Initial implementation of a REST Export serializer for IIIF Manifests (#157)

* Initial implementation of a REST Export serializer for IIIF Manifests

* Coding standards

* Pass full URL to IIIF

* Basic implementation of manifest per https://iiif.io/api/presentation/2.1/#manifest

* Remove unused variable

* Remove dependency for OSD, add config variable for IIIF server

* Update settings.yml

* Fix key name

* fix schema/settings issue

* Broaden approach of discovering file/image fields

modules/islandora_iiif/config/install/islandora_iiif.settings.yml

@@ -0,0 +1 @@
+iiif_server:

modules/islandora_iiif/config/schema/islandora_iiif.schema.yml

@@ -0,0 +1,7 @@
+islandora_iiif.settings:
+  type: config_object
+  label: 'Islandora IIIF Settings'
+  mapping:
+    iiif_server:
+      type: string
+      label: 'IIIF Server Url'

modules/islandora_iiif/islandora_iiif.info.yml

@@ -0,0 +1,7 @@
+name: 'Islandora IIIF'
+type: module
+description: 'IIIF support for Islandora'
+core: 8.x
+package: Islandora
+dependencies:
+  - islandora

modules/islandora_iiif/islandora_iiif.links.menu.yml

@@ -0,0 +1,6 @@
+islandora_iiif.islandora_iiif_config_form:
+  title: 'IIIF Settings'
+  route_name: islandora_iiif.islandora_iiif_config_form
+  description: 'Configure Islandora IIIF settings'
+  parent: system.admin_config_islandora
+  weight: 99

modules/islandora_iiif/islandora_iiif.module

@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * @file
+ * Contains islandora_iiif.module.
+ */
+
+use Drupal\Core\Routing\RouteMatchInterface;
+
+/**
+ * Implements hook_help().
+ */
+function islandora_iiif_help($route_name, RouteMatchInterface $route_match) {
+  switch ($route_name) {
+    // Main module help for the islandora_iiif module.
+    case 'help.page.islandora_iiif':
+      $output = '';
+      $output .= '<h3>' . t('About') . '</h3>';
+      $output .= '<p>' . t('IIIF support for Islandora') . '</p>';
+      return $output;
+
+    default:
+  }
+}

modules/islandora_iiif/islandora_iiif.routing.yml

@@ -0,0 +1,9 @@
+islandora_iiif.islandora_iiif_config_form:
+  path: '/admin/config/islandora/iiif'
+  defaults:
+    _form: '\Drupal\islandora_iiif\Form\IslandoraIIIFConfigForm'
+    _title: 'IslandoraIIIFConfigForm'
+  requirements:
+    _permission: 'access administration pages'
+  options:
+    _admin_route: TRUE

modules/islandora_iiif/src/Form/IslandoraIIIFConfigForm.php

@@ -0,0 +1,92 @@
+<?php
+
+namespace Drupal\islandora_iiif\Form;
+
+use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Component\Utility\UrlHelper;
+use GuzzleHttp\Exception\ClientException;
+
+/**
+ * Class IslandoraIIIFConfigForm.
+ */
+class IslandoraIIIFConfigForm extends ConfigFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEditableConfigNames() {
+    return [
+      'islandora_iiif.settings',
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'islandora_iiif_config_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $config = $this->config('islandora_iiif.settings');
+    $form['iiif_server'] = [
+      '#type' => 'url',
+      '#title' => $this->t('IIIF Image server location'),
+      '#description' => $this->t('Please enter the image server location without trailing slash. e.g. http://www.example.org/iiif/2.'),
+      '#default_value' => $config->get('iiif_server'),
+    ];
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    if (!empty($form_state->getValue('iiif_server'))) {
+      $server = $form_state->getValue('iiif_server');
+      if (!UrlHelper::isValid($server, UrlHelper::isExternal($server))) {
+        $form_state->setErrorByName('iiif_server', "IIIF Server address is not a valid URL");
+      }
+      elseif (!$this->validateIiifUrl($server)) {
+        $form_state->setErrorByName('iiif_server', "IIIF Server does not seem to be accessible.");
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    parent::submitForm($form, $form_state);
+
+    $this->config('islandora_iiif.settings')
+      ->set('iiif_server', $form_state->getValue('iiif_server'))
+      ->save();
+  }
+
+  /**
+   * Ensure the IIIF server is accessible.
+   *
+   * @param string $server_uri
+   *   The absolute or relative URI to the server.
+   *
+   * @return bool
+   *   True if server returns 200 on a HEAD request.
+   */
+  private function validateIiifUrl($server_uri) {
+    $client = \Drupal::httpClient();
+    try {
+      $result = $client->head($server_uri);
+      return ($result->getStatusCode() == 200);
+    }
+    catch (ClientException $e) {
+      return FALSE;
+    }
+
+  }
+
+}

