/**
 * Copyright 2014 Craig Campbell
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * GATOR.JS
 * Simple Event Delegation
 *
 * @version 1.2.4
 *
 * Compatible with IE 9+, FF 3.6+, Safari 5+, Chrome
 *
 * Include legacy.js for compatibility with older browsers
 *
 *             .-._   _ _ _ _ _ _ _ _
 *  .-''-.__.-'00  '-' ' ' ' ' ' ' ' '-.
 * '.___ '    .   .--_'-' '-' '-' _'-' '._
 *  V: V 'vv-'   '_   '.       .'  _..' '.'.
 *    '=.____.=_.--'   :_.__.__:_   '.   : :
 *            (((____.-'        '-.  /   : :
 *                              (((-'\ .' /
 *                            _____..'  .'
 *                           '-._____.-'
 */
(function() {
    var _matcher,
        _level = 0,
        _id = 0,
        _handlers = {},
        _gatorInstances = {};

    function _addEvent(gator, type, callback) {

        // blur and focus do not bubble up but if you use event capturing
        // then you will get them
        var useCapture = type == 'blur' || type == 'focus';
        gator.element.addEventListener(type, callback, useCapture);
    }

    function _cancel(e) {
        e.preventDefault();
        e.stopPropagation();
    }

    /**
     * returns function to use for determining if an element
     * matches a query selector
     *
     * @returns {Function}
     */
    function _getMatcher(element) {
        if (_matcher) {
            return _matcher;
        }

        if (element.matches) {
            _matcher = element.matches;
            return _matcher;
        }

        if (element.webkitMatchesSelector) {
            _matcher = element.webkitMatchesSelector;
            return _matcher;
        }

        if (element.mozMatchesSelector) {
            _matcher = element.mozMatchesSelector;
            return _matcher;
        }

        if (element.msMatchesSelector) {
            _matcher = element.msMatchesSelector;
            return _matcher;
        }

        if (element.oMatchesSelector) {
            _matcher = element.oMatchesSelector;
            return _matcher;
        }

        // if it doesn't match a native browser method
        // fall back to the gator function
        _matcher = Gator.matchesSelector;
        return _matcher;
    }

    /**
     * determines if the specified element matches a given selector
     *
     * @param {Node} element - the element to compare against the selector
     * @param {string} selector
     * @param {Node} boundElement - the element the listener was attached to
     * @returns {void|Node}
     */
    function _matchesSelector(element, selector, boundElement) {

        // no selector means this event was bound directly to this element
        if (selector == '_root') {
            return boundElement;
        }

        // if we have moved up to the element you bound the event to
        // then we have come too far
        if (element === boundElement) {
            return;
        }

        // if this is a match then we are done!
        if (_getMatcher(element).call(element, selector)) {
            return element;
        }

        // if this element did not match but has a parent we should try
        // going up the tree to see if any of the parent elements match
        // for example if you are looking for a click on an <a> tag but there
        // is a <span> inside of the a tag that it is the target,
        // it should still work
        if (element.parentNode) {
            _level++;
            return _matchesSelector(element.parentNode, selector, boundElement);
        }
    }

    function _addHandler(gator, event, selector, callback) {
        if (!_handlers[gator.id]) {
            _handlers[gator.id] = {};
        }

        if (!_handlers[gator.id][event]) {
            _handlers[gator.id][event] = {};
        }

        if (!_handlers[gator.id][event][selector]) {
            _handlers[gator.id][event][selector] = [];
        }

        _handlers[gator.id][event][selector].push(callback);
    }

    function _removeHandler(gator, event, selector, callback) {

        // if there are no events tied to this element at all
        // then don't do anything
        if (!_handlers[gator.id]) {
            return;
        }

        // if there is no event type specified then remove all events
        // example: Gator(element).off()
        if (!event) {
            for (var type in _handlers[gator.id]) {
                if (_handlers[gator.id].hasOwnProperty(type)) {
                    _handlers[gator.id][type] = {};
                }
            }
            return;
        }

        // if no callback or selector is specified remove all events of this type
        // example: Gator(element).off('click')
        if (!callback && !selector) {
            _handlers[gator.id][event] = {};
            return;
        }

        // if a selector is specified but no callback remove all events
        // for this selector
        // example: Gator(element).off('click', '.sub-element')
        if (!callback) {
            delete _handlers[gator.id][event][selector];
            return;
        }

