codenothing/CSSCompressor

/**
 * 
 * Sort Multi Selectors
 * 
 * @author: Corey Hart <http://www.codenothing.com>
 * @description: Sorts comma separated selectors for a better chance at compression during gzip
 * 
 * @before:
 *     span, b, div, a {
 *         color: red;
 *     }
 * 
 * @after:
 *     a, b, div, span {
 *         color: red;
 *     }
 * 
 */

var CSSCompressor = global.CSSCompressor;

CSSCompressor.rule({

    name: 'Sort Multi Selectors',
    type: CSSCompressor.RULE_TYPE_BLOCK,
    group: 'GZIP',
    description: "Sorts comma separated selectors for a better chance at compression during gzip",
    priority: CSSCompressor.PRIORITY_LOW,

    callback: function( branch, compressor ) {
        if ( ! branch.selector || ! branch.parts || ! branch.parts.length ) {
            return;
        }

        var section = { selector: '', parts: [] },
            sections = [ section ],
            parts = [], compare;

        // Build out each section for reference
        branch.parts.forEach(function( part ) {
            if ( part == ',' ) {
                sections.push( section = { selector: '', parts: [] } );
            }
            else {
                if ( section.selector.length ) {
                    section.selector += ' ';
                }

                section.selector += CSSCompressor.isArray( part ) ? part.join( '' ) : part;
                section.parts.push( part );
            }
        });

        // Generate a sorted comparison array to see if order has changed
        compare = sections.slice( 0 ).sort(function( a, b ) {
            if ( a.selector.length && b.selector.length ) {
                return a.selector == b.selector ? 0 :
                    a.selector > b.selector ? 1 : -1;
            }
            else {
                return a.selector.length ? 1 : -1;
            }
        });

        // Order changed, apply and log
        if ( ! CSSCompressor.objectsMatch( compare, sections ) ) {
            compare.forEach(function( section, i ) {
                parts = parts.concat( section.parts );
                if ( i + 1 !== compare.length ) {
                    parts.push( ',' );
                }
            });
            branch.parts = parts;
            compressor.log( 'Sorted comma separated selectors', branch.position );
        }
    }

});