modules/islandora_iiif/src/Plugin/views/style/IIIFManifest.php

@@ -0,0 +1,267 @@
+<?php
+
+namespace Drupal\islandora_iiif\Plugin\views\style;
+
+use Drupal\views\Plugin\views\style\StylePluginBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\views\ResultRow;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\Serializer\SerializerInterface;
+use Symfony\Component\HttpFoundation\Request;
+use Drupal\Core\Config\ImmutableConfig;
+
+/**
+ * Provide serializer format for IIIF Manifest.
+ *
+ * @ingroup views_style_plugins
+ *
+ * @ViewsStyle(
+ *   id = "iiif_manifest",
+ *   title = @Translation("IIIF Manifest"),
+ *   help = @Translation("Display images as an IIIF Manifest."),
+ *   display_types = {"data"}
+ * )
+ */
+class IIIFManifest extends StylePluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $usesRowPlugin = TRUE;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $usesGrouping = FALSE;
+
+  /**
+   * The allowed formats for this serializer. Default to only JSON.
+   *
+   * @var array
+   */
+  protected $formats = ['json'];
+
+  /**
+   * The serializer which serializes the views result.
+   *
+   * @var \Symfony\Component\Serializer\Serializer
+   */
+  protected $serializer;
+
+  /**
+   * The request service.
+   *
+   * @var \Symfony\Component\HttpFoundation\Request
+   */
+  protected $request;
+
+  /**
+   * This module's config.
+   *
+   * @var \Drupal\Core\Config\ImmutableConfig
+   */
+  protected $iiifConfig;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, SerializerInterface $serializer, Request $request, ImmutableConfig $iiif_config) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+
+    $this->serializer = $serializer;
+    $this->request = $request;
+    $this->iiifConfig = $iiif_config;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('serializer'),
+      $container->get('request_stack')->getCurrentRequest(),
+      $container->get('config.factory')->get('islandora_iiif.settings')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function render() {
+    $json = [];
+    $iiif_address = $this->iiifConfig->get('iiif_server');
+    if (!is_null($iiif_address) && !empty($iiif_address)) {
+      // Get the current URL being requested.
+      $request_url = $this->request->getSchemeAndHttpHost() . $this->request->getRequestUri();
+      // Strip off the last URI component to get the base ID of the URL.
+      // @todo assumming the view is a path like /node/1/manifest.json
+      $url_components = explode('/', $request_url);
+      array_pop($url_components);
+      $iiif_base_id = implode('/', $url_components);
+      // @see https://iiif.io/api/presentation/2.1/#manifest
+      $json += [
+        '@type' => 'sc:Manifest',
+        '@id' => $request_url,
+        '@context' => 'http://iiif.io/api/presentation/2/context.json',
+        // @see https://iiif.io/api/presentation/2.1/#sequence
+        'sequences' => [
+          '@context' => 'http://iiif.io/api/presentation/2/context.json',
+          '@id' => $iiif_base_id . '/sequence/normal',
+          '@type' => 'sc:Sequence',
+        ],
+      ];
+      // For each row in the View result.
+      foreach ($this->view->result as $row) {
+        // Add the IIIF URL to the image to print out as JSON.
+        $canvases = $this->getTileSourceFromRow($row, $iiif_address, $iiif_base_id);
+        foreach ($canvases as $tile_source) {
+          $json['sequences'][0]['canvases'][] = $tile_source;
+        }
+      }
+    }
+    unset($this->view->row_index);
+
+    $content_type = 'json';
+
+    return $this->serializer->serialize($json, $content_type, ['views_style_plugin' => $this]);
+  }
+
+  /**
+   * Render array from views result row.
+   *
+   * @param \Drupal\views\ResultRow $row
+   *   Result row.
+   * @param string $iiif_address
+   *   The URL to the IIIF server endpoint.
+   * @param string $iiif_base_id
+   *   The URL for the request, minus the last part of the URL,
+   *   which is likely "manifest".
+   *
+   * @return array
+   *   List of IIIF URLs to display in the Openseadragon viewer.
+   */
+  protected function getTileSourceFromRow(ResultRow $row, $iiif_address, $iiif_base_id) {
+    $canvases = [];
