/* document.getElementsBySelector(selector)
 - returns an array of element objects from the current document
 matching the CSS selector. Selectors can contain element names,
 class names and ids and can be nested. For example:

 elements = document.getElementsBySelect('div#main p a.external')

 Will return an array of all 'a' elements with 'external' in their
 class attribute that are contained inside 'p' elements that are
 contained inside the 'div' element which has id="main"

 New in version 0.4: Support for CSS2 and CSS3 attribute selectors:
 See http://www.w3.org/TR/css3-selectors/#attribute-selectors

 Version 0.4 - Simon Willison, March 25th 2003
 -- Works in Phoenix 0.5, Mozilla 1.3, Opera 7, Internet Explorer 6, Internet Explorer 5 on Windows
 -- Opera 7 fails
 */

function getAllChildren(e) {
    // Returns all children of element. Workaround required for IE5/Windows. Ugh.
    return e.all ? e.all : e.getElementsByTagName('*');
}

document.getElementsBySelector = function(selector) {
    // Attempt to fail gracefully in lesser browsers
    if (!document.getElementsByTagName) {
        return new Array();
    }
    // Split selector in to tokens
    var tokens = selector.split(' ');
    var currentContext = new Array(document);
    for (var i = 0; i < tokens.length; i++) {
        token = tokens[i].replace(/^\s+/, '').replace(/\s+$/, '');
        ;
        if (token.indexOf('#') > -1) {
            // Token is an ID selector
            var bits = token.split('#');
            var tagName = bits[0];
            var id = bits[1];
            var element = document.getElementById(id);
            if (!element || (tagName && element.nodeName.toLowerCase() != tagName)) {
                // ID not found or tag with that ID not found, return false.
                return new Array();
            }
            // Set currentContext to contain just this element
            currentContext = new Array(element);
            continue; // Skip to next token
        }
        if (token.indexOf('.') > -1) {
            // Token contains a class selector
            var bits = token.split('.');
            var tagName = bits[0];
            var className = bits[1];
            if (!tagName) {
                tagName = '*';
            }
            // Get elements matching tag, filter them for class selector
            var found = new Array;
            var foundCount = 0;
            for (var h = 0; h < currentContext.length; h++) {
                var elements;
                if (tagName == '*') {
                    elements = getAllChildren(currentContext[h]);
                } else {
                    try {
                        elements = currentContext[h].getElementsByTagName(tagName);
                    }
                    catch(e) {
                        elements = [];
                    }
                }
                for (var j = 0; j < elements.length; j++) {
                    found[foundCount++] = elements[j];
                }
            }
            currentContext = new Array;
            var currentContextIndex = 0;
            for (var k = 0; k < found.length; k++) {
                if (found[k].className && found[k].className.match(new RegExp('\\b' + className + '\\b'))) {
                    currentContext[currentContextIndex++] = found[k];
                }
            }
            continue; // Skip to next token
        }
        // Code to deal with attribute selectors
        if (token.match(/^(\w*)\[(\w+)([=~\|\^\$\*]?)=?"?([^\]"]*)"?\]$/)) {
            var tagName = RegExp.$1;
            var attrName = RegExp.$2;
            var attrOperator = RegExp.$3;
            var attrValue = RegExp.$4;
            if (!tagName) {
                tagName = '*';
            }
            // Grab all of the tagName elements within current context
            var found = new Array;
            var foundCount = 0;
            for (var h = 0; h < currentContext.length; h++) {
                var elements;
                if (tagName == '*') {
                    elements = getAllChildren(currentContext[h]);
                } else {
                    elements = currentContext[h].getElementsByTagName(tagName);
                }
                for (var j = 0; j < elements.length; j++) {
                    found[foundCount++] = elements[j];
                }
            }
            currentContext = new Array;
            var currentContextIndex = 0;
            var checkFunction; // This function will be used to filter the elements
            switch (attrOperator) {
                case '=': // Equality
                    checkFunction = function(e) {
                        return (e.getAttribute(attrName) == attrValue);
                    };
                    break;
                case '~': // Match one of space seperated words
                    checkFunction = function(e) {
                        return (e.getAttribute(attrName).match(new RegExp('\\b' + attrValue + '\\b')));
                    };
                    break;
                case '|': // Match start with value followed by optional hyphen
                    checkFunction = function(e) {
                        return (e.getAttribute(attrName).match(new RegExp('^' + attrValue + '-?')));
                    };
                    break;
                case '^': // Match starts with value
                    checkFunction = function(e) {
                        return (e.getAttribute(attrName).indexOf(attrValue) == 0);
                    };
                    break;
                case '$': // Match ends with value - fails with "Warning" in Opera 7
                    checkFunction = function(e) {
                        return (e.getAttribute(attrName).lastIndexOf(attrValue) == e.getAttribute(attrName).length - attrValue.length);
                    };
                    break;
                case '*': // Match ends with value
                    checkFunction = function(e) {
                        return (e.getAttribute(attrName).indexOf(attrValue) > -1);
                    };
                    break;
                default :
                    // Just test for existence of attribute
                    checkFunction = function(e) {
                        return e.getAttribute(attrName);
                    };
            }
            currentContext = new Array;
            var currentContextIndex = 0;
            for (var k = 0; k < found.length; k++) {
                if (checkFunction(found[k])) {
                    currentContext[currentContextIndex++] = found[k];
                }
            }
            // alert('Attribute Selector: '+tagName+' '+attrName+' '+attrOperator+' '+attrValue);
            continue; // Skip to next token
        }
        // If we get here, token is JUST an element (not a class or ID selector)
        tagName = token;
        var found = new Array;
        var foundCount = 0;
        for (var h = 0; h < currentContext.length; h++) {
            var elements = currentContext[h].getElementsByTagName(tagName);
            for (var j = 0; j < elements.length; j++) {
                found[foundCount++] = elements[j];
            }
        }
        currentContext = found;
    }
    return currentContext;
}

/* That revolting regular expression explained 
 /^(\w+)\[(\w+)([=~\|\^\$\*]?)=?"?([^\]"]*)"?\]$/
 \---/  \---/\-------------/    \-------/
 |      |         |               |
 |      |         |           The value
 |      |    ~,|,^,$,* or =
 |   Attribute
 Tag
 */
