent to <mailto:community@islandora.ca>
+
+_If you are interested in contributing code to Islandora but do not know where to begin:_
+
+In this case you should [browse open issues](https://github.com/Islandora/documentation/issues) and check out [use cases](https://github.com/Islandora/documentation/labels/use%20case).
+
+If you are contributing Drupal code, it must adhere to [Drupal Coding Standards](https://www.drupal.org/coding-standards); Travis CI will check for this on pull requests.
+
+Contributions to the Islandora codebase should be sent as GitHub pull requests. See section _Create a pull request_ below for details. If there is any problem with the pull request we can work through it using the commenting features of GitHub.
+
+* For _small patches_, feel free to submit pull requests directly for those patches.
+* For _larger code contributions_, please use the following process. The idea behind this process is to prevent any wasted work and catch design issues early on.
+
+    1. [Open an issue](https://github.com/Islandora/documentation/issues), prepending "Enhancement:" in the title if a similar issue does not exist already. If a similar issue does exist, then you may consider participating in the work on the existing issue.
+    2. Comment on the issue with your plan for implementing the issue. Explain what pieces of the codebase you are going to touch and how everything is going to fit together.
+    3. Islandora committers will work with you on the design to make sure you are on the right track.
+    4. Implement your issue, create a pull request (see below), and iterate from there.
+
+### Create a pull request
+
+Take a look at [Creating a pull request](https://help.github.com/articles/creating-a-pull-request). In a nutshell you need to:
+
+1. [Fork](https://help.github.com/articles/fork-a-repo) this repository to your personal or institutional GitHub account (depending on the CLA you are working under). Be cautious of which branches you work from though (you'll want to base your work off master, or for Drupal modules use the most recent version branch). See [Fork a repo](https://help.github.com/articles/fork-a-repo) for detailed instructions.
+2. Commit any changes to your fork.
+3. Send a [pull request](https://help.github.com/articles/creating-a-pull-request) using the [pull request template](https://github.com/Islandora/documentation/blob/master/.github/PULL_REQUEST_TEMPLATE.md) to the Islandora GitHub repository that you forked in step 1.  If your pull request is related to an existing issue -- for instance, because you reported a [bug/issue](https://github.com/Islandora/documentation/issues) earlier -- prefix the title of your pull request with the corresponding issue number (e.g. `issue-123: ...`). Please also include a reference to the issue in the description of the pull. This can be done by using '#' plus the issue number like so '#123', also try to pick an appropriate name for the branch in which you're issuing the pull request from.
+
+You may want to read [Syncing a fork](https://help.github.com/articles/syncing-a-fork) for instructions on how to keep your fork up to date with the latest changes of the upstream (official) repository.
+
+## License Agreements
+
+The Islandora Foundation requires that contributors complete a [Contributor License Agreement](http://islandora.ca/sites/default/files/islandora_cla.pdf) or be covered by a [Corporate Contributor License Agreement](http://islandora.ca/sites/default/files/islandora_ccla.pdf). The signed copy of the license agreement should be sent to <a href="mailto:community@islandora.ca?Subject=Contributor%20License%20Agreement" target="_top">community@islandora.ca</a>. This license is for your protection as a contributor as well as the protection of the Foundation and its users; it does not change your rights to use your own contributions for any other purpose. A list of current CLAs is kept [here](https://github.com/Islandora/islandora/wiki/Contributor-License-Agreements).

modules/islandora_advanced_search/LICENSE

@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
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modules/islandora_advanced_search/README.md

@@ -0,0 +1,240 @@
+# Islandora Advanced Search <!-- omit in toc -->
+
+- [Introduction](#introduction)
+- [Requirements](#requirements)
+- [Installation](#installation)
+- [Configuration](#configuration)
+- [Configuring Solr](#configuring-solr)
+- [Configure Collection Search](#configure-collection-search)
+- [Configure Views](#configure-views)
+  - [Collection Search](#collection-search)
+  - [Paging](#paging)
+  - [Sorting](#sorting)
+- [Configure Facets](#configure-facets)
+  - [Include / Exclude Facets](#include--exclude-facets)
+- [Configure Blocks](#configure-blocks)
+  - [Advanced Search Block](#advanced-search-block)
+- [Documentation](#documentation)
+- [Troubleshooting/Issues](#troubleshootingissues)
+- [Maintainers](#maintainers)
+- [Sponsors](#sponsors)
+- [Development](#development)
+- [License](#license)
+
+## Introduction
+
+This module creates several blocks to support searching. It also enables the use
+of Ajax with search blocks, facets, and search results.
+
+![image](./docs/demo.gif)
+
+## Requirements
+
+Use composer to download the required libraries and modules.
+
+```bash
+composer require drupal/facets "^1.3"
+composer require drupal/search_api_solr "^4.1"
+composer require drupal/search_api "^1.5"
+```
+
+However, for reference, `islandora_advanced_search` requires the following
+drupal modules:
+
+- [facets](https://www.drupal.org/project/facets)
+- [search_api_solr](https://www.drupal.org/project/search_api_solr)
+
+## Installation
+
+To download/enable just this module, use the following from the command line:
+
+```bash
+composer require islandora/islandora
+drush en islandora_advanced_search
+```
+
+## Configuration
+
+You can set the following configuration at
+`admin/config/islandora/advanced_search`:
+
+![image](./docs/islandora_advanced_search_settings.png)
+
+## Configuring Solr
+
+Please review
+[Islandora Documentation](https://islandora.github.io/documentation/user-documentation/searching/)
+before continuing. The following assumes you already have a working Solr and the
+Drupal Search API setup.
+
+## Configure Collection Search
+
+To support collection based searches you need to index the `field_member_of` for
+every repository item as well define a new field that captures the full
+hierarchy of `field_member_of` for each repository item.
+
+Add a new `Content` solr field `field_decedent_of` to the solr index at
+`admin/config/search/search-api/index/default_solr_index/fields`.
+
+![image](./docs/field_decedent_of.png)
+
+Then under `admin/config/search/search-api/index/default_solr_index/processors`
+enable `Index hierarchy` and setup the new field to index the hierarchy.
+
+![image](./docs/enable_index_hierarchy.png)
+
+![image](./docs/enable_index_hierarchy_processor.png)
+
+The field can now be used limit a search to all the decedents of a given object.
+
+> N.B. You may have to re-index to make sure the field is populated.
+
+## Configure Views
+
+The configuration of views is outside of the scope of this document, please read
+the [Drupal Documentation](https://www.drupal.org/docs/8/core/modules/views), as
+well as the
+[Search API Documentation](https://www.drupal.org/docs/contributed-modules/search-api).
+
+### Collection Search
+
+That being said it will be typical that you require the following
+`Relationships` and `Contextual Filters` when setting up a search view to enable
+`Collection Search` searches.
+
+![image](./docs/view_advanced_setting.png)
+
+Here a relationship is setup with `Member Of` field and we have **two**
+contextual filters:
+
+1. `field_member_of` (Direct decedents of the Entity)
+2. `field_decedent_of` (All decedents of the Entity)
+
+Both of these filters are configured the exact same way.
+
+![image](./docs/contextual_filter_settings.png)
+
+These filters are toggled by the Advanced Search block to allow the search to
+include all decedents or just direct decedents (*documented below*).
+
+### Paging
+
+The paging options specified here can have an affect on the pager block
+(*documented below*).
+
+![image](./docs/pager_settings.png)
+
+### Sorting
+
+Additional the fields listed as `Sort Criteria` as `Exposed` will be made
+available in the pager block (*documented below*).
+
+![image](./docs/sort_criteria.png)
+
+## Configure Facets
+
+The facets can be configured at `admin/config/search/facets`. Facets are linked
+to a **Source** which is a **Search API View Display** so it will be typically
+to have to duplicate your configuration for a given facet across each of the
+displays where you want it to show up.
+
+### Include / Exclude Facets
+
+To be able to display exclude facet links as well as include links in the facets
+block we have to duplicate the configuration for the facet like so.
+
+![image](./docs/include_exclude_facets.png)
+
+Both the include / exclude facets must use the widget
+`List of links that allow the user to include / exclude facets`
+
+![image](./docs/include_exclude_facets_settings.png)
+
+The excluded facet also needs the following settings to appear and function
+correctly.
+
+The `URL alias` must match the same value as the include facet except it must be
+prefixed with `~` character that is what links to the two facets to each other.
+
+![image](./docs/exclude_facet_settings_url_alias.png)
+
+And it must also explicitly be set to exclude:
+
+![image](./docs/exclude_facet_settings_exclude.png)
+
+You may also want to enable `Hide active items` and `Hide non-narrowing results`
+for a cleaner presentation of facets.
+
+## Configure Blocks
+
+For each block type:
+
+- Facet
+- Pager
+- Advanced Search
+
+There will be **one block** per `View Display`. The block should be limited to
+only appear when the view it was derived from is also being displayed on the
+same page.
+
+This requires configuring the `visibility` of the block as appropriate. For
+collection based searches be sure to limit the display of the Facets block to
+the models you want to display the search on, e.g:
+
+![image](./docs/facet_block_settings.png)
+
+### Advanced Search Block
+
+For any valid search field, you can drag / drop and reorder the fields to
+display in the advanced search form on. The configuration resides on the block
+so this can differ across views / displays if need be. Additionally if the View
+the block was derived from has multiple contextual filters you can choose which
+one corresponds to direct children, this will enable the recursive search
+checkbox.
+
+![image](./docs/advanced_search_block_settings.png)
+
+## Documentation
+
+Further documentation for this module is available on the
+[Islandora 8 documentation site](https://islandora.github.io/documentation/).
+
+## Troubleshooting/Issues
+
+Having problems or solved a problem? Check out the Islandora google groups for
+a solution.
+
+- [Islandora Group](https://groups.google.com/forum/?hl=en&fromgroups#!forum/islandora)
+- [Islandora Dev Group](https://groups.google.com/forum/?hl=en&fromgroups#!forum/islandora-dev)
+
+## Maintainers
+
+Current maintainers:
+
+- [Nigel Banks](https://github.com/nigelgbanks)
+
+## Sponsors
+
+- LYRASIS
+
+## Development
+
+If you would like to contribute, please get involved by attending our weekly
+[Tech Call](https://github.com/Islandora/documentation/wiki). We love to hear
+from you!
+
+If you would like to contribute code to the project, you need to be covered by
+an Islandora Foundation
+[Contributor License Agreement](http://islandora.ca/sites/default/files/islandora_cla.pdf)
+or
+[Corporate Contributor License Agreement](http://islandora.ca/sites/default/files/islandora_ccla.pdf).
+Please see the [Contributors](http://islandora.ca/resources/contributors) pages
+on Islandora.ca for more information.
+
+We recommend using the
+[islandora-playbook](https://github.com/Islandora-Devops/islandora-playbook) to
+get started.
+
+## License
+
+[GPLv2](http://www.gnu.org/licenses/gpl-2.0.txt)

modules/islandora_advanced_search/css/islandora_advanced_search.form.css

@@ -0,0 +1,37 @@
+.islandora-advanced-search-form .form-type-select {
+  display: inline-block;
+}
+
+.islandora-advanced-search-form .form-type-select__select-wrapper {
+  width: auto;
+}
+
+.islandora-advanced-search-form .form-select {
+  margin-right: 0.25em;
+}
+
+input.islandora-advanced-search-form__add,
+input.islandora-advanced-search-form__remove {
+  display: inline-block;
+  background: none !important;
+  border: none;
+  box-shadow: none;
+  color: #0c6170;
+  padding: 0 !important;
+  text-decoration: none;
+  margin: 0 0 1rem;
+}
+
+input.islandora-advanced-search-form__add:hover,
+input.islandora-advanced-search-form__add:focus,
+input.islandora-advanced-search-form__remove:hover,
+input.islandora-advanced-search-form__remove:focus {
+  text-decoration: underline;
+  color: #0c6170;
+  outline: none;
+}
+
+input.islandora-advanced-search-form__reset,
+input.islandora-advanced-search-form__search {
+  display: inline-block;
+}

modules/islandora_advanced_search/css/islandora_advanced_search.pager.css

@@ -0,0 +1,111 @@
+.islandora_advanced_search_result_pager .pager__summary {
+  font-weight: 700;
+}
+
+.islandora_advanced_search_result_pager .pager__group {
+  margin: 1.25rem 0;
+  padding: 1rem 0;
+  border-top: 1px solid;
+  border-bottom: 1px solid;
+  border-color: #e5e5e5;
+  display: flex;
+  justify-content: flex-start;
+  align-items: center;
+  flex-flow: row wrap;
+}
+
+@media all and (min-width: 45.063em) {
+  .islandora_advanced_search_result_pager .pager__group {
+    justify-content: flex-end;
+  }
+  .islandora_advanced_search_result_pager .pager__group > * {
+    margin: 0.47214rem 0 0.47214rem 2.61803rem;
+  }
+  .islandora_advanced_search_result_pager .pager__group > *:first-child {
+    margin-left: 0;
+  }
+}
+
+.islandora_advanced_search_result_pager .pager__group > * {
+  margin: 0.47214rem 2rem 0.47214rem 0;
+}
+
+.islandora_advanced_search_result_pager .pager__group > *:last-child {
+  margin-right: 0;
+}
+
+.islandora_advanced_search_result_pager .pager__group .item-list__list,
+.islandora_advanced_search_result_pager .pager__group .item-list__title,
+.islandora_advanced_search_result_pager .pager__group .item-list__item {
+  display: inline;
+}
+
+.islandora_advanced_search_result_pager .pager__group .item-list__title {
+  font-size: initial;
+  margin: 0.25rem;
+}
+
+.pager {
+  margin: initial;
+}
+
+.pager__item {
+  margin: 0.125rem;
+  text-align: center;
+}
+
+.pager__items {
+  text-align: right;
+}
+
+@media all and (max-width: 45em) {
+  .pager__items {
+    text-align: center;
+  }
+}
+
+.pager__items__first-previous,
+.pager__items__num-pages,
+.pager__items__next-last {
+  display: inline;
+}
+
+.pager__items__first-previous,
+.pager__items__next-last {
+  float: none;
+}
+
+.pager__items__first-previous .pager__item,
+.pager__items__next-last .pager__item {
+  display: inline;
+}
+
+.pager .pager__link,
+.pager__results .pager__link {
+  display: inline-block;
+  border-radius: 0.125em;
+  border: 1px solid;
+  transition: all, 0.2s, ease-in-out;
+  min-width: 1.75em;
+  padding: 0.125rem 0.4375rem 0;
+}
+
+.pager .pager__link:focus,
+.pager .pager__link:hover,
+.pager__results .pager__link:focus,
+.pager__results .pager__link:hover {
+  text-decoration: underline;
+}
+
+.pager__display .pager__link {
+  background-color: #ffffff;
+}
+
+.pager__display .pager__link:hover,
+.pager__display .pager__link:focus {
+  background-color: #ffffff;
+}
+
+.pager__link--is-active {
+  text-decoration: underline;
+}

modules/islandora_advanced_search/islandora_advanced_search.info.yml

@@ -0,0 +1,11 @@
+# This .info.yml files provides the basic information about our module to Drupal
+# More: https://www.drupal.org/node/2000204
+name: 'Islandora Advanced Search'
+description: "Creates an Advanced Search block and other enhancements to search."
+type: module
+package: Islandora
+core_version_requirement: ^8 || ^9
+dependencies:
+  - drupal:facets
+  - drupal:facets_summary
+  - drupal:search_api_solr

modules/islandora_advanced_search/islandora_advanced_search.libraries.yml

@@ -0,0 +1,17 @@
+advanced.search.admin:
+  js:
+    js/islandora_advanced_search.admin.js: {}
+  dependencies:
+    - core/drupal.tabledrag
+
+advanced.search.form:
+  js:
+    js/islandora_advanced_search.form.js: {}
+  css:
+    component:
+      css/islandora_advanced_search.form.css: {}
+
+advanced.search.pager:
+  css:
+    component:
+      css/islandora_advanced_search.pager.css: {}

modules/islandora_advanced_search/islandora_advanced_search.links.menu.yml

@@ -0,0 +1,6 @@
+islandora_advanced_search.settings:
+  title: 'Advanced Search Settings'
+  route_name: islandora_advanced_search.settings
+  description: 'Configure Islandora Advanced Search settings'
+  parent: system.admin_config_islandora
+  weight: 99

