YUI.add('dd-ddm-drop', function (Y, NAME) {

    /**

     * Extends the dd-ddm Class to add support for the placement of Drop Target

     * shims inside the viewport shim. It also handles all Drop Target related events and interactions.

     * @module dd

     * @submodule dd-ddm-drop

     * @for DDM

     * @namespace DD

     */

    //TODO CSS class name for the bestMatch..

    Y.mix(Y.DD.DDM, {

        /**

        * This flag turns off the use of the mouseover/mouseout shim. It should not be used unless you know what you are doing.

        * @private

        * @property _noShim

        * @type {Boolean}

        */

        _noShim: false,

        /**

        * Placeholder for all active shims on the page

        * @private

        * @property _activeShims

        * @type {Array}

        */

        _activeShims: [],

        /**

        * This method checks the _activeShims Object to see if there is a shim active.

        * @private

        * @method _hasActiveShim

        * @return {Boolean}

        */

        _hasActiveShim: function() {

            if (this._noShim) {

                return true;

            }

            return this._activeShims.length;

        },

        /**

        * Adds a Drop Target to the list of active shims

        * @private

        * @method _addActiveShim

        * @param {Object} d The Drop instance to add to the list.

        */

        _addActiveShim: function(d) {

            this._activeShims.push(d);

        },

        /**

        * Removes a Drop Target to the list of active shims

        * @private

        * @method _removeActiveShim

        * @param {Object} d The Drop instance to remove from the list.

        */

        _removeActiveShim: function(d) {

            var s = [];

            Y.Array.each(this._activeShims, function(v) {

                if (v._yuid !== d._yuid) {

                    s.push(v);

                }

            });

            this._activeShims = s;

        },

        /**

        * This method will sync the position of the shims on the Drop Targets that are currently active.

        * @method syncActiveShims

        * @param {Boolean} force Resize/sync all Targets.

        */

        syncActiveShims: function(force) {

            Y.later(0, this, function(force) {

                var drops = ((force) ? this.targets : this._lookup());

                Y.Array.each(drops, function(v) {

                    v.sizeShim.call(v);

                }, this);

            }, force);

        },

        /**

        * The mode that the drag operations will run in 0 for Point, 1 for Intersect, 2 for Strict

        * @private

        * @property mode

        * @type Number

        */

        mode: 0,

        /**

        * In point mode, a Drop is targeted by the cursor being over the Target

        * @private

        * @property POINT

        * @type Number

        */

        POINT: 0,

        /**

        * In intersect mode, a Drop is targeted by "part" of the drag node being over the Target

        * @private

        * @property INTERSECT

        * @type Number

        */

        INTERSECT: 1,

        /**

        * In strict mode, a Drop is targeted by the "entire" drag node being over the Target

        * @private

        * @property STRICT

        * @type Number

        */

        STRICT: 2,

        /**

        * Should we only check targets that are in the viewport on drags (for performance), default: true

        * @property useHash

        * @type {Boolean}

        */

        useHash: true,

        /**

        * A reference to the active Drop Target

        * @property activeDrop

        * @type {Object}

        */

        activeDrop: null,

        /**

        * An array of the valid Drop Targets for this interaction.

        * @property validDrops

        * @type {Array}

        */

        //TODO Change array/object literals to be in sync..

        validDrops: [],

        /**

        * An object literal of Other Drop Targets that we encountered during this interaction (in the case of overlapping Drop Targets)

        * @property otherDrops

        * @type {Object}

        */

        otherDrops: {},

        /**

        * All of the Targets

        * @property targets

        * @type {Array}

        */

        targets: [],

        /**

        * Add a Drop Target to the list of Valid Targets. This list get's regenerated on each new drag operation.

        * @private

        * @method _addValid

        * @param {Object} drop

        * @chainable

        */

        _addValid: function(drop) {

            this.validDrops.push(drop);

            return this;

        },

        /**

        * Removes a Drop Target from the list of Valid Targets. This list get's regenerated on each new drag operation.

        * @private

        * @method _removeValid

        * @param {Object} drop

        * @chainable

        */

        _removeValid: function(drop) {

            var drops = [];

            Y.Array.each(this.validDrops, function(v) {

                if (v !== drop) {

                    drops.push(v);

                }

            });

            this.validDrops = drops;

            return this;

        },

        /**

        * Check to see if the Drag element is over the target, method varies on current mode

        * @method isOverTarget

        * @param {Object} drop The drop to check against

        * @return {Boolean}

        */

        isOverTarget: function(drop) {

            if (this.activeDrag && drop) {

                var xy = this.activeDrag.mouseXY, r, dMode = this.activeDrag.get('dragMode'),

                    aRegion, node = drop.shim;

                if (xy && this.activeDrag) {

                    aRegion = this.activeDrag.region;

                    if (dMode === this.STRICT) {

                        return this.activeDrag.get('dragNode').inRegion(drop.region, true, aRegion);

                    }

                    if (drop && drop.shim) {

                        if ((dMode === this.INTERSECT) && this._noShim) {

                            r = aRegion || this.activeDrag.get('node');

                            return drop.get('node').intersect(r, drop.region).inRegion;

                        }

                        if (this._noShim) {

                            node = drop.get('node');

                        }

                        return node.intersect({

                            top: xy[1],

                            bottom: xy[1],

                            left: xy[0],

                            right: xy[0]

                        }, drop.region).inRegion;

                    }

                }

            }

            return false;

        },

        /**

        * Clears the cache data used for this interaction.

