codenothing/CSSCompressor

/**
 * 
 * Calc Units
 * 
 * @author: Corey Hart <http://www.codenothing.com>
 * @description: Compresses individual units in calc function, and removes whitespace
 * 
 * @before:
 *     .example {
 *         width: calc( 100% - 10.0px );
 *     }
 * 
 * @after:
 *     .example {
 *         width: calc(100% - 10px);
 *     }
 * 
 */

var CSSCompressor = global.CSSCompressor,
    StringIterator = CSSCompressor.StringIterator,
    rcalc = /^((-webkit-|-moz-)?calc)\(([^\)]+)\)$/i,
    rwhitespace = /\r\n|\r|\n|\t|\s/,
    roperator = /^\*|\/|\+|\-$/;

CSSCompressor.rule({

    name: 'Calc Units',
    type: CSSCompressor.RULE_TYPE_VALUE,
    group: 'Numeric',
    description: "Compresses individual units in calc function, and removes whitespace",

    callback: function( value, position, compressor ) {
        var m = rcalc.exec( value ),
            before = value,
            prefix = ( m || [] )[ 1 ] || '',
            iter = new StringIterator( ( m || [] )[ 3 ] || '' ),
            string = '', parts = [];

        if ( iter.length > 0 ) {
            iter.each(function( c ) {
                if ( c == "\\" ) {
                    string += c + iter.skip();
                }
                else if ( c == '*' || c == '/' ) {
                    parts.push( string.trim() );
                    parts.push( c );
                    string = '';
                }
                else if ( ( c == '-' || c == '+' ) && rwhitespace.exec( iter.next ) ) {
                    parts.push( string.trim() );
                    parts.push( c );
                    string = '';
                }
                else {
                    string += c;
                }
            });

            // Catch last part
            if ( string.length ) {
                parts.push( string.trim() );
            }

            // Only work if you have values
            if ( parts.length ) {
                string = prefix + '(';

                // Compress individual units
                parts.forEach(function( part ) {
                    if ( ! roperator.exec( part ) ) {
                        part = compressor.value( part );
                    }

                    if ( part == '+' || part == '-' ) {
                        part = ' ' + part + ' ';
                    }

                    string += part;
                });

                // Finalize calc
                string += ')';

                // Only log if a change actually occured
                if ( string !== value ) {
                    compressor.log(
                        "Removing unecesary trailing zeroes '" + before + "' => '" + string + "'",
                        position
                    );

                    return string;
                }
            }
        }
    }

});