[DependencyInjection] refactored loaders

 * refactored the import mechanism for better flexibility
 * added two methods to LoaderInterface: supports() and setResolver()
 * added a LoaderResolver interface
 * added a Loader base class
 * added new loaders: DelegatingLoader, PhpFileLoader, and ClosureLoader

src/Symfony/Components/DependencyInjection/Loader/ClosureLoader.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Symfony\Components\DependencyInjection\Loader;
+
+/*
+ * This file is part of the Symfony framework.
+ *
+ * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+/**
+ * ClosureLoader loads service definitions from a PHP closure.
+ *
+ * The Closure has access to the container as its first argument.
+ *
+ * @package    Symfony
+ * @subpackage Components_DependencyInjection
+ * @author     Fabien Potencier <fabien.potencier@symfony-project.com>
+ */
+class ClosureLoader extends Loader
+{
+    /**
+     * Loads a Closure.
+     *
+     * @param \Closure $resource The resource
+     */
+    public function load($closure)
+    {
+        call_user_func($closure, $this->container);
+    }
+
+    /**
+     * Returns true if this class supports the given resource.
+     *
+     * @param  mixed $resource A resource
+     *
+     * @return Boolean true if this class supports the given resource, false otherwise
+     */
+    public function supports($resource)
+    {
+        return $resource instanceof \Closure;
+    }
+}

src/Symfony/Components/DependencyInjection/Loader/DelegatingLoader.php

@@ -0,0 +1,68 @@
+<?php
+
+namespace Symfony\Components\DependencyInjection\Loader;
+
+/*
+ * This file is part of the Symfony framework.
+ *
+ * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+/**
+ * DelegatingLoader delegates loading to other loaders using a loader resolver.
+ *
+ * @package    Symfony
+ * @subpackage Components_DependencyInjection
+ * @author     Fabien Potencier <fabien.potencier@symfony-project.com>
+ */
+class DelegatingLoader extends Loader
+{
+    protected $resolver;
+
+    /**
+     * Constructor.
+     *
+     * @param \Symfony\Components\DependencyInjection\Loader\LoaderResolverInterface $resolver A LoaderResolverInterface instance
+     */
+    public function __construct(LoaderResolverInterface $resolver)
+    {
+        $this->resolver = $resolver;
+    }
+
+    /**
+     * Loads a resource.
+     *
+     * @param mixed $resource A resource
+     */
+    public function load($resource)
+    {
+        $loader = $this->resolver->resolve($resource);
+
+        if (false === $loader) {
+            throw new \InvalidArgumentException(sprintf('Unable to load the "%s" container resource.', is_string($resource) ? $resource : (is_object($resource) ? get_class($resource) : 'RESOURCE')));
+        }
+
+        return $loader->load($resource);
+    }
+
+    /**
+     * Returns true if this class supports the given resource.
+     *
+     * @param  mixed $resource A resource
+     *
+     * @return Boolean true if this class supports the given resource, false otherwise
+     */
+    public function supports($resource)
+    {
+        foreach ($this->resolver->getLoaders() as $loader) {
+            if ($loader->supports($resource)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}

src/Symfony/Components/DependencyInjection/Loader/FileLoader.php

@@ -22,6 +22,7 @@
  */
 abstract class FileLoader extends Loader
 {
+    protected $currentDir;
     protected $paths;
 
     /**
@@ -41,6 +42,22 @@ public function __construct(ContainerBuilder $container, $paths = array())
         $this->paths = $paths;
     }
 
+    /**
+     * Adds definitions and parameters from a resource.
+     *
+     * @param mixed $resource A Resource
+     */
+    public function import($resource)
+    {
+        $loader = $this->resolve($resource);
+
+        if ($loader instanceof FileLoader && null !== $this->currentDir) {
+            $resource = $this->getAbsolutePath($resource, $this->currentDir);
+        }
+
+        $loader->load($resource);
+    }
+
     /**
      * @throws \InvalidArgumentException When provided file does not exist
      */

src/Symfony/Components/DependencyInjection/Loader/IniFileLoader.php

@@ -47,4 +47,16 @@ public function load($file)
             }
         }
     }
+
+    /**
+     * Returns true if this class supports the given resource.
+     *
+     * @param  mixed $resource A resource
+     *
+     * @return Boolean true if this class supports the given resource, false otherwise
+     */
+    public function supports($resource)
+    {
+        return is_string($resource) && 'ini' === pathinfo($resource, PATHINFO_EXTENSION);
+    }
 }

src/Symfony/Components/DependencyInjection/Loader/Loader.php

@@ -23,6 +23,7 @@
 abstract class Loader implements LoaderInterface
 {
     protected $container;
+    protected $resolver;
 
