<?php
/**
 * JShrink
 *
 * Copyright (c) 2009-2012, Robert Hafner <tedivm@tedivm.com>.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in
 *     the documentation and/or other materials provided with the
 *     distribution.
 *
 *   * Neither the name of Robert Hafner nor the names of his
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * @package    JShrink
 * @author     Robert Hafner <tedivm@tedivm.com>
 * @copyright  2009-2012 Robert Hafner <tedivm@tedivm.com>
 * @license    http://www.opensource.org/licenses/bsd-license.php  BSD License
 * @link       https://github.com/tedivm/JShrink
 * @version    Release: 0.5.1
 */


/**
 * JShrink_Minifier
 *
 * Usage - JShrink_Minifier::minify($js);
 * Usage - JShrink_Minifier::minify($js, $options);
 * Usage - JShrink_Minifier::minify($js, array('flaggedComments' => false));
 *
 * @package	JShrink
 * @author	Robert Hafner <tedivm@tedivm.com>
 * @license	http://www.opensource.org/licenses/bsd-license.php  BSD License
 */
class JShrink_Minifier
{
	/**
	 * The input javascript to be minified.
	 *
	 * @var string
	 */
	protected $input;

	/**
	 * The location of the character (in the input string) that is next to be
     * processed.
	 *
	 * @var int
	 */
	protected $index = 0;

	/**
	 * The first of the characters currently being looked at.
	 *
	 * @var string
	 */
	protected $a = '';


	/**
	 * The next character being looked at (after a);
	 *
	 * @var string
	 */
	protected $b = '';

	/**
	 * This character is only active when certain look ahead actions take place.
	 *
	 *  @var string
	 */
	protected $c;

	/**
	 * Contains the options for the current minification process.
	 *
	 * @var array
	 */
	protected $options;

	/**
	 * Contains the default options for minification. This array is merged with
     * the one passed in by the user to create the request specific set of
     * options (stored in the $options attribute).
	 *
	 * @var array
	 */
	static protected $defaultOptions = array('flaggedComments' => true);

	/**
	 * Contains a copy of the JShrink object used to run minification. This is
     * only used internally, and is only stored for performance reasons. There
     * is no internal data shared between minification requests.
	 */
	static protected $jshrink;

	/**
	 * Minifier::minify takes a string containing javascript and removes
     * unneeded characters in order to shrink the code without altering it's
     * functionality.
	 */
	static public function minify($js, $options = array())
	{
		try{
			ob_start();
			$currentOptions = array_merge(self::$defaultOptions, $options);

			if(!isset(self::$jshrink))
				self::$jshrink = new JShrink_Minifier();

			self::$jshrink->breakdownScript($js, $currentOptions);
			return ob_get_clean();

		}catch(Exception $e){
			if(isset(self::$jshrink))
				self::$jshrink->clean();

			ob_end_clean();
			throw $e;
		}
	}

	/**
	 * Processes a javascript string and outputs only the required characters,
     * stripping out all unneeded characters.
	 *
	 * @param string $js The raw javascript to be minified
	 * @param array $currentOptions Various runtime options in an associative array
	 */
	protected function breakdownScript($js, $currentOptions)
	{
		// reset work attributes in case this isn't the first run.
		$this->clean();

		$this->options = $currentOptions;

		$js = str_replace("\r\n", "\n", $js);
		$this->input = str_replace("\r", "\n", $js);


		$this->a = $this->getReal();

		// the only time the length can be higher than 1 is if a conditional
        // comment needs to be displayed and the only time that can happen for
        // $a is on the very first run
		while(strlen($this->a) > 1)
		{
			echo $this->a;
			$this->a = $this->getReal();
		}

		$this->b = $this->getReal();

		while($this->a !== false && !is_null($this->a) && $this->a !== '')
		{

			// now we give $b the same check for conditional comments we gave $a
            // before we began looping
			if(strlen($this->b) > 1)
			{
				echo $this->a . $this->b;
				$this->a = $this->getReal();
				$this->b = $this->getReal();
				continue;
			}

			switch($this->a)
			{
				// new lines
				case "\n":
					// if the next line is something that can't stand alone
                    // preserve the newline
					if(strpos('(-+{[@', $this->b) !== false)
					{
						echo $this->a;
						$this->saveString();
						break;
					}

					// if its a space we move down to the string test below
					if($this->b === ' ')
						break;

					// otherwise we treat the newline like a space

				case ' ':
					if(self::isAlphaNumeric($this->b))
						echo $this->a;

					$this->saveString();
					break;

				default:
					switch($this->b)
					{
						case "\n":
							if(strpos('}])+-"\'', $this->a) !== false)
							{
								echo $this->a;
								$this->saveString();
								break;
							}else{
								if(self::isAlphaNumeric($this->a))
								{
									echo $this->a;
									$this->saveString();
								}
							}
							break;

						case ' ':
							if(!self::isAlphaNumeric($this->a))
								break;

						default:
							// check for some regex that breaks stuff
							if($this->a == '/' && ($this->b == '\'' || $this->b == '"'))
							{
								$this->saveRegex();
								continue;
							}

							echo $this->a;
							$this->saveString();
							break;
					}
			}

			// do reg check of doom
			$this->b = $this->getReal();

			if(($this->b == '/' && strpos('(,=:[!&|?', $this->a) !== false))
				$this->saveRegex();
		}
		$this->clean();
	}