modules/islandora_advanced_search/islandora_advanced_search.module

@@ -0,0 +1,191 @@
+<?php
+
+/**
+ * @file
+ * Contains islandora_advanced_search.module.
+ *
+ * This file is part of the Islandora Project.
+ *
+ * (c) Islandora Foundation
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Drupal\block\Entity\Block;
+use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\islandora_advanced_search\AdvancedSearchQuery;
+use Drupal\islandora_advanced_search\Form\SettingsForm;
+use Drupal\islandora_advanced_search\Utilities;
+use Drupal\search_api\Query\QueryInterface as DrupalQueryInterface;
+use Drupal\views\ViewExecutable;
+use Solarium\Core\Query\QueryInterface as SolariumQueryInterface;
+
+/**
+ * Implements hook_theme().
+ */
+function islandora_advanced_search_theme() {
+  return [
+    'facets_item_list__include_exclude_links' => [
+      'template' => 'facets/facets-item-list--include-exclude-links',
+      'base hook' => 'facets_item_list',
+    ],
+    'facets_result_item__include_exclude_links' => [
+      'template' => 'facets/facets-result-item--include-exclude-links',
+      'base hook' => 'facets_result_item',
+    ],
+    'facets_result_item__summary' => [
+      'template' => 'facets/facets-result-item--summary',
+      'base hook' => 'facets_result_item',
+    ],
+  ];
+}
+
+/**
+ * Implements hook_library_info_alter().
+ */
+function islandora_advanced_search_library_info_alter(&$libraries, $extension) {
+  if ($extension == 'facets') {
+    // Override facets module javascript with customizations.
+    $path = '/' . drupal_get_path('module', 'islandora_advanced_search') . '/js/facets';
+    $libraries['soft-limit']['js'] = [
+      "$path/soft-limit.js" => [],
+    ];
+    $libraries['drupal.facets.views-ajax']['js'] = [
+      "$path/facets-views-ajax.js" => [],
+    ];
+  }
+}
+
+/**
+ * Implements hook_search_api_solr_converted_query_alter().
+ */
+function islandora_advanced_search_search_api_solr_converted_query_alter(SolariumQueryInterface $solarium_query, DrupalQueryInterface $search_api_query) {
+  // We must modify the query itself rather than the representation the
+  // search_api presents as it is not possible to use the 'OR' operator
+  // with it as it converts conditions into separate filter queries.
+  // Additionally filter queries do not affect the score so are not
+  // suitable for use in the advanced search queries.
+  $advanced_search_query = new AdvancedSearchQuery();
+  $advanced_search_query->alterQuery(\Drupal::request(), $solarium_query, $search_api_query);
+}
+
+/**
+ * Implements hook_form_form_id_alter().
+ */
+function islandora_advanced_search_form_block_form_alter(&$form, FormStateInterface $form_state, $form_id) {
+  // Islandora removes this condition from the form, but we require it.
+  // So we can show blocks for nodes which belong to specific models.
+  // Allowing us to add a block for collections only.
+  $visibility = [];
+  $entity_id = $form['id']['#default_value'];
+  $block = Block::load($entity_id);
+  if ($block) {
+    $visibility = $block->getVisibility();
+  }
+  $manager = \Drupal::getContainer()->get('plugin.manager.condition');
+  $condition_id = 'node_has_term';
+
+  /** @var \Drupal\Core\Condition\ConditionInterface $condition */
+  $condition = $manager->createInstance($condition_id, isset($visibility[$condition_id]) ? $visibility[$condition_id] : []);
+  $form_state->set(['conditions', $condition_id], $condition);
+  $condition_form = $condition->buildConfigurationForm([], $form_state);
+  $condition_form['#type'] = 'details';
+  $condition_form['#title'] = $condition->getPluginDefinition()['label'];
+  $condition_form['#group'] = 'visibility_tabs';
+  // Not all blocks are required to give this field.
+  $condition_form['term']['#required'] = FALSE;
+  $form['visibility'][$condition_id] = $condition_form;
+}
+
+/**
+ * Implements hook_preprocess_block__facets_summary().
+ */
+function islandora_advanced_search_preprocess_block__facets_summary(&$variables) {
+  // Copy data-attributes to the content as the javascript expects
+  // there to be no elements between the data declaration and the
+  // content of the block.
+  foreach ($variables['attributes'] as $key => $value) {
+    if (substr($key, 0, 4) === "data") {
+      $variables['content_attributes'][$key] = $value;
+    }
+  }
+}
+
+/**
+ * Implements hook_preprocess_preprocess_views_view().
+ */
+function islandora_advanced_search_preprocess_views_view(&$variables) {
+  /** @var \Drupal\views\ViewExecutable $view */
+  $view = &$variables['view'];
+  $views = Utilities::getPagerViewDisplays();
+  // Only add the toggle class for view display on displays in which the pager
+  // has been created for.
+  if (in_array([$view->id(), $view->current_display], $views)) {
+    // Toggle between 'list' and 'grid' display depending on url parameter.
+    $format = \Drupal::request()->query->get('display') ?? 'list';
+    $variables['attributes']['class'][] = "view-{$format}";
+    $view->element['#attached']['library'][] = 'islandora_advanced_search/advanced.search.pager';
+  }
+  $view = &$variables['view'];
+}
+
+/**
+ * Implements hook_views_pre_view().
+ */
+function islandora_advanced_search_views_pre_view(ViewExecutable $view, $display_id, array &$args) {
+  // Allow for recursive searches by disabling contextual filter.
+  $advanced_search_query = new AdvancedSearchQuery();
+  $advanced_search_query->alterView(\Drupal::request(), $view, $display_id);
+}
+
+/**
+ * Implements hook_preprocess_facets_summary_item_list().
+ */
+function islandora_advanced_search_preprocess_facets_summary_item_list(&$variables) {
+  foreach ($variables['items'] as &$item) {
+    $item['attributes']['class'][] = 'facet-summary-item';
+  }
+}
+
+/**
+ * Implements hook_preprocess_facets_item_list().
+ */
+function islandora_advanced_search_preprocess_facets_item_list(&$variables) {
+  $widget = $variables['facet']->getWidget();
+  $soft_limit = $widget['config']['soft_limit'];
+  // Break into two groups less / more which can display be toggled as a single
+  // element change rather than showing / hiding all <li> elements individually.
+  // As its slow and causes the page to snap when loading.
+  $variables['less'] = array_slice($variables['items'], 0, $soft_limit);
+  $variables['more'] = array_slice($variables['items'], $soft_limit);
+  $variables['show_more_label'] = $widget['config']['soft_limit_settings']['show_more_label'];
+}
+
+/**
+ * Implements hook_preprocess_facets_result_item().
+ */
+function islandora_advanced_search_preprocess_facets_result_item(&$variables) {
+  $settings = \Drupal::config(SettingsForm::CONFIG_NAME);
+  $length = $settings->get(SettingsForm::FACET_TRUNCATE);
+  if (is_numeric($length)) {
+    // Limit the length of facets display to at most 32 characters.
+    if (is_string($variables['value'])) {
+      $variables['value'] = Unicode::truncate(
+        $variables['value'],
+        $length,
+        TRUE,
+        TRUE
+      );
+    }
+    elseif (is_string($variables['value']['text']['#title'])) {
+      $variables['value']['text']['#title'] = Unicode::truncate(
+        $variables['value']['text']['#title'],
+        $length,
+        TRUE,
+        TRUE
+          );
+    }
+  }
+}

modules/islandora_advanced_search/islandora_advanced_search.routing.yml

@@ -0,0 +1,17 @@
+islandora_advanced_search.ajax.blocks:
+  path: '/islandora-advanced-search-ajax-blocks'
+  defaults:
+    _controller: '\Drupal\islandora_advanced_search\Controller\AjaxBlocksController::respond'
+  requirements:
+    # Allow public access to search blocks.
+    _access: 'TRUE'
+
+islandora_advanced_search.settings:
+  path: '/admin/config/search/advanced'
+  defaults:
+    _form: '\Drupal\islandora_advanced_search\Form\SettingsForm'
+    _title: 'Islandora Advanced Search Settings'
+  requirements:
+    _permission: 'administer site configuration'
+  options:
+    _admin_route: TRUE

modules/islandora_advanced_search/js/facets/facets-views-ajax.js

@@ -0,0 +1,146 @@
+//# sourceURL=modules/contrib/islandora/modules/islandora_advanced_search/js/facets/facets-view.ajax.js
+/**
+ * @file
+ * Overrides the facets-view-ajax.js behavior from the 'facets' module.
+ */
+(function ($, Drupal) {
+  "use strict";
+
+  // Generate events on push state.
+  (function (history) {
+    var pushState = history.pushState;
+    history.pushState = function (state, title, url) {
+      var ret = pushState.apply(this, arguments);
+      var event = new Event("pushstate");
+      window.dispatchEvent(event);
+      return ret;
+    };
+  })(window.history);
+
+  function reload(url) {
+    // Update View.
+    if (drupalSettings && drupalSettings.views && drupalSettings.views.ajaxViews) {
+      var view_path = drupalSettings.views.ajax_path;
+      $.each(drupalSettings.views.ajaxViews, function (views_dom_id) {
+        var views_parameters = Drupal.Views.parseQueryString(url);
+        var views_arguments = Drupal.Views.parseViewArgs(url, "search");
+        var views_settings = $.extend(
+          {},
+          Drupal.views.instances[views_dom_id].settings,
+          views_arguments,
+          views_parameters
+        );
+        var views_ajax_settings =
+          Drupal.views.instances[views_dom_id].element_settings;
+        views_ajax_settings.submit = views_settings;
+        views_ajax_settings.url =
+          view_path + "?" + $.param(Drupal.Views.parseQueryString(url));
+        Drupal.ajax(views_ajax_settings).execute();
+      });
+    }
+
+    // Replace filter, pager, summary, and facet blocks.
+    var blocks = {};
+    $(
+      ".block[class*='block-plugin-id--islandora-advanced-search-result-pager'], .block[class*='block-plugin-id--views-exposed-filter-block'], .block[class*='block-plugin-id--facet']"
+    ).each(function () {
+      var id = $(this).attr("id");
+      var block_id = id
+        .slice("block-".length, id.length)
+        .replace(/--.*$/g, "")
+        .replace(/-/g, "_");
+      blocks[block_id] = "#" + id;
+    });
+    Drupal.ajax({
+      url: Drupal.url("islandora-advanced-search-ajax-blocks"),
+      submit: {
+        link: url,
+        blocks: blocks,
+      },
+    }).execute();
+  }
+
+  // On location change reload all the blocks / ajax view.
+  window.addEventListener("pushstate", function (e) {
+    reload(window.location.href);
+  });
+
+  window.addEventListener("popstate", function (e) {
+    if (e.state != null) {
+      reload(window.location.href);
+    }
+  });
+
+  /*** Push state on form/pager/facet change.
+   */
+  Drupal.behaviors.islandoraAdvancedSearchViewsAjax = {
+    attach: function (context, settings) {
+      window.historyInitiated = true;
+
+      // Remove existing behavior from form.
+      if (settings && settings.views && settings.views.ajaxViews) {
+        $.each(settings.views.ajaxViews, function (index, settings) {
+          var exposed_form = $(
+            "form#views-exposed-form-" +
+            settings.view_name.replace(/_/g, "-") +
+            "-" +
+            settings.view_display_id.replace(/_/g, "-")
+          );
+          exposed_form
+            .once()
+            .find("input[type=submit], input[type=image]")
+            .not("[data-drupal-selector=edit-reset]")
+            .each(function (index) {
+              $(this).unbind("click");
+              $(this).click(function (e) {
+                // Let ctrl/cmd click open in a new window.
+                if (e.shiftKey || e.ctrlKey || e.metaKey) {
+                  return;
+                }
+                e.preventDefault();
+                e.stopPropagation();
+                var href = window.location.href;
+                var params = Drupal.Views.parseQueryString(href);
+                // Remove the page if set as submitting the form should always take
+                // the user to the first page (facets do the same).
+                delete params.page;
+                // Include values from the form in the URL.
+                $.each(exposed_form.serializeArray(), function () {
+                  params[this.name] = this.value;
+                });
+                href = href.split("?")[0] + "?" + $.param(params);
+                window.history.pushState(null, document.title, href);
+              });
+            });
+        });
+      }
+
+      // Attach behavior to pager, summary, facet links.
+      $("[data-drupal-pager-id], [data-drupal-facets-summary-id], [data-drupal-facet-id]")
+        .once()
+        .find("a:not(.facets-soft-limit-link)")
+        .click(function (e) {
+          // Let ctrl/cmd click open in a new window.
+          if (e.shiftKey || e.ctrlKey || e.metaKey) {
+            return;
+          }
+          e.preventDefault();
+          window.history.pushState(null, document.title, $(this).attr("href"));
+        });
+
+      // Trigger on sort change.
+      $('[data-drupal-pager-id] select[name="order"]')
+        .once()
+        .change(function () {
+          var href = window.location.href;
+          var params = Drupal.Views.parseQueryString(href);
+          var selection = $(this).val();
+          var option = $('option[value="' + selection + '"]');
+          params.sort_order = option.data("sort_order");
+          params.sort_by = option.data("sort_by");
+          href = href.split("?")[0] + "?" + $.param(params);
+          window.history.pushState(null, document.title, href);
+        });
+    },
+  };
+})(jQuery, Drupal);

modules/islandora_advanced_search/js/facets/soft-limit.js

@@ -0,0 +1,70 @@
+//# sourceURL=modules/contrib/islandora/modules/islandora_advanced_search/js/facets/soft-limit.js
+/**
+ * @file
+ * Overrides the soft-limit.js behavior from the 'facets' module.
+ * As when having many facets the original version causes the page to slow down and snap to hidden when rendering.
+ */
+(function ($) {
+
+  'use strict';
+
+  Drupal.behaviors.facetSoftLimit = {
+    attach: function (context, settings) {
+      if (settings.facets.softLimit !== 'undefined') {
+        $.each(settings.facets.softLimit, function (facet, limit) {
+          Drupal.facets.applySoftLimit(facet, limit, settings);
+        });
+      }
+    }
+  };
+
+  Drupal.facets = Drupal.facets || {};
+
+  /**
+   * Applies the soft limit UI feature to a specific facets list.
+   *
+   * @param {string} facet
+   *   The facet id.
+   * @param {string} limit
+   *   The maximum amount of items to show.
+   * @param {object} settings
+   *   Settings.
+   */
+  Drupal.facets.applySoftLimit = function (facet, limit, settings) {
+    var zero_based_limit = (limit - 1);
+    var facet_id = facet;
+    var facetsList = $('ul[data-drupal-facet-id="' + facet_id + '"]');
+
+    // In case of multiple instances of a facet, we need to key them.
+    if (facetsList.length > 1) {
+      facetsList.each(function (key, $value) {
+        $(this).attr('data-drupal-facet-id', facet_id + '-' + key);
+      });
+    }
+
+    // Add "Show more" / "Show less" links.
+    facetsList.filter(function () {
+      return $(this).next('ul').length == 1; // Has expanding list.
+    }).each(function () {
+      var facet = $(this);
+      var expand = facet.next('ul');
+      var link = expand.next('a');
+      var showLessLabel = settings.facets.softLimitSettings[facet_id].showLessLabel;
+      var showMoreLabel = settings.facets.softLimitSettings[facet_id].showMoreLabel;
+      link.text(showMoreLabel)
+        .once()
+        .on('click', function () {
+          if (!expand.is(":visible")) {
+            expand.slideDown();
+            $(this).addClass('open').text(showLessLabel);
+          }
+          else {
+            expand.slideUp();
+            $(this).removeClass('open').text(showMoreLabel);
+          }
+          return false;
+        })
+    });
+  };
+
+})(jQuery);

