<?php

/*BSD 3-Clause License

Copyright (c) 2009, Robert Hafner
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.

2. 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.

3. Neither the name of the copyright holder nor the names of its
   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 HOLDER 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.*/


/*
 * This file is part of the JShrink package.
 *
 * (c) Robert Hafner <tedivm@tedivm.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * JShrink
 *
 *
 * @package    JShrink
 * @author     Robert Hafner <tedivm@tedivm.com>
 */


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

    /**
     * Length of input javascript.
     *
     * @var int
     */
    protected $len = 0;

    /**
     * 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;

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

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

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

    /**
     * These characters are used to define strings.
     */
    protected $stringDelimiters = ['\'' => true, '"' => true, '`' => true];

    /**
     * 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
     */
    protected static $defaultOptions = ['flaggedComments' => true];


    protected static $keywords = ["delete", "do", "for", "in", "instanceof", "return", "typeof", "yield"];

    protected $max_keyword_len;

    /**
     * Contains lock ids which are used to replace certain code patterns and
     * prevent them from being minified
     *
     * @var array
     */
    protected $locks = [];

    /**
     * Takes a string containing javascript and removes unneeded characters in
     * order to shrink the code without altering it's functionality.
     *
     * @param  string      $js      The raw javascript to be minified
     * @param  array       $options Various runtime options in an associative array
     * @throws \Exception
     * @return bool|string
     */
    public static function minify($js, $options = [])
    {
        try {
            $jshrink = new Minifier();
            $js = $jshrink->lock($js);
            $js = ltrim($jshrink->minifyToString($js, $options));
            $js = $jshrink->unlock($js);
            unset($jshrink);
            return $js;
        } catch (\Exception $e) {
            if (isset($jshrink)) {
                // Since the breakdownScript function probably wasn't finished
                // we clean it out before discarding it.
                $jshrink->clean();
                unset($jshrink);
            }
            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  $options Various runtime options in an associative array
     */
    protected function minifyToString($js, $options)
    {
        $this->initialize($js, $options);
        $this->loop();
        $this->clean();
        return $this->output;
    }

    /**
     *  Initializes internal variables, normalizes new lines,
     *
     * @param string $js      The raw javascript to be minified
     * @param array  $options Various runtime options in an associative array
     */
    protected function initialize($js, $options)
    {
        $this->options = array_merge(static::$defaultOptions, $options);
        $this->input = $js;

        // We add a newline to the end of the script to make it easier to deal
        // with comments at the bottom of the script- this prevents the unclosed
        // comment error that can otherwise occur.
        $this->input .= PHP_EOL;

        // save input length to skip calculation every time
        $this->len = strlen($this->input);

        // Populate "a" with a new line, "b" with the first character, before
        // entering the loop
        $this->a = "\n";
        $this->b = "\n";
        $this->last_char = "\n";
        $this->output = "";

        $this->max_keyword_len = max(array_map('strlen', static::$keywords));
    }

    /**
     * Characters that can't stand alone preserve the newline.
     *
     * @var array
     */
    protected $noNewLineCharacters = [
        '(' => true,
        '-' => true,
        '+' => true,
        '[' => true,
        '#' => true,
        '@' => true];


    protected function echo($char) {
        $this->output .= $char;
        $this->last_char = $char[-1];
    }


    /**
     * The primary action occurs here. This function loops through the input string,
     * outputting anything that's relevant and discarding anything that is not.
     */
    protected function loop()
    {
        while ($this->a !== false && !is_null($this->a) && $this->a !== '') {
            switch ($this->a) {
                // new lines
                case "\r":
                case "\n":
                    // if the next line is something that can't stand alone preserve the newline
                    if ($this->b !== false && isset($this->noNewLineCharacters[$this->b])) {
                        $this->echo($this->a);
                        $this->saveString();
                        break;
                    }

                    // if B is a space we skip the rest of the switch block and go down to the
                    // string/regex check below, resetting $this->b with getReal
                    if ($this->b === ' ') {
                        break;
                    }

                // otherwise we treat the newline like a space

                // no break
                case ' ':
                    if (static::isAlphaNumeric($this->b)) {
                        $this->echo($this->a);
                    }

                    $this->saveString();
                    break;

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

                        case ' ':
                            if (!static::isAlphaNumeric($this->a)) {
                                break;
                            }

                        // no break
                        default:
                            // check for some regex that breaks stuff
                            if ($this->a === '/' && ($this->b === '\'' || $this->b === '"')) {
                                $this->saveRegex();
                                continue 3;
                            }

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

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

            if ($this->b == '/') {
                $valid_tokens = "(,=:[!&|?\n";