	/**
	 * Returns the next string for processing based off of the current index.
	 *
	 * @return string
	 */
	protected function getChar()
	{
		if(isset($this->c))
		{
			$char = $this->c;
			unset($this->c);
		}else{
			$tchar = substr($this->input, $this->index, 1);
			if(isset($tchar) && $tchar !== false)
			{
				$char = $tchar;
				$this->index++;
			}else{
				return false;
			}
		}

		if($char !== "\n" && ord($char) < 32)
			return ' ';

		return $char;
	}

	/**
	 * This function gets the next "real" character. It is essentially a wrapper
     * around the getChar function that skips comments. This has significant
     * performance benefits as the skipping is done using native functions (ie,
     * c code) rather than in script php.
	 *
	 * @return string Next 'real' character to be processed.
	 */
	protected function getReal()
	{
		$startIndex = $this->index;
		$char = $this->getChar();

		if($char == '/')
		{
			$this->c = $this->getChar();

			if($this->c == '/')
			{
				$thirdCommentString = substr($this->input, $this->index, 1);

				// kill rest of line
				$char = $this->getNext("\n");

				if($thirdCommentString == '@')
				{
					$endPoint = ($this->index) - $startIndex;
					unset($this->c);
					$char = "\n" . substr($this->input, $startIndex, $endPoint);
				}else{
					$char = $this->getChar();
					$char = $this->getChar();
				}

			}elseif($this->c == '*'){

				$this->getChar(); // current C
				$thirdCommentString = $this->getChar();

				if($thirdCommentString == '@')
				{
					// conditional comment

					// we're gonna back up a bit and and send the comment back,
                    // where the first char will be echoed and the rest will be
                    // treated like a string
					$this->index = $this->index-2;
					return '/';

				}elseif($this->getNext('*/')){
				// kill everything up to the next */

					$this->getChar(); // get *
					$this->getChar(); // get /

					$char = $this->getChar(); // get next real character

					// if YUI-style comments are enabled we reinsert it into the stream
					if($this->options['flaggedComments'] && $thirdCommentString == '!')
					{
						$endPoint = ($this->index - 1) - $startIndex;
						echo "\n" . substr($this->input, $startIndex, $endPoint) . "\n";
					}

				}else{
					$char = false;
				}

				if($char === false)
					throw new RuntimeException('Stray comment. ' . $this->index);

				// if we're here c is part of the comment and therefore tossed
				if(isset($this->c))
					unset($this->c);
			}
		}
		return $char;
	}

	/**
	 * Pushes the index ahead to the next instance of the supplied string. If it
     * is found the first character of the string is returned.
	 *
	 * @return string|false Returns the first character of the string or false.
	 */
	protected function getNext($string)
	{
		$pos = strpos($this->input, $string, $this->index);

		if($pos === false)
			return false;

		$this->index = $pos;
		return substr($this->input, $this->index, 1);
	}

	/**
	 * When a javascript string is detected this function crawls for the end of
     * it and saves the whole string.
	 *
	 */
	protected function saveString()
	{
		$this->a = $this->b;
		if($this->a == "'" || $this->a == '"') // is the character a quote
		{
			// save literal string
			$stringType = $this->a;

			while(1)
			{
				echo $this->a;
				$this->a = $this->getChar();

				switch($this->a)
				{
					case $stringType:
						break 2;

					case "\n":
						throw new RuntimeException('Unclosed string. ' . $this->index);
						break;

					case '\\':
						echo $this->a;
						$this->a = $this->getChar();
				}
			}
		}
	}

	/**
	 * When a regular expression is detected this funcion crawls for the end of
     * it and saves the whole regex.
	 */
	protected function saveRegex()
	{
		echo $this->a . $this->b;

		while(($this->a = $this->getChar()) !== false)
		{
			if($this->a == '/')
				break;

			if($this->a == '\\')
			{
				echo $this->a;
				$this->a = $this->getChar();
			}

			if($this->a == "\n")
				throw new RuntimeException('Stray regex pattern. ' . $this->index);

			echo $this->a;
		}
		$this->b = $this->getReal();
	}

	/**
	 * Resets attributes that do not need to be stored between requests so that
     * the next request is ready to go.
	 */
	protected function clean()
	{
		unset($this->input);
		$this->index = 0;
		$this->a = $this->b = '';
		unset($this->c);
		unset($this->options);
	}

	/**
	 * Checks to see if a character is alphanumeric.
	 *
	 * @return bool
	 */
	static protected function isAlphaNumeric($char)
	{
		return preg_match('/^[\w\$]$/', $char) === 1 || $char == '/';
	}

}