define([], function () {
    // this makes recursing a lot simpler
    var isArray = function (A) {
        return Object.prototype.toString.call(A)==='[object Array]';
    };

    var parseStyle = function(el){
      var style = el.style;
      var output = {};
      for (var i = 0; i < style.length; ++i) {
        var item = style.item(i);
        output[item] = style[item];
      }
      return output;
    };

    var callOnHyperJSON = function (hj, cb) {
        var children;

        if (hj && hj[2]) {
            children = hj[2].map(function (child) {
                if (isArray(child)) {
                    // if the child is an array, recurse
                    return callOnHyperJSON(child, cb);
                } else if (typeof (child) === 'string') {
                    // string nodes have leading and trailing quotes
                    return child.replace(/(^"|"$)/g,"");
                } else {
                    // the above branches should cover all methods
                    // if we hit this, there is a problem
                    throw new Error();
                }
            });
        } else {
            children = [];
        }
        // this should return the top level element of your new DOM
        return cb(hj[0], hj[1], children);
    };

    var classify = function (token) {
        return '.' + token.trim();
    };

    var isValidClass = function (x) {
        if (x && /\S/.test(x)) {
            return true;
        }
    };

    var isTruthy = function (x) {
        return x;
    };

    /* DOM2HyperJSON accepts a DOM element/node
        and converts it into Hyperjson. It optionally accepts a predicate
        which is used for filtering out subtrees of the DOM from the result.

        The function, if provided, must return true for elements which
        should be preserved, and 'false' for elements which should be removed.
    */
    var DOM2HyperJSON = function(el, predicate, filter){
        if(!el.tagName && el.nodeType === Node.TEXT_NODE){
            return el.textContent;
        }
        if(!el.attributes){
          return;
        }
        if (predicate) {
            if (!predicate(el)) {
                // shortcircuit
                return;
            }
        }

        var attributes = {};

        var i = 0;
        for(;i < el.attributes.length; i++){
          var attr = el.attributes[i];
          if(attr.name && attr.value){
            if(attr.name === "style"){
              attributes.style = parseStyle(el);
            }
            else{
              attributes[attr.name] = attr.value;
            }
          }
        }

        // this should never be longer than three elements
        var result = [];

        // get the element type, id, and classes of the element
        // and push them to the result array
        var sel = el.tagName;

        if(attributes.id){
            // we don't have to do much to validate IDs because the browser
            // will only permit one id to exist
            // unless we come across a strange browser in the wild
          sel = sel +'#'+ attributes.id;
          delete attributes.id;
        }
        if(attributes.class){
            // actually parse out classes so that we produce a valid selector
            // string. leading or trailing spaces would have caused it to choke
            // these are really common in generated html
            /* TODO this can be done with RegExps alone, and it will be faster
                but this works and is a little less error prone, albeit slower
                come back and speed it up when it comes time to optimize */
          sel = sel + attributes.class
            .split(/\s+/g)
            .filter(isValidClass)
            .map(classify)
            .join('')
            .replace(/\.\./g, '.');
          delete attributes.class;
        }
        result.push(sel);

        // second element of the array is the element attributes
        result.push(attributes);

        // third element of the array is an array of child nodes
        var children = [];

        // js hint complains if we use 'var' here
        i = 0;
        for(; i < el.childNodes.length; i++){
            children.push(DOM2HyperJSON(el.childNodes[i], predicate, filter));
        }
        result.push(children.filter(isTruthy));

        if (filter) {
            return filter(result);
        } else {
            return result;
        }
    };

    return {
        fromDOM: DOM2HyperJSON,
        callOn: callOnHyperJSON
    };
});