<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Loader
 * @subpackage Autoloader
 * @copyright  Copyright (c) 2005-2008 Zend Technologies USA Inc. (http://www.zend.com)
 * @version    $Id: Autoloader.php 15508 2009-05-11 03:29:01Z matthew $
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */

/** Zend_Loader */
require_once 'Zend/Loader.php';

/**
 * Autoloader stack and namespace autoloader
 * 
 * @uses       Zend_Loader_Autoloader
 * @package    Zend_Loader
 * @subpackage Autoloader
 * @copyright  Copyright (c) 2005-2008 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    New BSD {@link http://framework.zend.com/license/new-bsd}
 */
class Zend_Loader_Autoloader
{
    /**
     * @var Zend_Loader_Autoloader Singleton instance
     */
    protected static $_instance;

    /**
     * @var array Concrete autoloader callback implementations
     */
    protected $_autoloaders = array();

    /**
     * @var array Default autoloader callback
     */
    protected $_defaultAutoloader = array('Zend_Loader', 'loadClass');

    /**
     * @var bool Whether or not to act as a fallback autoloader
     */
    protected $_fallbackAutoloader = false;

    /**
     * @var array Callback for internal autoloader implementation
     */
    protected $_internalAutoloader;

    /**
     * @var array Supported namespaces 'Zend' and 'ZendX' by default.
     */
    protected $_namespaces = array(
        'Zend_'  => true,
        'ZendX_' => true,
    );

    /**
     * @var array Namespace-specific autoloaders
     */
    protected $_namespaceAutoloaders = array();

    /**
     * @var bool Whether or not to suppress file not found warnings
     */
    protected $_suppressNotFoundWarnings = false;

    /**
     * Retrieve singleton instance
     * 
     * @return Zend_Loader_Autoloader
     */
    public static function getInstance()
    {
        if (null === self::$_instance) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    /**
     * Reset the singleton instance
     * 
     * @return void
     */
    public static function resetInstance()
    {
        self::$_instance = null;
    }

    /**
     * Autoload a class
     * 
     * @param  string $class 
     * @return bool
     */
    public static function autoload($class)
    {
        $self = self::getInstance();

        foreach ($self->getClassAutoloaders($class) as $autoloader) {
            if ($autoloader instanceof Zend_Loader_Autoloader_Interface) {
                if ($autoloader->autoload($class)) {
                    return true;
                }
            } elseif (is_string($autoloader)) {
                if ($autoloader($class)) {
                    return true;
                }
            } elseif (is_array($autoloader)) {
                $object = array_shift($autoloader);
                $method = array_shift($autoloader);
                if (call_user_func(array($object, $method), $class)) {
                    return true;
                }
            }
        }

        return false;
    }

    /**
     * Set the default autoloader implementation
     * 
     * @param  string|array $callback PHP callback
     * @return void
     */
    public function setDefaultAutoloader($callback)
    {
        if (!is_callable($callback)) {
            throw new Zend_Loader_Exception('Invalid callback specified for default autoloader');
        }

        $this->_defaultAutoloader = $callback;
        return $this;
    }

    /**
     * Retrieve the default autoloader callback
     * 
     * @return string|array PHP Callback
     */
    public function getDefaultAutoloader()
    {
        return $this->_defaultAutoloader;
    }

    /**
     * Set several autoloader callbacks at once
     * 
     * @param  array $autoloaders Array of PHP callbacks (or Zend_Loader_Autoloader_Interface implementations) to act as autoloaders
     * @return Zend_Loader_Autoloader
     */
    public function setAutoloaders(array $autoloaders)
    {
        $this->_autoloaders = $autoloaders;
        return $this;
    }

    /**
     * Get attached autoloader implementations
     * 
     * @return array
     */
    public function getAutoloaders()
    {
        return $this->_autoloaders;
    }