modules/islandora_advanced_search/js/islandora_advanced_search.admin.js

@@ -0,0 +1,113 @@
+//# sourceURL=modules/contrib/islandora_advanced_search/js/islandora-advanced-search.admin.js
+/**
+ * @file
+ * Largely based on core/modules/blocks/js/blocks.js
+ * 
+ * This file allows for moving rows between two regions in a table and have the
+ * 'region' field update appropriately.
+ */
+(function ($, window, Drupal) {
+  Drupal.behaviors.islandoraAdvancedSearchAdmin = {
+    attach: function attach(context, settings) {
+      if (typeof Drupal.tableDrag === 'undefined' || typeof Drupal.tableDrag['advanced-search-fields'] === 'undefined') {
+        return;
+      }
+
+      function checkEmptyRegions(table, rowObject) {
+        table.find('tr.region-message').each(function () {
+          var $this = $(this);
+
+          if ($this.prev('tr').get(0) === rowObject.element) {
+            if (rowObject.method !== 'keyboard' || rowObject.direction === 'down') {
+              rowObject.swap('after', this);
+            }
+          }
+
+          if ($this.next('tr').is(':not(.draggable)') || $this.next('tr').length === 0) {
+            $this.removeClass('region-populated').addClass('region-empty');
+          } else if ($this.is('.region-empty')) {
+              $this.removeClass('region-empty').addClass('region-populated');
+            }
+        });
+      }
+
+      function updateLastPlaced(table, rowObject) {
+        table.find('.color-success').removeClass('color-success');
+
+        var $rowObject = $(rowObject);
+        if (!$rowObject.is('.drag-previous')) {
+          table.find('.drag-previous').removeClass('drag-previous');
+          $rowObject.addClass('drag-previous');
+        }
+      }
+
+      function updateFieldWeights(table, region) {
+        var weight = -Math.round(table.find('.draggable').length / 2);
+
+        table.find('.region-' + region + '-message').nextUntil('.region-title').find('select.field-weight').val(function () {
+          return ++weight;
+        });
+      }
+
+      var table = $('#advanced-search-fields');
+
+      var tableDrag = Drupal.tableDrag['advanced-search-fields'];
+
+      tableDrag.row.prototype.onSwap = function (swappedRow) {
+        checkEmptyRegions(table, this);
+        updateLastPlaced(table, this);
+      };
+
+      tableDrag.onDrop = function () {
+        var dragObject = this;
+        var $rowElement = $(dragObject.rowObject.element);
+
+        var regionRow = $rowElement.prevAll('tr.region-message').get(0);
+        var regionName = regionRow.className.replace(/([^ ]+[ ]+)*region-([^ ]+)-message([ ]+[^ ]+)*/, '$2');
+        var regionField = $rowElement.find('select.field-display');
+
+        if (regionField.find('option[value=' + regionName + ']').length === 0) {
+          window.alert(Drupal.t('The field cannot be placed in this region.'));
+
+          regionField.trigger('change');
+        }
+
+        if (!regionField.is('.field-display-' + regionName)) {
+          var weightField = $rowElement.find('select.field-weight');
+          var oldRegionName = weightField[0].className.replace(/([^ ]+[ ]+)*field-weight-([^ ]+)([ ]+[^ ]+)*/, '$2');
+          regionField.removeClass('field-display-' + oldRegionName).addClass('field-display-' + regionName);
+          weightField.removeClass('field-weight-' + oldRegionName).addClass('field-weight-' + regionName);
+          regionField.val(regionName);
+        }
+
+        updateFieldWeights(table, regionName);
+      };
+
+      $(context).find('select.field-display').once('field-display').on('change', function (event) {
+        var row = $(this).closest('tr');
+        var select = $(this);
+
+        tableDrag.rowObject = new tableDrag.row(row[0]);
+        var regionMessage = table.find('.region-' + select[0].value + '-message');
+        var regionItems = regionMessage.nextUntil('.region-message, .region-title');
+        if (regionItems.length) {
+          regionItems.last().after(row);
+        } else {
+            regionMessage.after(row);
+          }
+        updateFieldWeights(table, select[0].value);
+
+        checkEmptyRegions(table, tableDrag.rowObject);
+
+        updateLastPlaced(table, row);
+
+        if (!tableDrag.changed) {
+          $(Drupal.theme('tableDragChangedWarning')).insertBefore(tableDrag.table).hide().fadeIn('slow');
+          tableDrag.changed = true;
+        }
+
+        select.trigger('blur');
+      });
+    }
+  };
+})(jQuery, window, Drupal);

modules/islandora_advanced_search/js/islandora_advanced_search.form.js

@@ -0,0 +1,114 @@
+//# sourceURL=modules/contrib/islandora/modules/islandora_advanced_search/js/islandora-advanced-search.form.js
+/**
+ * @file
+ * Handles Ajax submission / updating form action on url change, etc.
+ */
+(function ($, Drupal, drupalSettings) {
+
+  // Gets current parameters minus ones provided by the form.
+  function getParams(query_parameter, recurse_parameter) {
+    var params = Drupal.Views.parseQueryString(window.location.href);
+    // Remove Advanced Search Query Parameters.
+    const param_match = "query\\[\\d+\\]\\[.+\\]".replace("query", query_parameter);
+    const param_regex = new RegExp(param_match, "g");
+    for (const param in params) {
+      if (param.match(param_regex)) {
+        delete params[param];
+      }
+    }
+    // Remove Recurse parameter.
+    delete params[recurse_parameter];
+    return params;
+  }
+
+  // Groups form inputs by search term.
+  function getTerms(inputs) {
+    const input_regex = /terms\[(?<index>\d+)\]\[(?<component>.*)\]/;
+    const terms = [];
+    for (const input in inputs) {
+      const name = inputs[input].name;
+      const value = inputs[input].value;
+      const found = name.match(input_regex);
+      if (found) {
+        const index = parseInt(found.groups.index);
+        const component = found.groups.component;
+        if (typeof terms[index] !== 'object') {
+          terms[index] = {};
+        }
+        terms[index][component] = value;
+      }
+    }
+    return terms;
+  }
+
+  // Checks if the form user has set recursive to true in the form.
+  function getRecurse(inputs) {
+    for (const input in inputs) {
+      const name = inputs[input].name;
+      const value = inputs[input].value;
+      if (name == "recursive" && value == "1") {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  function url(inputs, settings) {
+    const terms = getTerms(inputs);
+    const recurse = getRecurse(inputs);
+    const params = getParams(settings.query_parameter, settings.recurse_parameter);
+    for (const index in terms) {
+      const term = terms[index];
+      // Do not include terms with no value.
+      if (term.value.length != 0) {
+        for (const component in term) {
+          const value = term[component];
+          const param = "query[index][component]"
+            .replace("query", settings.query_parameter)
+            .replace("index", index)
+            .replace("component", settings.mapping[component]);
+          params[param] = value;
+        }
+      }
+    }
+    if (recurse) {
+      params[settings.recurse_parameter] = '1';
+    }
+    return window.location.href.split("?")[0] + "?" + $.param(params);
+  }
+
+  Drupal.behaviors.islandora_advanced_search_form = {
+    attach: function (context, settings) {
+      if (settings.islandora_advanced_search_form.id !== 'undefined') {
+        const $form = $('form#' + settings.islandora_advanced_search_form.id).once();
+        if ($form.length > 0) {
+          window.addEventListener("pushstate", function (e) {
+            $form.attr('action', window.location.pathname + window.location.search);
+          });
+          window.addEventListener("popstate", function (e) {
+            if (e.state != null) {
+              $form.attr('action', window.location.pathname + window.location.search);
+            }
+          });
+          // Prevent form submission and push state instead.
+          //
+          // Logic server side / client side should match to generate the 
+          // approprirate URL with javascript enabled or disable.
+          $form.submit(function (e) {
+            e.preventDefault();
+            e.stopPropagation();
+            const inputs = $form.serializeArray();
+            const href = url(inputs, settings.islandora_advanced_search_form);
+            window.history.pushState(null, document.title, href);
+          });
+          // Reset should trigger refresh of AJAX Blocks / Views.
+          $form.find('input[data-drupal-selector = "edit-reset"]').mousedown(function (e) {
+            const inputs = [];
+            const href = url(inputs, settings.islandora_advanced_search_form);
+            window.history.pushState(null, document.title, href);
+          });
+        }
+      }
+    }
+  };
+})(jQuery, Drupal, drupalSettings);

modules/islandora_advanced_search/src/AdvancedSearchQuery.php

@@ -0,0 +1,243 @@
+<?php
+
+namespace Drupal\islandora_advanced_search;
+
+use Drupal\block\Entity\Block;
+use Drupal\Core\Url;
+use Drupal\islandora_advanced_search\Form\SettingsForm;
+use Drupal\islandora_advanced_search\Plugin\Block\AdvancedSearchBlock;
+use Drupal\search_api\Query\QueryInterface as DrupalQueryInterface;
+use Drupal\views\ViewExecutable;
+use Solarium\Core\Query\QueryInterface as SolariumQueryInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Alter current search query / view from using URL parameters.
+ */
+class AdvancedSearchQuery {
+
+  use GetConfigTrait;
+
+  // User can set this configuration for the module.
+  const DEFAULT_QUERY_PARAM = 'a';
+  const DEFAULT_RECURSE_PARAM = 'r';
+
+  /**
+   * The query parameter is how terms are passed to the query.
+   *
+   * @var string
+   */
+  protected $queryParameter;
+
+  /**
+   * The recurse parameter indicates the search should be recursive or not.
+   *
+   * @var string
+   */
+  protected $recurseParameter;
+
+  /**
+   * Constructs a FacetBlockAjaxController object.
+   *
+   * @param string $query_parameter
+   *   The field to search against.
+   * @param string $recurse_parameter
+   *   The field that signifies the search should be recursive.
+   */
+  public function __construct(string $query_parameter = self::DEFAULT_QUERY_PARAM, string $recurse_parameter = self::DEFAULT_RECURSE_PARAM) {
+    $this->queryParameter = $query_parameter;
+    $this->recurseParameter = $recurse_parameter;
+  }
+
+  /**
+   * Gets the query parameter to use that stores the search terms.
+   *
+   * @return string
+   *   The query parameter to use that stores the search terms.
+   */
+  public static function getQueryParameter() {
+    return self::getConfig(SettingsForm::SEARCH_QUERY_PARAMETER, self::DEFAULT_QUERY_PARAM);
+  }
+
+  /**
+   * Gets the query parameter to use that stores the search terms.
+   *
+   * @return string
+   *   The recurse parameter used to indicate that the search should be
+   *   recursive.
+   */
+  public static function getRecurseParameter() {
+    return self::getConfig(SettingsForm::SEARCH_RECURSIVE_PARAMETER, self::DEFAULT_RECURSE_PARAM);
+  }
+
+  /**
+   * Extracts a list of AdvancedSearchQueryTerms from the given request.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request to parse terms from.
+   *
+   * @return \Drupal\islandora_advanced_search\AdvancedSearchQueryTerm[]
+   *   A list of search terms.
+   */
+  public function getTerms(Request $request) {
+    $terms = [];
+    if ($request->query->has($this->queryParameter)) {
+      $query_params = $request->query->get($this->queryParameter);
+      if (is_array($query_params)) {
+        foreach ($query_params as $params) {
+          $terms[] = AdvancedSearchQueryTerm::fromQueryParams($params);
+        }
+      }
+    }
+    return array_filter($terms);
+  }
+
+  /**
+   * Checks if the query should recursively include sub-collections.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request to parse.
+   *
+   * @return bool
+   *   TRUE if the search should recurse FALSE otherwise.
+   */
+  public function shouldRecurse(Request $request) {
+    if ($request->query->has($this->recurseParameter)) {
+      $recurse_param = $request->query->get($this->recurseParameter);
+      return filter_var($recurse_param, FILTER_VALIDATE_BOOLEAN);
+    }
+    return FALSE;
+  }
+
+  /**
+   * Checks if the all of the given terms are negations or not.
+   *
+   * @param \Drupal\islandora_advanced_search\AdvancedSearchQueryTerm[] $terms
+   *   The terms to search for.
+   *
+   * @return bool
+   *   TRUE if all terms are to be excluded otherwise FALSE.
+   */
+  protected function negativeQuery(array $terms) {
+    foreach ($terms as $term) {
+      if ($term->getInclude()) {
+        return FALSE;
+      }
+    }
+    return TRUE;
+  }
+
+  /**
+   * Alters the given query using search terms provided in the given request.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request to parse terms from.
+   * @param \Solarium\Core\Query\QueryInterface $solarium_query
+   *   The solr query to modify.
+   * @param \Drupal\search_api\Query\QueryInterface $search_api_query
+   *   The search api query from which the solr query was build.
+   */
+  public function alterQuery(Request $request, SolariumQueryInterface &$solarium_query, DrupalQueryInterface $search_api_query) {
+    // Only apply if a Advanced Search Query was made.
+    $terms = $this->getTerms($request);
+    if (!empty($terms)) {
+      $index = $search_api_query->getIndex();
+      /** @var \Drupal\search_api_solr\Plugin\search_api\backend\SearchApiSolrBackend $backend */
+      $backend = $index->getServerInstance()->getBackend();
+      $language_ids = $search_api_query->getLanguages();
+      $field_mapping = $backend->getSolrFieldNamesKeyedByLanguage($language_ids, $index);
+      $q[] = "{!boost b=boost_document}";
+      // To support negative queries we must first bring in all documents.
+      $q[] = $this->negativeQuery($terms) ? "*:*" : "";
+      $term = array_shift($terms);
+      $q[] = $term->toSolrQuery($field_mapping);
+      foreach ($terms as $term) {
+        $q[] = $term->getConjunction();
+        $q[] = $term->toSolrQuery($field_mapping);
+      }
+      $q = implode(' ', $q);
+      /** @var Solarium\QueryType\Select\Query\Query $solarium_query */
+      $solarium_query->setQuery($q);
+    }
+  }
+
+  /**
+   * Alters the given view to be recursive if applicable.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request to parse terms from.
+   * @param \Drupal\views\ViewExecutable $view
+   *   The view to modify.
+   * @param string $display_id
+   *   The view display to potentially alter.
+   */
+  public function alterView(Request $request, ViewExecutable $view, $display_id) {
+    $views = Utilities::getAdvancedSearchViewDisplays();
+    // Only specify contextual filters for views which the advanced search
+    // blocks are derived from.
+    $block_id = array_search([$view->id(), $display_id], $views);
+    if ($block_id !== FALSE) {
+      $block = Block::load($block_id);
+      $settings = $block->get('settings');
+      // Ignore the immediate children contextual filter in the query to allow
+      // for recursive search.
+      if (isset($settings[AdvancedSearchBlock::SETTING_CONTEXTUAL_FILTER])) {
+        $display = $view->getDisplay();
+        $display_arguments = $display->getOption('arguments');
+        $immediate_children_contextual_filter = $settings[AdvancedSearchBlock::SETTING_CONTEXTUAL_FILTER];
+        $index = array_search($immediate_children_contextual_filter, array_keys($display_arguments));
+        if ($this->shouldRecurse($request)) {
+          // Change the argument to the exception value which should cause the
+          // contextual filter to be ignored.
+          $view->args[$index] = $display_arguments[$immediate_children_contextual_filter]['exception']['value'];
+        }
+        else {
+          // Explicitly set the default argument for AJAX requests.
+          // We need to restore the default as that functionality is currently
+          // broken. @see https://www.drupal.org/project/drupal/issues/3173778
+          //
+          // We fake the current request from the refer only to set the default
+          // argument in case it is build from the URL. If this is not an AJAX
+          // request this logic can be ignored.
+          if ($request->isXmlHttpRequest()) {
+            $view->initHandlers();
+            $request_stack = \Drupal::requestStack();
+            $refer = Request::create($request->server->get('HTTP_REFERER'));
+            $refer->getPathInfo();
+            $refer->attributes->add(\Drupal::getContainer()->get('router')->matchRequest($refer));
+            $request_stack->push($refer);
+            $plugin = $view->argument[$immediate_children_contextual_filter]->getPlugin('argument_default');
+            if ($plugin) {
+              $view->args[$index] = $plugin->getArgument();
+            }
+            $request_stack->pop();
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Get query parameter for all search terms.
+   *
+   * @return \Drupal\Core\Url
+   *   Url for the given request combined with search query parameters.
+   */
+  public function toUrl(Request $request, array $terms, bool $recurse) {
+    $url = Url::createFromRequest($request);
+    $query_params = $request->query->all();
+    unset($query_params[$this->queryParameter]);
+    foreach ($terms as $term) {
+      $query_params[$this->queryParameter][] = $term->toQueryParams();
+    }
+    if ($recurse) {
+      $query_params[$this->recurseParameter] = '1';
+    }
+    else {
+      unset($query_params[$this->recurseParameter]);
+    }
+    $url->setOptions(['query' => $query_params]);
+    return $url;
+  }
+
+}