                # Find last "real" token, excluding spaces.
                $last_token = $this->a;
                if ($last_token == " ") {
                    $last_token = $this->last_char;
                }

                if (strpos($valid_tokens, $last_token) !== false) {
                    // Regex can appear unquoted after these symbols
                    $this->saveRegex();
                } else if ($this->endsInKeyword()) {
                    // This block checks for the "return" token before the slash.
                    $this->saveRegex();
                }
            }

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

    /**
     * Resets attributes that do not need to be stored between requests so that
     * the next request is ready to go. Another reason for this is to make sure
     * the variables are cleared and are not taking up memory.
     */
    protected function clean()
    {
        unset($this->input);
        $this->len = 0;
        $this->index = 0;
        $this->a = $this->b = '';
        unset($this->c);
        unset($this->options);
    }

    /**
     * Returns the next string for processing based off of the current index.
     *
     * @return string
     */
    protected function getChar()
    {
        // Check to see if we had anything in the look ahead buffer and use that.
        if (isset($this->c)) {
            $char = $this->c;
            unset($this->c);
        } else {
            // Otherwise we start pulling from the input.
            $char = $this->index < $this->len ? $this->input[$this->index] : false;

            // If the next character doesn't exist return false.
            if (isset($char) && $char === false) {
                return false;
            }

            // Otherwise increment the pointer and use this char.
            $this->index++;
        }

        # Convert all line endings to unix standard.
        # `\r\n` converts to `\n\n` and is minified.
        if ($char == "\r") {
            $char = "\n";
        }

        // Normalize all whitespace except for the newline character into a
        // standard space.
        if ($char !== "\n" && $char < "\x20") {
            return ' ';
        }

        return $char;
    }

    /**
     * This function returns the next character without moving the index forward.
     *
     *
     * @return string            The next character
     * @throws \RuntimeException
     */
    protected function peek()
    {
        if ($this->index >= $this->len) {
            return false;
        }

        $char = $this->input[$this->index];
        # Convert all line endings to unix standard.
        # `\r\n` converts to `\n\n` and is minified.
        if ($char == "\r") {
            $char = "\n";
        }

        // Normalize all whitespace except for the newline character into a
        // standard space.
        if ($char !== "\n" && $char < "\x20") {
            return ' ';
        }

        # Return the next character but don't push the index.
        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.
     * @throws \RuntimeException
     */
    protected function getReal()
    {
        $startIndex = $this->index;
        $char = $this->getChar();

        // Check to see if we're potentially in a comment
        if ($char !== '/') {
            return $char;
        }

        $this->c = $this->getChar();

        if ($this->c === '/') {
            $this->processOneLineComments($startIndex);

            return $this->getReal();
        } elseif ($this->c === '*') {
            $this->processMultiLineComments($startIndex);

            return $this->getReal();
        }

        return $char;
    }

    /**
     * Removed one line comments, with the exception of some very specific types of
     * conditional comments.
     *
     * @param  int  $startIndex The index point where "getReal" function started
     * @return void
     */
    protected function processOneLineComments($startIndex)
    {
        $thirdCommentString = $this->index < $this->len ? $this->input[$this->index] : false;

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

        unset($this->c);

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

    /**
     * Skips multiline comments where appropriate, and includes them where needed.
     * Conditional comments and "license" style blocks are preserved.
     *
     * @param  int               $startIndex The index point where "getReal" function started
     * @return void
     * @throws \RuntimeException Unclosed comments will throw an error
     */
    protected function processMultiLineComments($startIndex)
    {
        $this->getChar(); // current C
        $thirdCommentString = $this->getChar();

        // Detect a completely empty comment, ie `/**/`
        if ($thirdCommentString == "*") {
            $peekChar = $this->peek();
            if ($peekChar == "/") {
                $this->index++;
                return;
            }
        }

        // kill everything up to the next */ if it's there
        if ($this->getNext('*/')) {
            $this->getChar(); // get *
            $this->getChar(); // get /
            $char = $this->getChar(); // get next real character

            // Now we reinsert conditional comments and YUI-style licensing comments
            if (($this->options['flaggedComments'] && $thirdCommentString === '!')
                || ($thirdCommentString === '@')) {

                // If conditional comments or flagged comments are not the first thing in the script
                // we need to echo a and fill it with a space before moving on.
                if ($startIndex > 0) {
                    $this->echo($this->a);
                    $this->a = " ";

                    // If the comment started on a new line we let it stay on the new line
                    if ($this->input[($startIndex - 1)] === "\n") {
                        $this->echo("\n");
                    }
                }

                $endPoint = ($this->index - 1) - $startIndex;
                $this->echo(substr($this->input, $startIndex, $endPoint));

