A couple improvements

Show 400 if request is missing spec (instead of redirect)
Allow config.php to change factories for Minify and MinApp objects
These should've been separate commits, :(

config.php

@@ -187,5 +187,15 @@ $min_symlinks = array();
 $min_uploaderHoursBehind = 0;
 
 
+/**
+ * Advanced: you can replace some of the PHP classes Minify uses to serve requests.
+ * To do this, assign a callable to one of the elements of the $min_factories array.
+ *
+ * You can see the default implementations (and what gets passed in) in index.php.
+ */
+//$min_factories['minify'] = ... a callable
+//$min_factories['controller'] = ... a callable
+
+
 // try to disable output_compression (may not have an effect)
 ini_set('zlib.output_compression', '0');

index.php

@@ -28,6 +28,20 @@ if (isset($_GET['test'])) {
     include $min_configPaths['test'];
 }
 
+// setup factories
+$defaultFactories = array(
+    'minify' => function (Minify_CacheInterface $cache) {
+        return new Minify($cache);
+    },
+    'controller' => function (Minify_Env $env, Minify_Source_Factory $sourceFactory) {
+        return new Minify_Controller_MinApp($env, $sourceFactory);
+    },
+);
+if (!isset($min_factories)) {
+    $min_factories = array();
+}
+$min_factories = array_merge($defaultFactories, $min_factories);
+
 // use an environment object to encapsulate all input
 $server = $_SERVER;
 if ($min_documentRoot) {
@@ -37,18 +51,6 @@ $env = new Minify_Env(array(
     'server' => $server,
 ));
 
-// setup cache
-if (!isset($min_cachePath)) {
-    $min_cachePath = '';
-}
-if (is_string($min_cachePath)) {
-    $cache = new Minify_Cache_File($min_cachePath, $min_cacheFileLocking);
-} else {
-    $cache = $min_cachePath;
-}
-
-$server = new Minify($cache);
-
 // TODO probably should do this elsewhere...
 $min_serveOptions['minifierOptions']['text/css']['docRoot'] = $env->getDocRoot();
 $min_serveOptions['minifierOptions']['text/css']['symlinks'] = $min_symlinks;
@@ -81,32 +83,44 @@ if (null !== $env->get('v') || preg_match('/&\\d/', $env->server('QUERY_STRING')
 
 // need groups config?
 if (null !== $env->get('g')) {
-    // well need groups config
+    // we need groups config
     $min_serveOptions['minApp']['groups'] = (require $min_configPaths['groups']);
 }
 
-if ($env->get('f') || null !== $env->get('g')) {
-    // serving!
-    if (! isset($min_serveController)) {
-        $sourceFactoryOptions = array();
+// cache defaults
+if (!isset($min_cachePath)) {
+    $min_cachePath = '';
+}
+if (!isset($min_cacheFileLocking)) {
+    $min_cacheFileLocking = true;
+}
+if (is_string($min_cachePath)) {
+    $cache = new Minify_Cache_File($min_cachePath, $min_cacheFileLocking);
+} else {
+    // assume it meets interface.
+    $cache = $min_cachePath;
+}
+/* @var Minify_CacheInterface $cache */
 
-        // translate legacy setting to option for source factory
-        if (isset($min_serveOptions['minApp']['noMinPattern'])) {
+$minify = call_user_func($min_factories['minify'], $cache);
+/* @var Minify $minify */
+
+if (!$env->get('f') && $env->get('g') === null) {
+    // no spec given
+    $defaults = $minify->getDefaultOptions();
+    $url = 'https://github.com/mrclay/minify/blob/master/docs/UserGuide.wiki.md#creating-minify-urls';
+    $minify->errorExit($defaults['badRequestHeader'], $url);
+}
+
+$sourceFactoryOptions = array();
+
+// translate legacy setting to option for source factory
+if (isset($min_serveOptions['minApp']['noMinPattern'])) {
     $sourceFactoryOptions['noMinPattern'] = $min_serveOptions['minApp']['noMinPattern'];
-        }
-        $sourceFactory = new Minify_Source_Factory($env, $sourceFactoryOptions, $cache);
-
-        $min_serveController = new Minify_Controller_MinApp($env, $sourceFactory);
-    }
-    $server->serve($min_serveController, $min_serveOptions);
-    exit;
 }
+$sourceFactory = new Minify_Source_Factory($env, $sourceFactoryOptions, $cache);
 
-// not serving
-if ($min_enableBuilder) {
-    header('Location: builder/');
-    exit;
-}
+$controller = call_user_func($min_factories['controller'], $env, $sourceFactory);
+/* @var Minify_ControllerInterface $controller */
 
-header('Location: /');
-exit;
+$minify->serve($controller, $min_serveOptions);

lib/Minify.php

@@ -426,11 +426,16 @@ class Minify {
     }
 
     /**
-     * @param string $header
+     * Show an error page
      *
-     * @param string $url
+     * @param string $header E.g. 'HTTP/1.0 500 Internal Server Error'
+     * @param string $url    URL to direct the user to
+     *
+     * @return void
+     * @internal This is not part of the public API and is subject to change
+     * @access private
      */
-    protected function errorExit($header, $url)
+    public function errorExit($header, $url)
     {
         $url = htmlspecialchars($url, ENT_QUOTES);
         list(,$h1) = explode(' ', $header, 2);