    /**
     * Return all autoloaders for a given namespace
     * 
     * @param  string $namespace
     * @return array
     */
    public function getNamespaceAutoloaders($namespace)
    {
        $namespace = (string) $namespace;
        if (!array_key_exists($namespace, $this->_namespaceAutoloaders)) {
            return array();
        }
        return $this->_namespaceAutoloaders[$namespace];
    }

    /**
     * Register a namespace to autoload
     * 
     * @param  string $namespace 
     * @return Zend_Loader_Autoloader
     */
    public function registerNamespace($namespace)
    {
        if (is_string($namespace)) {
            $namespace = (array) $namespace;
        } elseif (!is_array($namespace)) {
            throw new Zend_Loader_Exception('Invalid namespace provided');
        }

        foreach ($namespace as $ns) {
            if (!isset($this->_namespaces[$ns])) {
                $this->_namespaces[$ns] = true;
            }
        }
        return $this;
    }

    /**
     * Unload a registered autoload namespace
     * 
     * @param  string $namespace 
     * @return Zend_Loader_Autoloader
     */
    public function unregisterNamespace($namespace)
    {
        if (is_string($namespace)) {
            $namespace = (array) $namespace;
        } elseif (!is_array($namespace)) {
            throw new Zend_Loader_Exception('Invalid namespace provided');
        }

        foreach ($namespace as $ns) {
            if (isset($this->_namespaces[$ns])) {
                unset($this->_namespaces[$ns]);
            }
        }
        return $this;
    }

    /**
     * Get a list of registered autoload namespaces
     * 
     * @return array
     */
    public function getRegisteredNamespaces()
    {
        return array_keys($this->_namespaces);
    }

    /**
     * Get or set the value of the "suppress not found warnings" flag
     * 
     * @param  null|bool $flag 
     * @return bool|Zend_Loader_Autoloader Returns boolean if no argument is passed, object instance otherwise
     */
    public function suppressNotFoundWarnings($flag = null)
    {
        if (null === $flag) {
            return $this->_suppressNotFoundWarnings;
        }
        $this->_suppressNotFoundWarnings = (bool) $flag;
        return $this;
    }

    /**
     * Indicate whether or not this autoloader should be a fallback autoloader
     * 
     * @param  bool $flag 
     * @return Zend_Loader_Autoloader
     */
    public function setFallbackAutoloader($flag)
    {
        $this->_fallbackAutoloader = (bool) $flag;
        return $this;
    }

    /**
     * Is this instance acting as a fallback autoloader?
     * 
     * @return bool
     */
    public function isFallbackAutoloader()
    {
        return $this->_fallbackAutoloader;
    }

    /**
     * Get autoloaders to use when matching class
     *
     * Determines if the class matches a registered namespace, and, if so, 
     * returns only the autoloaders for that namespace. Otherwise, it returns 
     * all non-namespaced autoloaders.
     *
     * @param  string $class 
     * @return array Array of autoloaders to use
     */
    public function getClassAutoloaders($class)
    {
        $namespace   = false;
        $autoloaders = array();

        // Add concrete namespaced autoloaders
        foreach (array_keys($this->_namespaceAutoloaders) as $ns) {
            if ('' == $ns) {
                continue;
            }
            if (0 === strpos($class, $ns)) {
                $namespace   = $ns;
                $autoloaders = $autoloaders + $this->getNamespaceAutoloaders($ns);
                break;
            }
        }

        // Add internal namespaced autoloader
        foreach ($this->getRegisteredNamespaces() as $ns) {
            if (0 === strpos($class, $ns)) {
                $namespace     = $ns;
                $autoloaders[] = $this->_internalAutoloader;
                break;
            }
        }

        // Add non-namespaced autoloaders
        $autoloaders = $autoloaders + $this->getNamespaceAutoloaders('');

