Extract autoloading process (#3283)

* Extract autoloading process

The process sits in its own file now to ease future improvements.

* Change the autoload process

Before, the autoload process was too restricted. It was really dependant on our
code tree. It was hard to add more classes to be loaded automatically. On top
of that, it did not support autoloading classes following the PSR-4 recommendation.

Now, the autoload process is more open. It supports partially the PSR-4 recommendation,
there is no specific code to load Minz classes or PHPMailer classes. This is the
starting point to reorganize the codebase to introduce long waiting changes as seen
in #789. It would be a nice to later rework the tree, rename classes, and add namespace
in a fashion that follows the PSR-4. Then specific FRSS workarounds in the autoload
could be dropped.

lib/autoload.php

@@ -0,0 +1,74 @@
+<?php
+
+class ClassLoader {
+    private $searchPath = [];
+
+    /**
+     * Register path in which to look for a class.
+     */
+    public function registerPath($path) {
+        if (is_string($path)) {
+            $this->searchPath[] = $path;
+        }
+        if (is_array($path)) {
+            array_push($this->searchPath, ...$path);
+        }
+    }
+
+    /**
+     * Load class file if found.
+     */
+    public function loadClass($class)
+    {
+        if ($file = $this->findFile($class)) {
+            require $file;
+        }
+    }
+
+    /**
+     * Find the file containing the class definition.
+     */
+    public function findFile($class) {
+        // This match most of classes directly
+        foreach ($this->searchPath as $path) {
+            $file = $path . DIRECTORY_SEPARATOR . str_replace(['\\', '_'], DIRECTORY_SEPARATOR, $class) . '.php';
+            if (file_exists($file)) {
+                return $file;
+            }
+        }
+
+        // This match FRSS model classes
+        $freshrssClass = str_replace('FreshRSS_', '', $class);
+        foreach ($this->searchPath as $path) {
+            $file = $path . DIRECTORY_SEPARATOR . str_replace(['\\', '_'], DIRECTORY_SEPARATOR, $freshrssClass) . '.php';
+            if (file_exists($file)) {
+                return $file;
+            }
+        }
+
+        // This match FRSS other classes
+        list(, $classType) = explode('_', $freshrssClass);
+        foreach ($this->searchPath as $path) {
+            $file = $path . DIRECTORY_SEPARATOR . $classType . 's' . DIRECTORY_SEPARATOR . str_replace('_', '', $freshrssClass) . '.php';
+            if (file_exists($file)) {
+                return $file;
+            }
+        }
+    }
+
+    /**
+     * Register the current loader in the autoload queue.
+     */
+    public function register($prepend = false) {
+        spl_autoload_register([$this, 'loadClass'], true, $prepend);
+    }
+}
+
+$loader = new ClassLoader();
+$loader->registerPath([
+    APP_PATH,
+    APP_PATH . DIRECTORY_SEPARATOR . 'Models',
+    LIB_PATH,
+    LIB_PATH . DIRECTORY_SEPARATOR . 'SimplePie',
+]);
+$loader->register();

lib/lib_rss.php

@@ -15,6 +15,8 @@ if (COPY_SYSLOG_TO_STDERR) {
 	openlog('FreshRSS', LOG_CONS | LOG_ODELAY | LOG_PID, LOG_USER);
 }
 
+require_once LIB_PATH . DIRECTORY_SEPARATOR . 'autoload.php';
+
 /**
  * Build a directory path by concatenating a list of directory names.
  *
@@ -26,33 +28,6 @@ function join_path() {
 	return join(DIRECTORY_SEPARATOR, $path_parts);
 }
 
-//<Auto-loading>
-function classAutoloader($class) {
-	if (strpos($class, 'FreshRSS') === 0) {
-		$components = explode('_', $class);
-		switch (count($components)) {
-			case 1:
-				include(APP_PATH . '/' . $components[0] . '.php');
-				return;
-			case 2:
-				include(APP_PATH . '/Models/' . $components[1] . '.php');
-				return;
-			case 3:	//Controllers, Exceptions
-				include(APP_PATH . '/' . $components[2] . 's/' . $components[1] . $components[2] . '.php');
-				return;
-		}
-	} elseif (strpos($class, 'Minz') === 0) {
-		include(LIB_PATH . '/' . str_replace('_', '/', $class) . '.php');
-	} elseif (strpos($class, 'SimplePie') === 0) {
-		include(LIB_PATH . '/SimplePie/' . str_replace('_', '/', $class) . '.php');
-	} elseif (strpos($class, 'PHPMailer') === 0) {
-		include(LIB_PATH . '/' . str_replace('\\', '/', $class) . '.php');
-	}
-}
-
-spl_autoload_register('classAutoloader');
-//</Auto-loading>
-
 function idn_to_puny($url) {
 	if (function_exists('idn_to_ascii')) {
 		$idn = parse_url($url, PHP_URL_HOST);