modules/islandora_advanced_search/src/AdvancedSearchQueryTerm.php

@@ -0,0 +1,294 @@
+<?php
+
+namespace Drupal\islandora_advanced_search;
+
+use Drupal\islandora_advanced_search\Form\AdvancedSearchForm;
+
+/**
+ * Defines a single search term.
+ *
+ * Used for parsing query parameters as well as form submission and generating
+ * search queries.
+ */
+class AdvancedSearchQueryTerm {
+  // Conjunctions.
+  // @see https://lucene.apache.org/solr/guide/7_1/the-standard-query-parser.html#TheStandardQueryParser-BooleanOperatorsSupportedbytheStandardQueryParser
+  const CONJUNCTION_AND = 'AND';
+  const CONJUNCTION_OR = 'OR';
+
+  // Used for serializing / deserializing query parameters.
+  // These are also hard-coded in islandora_advanced_search.form.js.
+  const CONJUNCTION_QUERY_PARAMETER = 'c';
+  const FIELD_QUERY_PARAMETER = 'f';
+  const INCLUDE_QUERY_PARAMETER = 'i';
+  const VALUE_QUERY_PARAMETER = 'v';
+
+  // Defaults.
+  const DEFAULT_CONJUNCTION = self::CONJUNCTION_AND;
+  const DEFAULT_INCLUDE = TRUE;
+
+  /**
+   * The field to search.
+   *
+   * @var string
+   */
+  protected $field;
+
+  /**
+   * Include / exclude results where 'value' is in the 'search' term.
+   *
+   * @var bool
+   */
+  protected $include = TRUE;
+
+  /**
+   * The value to filter with.
+   *
+   * @var string
+   */
+  protected $value;
+
+  /**
+   * The conjunction to use for the condition group – either 'AND' or 'OR'.
+   *
+   * @var string
+   */
+  protected $conjunction;
+
+  /**
+   * Constructs a FacetBlockAjaxController object.
+   *
+   * @param string $field
+   *   The field to search against.
+   * @param string $value
+   *   The value to search the field with.
+   * @param bool $include
+   *   Limit results to records whose field contains or does not contain the
+   *   given value.
+   * @param string $conjunction
+   *   The conjunction to apply when combining this search term along with
+   *   others.
+   */
+  public function __construct(string $field, string $value, bool $include = self::DEFAULT_INCLUDE, string $conjunction = self::DEFAULT_CONJUNCTION) {
+    $this->field = $field;
+    $this->value = $value;
+    switch ($conjunction) {
+      case self::CONJUNCTION_AND:
+      case self::CONJUNCTION_OR:
+        $this->conjunction = $conjunction;
+        break;
+
+      default:
+        throw new \InvalidArgumentException('Invalid value given for argument "conjunction": $conjunction');
+    }
+    if ($this->conjunction == self::CONJUNCTION_OR && !$include) {
+      throw new \InvalidArgumentException('Excluding terms with the conjunction "OR" is not supported');
+    }
+    $this->include = $include;
+  }
+
+  /**
+   * Validate 'include' or fallback to default value.
+   *
+   * @param string $include
+   *   The value to cast to a boolean if possible.
+   *
+   * @return bool
+   *   The normalized input for 'include' or its default.
+   */
+  protected static function normalizeInclude(string $include) {
+    switch (strtoupper($include)) {
+      case AdvancedSearchForm::IS_OP:
+        return TRUE;
+
+      case AdvancedSearchForm::NOT_OP:
+        return FALSE;
+
+      default:
+        $include = filter_var($include, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);
+        // Ignore include parameter if invalid and fallback to the default.
+        return is_bool($include) ? $include : self::DEFAULT_INCLUDE;
+    }
+  }
+
+  /**
+   * Validate 'conjunction' or fallback to default value.
+   *
+   * @param string $conjunction
+   *   The conjunction to validate.
+   *
+   * @return string
+   *   The normalized input for 'include' or its default.
+   */
+  protected static function normalizeConjunction(string $conjunction) {
+    switch (strtoupper($conjunction)) {
+      case self::CONJUNCTION_AND:
+        return self::CONJUNCTION_AND;
+
+      case self::CONJUNCTION_OR:
+        return self::CONJUNCTION_OR;
+
+      default:
+        return self::DEFAULT_CONJUNCTION;
+    }
+  }
+
+  /**
+   * Creates a AdvancedSearchQueryTerm from the given parameters if possible.
+   *
+   * @param array $params
+   *   An array representing the query parameters for a single search term.
+   *
+   * @return \Drupal\islandora_advanced_search\AdvancedSearchQueryTerm|null
+   *   An object which represents a valid search term.
+   */
+  public static function fromQueryParams(array $params) {
+    // Field & value are required values. We do not check if field is a valid
+    // value only that it is non-empty. All other fields will be cast to
+    // defaults if they are not valid / missing.
+    $has_required_params = isset($params[self::FIELD_QUERY_PARAMETER], $params[self::VALUE_QUERY_PARAMETER]);
+    $search_value_empty = isset($params[self::VALUE_QUERY_PARAMETER]) && empty($params[self::VALUE_QUERY_PARAMETER]);
+    if (!$has_required_params || $search_value_empty) {
+      return NULL;
+    }
+    $field = $params[self::FIELD_QUERY_PARAMETER];
+    $value = $params[self::VALUE_QUERY_PARAMETER];
+    $include = isset($params[self::INCLUDE_QUERY_PARAMETER]) ?
+      $include = self::normalizeInclude($params[self::INCLUDE_QUERY_PARAMETER]) :
+      self::DEFAULT_INCLUDE;
+    $conjunction = isset($params[self::CONJUNCTION_QUERY_PARAMETER]) ?
+      self::normalizeConjunction($params[self::CONJUNCTION_QUERY_PARAMETER]) :
+      self::DEFAULT_CONJUNCTION;
+    return new self($field, $value, $include, $conjunction);
+  }
+
+  /**
+   * Creates a AdvancedSearchQueryTerm from user submitted form values.
+   *
+   * @param array $input
+   *   An array representing the submitted form values for a single search term.
+   *
+   * @return \Drupal\islandora_advanced_search\AdvancedSearchQueryTerm|null
+   *   An object which represents a valid search term.
+   */
+  public static function fromUserInput(array $input) {
+    // Search field & value are required values we do not check if field is a
+    // valid value only that it is non-empty. All other fields will use
+    // defaults if they are not valid / missing.
+    $has_required_inputs = isset($input[AdvancedSearchForm::SEARCH_FORM_FIELD], $input[AdvancedSearchForm::VALUE_FORM_FIELD]);
+    $search_value_empty = isset($input[AdvancedSearchForm::VALUE_FORM_FIELD]) && empty($input[AdvancedSearchForm::VALUE_FORM_FIELD]);
+    if (!$has_required_inputs || $search_value_empty) {
+      return NULL;
+    }
+    $field = $input[AdvancedSearchForm::SEARCH_FORM_FIELD];
+    $value = $input[AdvancedSearchForm::VALUE_FORM_FIELD];
+    $include = self::DEFAULT_INCLUDE;
+    $conjunction = self::DEFAULT_CONJUNCTION;
+    if (isset($input[AdvancedSearchForm::CONJUNCTION_FORM_FIELD])) {
+      switch ($input[AdvancedSearchForm::CONJUNCTION_FORM_FIELD]) {
+        case AdvancedSearchForm::AND_OP:
+          $conjunction = self::CONJUNCTION_AND;
+          break;
+
+        case AdvancedSearchForm::OR_OP:
+          $conjunction = self::CONJUNCTION_OR;
+          break;
+      }
+    }
+    // Only allow users to specify include when using 'AND' conjunction.
+    if (
+      $conjunction == self::CONJUNCTION_AND
+      && isset($input[AdvancedSearchForm::INCLUDE_FORM_FIELD])
+    ) {
+      switch ($input[AdvancedSearchForm::INCLUDE_FORM_FIELD]) {
+        case AdvancedSearchForm::IS_OP:
+          $include = TRUE;
+          break;
+
+        case AdvancedSearchForm::NOT_OP:
+          $include = FALSE;
+          break;
+      }
+    }
+    return new self($field, $value, $include, $conjunction);
+  }
+
+  /**
+   * Get query parameter representation of this search term.
+   *
+   * @return array
+   *   Representation of this search term which can be serialized to a query
+   *   parameter.
+   */
+  public function toQueryParams() {
+    $params = [
+      self::FIELD_QUERY_PARAMETER => $this->field,
+      self::VALUE_QUERY_PARAMETER => $this->value,
+    ];
+    // No need to specify conjunction if it is equivalent to the default.
+    if ($this->conjunction != self::DEFAULT_CONJUNCTION) {
+      $params[self::CONJUNCTION_QUERY_PARAMETER] = $this->conjunction;
+    }
+    if ($this->include != self::DEFAULT_CONJUNCTION) {
+      $params[self::INCLUDE_QUERY_PARAMETER] = $this->include ? '1' : '0';
+    }
+    return $params;
+  }
+
+  /**
+   * Get user input of search form representation of this search term.
+   *
+   * @return array
+   *   Representation of this search term which can be used as input to the
+   *   advanced search form.
+   */
+  public function toUserInput() {
+    return [
+      AdvancedSearchForm::SEARCH_FORM_FIELD => $this->field,
+      AdvancedSearchForm::VALUE_FORM_FIELD => $this->value,
+      AdvancedSearchForm::INCLUDE_FORM_FIELD => $this->include ? AdvancedSearchForm::IS_OP : AdvancedSearchForm::NOT_OP,
+      AdvancedSearchForm::CONJUNCTION_FORM_FIELD => $this->conjunction == self::CONJUNCTION_AND ? AdvancedSearchForm::AND_OP : AdvancedSearchForm::OR_OP,
+    ];
+  }
+
+  /**
+   * Gets if this term should be included / excluded from results.
+   *
+   * @return bool
+   *   TRUE if the term should be include in results, FALSE otherwise.
+   */
+  public function getInclude() {
+    return $this->include;
+  }
+
+  /**
+   * Gets the conjunction for this term.
+   *
+   * @return string
+   *   The conjunction to use for this term.
+   */
+  public function getConjunction() {
+    return $this->conjunction;
+  }
+
+  /**
+   * Using the provided field mapping create a Solr Query string.
+   *
+   * @param array $solr_field_mapping
+   *   An array that maps search api fields to one or more solr fields.
+   *
+   * @return string
+   *   The conjunction to use for this term conjunction.
+   */
+  public function toSolrQuery(array $solr_field_mapping) {
+    $terms = [];
+    $query_helper = \Drupal::service('solarium.query_helper');
+    $value = $query_helper->escapePhrase(trim($this->value));
+    foreach ($solr_field_mapping[$this->field] as $field) {
+      $terms[] = "$field:$value";
+    }
+    $terms = implode(' ', $terms);
+    return $this->include ? "($terms)" : "-($terms)";
+  }
+
+}

modules/islandora_advanced_search/src/Controller/AjaxBlocksController.php

@@ -0,0 +1,165 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Controller;
+
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Ajax\ReplaceCommand;
+use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Path\CurrentPathStack;
+use Drupal\Core\PathProcessor\PathProcessorManager;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\Core\Routing\CurrentRouteMatch;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+use Symfony\Component\Routing\RouterInterface;
+
+/**
+ * Defines a controller to load a facet via AJAX.
+ */
+class AjaxBlocksController extends ControllerBase {
+
+  /**
+   * The entity storage for block.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $storage;
+
+  /**
+   * The renderer.
+   *
+   * @var \Drupal\Core\Render\RendererInterface
+   */
+  protected $renderer;
+
+  /**
+   * The current path.
+   *
+   * @var \Drupal\Core\Path\CurrentPathStack
+   */
+  protected $currentPath;
+
+  /**
+   * The dynamic router service.
+   *
+   * @var \Symfony\Component\Routing\Matcher\RequestMatcherInterface
+   */
+  protected $router;
+
+  /**
+   * The path processor service.
+   *
+   * @var \Drupal\Core\PathProcessor\InboundPathProcessorInterface
+   */
+  protected $pathProcessor;
+
+  /**
+   * The current route match service.
+   *
+   * @var \Drupal\Core\Routing\CurrentRouteMatch
+   */
+  protected $currentRouteMatch;
+
+  /**
+   * The service container this instance should use.
+   *
+   * @var \Symfony\Component\DependencyInjection\ContainerInterface
+   */
+  protected $container;
+
+  /**
+   * Constructs a FacetBlockAjaxController object.
+   *
+   * @param \Drupal\Core\Render\RendererInterface $renderer
+   *   The renderer service.
+   * @param \Drupal\Core\Path\CurrentPathStack $currentPath
+   *   The current path service.
+   * @param \Symfony\Component\Routing\RouterInterface $router
+   *   The router service.
+   * @param \Drupal\Core\PathProcessor\PathProcessorManager $pathProcessor
+   *   The path processor manager.
+   * @param \Drupal\Core\Routing\CurrentRouteMatch $currentRouteMatch
+   *   The current route match service.
+   * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
+   *   The drupal container.
+   */
+  public function __construct(RendererInterface $renderer, CurrentPathStack $currentPath, RouterInterface $router, PathProcessorManager $pathProcessor, CurrentRouteMatch $currentRouteMatch, ContainerInterface $container) {
+    $this->storage = $this->entityTypeManager()->getStorage('block');
+    $this->renderer = $renderer;
+    $this->currentPath = $currentPath;
+    $this->router = $router;
+    $this->pathProcessor = $pathProcessor;
+    $this->currentRouteMatch = $currentRouteMatch;
+    $this->container = $container;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('renderer'),
+      $container->get('path.current'),
+      $container->get('router'),
+      $container->get('path_processor_manager'),
+      $container->get('current_route_match'),
+      $container
+    );
+  }
+
+  /**
+   * Loads and renders the facet blocks via AJAX.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The current request object.
+   *
+   * @return \Drupal\Core\Ajax\AjaxResponse
+   *   The ajax response.
+   *
+   * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
+   *   Thrown when the view was not found.
+   */
+  public function respond(Request $request) {
+    $response = new AjaxResponse();
+
+    // Rebuild the request and the current path, needed for facets.
+    $path = $request->request->get('link');
+    $blocks = $request->request->get('blocks');
+
+    // Make sure we are not updating blocks multiple times.
+    $blocks = array_unique($blocks);
+
+    if (empty($path) || empty($blocks)) {
+      throw new NotFoundHttpException('No facet link or facet blocks found.');
+    }
+
+    $new_request = Request::create($path);
+    $request_stack = new RequestStack();
+    $processed = $this->pathProcessor->processInbound($new_request->getPathInfo(), $new_request);
+
+    $this->currentPath->setPath($processed);
+    $request->attributes->add($this->router->matchRequest($new_request));
+    $this->currentRouteMatch->resetRouteMatch();
+    $request_stack->push($new_request);
+    $this->container->set('request_stack', $request_stack);
+
+    // Build the facets blocks found for the current request and update.
+    foreach ($blocks as $block_id => $block_selector) {
+      $block_entity = $this->storage->load($block_id);
+
+      if ($block_entity) {
+        // Render a block, then add it to the response as a replace command.
+        $block_view = $this->entityTypeManager
+          ->getViewBuilder('block')
+          ->view($block_entity);
+
+        $block_view = (string) $this->renderer->renderPlain($block_view);
+        $response->addCommand(new ReplaceCommand($block_selector, $block_view));
+      }
+    }
+    return $response;
+  }
+
+}

