codenothing/CSSTree

var rselectornested = /[:#\[\.]/,
    rselectorpart = /[>~\+\*\,]/,
    rwhitespace = /(\s|\t|\r\n|\r|\n)/;


function Selector( selector, rules, position ) {
    var self = this;

    if ( ! ( self instanceof Selector ) ) {
        return new Selector( selector, rules, position );
    }

    self.selector = ( selector || '' ).trim();
    self.position = position;
    self.parts = [];
    self.rules = rules || [];
    self.breakdown();
}

Selector.prototype = {

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

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

            // Selector breaker (whitespace, comma, etc...)
            if ( rselectorpart.exec( c ) || rwhitespace.exec( c ) ) {
                part = part.trim();

                if ( nested !== null ) {
                    if ( part.length ) {
                        nested.push( part );
                    }

                    parts.push( nested );
                }
                else if ( part.length ) {
                    parts.push( part );
                }

                if ( ! rwhitespace.exec( c ) ) {
                    parts.push( c );
                }

                nested = null;
                part = '';
            }
            // Inside selector, but still need to break apart ('span.class')
            else if ( part.length && rselectornested.exec( c ) ) {
                part = part.trim();

                // Catch whitespace parts and just continue on
                if ( ! part.length ) {
                    part = c;
                    continue;
                }

                // Add part to nested array
                if ( nested === null ) {
                    nested = [ part ];
                }
                else {
                    nested.push( part );
                }

                // Create new part
                part = c;

                // Seek to closing brace
                if ( c == '[' ) {
                    for ( ; ++i < l; ) {
                        c = selector[ i ];
                        part += c;

                        if ( c == "\\" ) {
                            part += selector[ ++i ];
                        }
                        else if ( innerSeek !== null ) {
                            if ( c == innerSeek ) {
                                innerSeek = null;
                            }
                        }
                        else if ( c == '"' || c == "'" ) {
                            innerSeek = c;
                        }
                        else if ( c == ']' ) {
                            nested.push( part );
                            part = '';
                            break;
                        }
                    }
                }
            }
            else {
                part += c;
            }
        }

        // Catch the last part if it exists
        if ( ( part = part.trim() ).length || nested !== null ) {
            if ( nested !== null ) {
                if ( part.length ) {
                    nested.push( part );
                }

                parts.push( nested );
            }
            else {
                parts.push( part );
            }
        }

        // Apply parts back to object
        self.parts = parts;
    }

};

global.CSSTree.Selector = Selector;