        // if we have specified an event type, selector, and callback then we
        // need to make sure there are callbacks tied to this selector to
        // begin with.  if there aren't then we can stop here
        if (!_handlers[gator.id][event][selector]) {
            return;
        }

        // if there are then loop through all the callbacks and if we find
        // one that matches remove it from the array
        for (var i = 0; i < _handlers[gator.id][event][selector].length; i++) {
            if (_handlers[gator.id][event][selector][i] === callback) {
                _handlers[gator.id][event][selector].splice(i, 1);
                break;
            }
        }
    }

    function _handleEvent(id, e, type) {
        if (!_handlers[id][type]) {
            return;
        }

        var target = e.target || e.srcElement,
            selector,
            match,
            matches = {},
            i = 0,
            j = 0;

        // find all events that match
        _level = 0;
        for (selector in _handlers[id][type]) {
            if (_handlers[id][type].hasOwnProperty(selector)) {
                match = _matchesSelector(target, selector, _gatorInstances[id].element);

                if (match && Gator.matchesEvent(type, _gatorInstances[id].element, match, selector == '_root', e)) {
                    _level++;
                    _handlers[id][type][selector].match = match;
                    matches[_level] = _handlers[id][type][selector];
                }
            }
        }

        // stopPropagation() fails to set cancelBubble to true in Webkit
        // @see http://code.google.com/p/chromium/issues/detail?id=162270
        e.stopPropagation = function() {
            e.cancelBubble = true;
        };

        for (i = 0; i <= _level; i++) {
            if (matches[i]) {
                for (j = 0; j < matches[i].length; j++) {
                    if (matches[i][j].call(matches[i].match, e) === false) {
                        Gator.cancel(e);
                        return;
                    }

                    if (e.cancelBubble) {
                        return;
                    }
                }
            }
        }
    }

    /**
     * binds the specified events to the element
     *
     * @param {string|Array} events
     * @param {string} selector
     * @param {Function} callback
     * @param {boolean=} remove
     * @returns {Object}
     */
    function _bind(events, selector, callback, remove) {

        // fail silently if you pass null or undefined as an alement
        // in the Gator constructor
        if (!this.element) {
            return;
        }

        if (!(events instanceof Array)) {
            events = [events];
        }

        if (!callback && typeof(selector) == 'function') {
            callback = selector;
            selector = '_root';
        }

        var id = this.id,
            i;

        function _getGlobalCallback(type) {
            return function(e) {
                _handleEvent(id, e, type);
            };
        }

        for (i = 0; i < events.length; i++) {
            if (remove) {
                _removeHandler(this, events[i], selector, callback);
                continue;
            }

            if (!_handlers[id] || !_handlers[id][events[i]]) {
                Gator.addEvent(this, events[i], _getGlobalCallback(events[i]));
            }

            _addHandler(this, events[i], selector, callback);
        }

        return this;
    }

    /**
     * Gator object constructor
     *
     * @param {Node} element
     */
    function Gator(element, id) {

        // called as function
        if (!(this instanceof Gator)) {
            // only keep one Gator instance per node to make sure that
            // we don't create a ton of new objects if you want to delegate
            // multiple events from the same node
            //
            // for example: Gator(document).on(...
            for (var key in _gatorInstances) {
                if (_gatorInstances[key].element === element) {
                    return _gatorInstances[key];
                }
            }

            _id++;
            _gatorInstances[_id] = new Gator(element, _id);

            return _gatorInstances[_id];
        }

        this.element = element;
        this.id = id;
    }

    /**
     * adds an event
     *
     * @param {string|Array} events
     * @param {string} selector
     * @param {Function} callback
     * @returns {Object}
     */
    Gator.prototype.on = function(events, selector, callback) {
        return _bind.call(this, events, selector, callback);
    };

    /**
     * removes an event
     *
     * @param {string|Array} events
     * @param {string} selector
     * @param {Function} callback
     * @returns {Object}
     */
    Gator.prototype.off = function(events, selector, callback) {
        return _bind.call(this, events, selector, callback, true);
    };

    Gator.matchesSelector = function() {};
    Gator.cancel = _cancel;
    Gator.addEvent = _addEvent;
    Gator.matchesEvent = function() {
        return true;
    };

    if (typeof module !== 'undefined' && module.exports) {
        module.exports = Gator;
    }

    window.Gator = Gator;
}) ();