7.x islandora 1724 (#651)

* Make breadcrumb creation a hookable process.

* Forgot to add selection to admin page.

* Add more attribution and remove unused path.

* Fix admin form and coding standards.

* Add the new variable to be removed on uninstall

* Code review

* Code review

* Fix code style and add some docs to README

* Stop using Mulgara prefixes

README.md

@@ -42,6 +42,9 @@ The `islandora_drupal_filter` passes the username of 'anonymous' through to Fedo
 
 Drupal's cron can be run to remove expired authentication tokens.
 
+**Breadcrumb Generation** on the configuration page, allows you to choose the default breadcrumb generation
+ or a custom method (if implemented). 
+
 ### Customization
 
 [Customize ingest forms](http://github.com/Islandora/islandora/wiki/Multi-paged-Ingest-Forms)

includes/admin.form.inc

@@ -22,6 +22,17 @@ function islandora_repository_admin(array $form, array &$form_state) {
   $url = islandora_system_settings_form_default_value('islandora_base_url', 'http://localhost:8080/fedora', $form_state);
   $restrict_namespaces = islandora_system_settings_form_default_value('islandora_namespace_restriction_enforced', FALSE, $form_state);
   $confirmation_message = islandora_admin_settings_form_repository_access_message($url);
+
+  $breadcrumb_backend_options = module_invoke_all('islandora_breadcrumbs_backends');
+  $map_to_title = function ($backend) {
+    return $backend['title'];
+  };
+  // In case the selected breadcrumb backend is no longer available.
+  $breadcrumb_backend = variable_get('islandora_breadcrumbs_backends', ISLANDORA_BREADCRUMB_LEGACY_BACKEND);
+  if (!isset($breadcrumb_backend_options[$breadcrumb_backend])) {
+    $breadcrumb_backend = ISLANDORA_BREADCRUMB_LEGACY_BACKEND;
+  }
+
   $form = array(
     'islandora_tabs' => array(
       '#type' => 'vertical_tabs',
@@ -97,6 +108,18 @@ function islandora_repository_admin(array $form, array &$form_state) {
           '#description' => t('Larger sites may experience a notable performance improvement when disabled due to how breadcrumbs are constructed.'),
           '#default_value' => variable_get('islandora_render_drupal_breadcrumbs', TRUE),
         ),
+        'islandora_breadcrumbs_backends' => array(
+          '#type' => 'radios',
+          '#title' => t('Breadcrumb generation'),
+          '#description' => t('How breadcrumbs for Islandora objects are generated for display.'),
+          '#default_value' => $breadcrumb_backend,
+          '#options' => array_map($map_to_title, $breadcrumb_backend_options),
+          '#states' => array(
+            'visible' => array(
+              ':input[name="islandora_render_drupal_breadcrumbs"]' => array('checked' => TRUE),
+            ),
+          ),
+        ),
         'islandora_risearch_use_itql_when_necessary' => array(
           '#type' => 'checkbox',
           '#title' => t('Use iTQL for particular queries'),

includes/breadcrumb.inc

@@ -24,17 +24,43 @@
  *   not including the given object. For use in the function
  *   drupal_set_breadcrumb().
  */
-function islandora_get_breadcrumbs($object) {
+function islandora_get_breadcrumbs(AbstractObject $object) {
   $breadcrumbs = array();
   if (variable_get('islandora_render_drupal_breadcrumbs', TRUE)) {
-    $breadcrumbs = islandora_get_breadcrumbs_recursive($object->id, $object->repository);
+    $backend = variable_get('islandora_breadcrumbs_backends', ISLANDORA_BREADCRUMB_LEGACY_BACKEND);
-    array_pop($breadcrumbs);
+    $backends = module_invoke_all('islandora_breadcrumbs_backends');
+    if ($backend === ISLANDORA_BREADCRUMB_LEGACY_BACKEND || !isset($backends[$backend])) {
+      $breadcrumbs = islandora_get_breadcrumbs_legacy($object->id, $object->repository);
+    }
+    else {
+      if (isset($backends[$backend]['file'])) {
+        require_once $backends[$backend]['file'];
+      }
+      $breadcrumbs = call_user_func($backends[$backend]['callable'], $object);
+    }
     $context = 'islandora';
     drupal_alter('islandora_breadcrumbs', $breadcrumbs, $context, $object);
   }
   return $breadcrumbs;
 }
 
