codenothing/CSSTree

var rwhitespace = /(\s|\t|\r\n|\r|\n)/,
    rvalueseparator = /\/|,/,
    rvalueseek = /"|'|\(/;


function Rule( property, value, position ) {
    var self = this;

    if ( ! ( self instanceof Rule ) ) {
        return new Rule( property, value, position );
    }

    self.property = ( property || '' ).trim();
    self.value = ( value || '' ).trim();
    self.position = position;
    self.parts = [];
    self.breakdown();
}

Rule.prototype = {

    breakdown: function(){
        var self = this, value = self.value,
            parts = [], i = -1, l = value.length, part = '', c, seek;

        for ( ; ++i < l; ) {
            c = value[ i ];

            // Whitespace is a value separator
            if ( rwhitespace.exec( c ) ) {
                if ( ( part = part.trim() ).length ) {
                    parts.push( part );
                }

                part = '';
            }
            // Value separator
            else if ( rvalueseparator.exec( c ) ) {
                if ( ( part = part.trim() ).length ) {
                    parts.push( part );
                }

                parts.push( c );
                part = '';
            }
            // Read all characters in a seek sequence (url(...), "...", '...', etc)
            else if ( rvalueseek.exec( c ) ) {
                part += c;
                seek = c == '(' ? ')' : c;

                // Find end char
                for ( ; ++i < l; ) {
                    c = value[ i ];
                    part += c;

                    // End char found, break off and attach part
                    if ( c == seek ) {
                        break;
                    }
                    // Skip over escaped values
                    else if ( c == "\\" && value[ i + 1 ] ) {
                        part += value[ ++i ];
                    }
                }

                parts.push( part );
                part = '';
            }
            else {
                part += c;
            }
        }

        // Attach final leftover part
        if ( part.length ) {
            parts.push( part );
        }

        self.parts = parts;
    }

};

global.CSSTree.Rule = Rule;