modules/islandora_advanced_search/src/Form/AdvancedSearchForm.php

@@ -0,0 +1,382 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Form;
+
+use Drupal\Component\Utility\Html;
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\islandora_advanced_search\AdvancedSearchQuery;
+use Drupal\islandora_advanced_search\AdvancedSearchQueryTerm;
+use Drupal\islandora_advanced_search\GetConfigTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Form for building and Advanced Search Query.
+ */
+class AdvancedSearchForm extends FormBase {
+  use GetConfigTrait;
+
+  // Users can customize the operator to use font-awesome or some other icons.
+  // Its a limitation in the use of `input type=submit` rather than buttons in
+  // Drupal that we couldn't just rely on CSS.
+  // This is exposed in the module settings.
+  // @see https://www.drupal.org/project/drupal/issues/1671190
+  const DEFAULT_ADD_OP = '+';
+  const DEFAULT_REMOVE_OP = '-';
+
+  const AND_OP = 'AND';
+  const IS_OP = 'IS';
+  const NOT_OP = 'NOT';
+  const OR_OP = 'OR';
+
+  // These are also hard-coded in islandora_advanced_search.form.js.
+  const CONJUNCTION_FORM_FIELD = 'conjunction';
+  const SEARCH_FORM_FIELD = 'search';
+  const INCLUDE_FORM_FIELD = 'include';
+  const VALUE_FORM_FIELD = 'value';
+
+  const AJAX_WRAPPER = 'advanced-search-ajax';
+
+  /**
+   * The current request.
+   *
+   * @var \Symfony\Component\HttpFoundation\Request
+   */
+  protected $request;
+
+  /**
+   * Class constructor.
+   */
+  public function __construct(Request $request) {
+    $this->request = $request;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('request_stack')->getMasterRequest()
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'islandora_advanced_search_form';
+  }
+
+  /**
+   * Get the character to use for adding a facet to the query.
+   *
+   * @return string
+   *   The character to use for adding an facet to the query.
+   */
+  public static function getAddOperator() {
+    return self::getConfig(SettingsForm::SEARCH_ADD_OPERATOR, self::DEFAULT_ADD_OP);
+  }
+
+  /**
+   * Get the character to use for removing a facet from the query.
+   *
+   * @return string
+   *   The character to use for removing an facet to the query.
+   */
+  public static function getRemoveOperator() {
+    return self::getConfig(SettingsForm::SEARCH_REMOVE_OPERATOR, self::DEFAULT_REMOVE_OP);
+  }
+
+  /**
+   * Convert the list of fields to select options.
+   *
+   * @param \Drupal\search_api\Item\FieldInterface[] $fields
+   *   The fields to convert to select options.
+   *
+   * @return array
+   *   Array of fields which can be searched where the key is the search field
+   *   identifier and the value is its human readable label.
+   */
+  protected function fieldOptions(array $fields) {
+    $options = [];
+    foreach ($fields as $field) {
+      $id = $field->getFieldIdentifier();
+      $options[$id] = $field->getLabel();
+    }
+    return $options;
+  }
+
+  /**
+   * Gets possible include options for the given conjunction.
+   */
+  protected function includeOptions(string $conjunction) {
+    switch ($conjunction) {
+      case self::AND_OP:
+        return;
+
+      case self::OR_OP:
+        return [
+          self::IS_OP => $this->t('is'),
+        ];
+    }
+  }
+
+  /**
+   * Default values to for a term.
+   */
+  protected function defaultTermValues(array $options) {
+    return [
+      self::CONJUNCTION_FORM_FIELD => self::AND_OP,
+      // First item in list is default.
+      self::SEARCH_FORM_FIELD => key($options),
+      self::INCLUDE_FORM_FIELD => self::IS_OP,
+      self::VALUE_FORM_FIELD => NULL,
+    ];
+  }
+
+  /**
+   * Process input to the from either URL parameters or from the form input.
+   */
+  protected function processInput(FormStateInterface $form_state, array $term_default_values) {
+    $input = $form_state->getUserInput();
+    $recursive = isset($input['recursive']) ? $input['recursive'] : NULL;
+    $term_values = isset($input['terms']) && is_array($input['terms']) ? $input['terms'] : [];
+    // Form was not submitted see if we can rebuild from query parameters.
+    $advanced_search_query = new AdvancedSearchQuery();
+    if (empty($term_values)) {
+      $terms = $advanced_search_query->getTerms($this->request);
+      foreach ($terms as $term) {
+        $term_values[] = $term->toUserInput();
+      }
+    }
+    if (!isset($input['recursive'])) {
+      $recursive = $advanced_search_query->shouldRecurse($this->request);
+    }
+    // Form was submitted via +/- operators.
+    $trigger = $form_state->getTriggeringElement();
+    if ($trigger != NULL) {
+      $term_index = $trigger['#term_index'] ?? 0;
+      $value = $trigger['#value'] instanceof TranslatableMarkup ?
+        $trigger['#value']->getUntranslatedString() :
+        $trigger['#value'];
+      switch ($value) {
+        case $this->getAddOperator():
+          // Insert after the term listed.
+          array_splice($term_values, $term_index + 1, 0, [$term_default_values]);
+          break;
+
+        case $this->getRemoveOperator():
+          array_splice($term_values, $term_index, 1);
+          break;
+
+        case "Reset":
+          $recursive = FALSE;
+          $term_values = [];
+          break;
+
+        // Ignore unknown value for trigger.
+      }
+      // Place user input with updated values.
+      $input['terms'] = $term_values;
+      $input['recursive'] = $recursive;
+      $form_state->setUserInput($input);
+    }
+    return [$recursive, $term_values];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, array $fields = [], string $context_filter = NULL) {
+    $form['#attached']['library'][] = 'islandora_advanced_search/advanced.search.form';
+    $form['#attached']['drupalSettings']['islandora_advanced_search_form'] = [
+      'id' => Html::getId($this->getFormId()),
+      'query_parameter' => AdvancedSearchQuery::getQueryParameter(),
+      'recurse_parameter' => AdvancedSearchQuery::getRecurseParameter(),
+      'mapping' => [
+        self::CONJUNCTION_FORM_FIELD => AdvancedSearchQueryTerm::CONJUNCTION_QUERY_PARAMETER,
+        self::SEARCH_FORM_FIELD => AdvancedSearchQueryTerm::FIELD_QUERY_PARAMETER,
+        self::INCLUDE_FORM_FIELD => AdvancedSearchQueryTerm::INCLUDE_QUERY_PARAMETER,
+        self::VALUE_FORM_FIELD => AdvancedSearchQueryTerm::VALUE_QUERY_PARAMETER,
+      ],
+    ];
+
+    $options = $this->fieldOptions($fields);
+    $term_default_values = $this->defaultTermValues($options);
+    list($recursive, $term_values) = $this->processInput($form_state, $term_default_values);
+    $i = 0;
+    $term_elements = [];
+    $total_terms = count($term_values);
+    $block_class_prefix = str_replace('_', '-', $this->getFormId());
+    do {
+      // Either specified by the user in the request or use the default.
+      $first = $i == 0;
+      $term_value = !empty($term_values) ? array_shift($term_values) : $term_default_values;
+      $conjunction = isset($term_value[self::CONJUNCTION_FORM_FIELD]) ? $term_value[self::CONJUNCTION_FORM_FIELD] : $term_default_values[self::CONJUNCTION_FORM_FIELD];
+      $term_elements[] = [
+        // Only show on terms after the first.
+        self::CONJUNCTION_FORM_FIELD => $first ? NULL : [
+          '#type' => 'select',
+          '#options' => [
+            self::AND_OP => $this->t('and'),
+            self::OR_OP => $this->t('or'),
+          ],
+          '#default_value' => $conjunction,
+        ],
+        self::SEARCH_FORM_FIELD => [
+          '#type' => 'select',
+          '#options' => $options,
+          '#default_value' => $term_value[self::SEARCH_FORM_FIELD],
+        ],
+        self::INCLUDE_FORM_FIELD => [
+          '#type' => 'select',
+          '#options' => [
+            self::IS_OP => $this->t('is'),
+            self::NOT_OP => $this->t('is not'),
+          ],
+          '#default_value' => $term_value[self::INCLUDE_FORM_FIELD],
+          // Show only when conjunction is 'AND' as 'OR NOT' is not supported
+          // by solr and will be converted to 'AND NOT'.
+          '#states' => [
+            'visible' => [
+              ':input[name="terms[' . $i . '][' . self::CONJUNCTION_FORM_FIELD . ']"]' => ['value' => self::AND_OP],
+            ],
+          ],
+        ],
+        // Just markup to show when 'include' is not alterable due to the
+        // selected 'conjunction'. Hide for the first term.
+        'is' => $first ? NULL : [
+          '#type' => 'container',
+          '#attributes' => ['style' => 'display:inline;'],
+          '#states' => [
+            'visible' => [
+              ':input[name="terms[' . $i . '][' . self::CONJUNCTION_FORM_FIELD . ']"]' => ['value' => self::OR_OP],
+            ],
+          ],
+          'content' => [
+            '#markup' => $this->t('is'),
+          ],
+        ],
+        self::VALUE_FORM_FIELD => [
+          '#type' => 'textfield',
+          '#default_value' => $term_value[self::VALUE_FORM_FIELD],
+        ],
+        'actions' => [
+          '#type' => 'container',
+          'add' => [
+            '#type' => 'button',
+            '#value' => $this->getAddOperator(),
+            '#name' => 'add-term-' . $i,
+            '#term_index' => $i,
+            '#attributes' => [
+              'class' => [$block_class_prefix . '__add', 'fa'],
+            ],
+            '#ajax' => [
+              'callback' => [$this, 'ajaxCallback'],
+              'wrapper' => self::AJAX_WRAPPER,
+              'progress' => [
+                'type' => 'none',
+              ],
+            ],
+          ],
+          'remove' => $total_terms <= 1 ? NULL : [
+            '#type' => 'button',
+            '#value' => $this->getRemoveOperator(),
+            '#name' => 'remove-term-' . $i,
+            '#term_index' => $i,
+            '#attributes' => [
+              'class' => [$block_class_prefix . '__remove', 'fa'],
+            ],
+            '#ajax' => [
+              'callback' => [$this, 'ajaxCallback'],
+              'wrapper' => self::AJAX_WRAPPER,
+              'progress' => [
+                'type' => 'none',
+              ],
+            ],
+          ],
+        ],
+      ];
+      $i++;
+    } while (!empty($term_values));
+
+    $form['ajax'] = [
+      '#type' => 'container',
+      '#attributes' => ['id' => self::AJAX_WRAPPER],
+      'terms' => array_merge([
+        '#tree' => TRUE,
+        '#type' => 'container',
+      ], $term_elements),
+    ];
+
+    if ($context_filter != NULL) {
+      $form['ajax']['recursive'] = [
+        '#type' => 'checkbox',
+        '#title' => $this->t('Include Sub-Collections'),
+        '#default_value' => $recursive,
+      ];
+    }
+    $form['reset'] = [
+      '#type' => 'button',
+      '#value' => $this->t('Reset'),
+      '#attributes' => [
+        'class' => [$block_class_prefix . '__reset'],
+      ],
+      '#ajax' => [
+        'callback' => [$this, 'ajaxCallback'],
+        'wrapper' => self::AJAX_WRAPPER,
+        'progress' => [
+          'type' => 'none',
+        ],
+      ],
+    ];
+    $form['submit'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Search'),
+      '#attributes' => [
+        'class' => [$block_class_prefix . '__search'],
+      ],
+    ];
+    return $form;
+  }
+
+  /**
+   * Builds an Advanced Search Query Url from the submitted form values.
+   */
+  protected function buildUrl(FormStateInterface $form_state) {
+    $terms = [];
+    $values = $form_state->getValues();
+    foreach ($values['terms'] as $term) {
+      $terms[] = AdvancedSearchQueryTerm::fromUserInput($term);
+    }
+    $terms = array_filter($terms);
+    $recurse = filter_var($values['recursive'], FILTER_VALIDATE_BOOLEAN);
+    $advanced_search_query = new AdvancedSearchQuery();
+    return $advanced_search_query->toUrl($this->request, $terms, $recurse);
+  }
+
+  /**
+   * Callback for adding / removing terms from the search.
+   */
+  public function ajaxCallback(array &$form, FormStateInterface $form_state) {
+    return $form['ajax'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $trigger = (string) $form_state->getTriggeringElement()['#value'];
+    switch ($trigger) {
+      case $this->t('Search'):
+        $form_state->setRedirectUrl($this->buildUrl($form_state));
+        break;
+
+      default:
+        $form_state->setRebuild();
+    }
+  }
+
+}

modules/islandora_advanced_search/src/Form/SettingsForm.php

@@ -0,0 +1,122 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Form;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\islandora_advanced_search\AdvancedSearchQuery;
+use Drupal\islandora_advanced_search\GetConfigTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Config form for Islandora Advanced Search settings.
+ */
+class SettingsForm extends ConfigFormBase {
+
+  use GetConfigTrait;
+
+  const CONFIG_NAME = 'islandora_advanced_search.settings';
+  const SEARCH_QUERY_PARAMETER = 'search_query_parameter';
+  const SEARCH_RECURSIVE_PARAMETER = 'search_recursive_parameter';
+  const SEARCH_ADD_OPERATOR = 'search_add_operator';
+  const SEARCH_REMOVE_OPERATOR = 'search_remove_operator';
+  const FACET_TRUNCATE = 'facet_truncate';
+
+  /**
+   * Constructs a \Drupal\system\ConfigFormBase object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The factory for configuration objects.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory) {
+    $this->setConfigFactory($config_factory);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static($container->get('config.factory'));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'islandora_advanced_search_settings_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEditableConfigNames() {
+    return [
+      self::CONFIG_NAME,
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $form += [
+      'search' => [
+        '#type' => 'fieldset',
+        '#title' => $this->t('Advanced Search'),
+        self::SEARCH_QUERY_PARAMETER => [
+          '#type' => 'textfield',
+          '#title' => $this->t('Search Query Parameter'),
+          '#description' => $this->t('The url parameter in which the advanced search query is stored.'),
+          '#default_value' => AdvancedSearchQuery::getQueryParameter(),
+        ],
+        self::SEARCH_RECURSIVE_PARAMETER => [
+          '#type' => 'textfield',
+          '#title' => $this->t('Recurse Query Parameter'),
+          '#description' => $this->t('The url parameter which can toggle recursive search.'),
+          '#default_value' => AdvancedSearchQuery::getRecurseParameter(),
+        ],
+        self::SEARCH_ADD_OPERATOR => [
+          '#type' => 'textfield',
+          '#title' => $this->t('Facet Add Operator'),
+          '#description' => $this->t('Users can customize the operator for adding facets to use font-awesome or some other icon, etc.'),
+          '#default_value' => AdvancedSearchForm::getAddOperator(),
+        ],
+        self::SEARCH_REMOVE_OPERATOR => [
+          '#type' => 'textfield',
+          '#title' => $this->t('Facet Remove Operator'),
+          '#description' => $this->t('Users can customize the operator for removing facets to use font-awesome or some other icon, etc.'),
+          '#default_value' => AdvancedSearchForm::getRemoveOperator(),
+        ],
+      ],
+      'facets' => [
+        '#type' => 'fieldset',
+        '#title' => $this->t('Facets'),
+        self::FACET_TRUNCATE => [
+          '#type' => 'number',
+          '#title' => $this->t('Truncate Facet'),
+          '#description' => $this->t('Optionally truncate the length of facets titles in the display. If unspecified they will not be truncated.'),
+          '#default_value' => self::getConfig(self::FACET_TRUNCATE, 32),
+          '#min' => 1,
+        ],
+      ],
+    ];
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $config = $this->configFactory->getEditable(self::CONFIG_NAME);
+    $config
+      ->set(self::SEARCH_QUERY_PARAMETER, $form_state->getValue(self::SEARCH_QUERY_PARAMETER))
+      ->set(self::SEARCH_RECURSIVE_PARAMETER, $form_state->getValue(self::SEARCH_RECURSIVE_PARAMETER))
+      ->set(self::SEARCH_ADD_OPERATOR, $form_state->getValue(self::SEARCH_ADD_OPERATOR))
+      ->set(self::SEARCH_REMOVE_OPERATOR, $form_state->getValue(self::SEARCH_REMOVE_OPERATOR))
+      ->set(self::FACET_TRUNCATE, $form_state->getValue(self::FACET_TRUNCATE))
+      ->save();
+    parent::submitForm($form, $form_state);
+  }
+
+}

modules/islandora_advanced_search/src/GetConfigTrait.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Drupal\islandora_advanced_search;
+
+use Drupal\islandora_advanced_search\Form\SettingsForm;
+
+/**
+ * Simple trait for accessing this modules configuration.
+ */
+trait GetConfigTrait {
+
+  /**
+   * Get a config setting or returns a default.
+   *
+   * @return string
+   *   The config setting or default value.
+   */
+  protected static function getConfig($config, $default) {
+    $settings = \Drupal::config(SettingsForm::CONFIG_NAME);
+    $value = $settings->get($config);
+    return !empty($value) ? $value : $default;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/Block/AdvancedSearchBlock.php