+/**
+ * Call the legacy SPARQL recursive function and return the correct breadcrumbs.
+ *
+ * @param string $pid
+ *   The object id whose parent will be fetched for the next link.
+ * @param \IslandoraFedoraRepository $repository
+ *   The fedora repository.
+ *
+ * @return array
+ *   An array of links representing the breadcrumb trail, "root" first.
+ */
+function islandora_get_breadcrumbs_legacy($pid, IslandoraFedoraRepository $repository) {
+  $breadcrumbs = islandora_get_breadcrumbs_recursive($pid, $repository);
+  array_pop($breadcrumbs);
+  return $breadcrumbs;
+}
+
 /**
  * Builds an array of drupal links for use in breadcrumbs.
  *

islandora.api.php

@@ -907,3 +907,41 @@ function hook_islandora_edit_datastream_registry_alter(&$edit_registry, $context
 function hook_islandora_repository_connection_construction_alter(RepositoryConnection $instance) {
   $instance->userAgent = "Tuque/cURL";
 }
+
+/**
+ * Allow a overridable backend for generating breadcrumbs.
+ *
+ * Stolen shamelessly from @adam-vessey.
+ *
+ * @return array
+ *   Should return an associative array mapping unique (module-prefixed,
+ *   preferably) keys to associative arrays containing:
+ *   - title: A human-readable title for the backend.
+ *   - callable: A PHP callable to call for this backend, implementing
+ *     callback_islandora_basic_collection_query_backends().
+ *   - file: An optional file to load before attempting to call the callable.
+ */
+function hook_islandora_breadcrumbs_backends() {
+  return array(
+    'awesome_backend' => array(
+      'title' => t('Awesome Backend'),
+      'callable' => 'callback_islandora_breadcrumbs_backends',
+    ),
+  );
+}
+
+/**
+ * Generate an array of links for breadcrumbs leading to $object, root first.
+ *
+ * Stolen shamelessly from @adam-vessey.
+ *
+ * @param AbstractObject $object
+ *   The object to generate breadcrumbs for.
+ *
+ * @return array
+ *   Array of links from root to the parent of $object.
+ */
+function callback_islandora_breadcrumbs_backends(AbstractObject $object) {
+  // Do something to get an array of breadcrumb links for $object, root first.
+  return array($root_link, $collection_link, $object_link);
+}

islandora.install

@@ -58,6 +58,7 @@ function islandora_uninstall() {
     'islandora_use_object_semaphores',
     'islandora_semaphore_period',
     'islandora_require_obj_upload',
+    'islandora_breadcrumbs_backends',
   );
   array_walk($variables, 'variable_del');
 }

islandora.module

@@ -68,6 +68,8 @@ define('ISLANDORA_DERIVATIVE_CREATION_HOOK', 'islandora_derivative');
 define('ISLANDORA_CONTENT_MODELS_AUTOCOMPLETE', 'islandora/autocomplete/content-models');
 define('ISLANDORA_MIME_TYPES_AUTOCOMPLETE', 'islandora/autocomplete/mime-types');
 
+const ISLANDORA_BREADCRUMB_LEGACY_BACKEND = 'islandora_breadcrumbs_legacy_sparql';
+
 /**
  * Implements hook_menu().
  *
@@ -2152,9 +2154,9 @@ function islandora_schedule_cache_clear_for_batch() {
  */
 function islandora_islandora_get_breadcrumb_query_predicates(AbstractObject $object) {
   return array(
-    'fedora-rels-ext:isPartOf',
+    'info:fedora/fedora-system:def/relations-external#isPartOf',
-    'fedora-rels-ext:isMemberOfCollection',
+    'info:fedora/fedora-system:def/relations-external#isMemberOfCollection',
-    'fedora-rels-ext:isMemberOf',
+    'info:fedora/fedora-system:def/relations-external#isMemberOf',
   );
 }
 
@@ -2171,3 +2173,16 @@ function islandora_create_manage_overview(AbstractObject $object) {
   $output = theme('islandora_object_overview', array('islandora_object' => $object));
   return array('cmodels' => $output);
 }
+
+/**
+ * Implements hook_islandora_breadcrumbs_backends().
+ */
+function islandora_islandora_breadcrumbs_backends() {
+  return array(
+    ISLANDORA_BREADCRUMB_LEGACY_BACKEND => array(
+      'title' => t('Resource Index - Default'),
+      // Callback not needed as this is our legacy process and the
+      // default incase anything goes wrong.
+    ),
+  );
+}