                $this->c = $char;

                return;
            }
        } else {
            $char = false;
        }

        if ($char === false) {
            throw new \RuntimeException('Unclosed multiline comment at position: ' . ($this->index - 2));
        }

        // if we're here c is part of the comment and therefore tossed
        $this->c = $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 and the index is set
     * to it's position.
     *
     * @param  string       $string
     * @return string|false Returns the first character of the string or false.
     */
    protected function getNext($string)
    {
        // Find the next occurrence of "string" after the current position.
        $pos = strpos($this->input, $string, $this->index);

        // If it's not there return false.
        if ($pos === false) {
            return false;
        }

        // Adjust position of index to jump ahead to the asked for string
        $this->index = $pos;

        // Return the first character of that string.
        return $this->index < $this->len ? $this->input[$this->index] : false;
    }

    /**
     * When a javascript string is detected this function crawls for the end of
     * it and saves the whole string.
     *
     * @throws \RuntimeException Unclosed strings will throw an error
     */
    protected function saveString()
    {
        $startpos = $this->index;

        // saveString is always called after a gets cleared, so we push b into
        // that spot.
        $this->a = $this->b;

        // If this isn't a string we don't need to do anything.
        if (!isset($this->stringDelimiters[$this->a])) {
            return;
        }

        // String type is the quote used, " or '
        $stringType = $this->a;

        // Echo out that starting quote
        $this->echo($this->a);

        // Loop until the string is done
        // Grab the very next character and load it into a
        while (($this->a = $this->getChar()) !== false) {
            switch ($this->a) {

                // If the string opener (single or double quote) is used
                // output it and break out of the while loop-
                // The string is finished!
                case $stringType:
                    break 2;

                // New lines in strings without line delimiters are bad- actual
                // new lines will be represented by the string \n and not the actual
                // character, so those will be treated just fine using the switch
                // block below.
                case "\n":
                    if ($stringType === '`') {
                        $this->echo($this->a);
                    } else {
                        throw new \RuntimeException('Unclosed string at position: ' . $startpos);
                    }
                    break;

                // Escaped characters get picked up here. If it's an escaped new line it's not really needed
                case '\\':

                    // a is a slash. We want to keep it, and the next character,
                    // unless it's a new line. New lines as actual strings will be
                    // preserved, but escaped new lines should be reduced.
                    $this->b = $this->getChar();

                    // If b is a new line we discard a and b and restart the loop.
                    if ($this->b === "\n") {
                        break;
                    }

                    // echo out the escaped character and restart the loop.
                    $this->echo($this->a . $this->b);
                    break;


                // Since we're not dealing with any special cases we simply
                // output the character and continue our loop.
                default:
                $this->echo($this->a);
            }
        }
    }

    /**
     * When a regular expression is detected this function crawls for the end of
     * it and saves the whole regex.
     *
     * @throws \RuntimeException Unclosed regex will throw an error
     */
    protected function saveRegex()
    {
        if ($this->a != " ") {
            $this->echo($this->a);
        }

        $this->echo($this->b);

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

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

            if ($this->a === "\n") {
                throw new \RuntimeException('Unclosed regex pattern at position: ' . $this->index);
            }

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

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

    protected function endsInKeyword() {

        # When this function is called A is not yet assigned to output.
        # Regular expression only needs to check final part of output for keyword.
        $testOutput = substr($this->output . $this->a, -1 * ($this->max_keyword_len + 10));

        foreach(static::$keywords as $keyword) {
            if (preg_match('/[^\w]'.$keyword.'[ ]?$/i', $testOutput) === 1) {
                return true;
            }
        }
        return false;
    }



    /**
     * Replace patterns in the given string and store the replacement
     *
     * @param  string $js The string to lock
     * @return bool
     */
    protected function lock($js)
    {
        /* lock things like <code>"asd" + ++x;</code> */
        $lock = '"LOCK---' . crc32(time()) . '"';

        $matches = [];
        preg_match('/([+-])(\s+)([+-])/S', $js, $matches);
        if (empty($matches)) {
            return $js;
        }

        $this->locks[$lock] = $matches[2];

        $js = preg_replace('/([+-])\s+([+-])/S', "$1{$lock}$2", $js);
        /* -- */

        return $js;
    }

    /**
     * Replace "locks" with the original characters
     *
     * @param  string $js The string to unlock
     * @return bool
     */
    protected function unlock($js)
    {
        if (empty($this->locks)) {
            return $js;
        }

        foreach ($this->locks as $lock => $replacement) {
            $js = str_replace($lock, $replacement, $js);
        }

        return $js;
    }
}
