<?php
/**
* @package   Warp Theme Framework
* @author    YOOtheme http://www.yootheme.com
* @copyright Copyright (C) YOOtheme GmbH
* @license   http://www.gnu.org/licenses/gpl.html GNU/GPL
*/

namespace Warp\Asset\Filter;

/**
 * Javascript compressor, minifies javascript.
 * Based on JSMin (https://github.com/mrclay/minify, Ryan Grove <ryan@wonko.com>, Stephen Clay <steve@mrclay.org>, BSD License)
 */
class JsCompressorFilter implements FilterInterface
{
    const ORD_LF            = 10;
    const ORD_SPACE         = 32;
    const ACTION_KEEP_A     = 1;
    const ACTION_DELETE_A   = 2;
    const ACTION_DELETE_A_B = 3;

    protected $a           = "\n";
    protected $b           = '';
    protected $input       = '';
    protected $inputIndex  = 0;
    protected $inputLength = 0;
    protected $lookAhead   = null;
    protected $output      = '';
    protected $lastByteOut = '';

    /**
     * Filter callbacks,
     */
    public function filterLoad($asset) {}

    public function filterContent($asset)
    {
        $asset->setContent($this->process($asset->getContent()));
    }

    /**
     * Minify Javascript.
     *
     * @param string $script Javascript to be minified
     *
     * @return string
     */
    public function process($script)
    {
        // init vars
        $this->a           = "\n";
        $this->b           = '';
        $this->input       = $script;
        $this->inputIndex  = 0;
        $this->inputLength = 0;
        $this->lookAhead   = null;
        $this->output      = '';
        $this->lastByteOut = '';

        try {
            $script = trim($this->min());
        } catch (Exception $e) {}

        return $script;
    }

    /**
     * Perform minification, return result
     *
     * @return string
     */
    public function min()
    {
        if ($this->output !== '') { // min already run
            return $this->output;
        }

        $mbIntEnc = null;
        if (function_exists('mb_strlen') && ((int)ini_get('mbstring.func_overload') & 2)) {
            $mbIntEnc = mb_internal_encoding();
            mb_internal_encoding('8bit');
        }
        $this->input = str_replace("\r\n", "\n", $this->input);
        $this->inputLength = strlen($this->input);

        $this->action(self::ACTION_DELETE_A_B);

        while ($this->a !== null) {
            // determine next command
            $command = self::ACTION_KEEP_A; // default
            if ($this->a === ' ') {
                if (($this->lastByteOut === '+' || $this->lastByteOut === '-')
                    && ($this->b === $this->lastByteOut)) {
                    // Don't delete this space. If we do, the addition/subtraction
                    // could be parsed as a post-increment
                } elseif (! $this->isAlphaNum($this->b)) {
                    $command = self::ACTION_DELETE_A;
                }
            } elseif ($this->a === "\n") {
                if ($this->b === ' ') {
                    $command = self::ACTION_DELETE_A_B;
                // in case of mbstring.func_overload & 2, must check for null b,
                // otherwise mb_strpos will give WARNING
                } elseif ($this->b === null
                          || (false === strpos('{[(+-', $this->b)
                              && ! $this->isAlphaNum($this->b))) {
                    $command = self::ACTION_DELETE_A;
                }
            } elseif (! $this->isAlphaNum($this->a)) {
                if ($this->b === ' '
                    || ($this->b === "\n"
                        && (false === strpos('}])+-"\'', $this->a)))) {
                    $command = self::ACTION_DELETE_A_B;
                }
            }
            $this->action($command);
        }
        $this->output = trim($this->output);

        if ($mbIntEnc !== null) {
            mb_internal_encoding($mbIntEnc);
        }
        return $this->output;
    }

    /**
     * ACTION_KEEP_A = Output A. Copy B to A. Get the next B.
     * ACTION_DELETE_A = Copy B to A. Get the next B.
     * ACTION_DELETE_A_B = Get the next B.
     *
     * @param int $command
     * @throws Exception
     */
    protected function action($command)
    {
        if ($command === self::ACTION_DELETE_A_B
            && $this->b === ' '
            && ($this->a === '+' || $this->a === '-')) {
            // Note: we're at an addition/substraction operator; the inputIndex
            // will certainly be a valid index
            if ($this->input[$this->inputIndex] === $this->a) {
                // This is "+ +" or "- -". Don't delete the space.
                $command = self::ACTION_KEEP_A;
            }
        }
        switch ($command) {
            case self::ACTION_KEEP_A:
                $this->output .= $this->a;
                $this->lastByteOut = $this->a;

                // fallthrough
            case self::ACTION_DELETE_A:
                $this->a = $this->b;
                if ($this->a === "'" || $this->a === '"') { // string literal
                    $str = $this->a; // in case needed for exception
                    while (true) {
                        $this->output .= $this->a;
                        $this->lastByteOut = $this->a;

