ProxyUrl: Determine whether to proxy via web service

config/vufind/config.ini

@@ -1449,6 +1449,18 @@ replace_other_urls = true
 ; to false.
 ;prefixLinks = true
 
+; Use a web service to determine whether to prefix each link, ignoring prefixLinks
+; above.  Query the configured URL via HTTP GET and a single query parameter, 'url',
+; set to the link domain. The web service should return a body with a single number,
+; '1' to prefix and '0' if not.  The web service should be hosted closely such that
+; query time is minimal.
+; See https://github.com/lehigh-university-libraries/ezproxy-url-checker for an OSS
+; implementation of this protocol that extrats the answers from EZproxy config.
+;prefixLinksWebServiceUrl = http://localhost:8888/proxyUrl
+
+; Duration (seconds) to cache web service response data.  Default is 600.
+;prefixLinksWebServiceCacheLifetime = 600
+
 ; Uncomment the following line and change the password to something secret to enable
 ; EZproxy ticket authentication.
 ;secret = "verysecretpassword"

module/VuFind/src/VuFind/View/Helper/Root/ProxyUrl.php

@@ -29,6 +29,11 @@
 
 namespace VuFind\View\Helper\Root;
 
+use Exception;
+use Laminas\Cache\Storage\Adapter\AbstractAdapter as CacheAdapter;
+
+use function intval;
+
 /**
  * Proxy URL view helper
  *
@@ -38,8 +43,14 @@
  * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
  * @link     https://vufind.org/wiki/development Wiki
  */
-class ProxyUrl extends \Laminas\View\Helper\AbstractHelper
+class ProxyUrl extends \Laminas\View\Helper\AbstractHelper implements
+    \Laminas\Log\LoggerAwareInterface,
+    \VuFindHttp\HttpServiceAwareInterface
 {
+    use \VuFind\Cache\CacheTrait;
+    use \VuFind\Log\LoggerAwareTrait;
+    use \VuFindHttp\HttpServiceAwareTrait;
+
     /**
      * VuFind configuration
      *
@@ -50,11 +61,14 @@ class ProxyUrl extends \Laminas\View\Helper\AbstractHelper
     /**
      * Constructor
      *
+     * @param CacheAdapter           $cache  Cache for web service repsonses
      * @param \Laminas\Config\Config $config VuFind configuration
      */
-    public function __construct($config = null)
+    public function __construct(CacheAdapter $cache = null, $config = null)
     {
         $this->config = $config;
+        $this->setCacheStorage($cache);
+        $this->cacheLifetime = intval($config->EZproxy->prefixLinksWebServiceCacheLifetime ?? 600);
     }
 
     /**
@@ -66,10 +80,67 @@ public function __construct($config = null)
      */
     public function __invoke($url)
     {
-        $usePrefix = !isset($this->config->EZproxy->prefixLinks)
-            || $this->config->EZproxy->prefixLinks;
+        $useWebService = $this->config->EZproxy->prefixLinksWebServiceUrl ?? false;
+        if ($useWebService) {
+            $usePrefix = $this->checkUrl($url) ?? $this->checkConfig();
+        } else {
+            $usePrefix = $this->checkConfig();
+        }
+
         return ($usePrefix && isset($this->config->EZproxy->host))
             ? $this->config->EZproxy->host . '/login?qurl=' . urlencode($url)
             : $url;
     }
+
+    /**
+     * Return the configured prefixLinks setting.
+     *
+     * @return bool The configured setting, or the default
+     */
+    private function checkConfig()
+    {
+        return $this->config->EZproxy->prefixLinks ?? true;
+    }
+
+    /**
+     * Check whether the given URL requires the proxy prefix.  Cache the repsonse.
+     *
+     * @param string $url The raw URL to check
+     *
+     * @return mixed Whether the URL should be prefixed, or null if it can't be determined
+     */
+    protected function checkUrl($url)
+    {
+        $domain = parse_url($url, PHP_URL_SCHEME)
+         . '://'
+         . parse_url($url, PHP_URL_HOST);
+        $usePrefix = $this->getCachedData("proxyUrl-domainToUsePrefix-$domain");
+        if (null === $usePrefix) {
+            $usePrefix = $this->queryWebService($domain);
+            $this->putCachedData("proxyUrl-domainToUsePrefix-$domain", $usePrefix);
+        }
+        return $usePrefix;
+    }
+
+    /**
+     * Query the web service on whether to prefix URLs to a given domain.
+     *
+     * @param $domain The domain
+     *
+     * @return mixed Whether the URL should be prefixed, or null if it can't be determined
+     */
+    protected function queryWebService($domain)
+    {
+        $prefixLinksWebServiceUrl = $this->config->EZproxy->prefixLinksWebServiceUrl;
+        $queryUrl = $prefixLinksWebServiceUrl . '?url=' . $domain;
+        try {
+            $client  = $this->httpService->createClient($queryUrl);
+            $response = $client->send();
+            $responseData = $response->getContent();
+        } catch (Exception $ex) {
+            $this->logError('Exception during EZproxy web service request: ' . $ex->getMessage());
+            return null;
+        }
+        return '1' === $responseData;
+    }
 }

module/VuFind/src/VuFind/View/Helper/Root/ProxyUrlFactory.php

@@ -68,8 +68,10 @@ public function __invoke(
         if (!empty($options)) {
             throw new \Exception('Unexpected options sent to factory.');
         }
+        $cache = $container->get(\VuFind\Cache\Manager::class)
+            ->getCache('object');
         $config = $container->get(\VuFind\Config\PluginManager::class)
             ->get('config');
-        return new $requestedName($config);
+        return new $requestedName($cache, $config);
     }
 }