        // Add fallback autoloader
        if (!$namespace && $this->isFallbackAutoloader()) {
            $autoloaders[] = $this->_internalAutoloader;
        }

        return $autoloaders;
    }

    /**
     * Add an autoloader to the beginning of the stack
     * 
     * @param  object|array|string $callback PHP callback or Zend_Loader_Autoloader_Interface implementation
     * @param  string|array $namespace Specific namespace(s) under which to register callback
     * @return Zend_Loader_Autoloader
     */
    public function unshiftAutoloader($callback, $namespace = '')
    {
        $autoloaders = $this->getAutoloaders();
        array_unshift($autoloaders, $callback);
        $this->setAutoloaders($autoloaders);

        $namespace = (array) $namespace;
        foreach ($namespace as $ns) {
            $autoloaders = $this->getNamespaceAutoloaders($ns);
            array_unshift($autoloaders, $callback);
            $this->_setNamespaceAutoloaders($autoloaders, $ns);
        }

        return $this;
    }

    /**
     * Append an autoloader to the autoloader stack
     * 
     * @param  object|array|string $callback PHP callback or Zend_Loader_Autoloader_Interface implementation
     * @param  string|array $namespace Specific namespace(s) under which to register callback
     * @return Zend_Loader_Autoloader
     */
    public function pushAutoloader($callback, $namespace = '')
    {
        $autoloaders = $this->getAutoloaders();
        array_push($autoloaders, $callback);
        $this->setAutoloaders($autoloaders);

        $namespace = (array) $namespace;
        foreach ($namespace as $ns) {
            $autoloaders = $this->getNamespaceAutoloaders($ns);
            array_push($autoloaders, $callback);
            $this->_setNamespaceAutoloaders($autoloaders, $ns);
        }

        return $this;
    }

    /**
     * Remove an autoloader from the autoloader stack
     * 
     * @param  object|array|string $callback PHP callback or Zend_Loader_Autoloader_Interface implementation
     * @param  null|string|array $namespace Specific namespace(s) from which to remove autoloader
     * @return Zend_Loader_Autoloader
     */
    public function removeAutoloader($callback, $namespace = null)
    {
        if (null === $namespace) {
            $autoloaders = $this->getAutoloaders();
            if (false !== ($index = array_search($callback, $autoloaders, true))) {
                unset($autoloaders[$index]);
                $this->setAutoloaders($autoloaders);
            }

            foreach ($this->_namespaceAutoloaders as $ns => $autoloaders) {
                if (false !== ($index = array_search($callback, $autoloaders, true))) {
                    unset($autoloaders[$index]);
                    $this->_setNamespaceAutoloaders($autoloaders, $ns);
                }
            }
        } else {
            $namespace = (array) $namespace;
            foreach ($namespace as $ns) {
                $autoloaders = $this->getNamespaceAutoloaders($ns);
                if (false !== ($index = array_search($callback, $autoloaders, true))) {
                    unset($autoloaders[$index]);
                    $this->_setNamespaceAutoloaders($autoloaders, $ns);
                }
            }
        }

        return $this;
    }

    /**
     * Constructor
     *
     * Registers instance with spl_autoload stack
     * 
     * @return void
     */
    protected function __construct()
    {
        spl_autoload_register(array(__CLASS__, 'autoload'));
        $this->_internalAutoloader = array($this, '_autoload');
    }

    /**
     * Internal autoloader implementation
     * 
     * @param  string $class 
     * @return bool
     */
    protected function _autoload($class)
    {
        $callback = $this->getDefaultAutoloader();
        try {
            if ($this->suppressNotFoundWarnings()) {
                @call_user_func($callback, $class);
            } else {
                call_user_func($callback, $class);
            }
            return $class;
        } catch (Zend_Exception $e) {
            return false;
        }
    }

    /**
     * Set autoloaders for a specific namespace
     * 
     * @param  array $autoloaders 
     * @param  string $namespace 
     * @return Zend_Loader_Autoloader
     */
    protected function _setNamespaceAutoloaders(array $autoloaders, $namespace = '')
    {
        $namespace = (string) $namespace;
        $this->_namespaceAutoloaders[$namespace] = $autoloaders;
        return $this;
    }
}