+    $viewsField = $this->view->field[$this->options['iiif_tile_field']];
+    $entity = $viewsField->getEntity($row);
+
+    if (isset($entity->{$viewsField->definition['field_name']})) {
+
+      /** @var \Drupal\Core\Field\FieldItemListInterface $images */
+      $images = $entity->{$viewsField->definition['field_name']};
+      foreach ($images as $image) {
+        // Create the IIIF URL for this file
+        // Visiting $iiif_url will resolve to the info.json for the image.
+        $file_url = $image->entity->url();
+        $iiif_url = rtrim($iiif_address, '/') . '/' . urlencode($file_url);
+
+        // Create the necessary ID's for the canvas and annotation.
+        $canvas_id = $iiif_base_id . '/canvas/' . $entity->id();
+        $annotation_id = $iiif_base_id . '/annotation/' . $entity->id();
+
+        $canvases[] = [
+          // @see https://iiif.io/api/presentation/2.1/#canvas
+          '@id' => $canvas_id,
+          '@type' => 'sc:Canvas',
+          'label' => $entity->label(),
+          // @see https://iiif.io/api/presentation/2.1/#image-resources
+          'images' => [[
+            '@id' => $annotation_id,
+            "@type" => "oa:Annotation",
+            'motivation' => 'sc:painting',
+            'resource' => [
+              '@id' => $iiif_url . '/full/full/0/default.jpg',
+              'service' => [
+                '@id' => $iiif_url,
+                '@context' => 'http://iiif.io/api/image/2/context.json',
+                'profile' => 'http://iiif.io/api/image/2/profiles/level2.json',
+              ],
+            ],
+            'on' => $canvas_id,
+          ],
+          ],
+        ];
+      }
+    }
+
+    return $canvases;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function defineOptions() {
+    $options = parent::defineOptions();
+
+    $options['iiif_tile_field'] = ['default' => ''];
+
+    return $options;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
+    parent::buildOptionsForm($form, $form_state);
+
+    $field_options = [];
+
+    $fields = $this->displayHandler->getHandlers('field');
+    $islandora_default_file_fields = [
+      'field_media_file',
+      'field_media_image',
+    ];
+    $file_views_field_formatters = [
+      // Image formatters.
+      'image', 'image_url',
+      // File formatters.
+      'file_default', 'file_url_plain',
+    ];
+    /** @var \Drupal\views\Plugin\views\field\FieldPluginBase[] $fields */
+    foreach ($fields as $field_name => $field) {
+      // If this is a known Islandora file/image field
+      // OR it is another/custom field add it as an available option.
+      // @todo find better way to identify file fields
+      // Currently $field->options['type'] is storing the "formatter" of the
+      // file/image so there are a lot of possibilities.
+      // The default formatters are 'image' and 'file_default'
+      // so this approach should catch most...
+      if (in_array($field_name, $islandora_default_file_fields) ||
+        (!empty($field->options['type']) && in_array($field->options['type'], $file_views_field_formatters))) {
+        $field_options[$field_name] = $field->adminLabel();
+      }
+    }
+
+    // If no fields to choose from, add an error message indicating such.
+    if (count($field_options) == 0) {
+      drupal_set_message($this->t('No image or file fields were found in the View.
+        You will need to add a field to this View'), 'error');
+    }
+
+    $form['iiif_tile_field'] = [
+      '#title' => $this->t('Tile source field'),
+      '#type' => 'select',
+      '#default_value' => $this->options['iiif_tile_field'],
+      '#description' => $this->t("The source of image for each entity."),
+      '#options' => $field_options,
+      // Only make the form element required if
+      // we have more than one option to choose from
+      // otherwise could lock up the form when setting up a View.
+      '#required' => count($field_options) > 0,
+    ];
+  }
+
+  /**
+   * Returns an array of format options.
+   *
+   * @return string[]
+   *   An array of the allowed serializer formats. In this case just JSON.
+   */
+  public function getFormats() {
+    return ['json' => 'json'];
+  }
+
+}