<?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;

/**
 * Stylesheet compressor, minifies css.
 * Based on Minify_CSS_Compressor (https://github.com/mrclay/minify, Ryan Grove <ryan@wonko.com>, Stephen Clay <steve@mrclay.org>, BSD License)
 */
class CssCompressorFilter implements FilterInterface
{
    /**
     * @var bool Are we "in" a hack?
     *
     * I.e. are some browsers targetted until the next comment?
     */
    protected $_inHack = false;

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

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

    /**
     * Minify a CSS string
     *
     * @param string $css
     *
     * @return string
     */
    public function process($css)
    {
        $css = str_replace("\r\n", "\n", $css);

        // preserve empty comment after '>'
        // http://www.webdevout.net/css-hacks#in_css-selectors
        $css = preg_replace('@>/\\*\\s*\\*/@', '>/*keep*/', $css);

        // preserve empty comment between property and value
        // http://css-discuss.incutio.com/?page=BoxModelHack
        $css = preg_replace('@/\\*\\s*\\*/\\s*:@', '/*keep*/:', $css);
        $css = preg_replace('@:\\s*/\\*\\s*\\*/@', ':/*keep*/', $css);

        // apply callback to all valid comments (and strip out surrounding ws
        $css = preg_replace_callback('@\\s*/\\*([\\s\\S]*?)\\*/\\s*@'
            ,array($this, '_commentCB'), $css);

        // remove ws around { } and last semicolon in declaration block
        $css = preg_replace('/\\s*{\\s*/', '{', $css);
        $css = preg_replace('/;?\\s*}\\s*/', '}', $css);

        // remove ws surrounding semicolons
        $css = preg_replace('/\\s*;\\s*/', ';', $css);

        // remove ws around urls
        $css = preg_replace('/
                url\\(      # url(
                \\s*
                ([^\\)]+?)  # 1 = the URL (really just a bunch of non right parenthesis)
                \\s*
                \\)         # )
            /x', 'url($1)', $css);

        // remove ws between rules and colons
        $css = preg_replace('/
                \\s*
                ([{;])              # 1 = beginning of block or rule separator
                \\s*
                ([\\*_]?[\\w\\-]+)  # 2 = property (and maybe IE filter)
                \\s*
                :
                \\s*
                (\\b|[#\'"-])       # 3 = first character of a value
            /x', '$1$2:$3', $css);

        // remove ws in selectors
        $css = preg_replace_callback('/
                (?:              # non-capture
                    \\s*
                    [^~>+,\\s]+  # selector part
                    \\s*
                    [,>+~]       # combinators
                )+
                \\s*
                [^~>+,\\s]+      # selector part
                {                # open declaration block
            /x'
            ,array($this, '_selectorsCB'), $css);

        // minimize hex colors
        $css = preg_replace('/([^=])#([a-f\\d])\\2([a-f\\d])\\3([a-f\\d])\\4([\\s;\\}])/i'
            , '$1#$2$3$4$5', $css);

        // remove spaces between font families
        $css = preg_replace_callback('/font-family:([^;}]+)([;}])/'
            ,array($this, '_fontFamilyCB'), $css);

        $css = preg_replace('/@import\\s+url/', '@import url', $css);

        // replace any ws involving newlines with a single newline
        $css = preg_replace('/[ \\t]*\\n+\\s*/', "\n", $css);

        // separate common descendent selectors w/ newlines (to limit line lengths)
        $css = preg_replace('/([\\w#\\.\\*]+)\\s+([\\w#\\.\\*]+){/', "$1\n$2{", $css);

        // Use newline after 1st numeric value (to limit line lengths).
        $css = preg_replace('/
            ((?:padding|margin|border|outline):\\d+(?:px|em)?) # 1 = prop : 1st numeric value
            \\s+
            /x'
            ,"$1\n", $css);

        // prevent triggering IE6 bug: http://www.crankygeek.com/ie6pebug/
        $css = preg_replace('/:first-l(etter|ine)\\{/', ':first-l$1 {', $css);

        return trim($css);
    }

    /**
     * Replace what looks like a set of selectors
     *
     * @param array $m regex matches
     *
     * @return string
     */
    protected function _selectorsCB($m)
    {
        // remove ws around the combinators
        return preg_replace('/\\s*([,>+~])\\s*/', '$1', $m[0]);
    }

    /**
     * Process a comment and return a replacement
     *
     * @param array $m regex matches
     *
     * @return string
     */
    protected function _commentCB($m)
    {
        $hasSurroundingWs = (trim($m[0]) !== $m[1]);
        $m = $m[1];

        // $m is the comment content w/o the surrounding tokens,
        // but the return value will replace the entire comment.
        if ($m === 'keep') {
            return '/**/';
        }

        if ($m === '" "') {
            // component of http://tantek.com/CSS/Examples/midpass.html
            return '/*" "*/';
        }

        if (preg_match('@";\\}\\s*\\}/\\*\\s+@', $m)) {
            // component of http://tantek.com/CSS/Examples/midpass.html
            return '/*";}}/* */';
        }

        if ($this->_inHack) {
            // inversion: feeding only to one browser
            if (preg_match('@
                    ^/               # comment started like /*/
                    \\s*
                    (\\S[\\s\\S]+?)  # has at least some non-ws content
                    \\s*
                    /\\*             # ends like /*/ or /**/
                @x', $m, $n)) {
                // end hack mode after this comment, but preserve the hack and comment content
                $this->_inHack = false;
                return "/*/{$n[1]}/**/";
            }
        }

        if (substr($m, -1) === '\\') { // comment ends like \*/
            // begin hack mode and preserve hack
            $this->_inHack = true;
            return '/*\\*/';
        }

        if ($m !== '' && $m[0] === '/') { // comment looks like /*/ foo */
            // begin hack mode and preserve hack
            $this->_inHack = true;
            return '/*/*/';
        }

        if ($this->_inHack) {
            // a regular comment ends hack mode but should be preserved
            $this->_inHack = false;
            return '/**/';
        }

        // Issue 107: if there's any surrounding whitespace, it may be important, so
        // replace the comment with a single space
        return $hasSurroundingWs // remove all other comments
            ? ' '
            : '';
    }

    /**
     * Process a font-family listing and return a replacement
     *
     * @param array $m regex matches
     *
     * @return string
     */
    protected function _fontFamilyCB($m)
    {
        $m[1] = preg_replace('/
                \\s*
                (
                    "[^"]+"      # 1 = family in double qutoes
                    |\'[^\']+\'  # or 1 = family in single quotes
                    |[\\w\\-]+   # or 1 = unquoted family
                )
                \\s*
            /x', '$1', $m[1]);

        return 'font-family:' . $m[1] . $m[2];
    }
}