     /**
      * Constructor.
@@ -33,4 +34,59 @@ public function __construct(ContainerBuilder $container)
     {
         $this->container = $container;
     }
+
+    /**
+     * Gets the loader resolver.
+     *
+     * @return \Symfony\Components\DependencyInjection\Loader\LoaderResolver A LoaderResolver instance
+     */
+    public function getResolver()
+    {
+        return $this->resolver;
+    }
+
+    /**
+     * Sets the loader resolver.
+     *
+     * @param \Symfony\Components\DependencyInjection\Loader\LoaderResolver $resolver A LoaderResolver instance
+     */
+    public function setResolver(LoaderResolver $resolver)
+    {
+        $this->resolver = $resolver;
+    }
+
+    /**
+     * Adds definitions and parameters from a resource.
+     *
+     * @param mixed $resource A Resource
+     */
+    public function import($resource)
+    {
+        $this->resolve($resource)->load($resource);
+    }
+
+    /**
+     * Finds a loader able to load an imported resource.
+     *
+     * @param mixed $resource A Resource
+     *
+     * @return Symfony\Components\DependencyInjection\Loader\LoaderInterface A LoaderInterface instance
+     *
+     * @throws \InvalidArgumentException if no loader is found
+     */
+    public function resolve($resource)
+    {
+        $loader = false;
+        if ($this->supports($resource)) {
+            $loader = $this;
+        } elseif (null !== $this->resolver) {
+            $loader = $this->resolver->resolve($resource);
+        }
+
+        if (false === $loader) {
+            throw new \InvalidArgumentException(sprintf('Unable to load the "%s" container resource.', is_string($resource) ? $resource : (is_object($resource) ? get_class($resource) : 'RESOURCE')));
+        }
+
+        return $loader;
+    }
 }

src/Symfony/Components/DependencyInjection/Loader/LoaderInterface.php

@@ -61,4 +61,27 @@ interface LoaderInterface
      * @param mixed $resource The resource
      */
     function load($resource);
+
+    /**
+     * Returns true if this class supports the given resource.
+     *
+     * @param  mixed $resource A resource
+     *
+     * @return Boolean true if this class supports the given resource, false otherwise
+     */
+    function supports($resource);
+
+    /**
+     * Gets the loader resolver.
+     *
+     * @return \Symfony\Components\Routing\Loader\LoaderResolver A LoaderResolver instance
+     */
+    function getResolver();
+
+    /**
+     * Sets the loader resolver.
+     *
+     * @param \Symfony\Components\Routing\Loader\LoaderResolver $resolver A LoaderResolver instance
+     */
+    function setResolver(LoaderResolver $resolver);
 }

src/Symfony/Components/DependencyInjection/Loader/LoaderResolver.php

@@ -0,0 +1,76 @@
+<?php
+
+namespace Symfony\Components\DependencyInjection\Loader;
+
+/*
+ * This file is part of the Symfony framework.
+ *
+ * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+/**
+ * LoaderResolver selects a loader for a given resource..
+ *
+ * @package    Symfony
+ * @subpackage Components_DependencyInjection
+ * @author     Fabien Potencier <fabien.potencier@symfony-project.com>
+ */
+class LoaderResolver implements LoaderResolverInterface
+{
+    protected $loaders;
+
+    /**
+     * Constructor.
+     *
+     * @param \Symfony\Components\DependencyInjection\Loader\LoaderInterface[] $loaders An array of loaders
+     */
+    public function __construct(array $loaders = array())
+    {
+        $this->loaders = array();
+        foreach ($loaders as $loader) {
+            $this->addLoader($loader);
+        }
+    }
+
+    /**
+     * Returns a loader able to load the resource.
+     *
+     * @param mixed  $resource A resource
+     *
+     * @return Symfony\Components\DependencyInjection\Loader\LoaderInterface A LoaderInterface instance
+     */
+    public function resolve($resource)
+    {
+        foreach ($this->loaders as $loader) {
+            if ($loader->supports($resource)) {
+                return $loader;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Sets a loader.
+     *
+     * @param \Symfony\Components\DependencyInjection\Loader\LoaderInterface $loader A LoaderInterface instance
+     */
+    public function addLoader(LoaderInterface $loader)
+    {
+        $this->loaders[] = $loader;
+        $loader->setResolver($this);
+    }
+
+    /**
+     * Returns the registered loaders.
+     *
+     * @return \Symfony\Components\DependencyInjection\Loader\LoaderInterface[] A array of LoaderInterface instances
+     */
+    public function getLoaders()
+    {
+        return $this->loaders;
+    }
+}

src/Symfony/Components/DependencyInjection/Loader/LoaderResolverInterface.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Symfony\Components\DependencyInjection\Loader;
+
+/*
+ * This file is part of the Symfony framework.
+ *
+ * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+/**
+ * LoaderResolverInterface selects a loader for a given resource.
+ *
+ * @package    Symfony
+ * @subpackage Components_DependencyInjection
+ * @author     Fabien Potencier <fabien.potencier@symfony-project.com>
+ */
+interface LoaderResolverInterface
+{
+    /**
+     * Returns a loader able to load the resource.
+     *
+     * @param mixed  $resource A resource
+     *
+     * @return Symfony\Components\DependencyInjection\Loader\LoaderInterface A LoaderInterface instance
+     */
+    function resolve($resource);
+}