codenothing/CSSCompressor

/**
 * 
 * Order Atrules
 * 
 * @author: Corey Hart <http://www.codenothing.com>
 * @description: Moves charset and import declarations to the top of the stylesheet (to help with concatenation)
 * 
 * @before:
 *     .example {
 *         color: red;
 *     }
 *
 *     @charset 'utf-8';
 *     @import 'home.css';
 * 
 * @after:
 *     @charset 'utf-8';
 *     @import 'home.css';
 *
 *     .example {
 *         color: red;
 *     }
 * 
 */

var CSSCompressor = global.CSSCompressor,
    rcharset = /^@charset$/i,
    rimport = /^@import$/i;

CSSCompressor.rule({

    name: 'Order Atrules',
    type: CSSCompressor.RULE_TYPE_SHEET,
    group: 'Selector',
    description: "Moves charset and import declarations to the top of the stylesheet (to help with concatenation)",

    callback: function( branches, compressor ) {
        var imports = [], charsets = [], pos = -1;

        // Find all import and charset declarations (after the first rule filled branch)
        branches.forEach(function( branch, i ) {
            if ( pos === -1 ) {
                if ( ( branch.rules && branch.rules.length ) || ( branch.branches && branch.branches.length ) ) {
                    pos = i;
                }
            }
            else if ( branch.atrule && branch.parts && branch.parts.length ) {
                if ( rcharset.exec( branch.parts[ 0 ] || '' ) ) {
                    charsets.push( branch );
                }
                else if ( rimport.exec( branch.parts[ 0 ] || '' ) ) {
                    imports.push( branch );
                }
            }
        });

        // Shift imports to the top
        if ( imports.length ) {
            imports.forEach(function( branch ) {
                CSSCompressor.removeItem( branches, branch );
                branches.splice( pos, 0, branch );
                compressor.log( 'Moving import to the top', branch.position );
            });
        }

        // Shift charset to the top after imports
        if ( charsets.length ) {
            charsets.forEach(function( branch ) {
                CSSCompressor.removeItem( branches, branch );
                branches.splice( pos, 0, branch );
                compressor.log( 'Moving charset to the top', branch.position );
            });
        }
    }

});