                        $this->a       = $this->get();
                        if ($this->a === $this->b) { // end quote
                            break;
                        }
                        if (ord($this->a) <= self::ORD_LF) {
                            throw new Exception(
                                "JSMin: Unterminated String at byte "
                                . $this->inputIndex . ": {$str}");
                        }
                        $str .= $this->a;
                        if ($this->a === '\\') {
                            $this->output .= $this->a;
                            $this->lastByteOut = $this->a;

                            $this->a       = $this->get();
                            $str .= $this->a;
                        }
                    }
                }
                // fallthrough
            case self::ACTION_DELETE_A_B:
                $this->b = $this->next();
                if ($this->b === '/' && $this->isRegexpLiteral()) { // RegExp literal
                    $this->output .= $this->a . $this->b;
                    $pattern = '/'; // in case needed for exception
                    while (true) {
                        $this->a = $this->get();
                        $pattern .= $this->a;
                        if ($this->a === '/') { // end pattern
                            break; // while (true)
                        } elseif ($this->a === '\\') {
                            $this->output .= $this->a;
                            $this->a       = $this->get();
                            $pattern      .= $this->a;
                        } elseif (ord($this->a) <= self::ORD_LF) {
                            throw new Exception(
                                "JSMin: Unterminated RegExp at byte "
                                . $this->inputIndex .": {$pattern}");
                        }
                        $this->output .= $this->a;
                        $this->lastByteOut = $this->a;
                    }
                    $this->b = $this->next();
                }
            // end case ACTION_DELETE_A_B
        }
    }

    /**
     * @return bool
     */
    protected function isRegexpLiteral()
    {
        if (false !== strpos("\n{;(,=:[!&|?", $this->a)) { // we aren't dividing
            return true;
        }
        if (' ' === $this->a) {
            $length = strlen($this->output);
            if ($length < 2) { // weird edge case
                return true;
            }
            // you can't divide a keyword
            if (preg_match('/(?:case|else|in|return|typeof)$/', $this->output, $m)) {
                if ($this->output === $m[0]) { // odd but could happen
                    return true;
                }
                // make sure it's a keyword, not end of an identifier
                $charBeforeKeyword = substr($this->output, $length - strlen($m[0]) - 1, 1);
                if (! $this->isAlphaNum($charBeforeKeyword)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Get next char. Convert ctrl char to space.
     *
     * @return string
     */
    protected function get()
    {
        $c = $this->lookAhead;
        $this->lookAhead = null;
        if ($c === null) {
            if ($this->inputIndex < $this->inputLength) {
                $c = $this->input[$this->inputIndex];
                $this->inputIndex += 1;
            } else {
                return null;
            }
        }
        if ($c === "\r" || $c === "\n") {
            return "\n";
        }
        if (ord($c) < self::ORD_SPACE) { // control char
            return ' ';
        }
        return $c;
    }

    /**
     * Get next char. If is ctrl character, translate to a space or newline.
     *
     * @return string
     */
    protected function peek()
    {
        $this->lookAhead = $this->get();
        return $this->lookAhead;
    }

    /**
     * Is $c a letter, digit, underscore, dollar sign, escape, or non-ASCII?
     *
     * @param string $c
     *
     * @return bool
     */
    protected function isAlphaNum($c)
    {
        return (preg_match('/^[0-9a-zA-Z_\\$\\\\]$/', $c) || ord($c) > 126);
    }

    /**
     * @return string
     */
    protected function singleLineComment()
    {
        $comment = '';
        while (true) {
            $get = $this->get();
            $comment .= $get;
            if (ord($get) <= self::ORD_LF) { // EOL reached
                // if IE conditional comment
                if (preg_match('/^\\/@(?:cc_on|if|elif|else|end)\\b/', $comment)) {
                    return "/{$comment}";
                }
                return $get;
            }
        }
    }

    /**
     * @return string
     * @throws Exception
     */
    protected function multipleLineComment()
    {
        $this->get();
        $comment = '';
        while (true) {
            $get = $this->get();
            if ($get === '*') {
                if ($this->peek() === '/') { // end of comment reached
                    $this->get();
                    // if comment preserved by YUI Compressor
                    if (0 === strpos($comment, '!')) {
                        return "\n/*!" . substr($comment, 1) . "*/\n";
                    }
                    // if IE conditional comment
                    if (preg_match('/^@(?:cc_on|if|elif|else|end)\\b/', $comment)) {
                        return "/*{$comment}*/";
                    }
                    return ' ';
                }
            } elseif ($get === null) {
                throw new Exception(
                    "JSMin: Unterminated comment at byte "
                    . $this->inputIndex . ": /*{$comment}");
            }
            $comment .= $get;
        }
    }

    /**
     * Get the next character, skipping over comments.
     * Some comments may be preserved.
     *
     * @return string
     */
    protected function next()
    {
        $get = $this->get();
        if ($get !== '/') {
            return $get;
        }
        switch ($this->peek()) {
            case '/': return $this->singleLineComment();
            case '*': return $this->multipleLineComment();
            default: return $get;
        }
    }
}