@@ -0,0 +1,394 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\Block;
+
+use Drupal\Core\Block\BlockBase;
+use Drupal\Core\Form\FormBuilderInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\search_api\Display\DisplayPluginManager;
+use Drupal\views\Entity\View;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Provides an Islandora Advanced Search block.
+ *
+ * @Block(
+ *  id = "islandora_advanced_search_block",
+ *  deriver = "Drupal\islandora_advanced_search\Plugin\Block\AdvancedSearchBlockDeriver",
+ *  admin_label = @Translation("Islandora Advanced Search"),
+ *  category = @Translation("Islandora"),
+ * )
+ */
+class AdvancedSearchBlock extends BlockBase implements ContainerFactoryPluginInterface {
+  use ViewAndDisplayIdentifiersTrait;
+
+  // CSS classes used to bind table-drag behavior to.
+  const WEIGHT_FIELD_CLASS = 'field-weight';
+  const DISPLAY_FIELD_CLASS = 'field-display';
+
+  // Regions in the table which denote if a given field
+  // is visible in the Advanced Search Form or not.
+  const REGION_VISIBLE = 'visible';
+  const REGION_HIDDEN = 'hidden';
+
+  // Keys for settings.
+  const SETTING_FIELDS = 'fields';
+  const SETTING_CONTEXTUAL_FILTER = 'context_filter';
+
+  /**
+   * The display plugin manager.
+   *
+   * @var \Drupal\search_api\Display\DisplayPluginManager
+   */
+  protected $displayPluginManager;
+
+  /**
+   * The clone of the current request object.
+   *
+   * @var \Symfony\Component\HttpFoundation\Request
+   */
+  protected $request;
+
+  /**
+   * The view this block affects.
+   *
+   * @var \Drupal\views\Entity\View
+   */
+  protected $view;
+
+  /**
+   * The view display this block affects.
+   *
+   * @var array
+   */
+  protected $display;
+
+  /**
+   * Form Builder.
+   *
+   * @var \Drupal\Core\Form\FormBuilderInterface
+   */
+  protected $formBuilder;
+
+  /**
+   * Construct a AdvancedSearchBlock instance.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param string $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\search_api\Display\DisplayPluginManager $display_plugin_manager
+   *   The display plugin manager.
+   * @param \Drupal\Core\Form\FormBuilderInterface $form_builder
+   *   The form builder service used to build the search form.
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   A request object for the current request.
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, DisplayPluginManager $display_plugin_manager, FormBuilderInterface $form_builder, Request $request) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+    $this->displayPluginManager = $display_plugin_manager;
+    list($view_id, $display_id) = preg_split('/__/', $this->getDerivativeId(), 2);
+    $this->view = View::Load($view_id);
+    $this->display = $this->view->getDisplay($display_id);
+    $this->formBuilder = $form_builder;
+    $this->request = clone $request;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('plugin.manager.search_api.display'),
+      $container->get('form_builder'),
+      $container->get('request_stack')->getMasterRequest()
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    return [
+      self::SETTING_FIELDS => [],
+      self::SETTING_CONTEXTUAL_FILTER => NULL,
+    ];
+  }
+
+  /**
+   * Fields which can be enabled / disabled for display in the search form.
+   *
+   * @return \Drupal\search_api\Item\FieldInterface[]
+   *   The $fields sorted by label.
+   */
+  protected function getFields() {
+    $fields = $this->getIndex()->getFields();
+    // First pass sort on label, secondary sort will be used
+    // when looking at existing configuration for this block.
+    uasort($fields, function ($a, $b) {
+      return strcmp($a->getLabel(), $b->getLabel());
+    });
+    return $fields;
+  }
+
+  /**
+   * Get regions of table to display.
+   *
+   * @return array
+   *   The properties of each region used for building the table of fields.
+   */
+  protected function getRegions() {
+    // Classes for select fields like 'weight' and 'display' are hard-coded
+    // and used in js/islandora-advanced-search.admin.js.
+    return [
+      'visible' => [
+        'title' => $this->t('Visible'),
+        'invisible' => TRUE,
+        'message' => $this->t('No search field is visible.'),
+        'weight' => self::WEIGHT_FIELD_CLASS . '-visible',
+        'display' => self::DISPLAY_FIELD_CLASS . '-visible',
+      ],
+      'hidden' => [
+        'title' => $this->t('Hidden'),
+        'invisible' => FALSE,
+        'message' => $this->t('No search field is hidden.'),
+        'weight' => self::WEIGHT_FIELD_CLASS . '-hidden',
+        'display' => self::DISPLAY_FIELD_CLASS . '-hidden',
+      ],
+    ];
+  }
+
+  /**
+   * Options for field display derived from the available regions.
+   *
+   * @return array
+   *   Display select field options.
+   */
+  protected function getDisplayOptions() {
+    $options = [];
+    foreach ($this->getRegions() as $region => $settings) {
+      $options[$region] = $settings['title'];
+    }
+    return $options;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function blockForm($form, FormStateInterface $form_state) {
+    // At most we will have one row per field.
+    $fields = $this->getFields();
+    $weight_delta = round(count($fields) / 2);
+
+    // Group each field into a region given our current configuration.
+    $visible_fields = $this->configuration[self::SETTING_FIELDS];
+    $regions = $this->getRegions();
+    $display_options = $this->getDisplayOptions();
+
+    // Field rows are grouped by the region in which they are displayed.
+    $field_rows = array_fill_keys(array_keys($regions), []);
+    foreach ($fields as $field) {
+      // If a field exists in the blocks configuration than it is 'visible' and
+      // its weight is equivalent to its order in the configuration,
+      // i.e. its index.
+      $identifier = $field->getFieldIdentifier();
+      $weight = array_search($identifier, $visible_fields);
+      $visible = $weight !== FALSE;
+      $region = $visible ? self::REGION_VISIBLE : self::REGION_HIDDEN;
+      $field_rows[$region][$identifier] = [
+        '#attributes' => [
+          'class' => ['draggable'],
+        ],
+        'label' => ['#plain_text' => $field->getLabel()],
+        'identifier' => ['#plain_text' => $identifier],
+        'weight' => [
+          '#type' => 'weight',
+          '#title' => $this->t('Weight'),
+          '#title_display' => 'invisible',
+          '#default_value' => $visible ? $weight : 0,
+          '#delta' => $weight_delta,
+          '#attributes' => [
+            'class' => [self::WEIGHT_FIELD_CLASS, $regions[$region]['weight']],
+          ],
+        ],
+        'display' => [
+          '#type' => 'select',
+          '#title' => $this->t('Display'),
+          '#title_display' => 'invisible',
+          '#options' => $display_options,
+          '#default_value' => $region,
+          '#attributes' => [
+            'class' => [self::DISPLAY_FIELD_CLASS, $regions[$region]['display']],
+          ],
+        ],
+      ];
+    }
+    // Sort the visible rows by their weight.
+    uasort($field_rows[self::REGION_VISIBLE], function ($a, $b) {
+      $a = $a['weight']['#default_value'];
+      $b = $b['weight']['#default_value'];
+      if ($a == $b) {
+        return 0;
+      }
+      return ($a < $b) ? -1 : 1;
+    });
+
+    // Build Rows.
+    $rows = [];
+    $table_drag = [];
+    foreach ($regions as $region => $properties) {
+      $rows += [
+        // Conditionally display region title as a row.
+        "region-$region" => $properties['invisible'] ? NULL : [
+          '#attributes' => [
+            'class' => ['region-title', "region-title-$region"],
+          ],
+          'label' => [
+            '#plain_text' => $properties['title'],
+            '#wrapper_attributes' => [
+              'colspan' => 4,
+            ],
+          ],
+        ],
+        // Will dynamically display if the region has fields or not controlled
+        // by Drupal behaviors in js/islandora-advanced-search.admin.js.
+        "region-$region-message" => [
+          '#attributes' => [
+            'class' => [
+              'region-message',
+              "region-$region-message",
+              empty($field_rows[$region]) ? 'region-empty' : 'region-populated',
+            ],
+          ],
+          'message' => [
+            '#markup' => '<em>' . $properties['message'] . '</em>',
+            '#wrapper_attributes' => [
+              'colspan' => 4,
+            ],
+          ],
+        ],
+      ];
+
+      // Include field rows in this region.
+      $rows += $field_rows[$region];
+
+      // Configure order by weight field in region.
+      $table_drag[] = [
+        'action' => 'order',
+        'relationship' => 'sibling',
+        'group' => self::WEIGHT_FIELD_CLASS,
+        'subgroup' => $properties['weight'],
+        'source' => self::WEIGHT_FIELD_CLASS,
+      ];
+
+      // Configure drag action for display field in region.
+      $table_drag[] = [
+        'action' => 'match',
+        'relationship' => 'sibling',
+        'group' => self::DISPLAY_FIELD_CLASS,
+        'subgroup' => $properties['display'],
+        'source' => self::DISPLAY_FIELD_CLASS,
+      ];
+    }
+
+    $form[self::SETTING_FIELDS] = [
+      '#type' => 'table',
+      '#attributes' => [
+        // Identifier is hard-coded and used in
+        // js/islandora-advanced-search.admin.js.
+        'id' => 'advanced-search-fields',
+      ],
+      '#header' => [
+        $this->t('Label'),
+        $this->t('Field'),
+        $this->t('Weight'),
+        $this->t('Display'),
+      ],
+      '#empty' => $this->t('No search fields, please check search index configuration.'),
+      '#tabledrag' => $table_drag,
+    ] + $rows;
+
+    // If there is contextual filters associated with the display that means
+    // we can filter on collection / sub-collection. Allow the user to choose
+    // which filters collections.
+    $id = NULL;
+    $field = NULL;
+    $options = [];
+    if (isset($this->display['display_options']['arguments'])) {
+      foreach ($this->display['display_options']['arguments'] as $context_filter) {
+        $id = $context_filter['id'];
+        $field = $context_filter['field'];
+        if (isset($fields[$field])) {
+          $options[$id] = $fields[$field]->getLabel() . ':' . $id;
+        }
+      }
+    }
+    if (count($options) > 1) {
+      $form[self::SETTING_CONTEXTUAL_FILTER] = [
+        '#type' => 'select',
+        '#title' => $this->t('Context Filter'),
+        '#description' => $this->t('If more than one <strong>Context Filter</strong> is defined, specify which is used to <strong>include</strong> only <strong>direct children</strong> of the Collection as it will disabled to allow recursive searching.'),
+        '#options' => $options,
+        '#default_value' => $this->configuration[self::SETTING_CONTEXTUAL_FILTER],
+        '#multiple' => FALSE,
+        '#required' => TRUE,
+        '#size' => count($options) + 1,
+      ];
+    }
+    $form['#attributes']['class'][] = 'clearfix';
+    $form['#attached']['library'][] = 'islandora_advanced_search/advanced.search.admin';
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function blockSubmit($form, FormStateInterface $form_state) {
+    $values = $form_state->getValues();
+    $fields = array_filter($values[self::SETTING_FIELDS], function ($field) {
+      return $field['display'] == 'visible';
+    });
+    uasort($fields, '\Drupal\Component\Utility\SortArray::sortByWeightElement');
+    $this->configuration[self::SETTING_FIELDS] = array_keys($fields);
+    if (isset($values[self::SETTING_CONTEXTUAL_FILTER])) {
+      $this->configuration[self::SETTING_CONTEXTUAL_FILTER] = $values[self::SETTING_CONTEXTUAL_FILTER];
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build() {
+    $fields = $this->getIndex()->getFields();
+    $configured_fields = [];
+    foreach ($this->configuration[self::SETTING_FIELDS] as $identifier) {
+      $configured_fields[$identifier] = $fields[$identifier];
+    }
+    return $this->formBuilder->getForm('Drupal\islandora_advanced_search\Form\AdvancedSearchForm', $configured_fields, $this->configuration[self::SETTING_CONTEXTUAL_FILTER]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheMaxAge() {
+    // The block cannot be cached, because it must always match the current
+    // search results.
+    return 0;
+  }
+
+  /**
+   * Get Search Index.
+   */
+  protected function getIndex() {
+    $id = $this->getDerivativeId();
+    return $this->displayPluginManager->createInstance("views_{$this->display['display_plugin']}:{$id}")->getIndex();
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/Block/AdvancedSearchBlockDeriver.php

@@ -0,0 +1,91 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\Block;
+
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * This deriver creates a block for every search_api.display.
+ */
+class AdvancedSearchBlockDeriver implements ContainerDeriverInterface {
+
+  use StringTranslationTrait;
+
+  /**
+   * List of derivative definitions.
+   *
+   * @var array
+   */
+  protected $derivatives = [];
+
+  /**
+   * The entity storage for the view.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $storage;
+
+  /**
+   * The display manager for the search_api.
+   *
+   * @var \Drupal\search_api\Display\DisplayPluginManager
+   */
+  protected $displayPluginManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, $base_plugin_id) {
+    $deriver = new static($container, $base_plugin_id);
+    $deriver->storage = $container->get('entity_type.manager')->getStorage('view');
+    $deriver->displayPluginManager = $container->get('plugin.manager.search_api.display');
+    return $deriver;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinition($derivative_id, $base_plugin_definition) {
+    $derivatives = $this->getDerivativeDefinitions($base_plugin_definition);
+    return isset($derivatives[$derivative_id]) ? $derivatives[$derivative_id] : NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinitions($base_plugin_definition) {
+    $base_plugin_id = $base_plugin_definition['id'];
+
+    if (!isset($this->derivatives[$base_plugin_id])) {
+      $plugin_derivatives = [];
+
+      foreach ($this->displayPluginManager->getDefinitions() as $display_definition) {
+        $view_id = $display_definition['view_id'];
+        $view_display = $display_definition['view_display'];
+        // The derived block needs both the view / display identifiers to
+        // construct the pager.
+        $machine_name = "${view_id}__${view_display}";
+
+        /** @var \Drupal\views\ViewEntityInterface $view */
+        $view = $this->storage->load($view_id);
+        $display = $view->getDisplay($view_display);
+
+        $plugin_derivatives[$machine_name] = [
+          'id' => $base_plugin_id . PluginBase::DERIVATIVE_SEPARATOR . $machine_name,
+          'label' => $this->t('Advanced Search'),
+          'admin_label' => $this->t(':view: Advanced Search for :display', [
+            ':view' => $view->label(),
+            ':display' => $display['display_title'],
+          ]),
+        ] + $base_plugin_definition;
+      }
+
+      $this->derivatives[$base_plugin_id] = $plugin_derivatives;
+    }
+    return $this->derivatives[$base_plugin_id];
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/Block/SearchResultsPagerBlock.php

