Add new method getCoverUrl to record drivers

Signed-off-by: Stefan Weil <sw@weilnetz.de>

Author: stweil

module/VuFind/src/VuFind/Content/Covers/RecordData.php

@@ -69,15 +69,6 @@ public function getUrl($key, $size, $ids)
         $recordId = $ids['recordid'];
         $source = $ids['source'] ?? DEFAULT_SEARCH_BACKEND;
         $driver = $this->recordLoader->load($recordId, $source);
-        $marc = $driver->getMarcReader();
-        $fields856 = $marc->getFields('856');
-        foreach ($fields856 as $field) {
-            $description = $marc->getSubfield($field, '3');
-            if (stripos($description, 'cover') !== false) {
-                $url = $marc->getSubfield($field, 'u');
-                return $url;
-            }
-        }
-        return false;
+        return $driver->getCoverUrl();
     }
 }

module/VuFind/src/VuFind/RecordDriver/DefaultRecord.php

@@ -433,6 +433,18 @@ public function getCorporateAuthorsRoles()
         return (array)($this->fields['author_corporate_role'] ?? []);
     }
 
+   /**
+     * Get URL of cover image.
+     * This method should be overridden by record driver implementations which
+     * can provide information about cover images.
+     *
+     * @return string|bool URL of the image, or false if no valid image is found
+     */
+    public function getCoverUrl()
+    {
+        return false;
+    }
+
     /**
      * Get the date coverage for a record which spans a period of time (i.e. a
      * journal). Use getPublicationDates for publication dates of particular

module/VuFind/src/VuFind/RecordDriver/Feature/MarcReaderTrait.php

@@ -103,6 +103,25 @@ public function getMarcReader()
         return $this->lazyMarcReader;
     }
 
+    /**
+     * Get URL of cover image from MARC field.
+     *
+     * @return string|bool URL of the image, or false if no valid image is found
+     */
+    public function getCoverUrl()
+    {
+        $marc = $this->getMarcReader();
+        $fields856 = $marc->getFields('856');
+        foreach ($fields856 as $field) {
+            $description = $marc->getSubfield($field, '3');
+            if (stripos($description, 'cover') !== false) {
+                $url = $marc->getSubfield($field, 'u');
+                return $url;
+            }
+        }
+        return false;
+    }
+
     /**
      * Return an array of all values extracted from the specified field/subfield
      * combination. If multiple subfields are specified and $concat is true, they