<?php 
/**
 *   Copyright (C) 2008  Stichting Phreamp.org
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/gpl.txt/>.
 * 
 *   The copright holder may be reached by emailing john@johnkleijn.nl
 */

require_once 'Phreamp/Controller/Loader/Exception.php';

/**
 * Singleton Loader class
 * 
 * WARNING: If the class you are trying to load contains parse errors,
 *          execution will stop without error feedback.
 *
 */
class Phreamp_Loader {
	
	/**
	 * Static instance
	 *
	 * @var Phreamp_Loader
	 */
	private static $_self;
	 
	/**
	 * Queue of directories to search when includepath doesn't resolve
	 *
	 * @var array
	 */
	private $_dirs = array();
	
	/**
	 * Get Singleton Instance
	 *
	 * @return Phreamp_Loader
	 */
	public static function getInstance()
	{
		if(!self::$_self)
		{
			self::$_self = new self();	
		}
		
		return self::$_self;
	}
	
	
	/**
	 * Singleton constructor
	 *
	 */
	private function __construct()
	{}
	
	/**
	 * Cloning not allowed
	 *
	 */
	private function __clone()
	{}
	
	/**
	 * Load a class unless loaded
	 *
	 * @param string $className
	 * @return void
	 */
	public static function load($className)
	{
		if(!class_exists($className, false))
		{
			self::getInstance()->_doLoad($className);			
		}
	}
	
	/**
	 * Load a class that wasn't loaded yet
	 *
	 * @param string $className
	 * @return void
	 */
	public static function autoload($className)
	{
		self::getInstance()->_doLoad($className);
	}
	
	/**
	 * Set directories to use besides includepath
	 *
	 * @param array $dirs
	 */
	public function setDirectories(array $dirs)
	{
		foreach($dirs as $dir)
		{
			if(!is_dir($dir))
			{
				throw new Phreamp_Loader_Exception("Directory $dir does not exist");
			}
		}
		
		$this->_dirs = $dirs;
	}
	
	/**
	 * Register autoload
	 *
	 */
	public static function registerAutoload()
	{
		spl_autoload_register(array('Phreamp_Loader', 'autoload'));
	}
	
	/**
	 * Load a class
	 *
	 * @param string $className
	 * 
	 * @throws Phreamp_Loader_Exception
	 */
	private function _doLoad($className)
	{
		/**
		 * Try simply including the file
		 */
		$relativePath = $this->_getRelativePath($className);
		
		@include_once $relativePath;
		
		/**
		 * Class not found?
		 */
		if(!class_exists($className, false))
		{
			try {
				$absolutePath = $this->_findAbsolutePath($relativePath);
				
				/**
				 * Try again
				 */
				include_once $absolutePath;
				
				if(!class_exists($className, false))
				{
					throw new Phreamp_Loader_Exception("File '$absolutePath' was loaded, class '$className' not found");
				}
			}
			catch (Phreamp_Loader_Exception $e)
			{
				throw new Phreamp_Loader_Exception("Class '$className'' not found: {$e->getMessage()}");
			}
		}
	}
	
	/**
	 * Translate class name to path
	 *
	 * @param string $className
	 * @return string
	 */
	private function _getRelativePath($className)
	{
		return str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';
	}
	
	/**
	 * Try to find pathn in directories set
	 *
	 * @param string $relativePath
	 * @throws Phreamp_Loader_Exception
	 * @return string
	 */
	private function _findAbsolutePath($relativePath)
	{
		if(!is_readable($relativePath))
		{
			foreach($this->_dirs as $dir)
			{
				if(is_readable($dir . DIRECTORY_SEPARATOR . $relativePath))
				{
					return $dir . DIRECTORY_SEPARATOR . $relativePath;
				}
			}
		}
		else 
		{
			return $relativePath;
		}
		
		throw new Phreamp_Loader_Exception("Relative path '$relativePath'' could not be resolved");
	}
}