/*
 * jquery.collision
 * https://github.com/ducksboard/gridster.js
 *
 * Copyright (c) 2012 ducksboard
 * Licensed under the MIT licenses.
 */

;(function($, window, document, undefined){

    var defaults = {
        colliders_context: document.body
        // ,on_overlap: function(collider_data){},
        // on_overlap_start : function(collider_data){},
        // on_overlap_stop : function(collider_data){}
    };


    /**
    * Detects collisions between a DOM element against other DOM elements or
    * Coords objects.
    *
    * @class Collision
    * @uses Coords
    * @param {HTMLElement} el The jQuery wrapped HTMLElement.
    * @param {HTMLElement|Array} colliders Can be a jQuery collection
    *  of HTMLElements or an Array of Coords instances.
    * @param {Object} [options] An Object with all options you want to
    *        overwrite:
    *   @param {Function} [options.on_overlap_start] Executes a function the first
    *    time each `collider ` is overlapped.
    *   @param {Function} [options.on_overlap_stop] Executes a function when a
    *    `collider` is no longer collided.
    *   @param {Function} [options.on_overlap] Executes a function when the
    * mouse is moved during the collision.
    * @return {Object} Collision instance.
    * @constructor
    */
    function Collision(el, colliders, options) {
        this.options = $.extend(defaults, options);
        this.$element = el;
        this.last_colliders = [];
        this.last_colliders_coords = [];
        if (typeof colliders === 'string' || colliders instanceof jQuery) {
            this.$colliders = $(colliders,
                 this.options.colliders_context).not(this.$element);
        }else{
            this.colliders = $(colliders);
        }

        this.init();
    }


    var fn = Collision.prototype;


    fn.init = function() {
        this.find_collisions();
    };


    fn.overlaps = function(a, b) {
        var x = false;
        var y = false;

        if ((b.x1 >= a.x1 && b.x1 <= a.x2) ||
            (b.x2 >= a.x1 && b.x2 <= a.x2) ||
            (a.x1 >= b.x1 && a.x2 <= b.x2)
        ) { x = true; }

        if ((b.y1 >= a.y1 && b.y1 <= a.y2) ||
            (b.y2 >= a.y1 && b.y2 <= a.y2) ||
            (a.y1 >= b.y1 && a.y2 <= b.y2)
        ) { y = true; }

        return (x && y);
    };


    fn.detect_overlapping_region = function(a, b){
        var regionX = '';
        var regionY = '';

        if (a.y1 > b.cy && a.y1 < b.y2) { regionX = 'N'; }
        if (a.y2 > b.y1 && a.y2 < b.cy) { regionX = 'S'; }
        if (a.x1 > b.cx && a.x1 < b.x2) { regionY = 'W'; }
        if (a.x2 > b.x1 && a.x2 < b.cx) { regionY = 'E'; }

        return (regionX + regionY) || 'C';
    };


    fn.calculate_overlapped_area_coords = function(a, b){
        var x1 = Math.max(a.x1, b.x1);
        var y1 = Math.max(a.y1, b.y1);
        var x2 = Math.min(a.x2, b.x2);
        var y2 = Math.min(a.y2, b.y2);

        return $({
            left: x1,
            top: y1,
             width : (x2 - x1),
            height: (y2 - y1)
          }).coords().get();
    };


    fn.calculate_overlapped_area = function(coords){
        return (coords.width * coords.height);
    };


    fn.manage_colliders_start_stop = function(new_colliders_coords, start_callback, stop_callback){
        var last = this.last_colliders_coords;

        for (var i = 0, il = last.length; i < il; i++) {
            if ($.inArray(last[i], new_colliders_coords) === -1) {
                start_callback.call(this, last[i]);
            }
        }

        for (var j = 0, jl = new_colliders_coords.length; j < jl; j++) {
            if ($.inArray(new_colliders_coords[j], last) === -1) {
                stop_callback.call(this, new_colliders_coords[j]);
            }

        }
    };


    fn.find_collisions = function(player_data_coords){
        var self = this;
        var colliders_coords = [];
        var colliders_data = [];
        var $colliders = (this.colliders || this.$colliders);
        var count = $colliders.length;
        var player_coords = self.$element.coords()
                             .update(player_data_coords || false).get();

        while(count--){
          var $collider = self.$colliders ?
                           $($colliders[count]) : $colliders[count];
          var $collider_coords_ins = ($collider.isCoords) ?
                  $collider : $collider.coords();
          var collider_coords = $collider_coords_ins.get();
          var overlaps = self.overlaps(player_coords, collider_coords);

          if (!overlaps) {
            continue;
          }

          var region = self.detect_overlapping_region(
              player_coords, collider_coords);

            //todo: make this an option
            if (region === 'C'){
                var area_coords = self.calculate_overlapped_area_coords(
                    player_coords, collider_coords);
                var area = self.calculate_overlapped_area(area_coords);
                var collider_data = {
                    area: area,
                    area_coords : area_coords,
                    region: region,
                    coords: collider_coords,
                    player_coords: player_coords,
                    el: $collider
                };

                if (self.options.on_overlap) {
                    self.options.on_overlap.call(this, collider_data);
                }
                colliders_coords.push($collider_coords_ins);
                colliders_data.push(collider_data);
            }
        }

        if (self.options.on_overlap_stop || self.options.on_overlap_start) {
            this.manage_colliders_start_stop(colliders_coords,
                self.options.on_overlap_stop, self.options.on_overlap_start);
        }

        this.last_colliders_coords = colliders_coords;

        return colliders_data;
    };


    fn.get_closest_colliders = function(player_data_coords){
        var colliders = this.find_collisions(player_data_coords);

        colliders.sort(function(a, b) {
            /* if colliders are being overlapped by the "C" (center) region,
             * we have to set a lower index in the array to which they are placed
             * above in the grid. */
            if (a.region === 'C' && b.region === 'C') {
                if (a.coords.y1 < b.coords.y1 || a.coords.x1 < b.coords.x1) {
                    return - 1;
                }else{
                    return 1;
                }
            }

            if (a.area < b.area) {
                return 1;
            }

            return 1;
        });
        return colliders;
    };


    //jQuery adapter
    $.fn.collision = function(collider, options) {
          return new Collision( this, collider, options );
    };


}(jQuery, window, document));