@@ -0,0 +1,314 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\Block;
+
+use Drupal\Core\Block\BlockBase;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\Core\Render\Markup;
+use Drupal\Core\Url;
+use Drupal\islandora_advanced_search\AdvancedSearchQuery;
+use Drupal\views\Entity\View;
+use Drupal\views\Plugin\views\pager\SqlBase;
+use Drupal\views\ViewExecutable;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Provides a 'AjaxViewBlock' block.
+ *
+ * @Block(
+ *  id = "islandora_advanced_search_result_pager",
+ *  deriver = "Drupal\islandora_advanced_search\Plugin\Block\SearchResultsPagerBlockDeriver",
+ *  admin_label = @Translation("Search Results Pager"),
+ *  category = @Translation("Islandora"),
+ * )
+ */
+class SearchResultsPagerBlock extends BlockBase implements ContainerFactoryPluginInterface {
+  use ViewAndDisplayIdentifiersTrait;
+
+  /**
+   * The clone of the current request object.
+   *
+   * @var \Symfony\Component\HttpFoundation\Request
+   */
+  protected $request;
+
+  /**
+   * Construct a FacetBlock instance.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param string $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   A request object for the current request.
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, Request $request) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+    $this->request = clone $request;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('request_stack')->getMasterRequest()
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build() {
+    $id = $this->getDerivativeId();
+    list($view_id, $display_id) = $this->getViewAndDisplayIdentifiers();
+    $view = View::Load($view_id);
+    $view_executable = $view->getExecutable();
+    $view_executable->setDisplay($display_id);
+    // Allow advanced search to alter the query.
+    $advanced_search_query = new AdvancedSearchQuery();
+    $advanced_search_query->alterView($this->request, $view_executable, $display_id);
+    $view_executable->execute();
+    $pager = $view_executable->getPager();
+    $exposed_input = $view_executable->getExposedInput();
+    $query_parameters = $this->request->query->all();
+    $build = [
+      '#attached' => [
+        'drupalSettings' => [
+          'islandora_advanced_search_pager_views_ajax' => [
+            $id => [
+              'view_id' => $view_id,
+              'current_display_id' => $display_id,
+              'ajax_path' => '/views/ajax',
+            ],
+          ],
+        ],
+      ],
+      '#attributes' => [
+        'class' => ['islandora_advanced_search_result_pager'],
+        'data-drupal-pager-id' => $id,
+      ],
+      'result_summary' => $this->buildResultsSummary($view_executable),
+      'container' => [
+        '#prefix' => '<div class="pager__group">',
+        '#suffix' => '</div>',
+        'results_per_page_links' => $this->buildResultsPerPageLinks($pager, $query_parameters),
+        'display_links' => $this->buildDisplayLinks($query_parameters),
+        'sort_by' => $this->buildSortByForm($view_executable->sort, $query_parameters),
+        'pager' => array_merge($pager->render($exposed_input), ['#wrapper_attributes' => ['class' => ['container']]]),
+      ],
+    ];
+    return $build;
+  }
+
+  /**
+   * Build the results summary portion of the pager.
+   *
+   * @param Drupal\views\ViewExecutable $view_executable
+   *   The view to build the summary for.
+   *
+   * @return array
+   *   A renderable array that represents the current page, and number of
+   *   results in the view.
+   */
+  protected function buildResultsSummary(ViewExecutable $view_executable) {
+    $current_page = (int) $view_executable->getCurrentPage() + 1;
+    $per_page = (int) $view_executable->getItemsPerPage();
+    $total = isset($view_executable->total_rows) ? $view_executable->total_rows : count($view_executable->result);
+    // If there is no result the "start" and "current_record_count" should be
+    // equal to 0. To have the same calculation logic, we use a "start offset"
+    // to handle all the cases.
+    $start_offset = empty($total) ? 0 : 1;
+    if ($per_page === 0) {
+      $start = $start_offset;
+      $end = $total;
+    }
+    else {
+      $total_count = $current_page * $per_page;
+      if ($total_count > $total) {
+        $total_count = $total;
+      }
+      $start = ($current_page - 1) * $per_page + $start_offset;
+      $end = $total_count;
+    }
+    if (!empty($total)) {
+      // Return as render array.
+      return [
+        '#prefix' => '<div class="pager__summary">',
+        '#suffix' => '</div>',
+        '#markup' => $this->t('Displaying @start - @end of @total', [
+          '@start' => $start,
+          '@end' => $end,
+          '@total' => $total,
+        ]),
+      ];
+    }
+    return [];
+  }
+
+  /**
+   * Build the results per page portion of the pager.
+   *
+   * @param Drupal\views\Plugin\views\pager\SqlBase $pager
+   *   The pager for the view.
+   * @param array $query_parameters
+   *   The query parameters used to change the number of results per page.
+   *
+   * @return array
+   *   A renderable array representing the results per page portion of pager.
+   */
+  protected function buildResultsPerPageLinks(SqlBase $pager, array $query_parameters) {
+    $active_items_per_page = $query_parameters['items_per_page'] ?? $pager->options['items_per_page'];
+    $items_per_page_options = array_map(function ($value) {
+      return trim($value);
+    }, explode(',', $pager->options['expose']['items_per_page_options']));
+    $items = [];
+    foreach ($items_per_page_options as $items_per_page) {
+      $url = Url::fromRoute('<current>', [], [
+        // When changing the number of items displayed always return the user
+        // to the first page.
+        'query' => array_merge($query_parameters, [
+          'items_per_page' => $items_per_page,
+          'page' => 0,
+        ]),
+        'absolute' => TRUE,
+      ]);
+      $active = $items_per_page == $active_items_per_page;
+      $items[] = [
+        '#type' => 'link',
+        '#url' => $url,
+        '#title' => $items_per_page,
+        '#attributes' => [
+          'class' => $active ? ['pager__link', 'pager__link--is-active'] : ['pager__link'],
+        ],
+        '#wrapper_attributes' => [
+          'class' => $active ? ['pager__item', 'is-active'] : ['pager__item'],
+        ],
+      ];
+    }
+    return [
+      '#theme' => 'item_list',
+      '#title' => $this->t('Results per page'),
+      '#list_type' => 'ul',
+      '#items' => $items,
+      '#attributes' => [],
+      '#wrapper_attributes' => ['class' => ['pager__results', 'container']],
+    ];
+  }
+
+  /**
+   * Build the display links portion of the pager (list/grid).
+   *
+   * @param array $query_parameters
+   *   The query parameters used to change the display format.
+   *
+   * @return array
+   *   A renderable array representing the display links portion of pager.
+   */
+  protected function buildDisplayLinks(array $query_parameters) {
+    $active_display = $query_parameters['display'] ?? 'list';
+    $display_options = [
+      'list' => [
+        'icon' => 'fa-list',
+        'title' => $this->t('List'),
+      ],
+      'grid' => [
+        'icon' => 'fa-th',
+        'title' => $this->t('Grid'),
+      ],
+    ];
+    $items = [];
+    foreach ($display_options as $display => $options) {
+      $url = Url::fromRoute('<current>', [], [
+        'query' => array_merge($query_parameters, ['display' => $display]),
+        'absolute' => TRUE,
+      ]);
+      $text = "<i class='fa {$options['icon']}' aria-hidden='true'>&nbsp;</i>{$options['title']}";
+      $active = $active_display == $display;
+      $items[] = [
+        '#type' => 'link',
+        '#url' => $url,
+        '#title' => Markup::create($text),
+        '#attributes' => [
+          'class' => $active ? ['pager__link', 'pager__link--is-active'] : ['pager__link'],
+        ],
+        '#wrapper_attributes' => [
+          'class' => $active ? ['pager__item', 'is-active'] : ['pager__item'],
+        ],
+      ];
+    }
+    return [
+      '#theme' => 'item_list',
+      '#list_type' => 'ul',
+      '#items' => $items,
+      '#attributes' => [],
+      '#wrapper_attributes' => ['class' => ['pager__display', 'container']],
+    ];
+  }
+
+  /**
+   * Build the sort by portion of the pager.
+   *
+   * @param array $sort_criteria
+   *   The search fields which can be sorted.
+   * @param array $query_parameters
+   *   The query parameters used to change the display format.
+   *
+   * @return array
+   *   A renderable array representing the sort by portion of pager.
+   */
+  protected function buildSortByForm(array $sort_criteria, array $query_parameters) {
+    $default_order = $query_parameters['sort_order'] ?? 'ASC';
+    $default_sort_by = $query_parameters['sort_by'] ?? 'search_api_relevance';
+    $default_value = $default_sort_by . '_' . strtolower($default_order);
+    $options = [];
+    $options_attributes = [];
+    // Not sure if this will work without defining a sort per direction.
+    foreach ($sort_criteria as $sort) {
+      if ($sort->options['exposed'] == TRUE) {
+        $id = $sort->options['id'];
+        // Label should be translated via views already.
+        $label = $sort->options['expose']['label'];
+        $asc = "{$id}_asc";
+        $desc = "{$id}_desc";
+        $options[$asc] = "{$label} ↑";
+        $options[$desc] = "{$label} ↓";
+        $options_attributes[$asc] = [
+          'data-sort_by' => $id,
+          'data-sort_order' => 'ASC',
+        ];
+        $options_attributes[$desc] = [
+          'data-sort_by' => $id,
+          'data-sort_order' => 'DESC',
+        ];
+      }
+    }
+    return [
+      '#type' => 'select',
+      '#title' => 'Sort',
+      '#title_display' => 'invisible',
+      '#options' => $options,
+      '#options_attributes' => $options_attributes,
+      '#attributes' => ['autocomplete' => 'off'],
+      '#wrapper_attributes' => ['class' => ['pager__sort', 'container']],
+      '#name' => 'order',
+      '#value' => $default_value,
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheMaxAge() {
+    // The block cannot be cached, because it must always match the current
+    // search results.
+    return 0;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/Block/SearchResultsPagerBlockDeriver.php

@@ -0,0 +1,91 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\Block;
+
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * This deriver creates a block for every search_api.display.
+ */
+class SearchResultsPagerBlockDeriver implements ContainerDeriverInterface {
+
+  use StringTranslationTrait;
+
+  /**
+   * List of derivative definitions.
+   *
+   * @var array
+   */
+  protected $derivatives = [];
+
+  /**
+   * The entity storage used for the view.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $storage;
+
+  /**
+   * The display manager for the search_api.
+   *
+   * @var \Drupal\search_api\Display\DisplayPluginManager
+   */
+  protected $displayPluginManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, $base_plugin_id) {
+    $deriver = new static($container, $base_plugin_id);
+    $deriver->storage = $container->get('entity_type.manager')->getStorage('view');
+    $deriver->displayPluginManager = $container->get('plugin.manager.search_api.display');
+    return $deriver;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinition($derivative_id, $base_plugin_definition) {
+    $derivatives = $this->getDerivativeDefinitions($base_plugin_definition);
+    return isset($derivatives[$derivative_id]) ? $derivatives[$derivative_id] : NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinitions($base_plugin_definition) {
+    $base_plugin_id = $base_plugin_definition['id'];
+
+    if (!isset($this->derivatives[$base_plugin_id])) {
+      $plugin_derivatives = [];
+
+      foreach ($this->displayPluginManager->getDefinitions() as $display_definition) {
+        $view_id = $display_definition['view_id'];
+        $view_display = $display_definition['view_display'];
+        // The derived block needs both the view / display identifiers
+        // to construct the pager.
+        $machine_name = "${view_id}__${view_display}";
+
+        /** @var \Drupal\views\ViewEntityInterface $view */
+        $view = $this->storage->load($view_id);
+        $display = $view->getDisplay($view_display);
+
+        $plugin_derivatives[$machine_name] = [
+          'id' => $base_plugin_id . PluginBase::DERIVATIVE_SEPARATOR . $machine_name,
+          'label' => $this->t('Search Results Pager'),
+          'admin_label' => $this->t(':view: Pager for :display', [
+            ':view' => $view->label(),
+            ':display' => $display['display_title'],
+          ]),
+        ] + $base_plugin_definition;
+      }
+
+      $this->derivatives[$base_plugin_id] = $plugin_derivatives;
+    }
+    return $this->derivatives[$base_plugin_id];
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/Block/ViewAndDisplayIdentifiersTrait.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\Block;
+
+/**
+ * Gets the view and display identifiers used to create this block.
+ *
+ * @see Drupal\Component\Plugin\Discovery\DiscoveryInterface
+ */
+trait ViewAndDisplayIdentifiersTrait {
+
+  /**
+   * {@inheritdoc}
+   */
+  abstract public function getDerivativeId();
+
+  /**
+   * Gets the View and View Display identifiers used to derive this block.
+   *
+   * @return string[]
+   *   Returns an array of two strings where the first is the View identifier
+   *   and the second is the View Display identifier associated with the view
+   *   used to derive this block.
+   */
+  public function getViewAndDisplayIdentifiers() {
+    $id = $this->getDerivativeId();
+    return preg_split('/__/', $id, 2);
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/Field/FieldFormatter/EntityReferenceCountFormatter.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\Field\FieldFormatter;
+
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceFormatterBase;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Plugin implementation of the 'entity reference ID' formatter.
+ *
+ * @FieldFormatter(
+ *   id = "entity_reference_url_title",
+ *   label = @Translation("Children Entity Count, Label."),
+ *   description = @Translation("Children Entity Count, Label."),
+ *   field_types = {
+ *     "entity_reference"
+ *   }
+ * )
+ */
+class EntityReferenceCountFormatter extends EntityReferenceFormatterBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'label' => 'Items in Collection',
+    ] + parent::defaultSettings();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsForm(array $form, FormStateInterface $form_state) {
+    $elements['separator'] = [
+      '#title' => $this->t("Text to appear next to the children's count"),
+      '#type' => 'textfield',
+      '#default_value' => $this->getSetting('label'),
+    ];
+    return $elements;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsSummary(): array {
+    $summary = [];
+    $summary[] = $this->getSetting('label') ? 'Label : ' . $this->getSetting('label') : $this->t('No label');
+    return $summary;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode): array {
+    $element = [];
+    $total_items = count($this->getEntitiesToView($items, $langcode));
+    $element[] = ['#markup' => "<span class='collection_children__total_count'>{$total_items}<span>" . ' ' . $this->formatPlural($total_items, '1 Item in Collection', '@count Items in Collection')];
+    return $element;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/facets/widget/IncludeExcludeLinksWidget.php

@@ -0,0 +1,84 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\facets\widget;
+
+use Drupal\facets\Plugin\facets\widget\LinksWidget;
+use Drupal\Core\Link;
+use Drupal\facets\Result\ResultInterface;
+
+/**
+ * The links widget.
+ *
+ * @FacetsWidget(
+ *   id = "include_exclude_links",
+ *   label = @Translation("List of links that allow the user to include / exclude facets."),
+ *   description = @Translation("A simple widget that shows a list of +/- links."),
+ * )
+ */
+class IncludeExcludeLinksWidget extends LinksWidget {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function prepareLink(ResultInterface $result) {
+    $facet = $result->getFacet();
+    $facet_source_id = $facet->getFacetSourceId();
+    $facet_manager = \Drupal::service('facets.manager');
+    $facets = $facet_manager->getFacetsByFacetSourceId($facet_source_id);
+    $raw_value = $result->getRawValue();
+    $count = $result->getCount();
+    $url = $result->getUrl();
+    $exclude_facet = $this->getExcludeFacet($facet, $facets);
+    $exclude_result = $this->getExcludeResult($exclude_facet, $raw_value);
+    $exclude_url = $exclude_result ? $exclude_result->getUrl() : NULL;
+    return [
+      '#theme' => 'facets_result_item',
+      '#is_active' => $result->isActive(),
+      '#value' => [
+        'text' => (new Link($result->getDisplayValue(), $url))->toRenderable(),
+        'include' => (new Link(' ', $url))->toRenderable() + [
+          '#attributes' => [
+            'class' => ['facet-item__include', 'fa', 'fa-plus'],
+          ],
+        ],
+        'exclude' => $exclude_url ? (new Link(' ', $exclude_url))->toRenderable() + [
+          '#attributes' => [
+            'class' => ['facet-item__exclude', 'fa', 'fa-minus'],
+          ],
+        ] : NULL,
+      ],
+      '#show_count' => $this->getConfiguration()['show_numbers'] && ($count !== NULL),
+      '#count' => $count,
+      '#facet' => $facet,
+      '#raw_value' => $raw_value,
+    ];
+  }
+
+  /**
+   * Looks for the excluded facet version of the included facet.
+   */
+  protected function getExcludeResult($facet, $raw_value) {
+    if ($facet) {
+      foreach ($facet->getResults() as $result) {
+        if ($result->getRawValue() === $raw_value) {
+          return $result;
+        }
+      }
+    }
+    return NULL;
+  }
+
+  /**
+   * Looks for the excluded facet version of the included facet.
+   */
+  protected function getExcludeFacet($include, $facets) {
+    $field_identifier = $include->getFieldIdentifier();
+    foreach ($facets as $facet) {
+      if ($field_identifier === $facet->getFieldIdentifier() && $facet->getExclude()) {
+        return $facet;
+      }
+    }
+    return NULL;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/facets_summary/processor/ResetRemovePage.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\facets_summary\processor;
+
+use Drupal\facets_summary\FacetsSummaryInterface;
+use Drupal\facets_summary\Processor\BuildProcessorInterface;
+
+/**
+ * Reset should also remove the page query attribute.
+ *
+ * @SummaryProcessor(
+ *   id = "reset_remove_page",
+ *   label = @Translation("Remove page from query when resetting facets/query."),
+ *   description = @Translation("Remove page from query when resetting facets/query."),
+ *   stages = {
+ *     "build" = 45
+ *   }
+ * )
+ */
+class ResetRemovePage extends ShowSearchQueryProcessor implements BuildProcessorInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(FacetsSummaryInterface $facets_summary, array $build, array $facets) {
+    // This processor is weighted to occur after the reset facets link.
+    // Which leaves two cases:
+    // - No facets selected so no reset link (we must add one).
+    // - Reset link exists at the top of the list (we must remove the
+    //   search term from the link as well).
+    $reset_index = $this->getResetLinkIndex($build);
+    if ($reset_index !== NULL) {
+      $reset = &$build['#items'][$reset_index];
+      // Remove query from reset url as well.
+      $query_params = $reset['#url']->getOption('query');
+      unset($query_params['page']);
+      $reset['#url']->setOption('query', $query_params);
+    }
+    return $build;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/facets_summary/processor/ShowActiveExcludedFacets.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\facets_summary\processor;
+
+use Drupal\Core\Link;
+use Drupal\Core\Url;
+use Drupal\facets_summary\FacetsSummaryInterface;
+use Drupal\facets_summary\Processor\BuildProcessorInterface;
+use Drupal\facets_summary\Processor\ProcessorPluginBase;
+
+/**
+ * Provides a processor that shows the search query.
+ *
+ * @SummaryProcessor(
+ *   id = "show_active_excluded_facets",
+ *   label = @Translation("Show active excluded facets."),
+ *   description = @Translation("When checked, negated facets will appear in the summary."),
+ *   stages = {
+ *     "build" = 20
+ *   }
+ * )
+ */
+class ShowActiveExcludedFacets extends ProcessorPluginBase implements BuildProcessorInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(FacetsSummaryInterface $facets_summary, array $build, array $facets) {
+    $request = \Drupal::request();
+    $query_params = $request->query->all();
+    foreach ($facets as $facet) {
+      if ($facet->getExclude()) {
+        $url_alias = $facet->getUrlAlias();
+        $filter_key = $facet->getFacetSourceConfig()->getFilterKey() ?: 'f';
+        $active_items = $facet->getActiveItems();
+        foreach ($active_items as $active_item) {
+          $url = Url::createFromRequest($request);
+          $modified_query_params = $query_params;
+          $modified_query_params[$filter_key] = array_filter($query_params[$filter_key], function ($query_param) use ($url_alias, $active_item) {
+            $pos = strpos($query_param, ':');
+            $alias = substr($query_param, 0, $pos);
+            $value = substr($query_param, $pos + 1);
+            return !($alias == $url_alias && $value == $active_item);
+          });
+          $url->setOption('query', $modified_query_params);
+          $item = [
+            '#theme' => 'facets_result_item__summary',
+            '#value' => $active_item,
+          // We do not have counts for excluded facets...
+            '#show_count' => FALSE,
+          // Do not know the count.
+            '#count' => 0,
+            '#is_active' => TRUE,
+            '#facet' => $facet,
+            '#raw_value' => $active_item,
+          ];
+          $item = (new Link($item, $url))->toRenderable();
+          $item['#wrapper_attributes'] = [
+            'class' => [
+              'facet-summary-item--facet',
+              'facet-summary-item--exclude',
+            ],
+          ];
+          $build['#items'][] = $item;
+        }
+      }
+    }
+    return $build;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/facets_summary/processor/ShowActiveFacets.php

@@ -0,0 +1,89 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\facets_summary\processor;
+
+use Drupal\Core\Link;
+use Drupal\facets_summary\FacetsSummaryInterface;
+use Drupal\facets_summary\Processor\BuildProcessorInterface;
+use Drupal\facets_summary\Processor\ProcessorPluginBase;
+use Drupal\facets\FacetInterface;
+use Drupal\facets\Result\ResultInterface;
+
+/**
+ * Provides a processor that shows the search query.
+ *
+ * @SummaryProcessor(
+ *   id = "show_active_facets",
+ *   label = @Translation("Shows active hidden facets."),
+ *   description = @Translation("When checked, undoes 'hide_active_items_processor', etc."),
+ *   stages = {
+ *     "build" = 20
+ *   }
+ * )
+ */
+class ShowActiveFacets extends ProcessorPluginBase implements BuildProcessorInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(FacetsSummaryInterface $facets_summary, array $build, array $facets) {
+    // Rebuild list of results, add back ones that have been removed.
+    $facet_manager = \Drupal::service('facets.manager');
+    $facet_source_id = $facets_summary->getFacetSourceId();
+    $facet_manager->updateResults($facet_source_id);
+    $facet_manager->processFacets($facet_source_id);
+    $facets_config = $facets_summary->getFacets();
+    foreach ($facets as $facet) {
+      $processors = $facet->getProcessors();
+      /** @var \Drupal\facets\Processor\BuildProcessorInterface $url_handler */
+      $url_handler = $processors['url_processor_handler'];
+      $results = $url_handler->build($facet, $facet->getResults());
+      foreach ($results as $result) {
+        if ($result->isActive() && $this->resultMissing($facet, $result, $build['#items'])) {
+          $item = [
+            '#theme' => 'facets_result_item__summary',
+            '#value' => $result->getDisplayValue(),
+            '#show_count' => $facets_config[$facet->id()]['show_count'],
+            '#count' => $result->getCount(),
+            '#is_active' => TRUE,
+            '#facet' => $result->getFacet(),
+            '#raw_value' => $result->getRawValue(),
+          ];
+          $item = (new Link($item, $result->getUrl()))->toRenderable();
+          $item['#wrapper_attributes'] = [
+            'class' => [
+              'facet-summary-item--facet',
+            ],
+          ];
+          $build['#items'][] = $item;
+        }
+      }
+    }
+    return $build;
+  }
+
+  /**
+   * Checks if the results are missing for the given facet.
+   *
+   * @param \Drupal\facets\FacetInterface $facet
+   *   The facet to check.
+   * @param \Drupal\facets\Result\ResultInterface $result
+   *   The result of the facet to check.
+   * @param array $items
+   *   The already completed render array of facets to check against.
+   *
+   * @return bool
+   *   TRUE if the result is missing FALSE otherwise.
+   */
+  protected function resultMissing(FacetInterface $facet, ResultInterface $result, array $items) {
+    foreach ($items as $item) {
+      $item_facet = $item['#title']['#facet'];
+      $raw_value = $item['#title']['#raw_value'];
+      if ($item_facet === $facet && $raw_value === $result->getRawValue()) {
+        return FALSE;
+      }
+    }
+    return TRUE;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/facets_summary/processor/ShowMissingFacets.php

@@ -0,0 +1,70 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\facets_summary\processor;
+
+use Drupal\Core\Link;
+use Drupal\Core\Url;
+use Drupal\facets_summary\FacetsSummaryInterface;
+use Drupal\facets_summary\Processor\BuildProcessorInterface;
+use Drupal\facets_summary\Processor\ProcessorPluginBase;
+
+/**
+ * Provides a processor that shows the search query.
+ *
+ * @SummaryProcessor(
+ *   id = "show_missing_facets",
+ *   label = @Translation("Shows facets from the url that are missing from the results."),
+ *   description = @Translation("When checked, show facets not included in the solr result but specified in the URL."),
+ *   stages = {
+ *     "build" = 20
+ *   }
+ * )
+ */
+class ShowMissingFacets extends ProcessorPluginBase implements BuildProcessorInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(FacetsSummaryInterface $facets_summary, array $build, array $facets) {
+    $request = \Drupal::request();
+    $query_params = $request->query->all();
+    foreach ($facets as $facet) {
+      if (!$facet->getExclude() && empty($facet->getResults())) {
+        $url_alias = $facet->getUrlAlias();
+        $filter_key = $facet->getFacetSourceConfig()->getFilterKey() ?: 'f';
+        $active_items = $facet->getActiveItems();
+        foreach ($active_items as $active_item) {
+          $url = Url::createFromRequest($request);
+          $modified_query_params = $query_params;
+          $modified_query_params[$filter_key] = array_filter($query_params[$filter_key], function ($query_param) use ($url_alias, $active_item) {
+            $pos = strpos($query_param, ':');
+            $alias = substr($query_param, 0, $pos);
+            $value = substr($query_param, $pos + 1);
+            return !($alias == $url_alias && $value == $active_item);
+          });
+          $url->setOption('query', $modified_query_params);
+          $item = [
+            '#theme' => 'facets_result_item__summary',
+            '#value' => $active_item,
+          // We do not have counts for missing facets...
+            '#show_count' => FALSE,
+          // Do not know the count.
+            '#count' => 0,
+            '#is_active' => TRUE,
+            '#facet' => $facet,
+            '#raw_value' => $active_item,
+          ];
+          $item = (new Link($item, $url))->toRenderable();
+          $item['#wrapper_attributes'] = [
+            'class' => [
+              'facet-summary-item--facet',
+            ],
+          ];
+          $build['#items'][] = $item;
+        }
+      }
+    }
+    return $build;
+  }
+
+}

modules/islandora_advanced_search/src/Plugin/facets_summary/processor/ShowSearchQueryProcessor.php

@@ -0,0 +1,101 @@
+<?php
+
+namespace Drupal\islandora_advanced_search\Plugin\facets_summary\processor;
+
+use Drupal\Core\Link;
+use Drupal\Core\Url;
+use Drupal\facets_summary\FacetsSummaryInterface;
+use Drupal\facets_summary\Processor\BuildProcessorInterface;
+use Drupal\facets_summary\Processor\ProcessorPluginBase;
+
+/**
+ * Provides a processor that shows the search query.
+ *
+ * @SummaryProcessor(
+ *   id = "show_search_query",
+ *   label = @Translation("Show the current search query"),
+ *   description = @Translation("When checked, this facet will show the search query."),
+ *   stages = {
+ *     "build" = 40
+ *   }
+ * )
+ */
+class ShowSearchQueryProcessor extends ProcessorPluginBase implements BuildProcessorInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(FacetsSummaryInterface $facets_summary, array $build, array $facets) {
+    $request = \Drupal::request();
+    $query_params = $request->query->all();
+    if (!empty($query_params['search_api_fulltext'])) {
+      $text = $query_params['search_api_fulltext'];
+      unset($query_params['search_api_fulltext']);
+      $url = Url::createFromRequest($request);
+      $url->setOption('query', $query_params);
+      $item = [
+        '#theme' => 'facets_result_item__summary',
+        '#is_active' => FALSE,
+        '#value' => $text,
+        '#show_count' => FALSE,
+      ];
+      $item = Link::fromTextAndUrl($item, $url)->toRenderable();
+      $item['#wrapper_attributes'] = [
+        'class' => [
+          'facet-summary-item--query',
+        ],
+      ];
+      // This processor is weighted to occur after the reset facets link.
+      // Which leaves two cases:
+      // - No facets selected so no reset link (we must add one).
+      // - Reset link exists at the top of the list (we must remove the search
+      //   term from the link as well).
+      $reset_index = $this->getResetLinkIndex($build);
+      if ($reset_index !== NULL) {
+        $reset = $build['#items'][$reset_index];
+        // Remove query from reset url as well.
+        $query_params = $reset['#url']->getOption('query');
+        unset($query_params['search_api_fulltext']);
+        $reset['#url']->setOption('query', $query_params);
+        array_splice($build['#items'], $reset_index + 1, 0, [$item]);
+      }
+      else {
+        array_unshift($build['#items'], $item);
+        $text = $this->t('Reset');
+        if (isset($facets_summary->getProcessorConfigs()['reset_facets']['settings']['link_text'])) {
+          $text = $facets_summary->getProcessorConfigs()['reset_facets']['settings']['link_text'];
+        }
+        $reset = Link::fromTextAndUrl($text, $url)->toRenderable();
+        $reset['#wrapper_attributes'] = [
+          'class' => [
+            'facet-summary-item--clear',
+          ],
+        ];
+        array_unshift($build['#items'], $reset);
+      }
+      return $build;
+    }
+    return $build;
+  }
+
+  /**
+   * Gets the index in the $build render array of the reset link.
+   *
+   * @param array $build
+   *   The render array of the FacetSummary block.
+   *
+   * @return mixed|null
+   *   The index of the reset link the $build render array.
+   */
+  protected function getResetLinkIndex(array $build) {
+    if (isset($build['#items'])) {
+      foreach ($build['#items'] as $index => $item) {
+        if (isset($item['#wrapper_attributes']['class']) && in_array('facet-summary-item--clear', $item['#wrapper_attributes']['class'])) {
+          return $index;
+        }
+      }
+    }
+    return NULL;
+  }
+
+}

modules/islandora_advanced_search/src/Utilities.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace Drupal\islandora_advanced_search;
+
+use Drupal\islandora_advanced_search\Plugin\Block\AdvancedSearchBlock;
+use Drupal\islandora_advanced_search\Plugin\Block\SearchResultsPagerBlock;
+
+/**
+ * Helper functions.
+ */
+class Utilities {
+
+  /**
+   * Gets the list of views for which pager blocks have been created.
+   *
+   * @return array
+   *   List of view and display ids which have that have been used to
+   *   derive a SearchResultsPagerBlock.
+   */
+  public static function getPagerViewDisplays() {
+    $views = &drupal_static(__FUNCTION__);
+    if (!isset($views)) {
+      $block_storage = \Drupal::entityTypeManager()->getStorage('block');
+      $active_theme = \Drupal::theme()->getActiveTheme();
+      $views = [];
+      /** @var \Drupal\block\Entity\Block $block */
+      foreach ($block_storage->loadByProperties(['theme' => $active_theme->getName()]) as $block) {
+        $plugin = $block->getPlugin();
+        if ($plugin instanceof SearchResultsPagerBlock) {
+          list($view_id, $display_id) = $plugin->getViewAndDisplayIdentifiers();
+          $views[$block->id()] = [$view_id, $display_id];
+        }
+      }
+    }
+    return $views;
+  }
+
+  /**
+   * Gets the list of views for which advanced search blocks have been created.
+   *
+   * @return array
+   *   List of view and display ids which have that have been used to
+   *   derive a SearchResultsPagerBlock.
+   */
+  public static function getAdvancedSearchViewDisplays() {
+    $views = &drupal_static(__FUNCTION__);
+    if (!isset($views)) {
+      $block_storage = \Drupal::entityTypeManager()->getStorage('block');
+      $active_theme = \Drupal::theme()->getActiveTheme();
+      $views = [];
+      /** @var \Drupal\block\Entity\Block $block */
+      foreach ($block_storage->loadByProperties(['theme' => $active_theme->getName()]) as $block) {
+        $plugin = $block->getPlugin();
+        if ($plugin instanceof AdvancedSearchBlock) {
+          list($view_id, $display_id) = $plugin->getViewAndDisplayIdentifiers();
+          $views[$block->id()] = [$view_id, $display_id];
+        }
+      }
+    }
+    return $views;
+  }
+
+}

modules/islandora_advanced_search/templates/facets/facets-item-list--include-exclude-links.html.twig

@@ -0,0 +1,58 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a facets item list.
+ *
+ * Available variables:
+ * - items: A list of items. Each item contains:
+ *   - attributes: HTML attributes to be applied to each list item.
+ *   - value: The content of the list element.
+ * - title: The title of the list.
+ * - list_type: The tag for list element ("ul" or "ol").
+ * - wrapper_attributes: HTML attributes to be applied to the list wrapper.
+ * - attributes: HTML attributes to be applied to the list.
+ * - empty: A message to display when there are no items. Allowed value is a
+ *   string or render array.
+ * - context: A list of contextual data associated with the list. May contain:
+ *   - list_style: The ID of the widget plugin this facet uses.
+ * - facet: The facet for this result item.
+ *   - id: the machine name for the facet.
+ *   - label: The facet label.
+ *
+ * @see facets_preprocess_facets_item_list()
+ *
+ * @ingroup themeable
+ */
+#}
+<div class="facets-widget- {{- facet.widget.type -}} ">
+  {% if facet.widget.type %}
+    {%- set attributes = attributes.addClass('item-list__' ~ facet.widget.type) %}
+  {% endif %}
+  {% if items or empty %}
+    {%- if title is not empty -%}
+      <h3>{{ title }}</h3>
+    {%- endif -%}
+
+    {%- if items -%}
+      <{{ list_type }}{{ attributes }}>
+        {%- for item in less -%}
+          <li{{ item.attributes }}>{{ item.value }}</li>
+        {%- endfor -%}
+      </{{ list_type }}>
+      {%- if more -%}
+      <{{ list_type }}{{ attributes }} style="display:none;margin-top:-1em">
+        {%- for item in more -%}
+          <li{{ item.attributes }}>{{ item.value }}</li>
+        {%- endfor -%}
+      </{{ list_type }}>
+      <a href="#" class="facets-soft-limit-link">{{ show_more_label }}</a>
+      {%- endif -%}
+    {%- else -%}
+      {{- empty -}}
+    {%- endif -%}
+  {%- endif %}
+
+{% if facet.widget.type == "dropdown" %}
+  <label id="facet_{{ facet.id }}_label">{{ 'Facet'|t }} {{ facet.label }}</label>
+{%- endif %}
+</div>

modules/islandora_advanced_search/templates/facets/facets-result-item--include-exclude-links.html.twig

@@ -0,0 +1,33 @@
+{#
+/**
+ * @file
+ * Default theme implementation of a facet result item.
+ *
+ * Available variables:
+ * - value: The item value.
+ * - raw_value: The raw item value.
+ * - show_count: If this facet provides count.
+ * - count: The amount of results.
+ * - is_active: The item is active.
+ * - facet: The facet for this result item.
+ *   - id: the machine name for the facet.
+ *   - label: The facet label.
+ *
+ * @ingroup themeable
+ */
+#}
+{% if value['text'] is defined %}
+<span class="facet-item__value">{{ value['text'] }}
+  {% if show_count %}
+  <span class="facet-item__count">({{ count }})</span>
+  {% endif %}
+  {% if value['exclude'] is defined %}
+    <span class="facet-item__operators">{{ value['include'] }} {{ value['exclude'] }}</span>
+  {% endif %}
+</span>
+{% else %}
+<span class="facet-item__value">{{ value }}</span>
+  {% if show_count %}
+    <span class="facet-item__count">({{ count }})</span>
+  {% endif %}
+{% endif %}

modules/islandora_advanced_search/templates/facets/facets-result-item--summary.html.twig

@@ -0,0 +1,20 @@
+{#
+/**
+ * @file
+ * Default theme implementation of a facet result item.
+ *
+ * Available variables:
+ * - value: The item value.
+ * - raw_value: The raw item value.
+ * - show_count: If this facet provides count.
+ * - count: The amount of results.
+ * - is_active: The item is active.
+ * - facet: The facet for this result item.
+ *   - id: the machine name for the facet.
+ *   - label: The facet label.
+ *
+ * @ingroup themeable
+ */
+#}
+<span class="facet-item__value">{{ value }}</span>
+<span class="fa fa-remove"></span>