        * @method clearCache

        */

        clearCache: function() {

            this.validDrops = [];

            this.otherDrops = {};

            this._activeShims = [];

        },

        /**

        * Clear the cache and activate the shims of all the targets

        * @private

        * @method _activateTargets

        */

        _activateTargets: function() {

            this._noShim = true;

            this.clearCache();

            Y.Array.each(this.targets, function(v) {

                v._activateShim([]);

                if (v.get('noShim') === true) {

                    this._noShim = false;

                }

            }, this);

            this._handleTargetOver();

        },

        /**

        * This method will gather the area for all potential targets and see which has the hightest covered area and return it.

        * @method getBestMatch

        * @param {Array} drops An Array of drops to scan for the best match.

        * @param {Boolean} all If present, it returns an Array. First item is best match, second is an Array of the other items in the original Array.

        * @return {Object or Array}

        */

        getBestMatch: function(drops, all) {

            var biggest = null, area = 0, out;

            Y.Object.each(drops, function(v) {

                var inter = this.activeDrag.get('dragNode').intersect(v.get('node'));

                v.region.area = inter.area;

                if (inter.inRegion) {

                    if (inter.area > area) {

                        area = inter.area;

                        biggest = v;

                    }

                }

            }, this);

            if (all) {

                out = [];

                //TODO Sort the others in numeric order by area covered..

                Y.Object.each(drops, function(v) {

                    if (v !== biggest) {

                        out.push(v);

                    }

                }, this);

                return [biggest, out];

            }

            return biggest;

        },

        /**

        * This method fires the drop:hit, drag:drophit, drag:dropmiss methods and deactivates the shims..

        * @private

        * @method _deactivateTargets

        */

        _deactivateTargets: function() {

            var other = [], tmp,

                activeDrag = this.activeDrag,

                activeDrop = this.activeDrop;

            //TODO why is this check so hard??

            if (activeDrag && activeDrop && this.otherDrops[activeDrop]) {

                if (!activeDrag.get('dragMode')) {

                    //TODO otherDrops -- private..

                    other = this.otherDrops;

                    delete other[activeDrop];

                } else {

                    tmp = this.getBestMatch(this.otherDrops, true);

                    activeDrop = tmp[0];

                    other = tmp[1];

                }

                activeDrag.get('node').removeClass(this.CSS_PREFIX + '-drag-over');

                if (activeDrop) {

                    activeDrop.fire('drop:hit', { drag: activeDrag, drop: activeDrop, others: other });

                    activeDrag.fire('drag:drophit', { drag: activeDrag,  drop: activeDrop, others: other });

                }

            } else if (activeDrag && activeDrag.get('dragging')) {

                activeDrag.get('node').removeClass(this.CSS_PREFIX + '-drag-over');

                activeDrag.fire('drag:dropmiss', { pageX: activeDrag.lastXY[0], pageY: activeDrag.lastXY[1] });

            }

            this.activeDrop = null;

            Y.Array.each(this.targets, function(v) {

                v._deactivateShim([]);

            }, this);

        },

        /**

        * This method is called when the move method is called on the Drag Object.

        * @private

        * @method _dropMove

        */

        _dropMove: function() {

            if (this._hasActiveShim()) {

                this._handleTargetOver();

            } else {

                Y.Object.each(this.otherDrops, function(v) {

                    v._handleOut.apply(v, []);

                });

            }

        },

        /**

        * Filters the list of Drops down to those in the viewport.

        * @private

        * @method _lookup

        * @return {Array} The valid Drop Targets that are in the viewport.

        */

        _lookup: function() {

            if (!this.useHash || this._noShim) {

                return this.validDrops;

            }

            var drops = [];

            //Only scan drop shims that are in the Viewport

            Y.Array.each(this.validDrops, function(v) {

                if (v.shim && v.shim.inViewportRegion(false, v.region)) {

                    drops.push(v);

                }

            });

            return drops;

        },

        /**

        * This method execs _handleTargetOver on all valid Drop Targets

        * @private

        * @method _handleTargetOver

        */

        _handleTargetOver: function() {

            var drops = this._lookup();

            Y.Array.each(drops, function(v) {

                v._handleTargetOver.call(v);

            }, this);

        },

        /**

        * Add the passed in Target to the targets collection

        * @private

        * @method _regTarget

        * @param {Object} t The Target to add to the targets collection

        */

        _regTarget: function(t) {

            this.targets.push(t);

        },

        /**

        * Remove the passed in Target from the targets collection

        * @private

        * @method _unregTarget

        * @param {Object} drop The Target to remove from the targets collection

        */

        _unregTarget: function(drop) {

            var targets = [], vdrops;

            Y.Array.each(this.targets, function(v) {

                if (v !== drop) {

                    targets.push(v);

                }

            }, this);

            this.targets = targets;

            vdrops = [];

            Y.Array.each(this.validDrops, function(v) {

                if (v !== drop) {

                    vdrops.push(v);

                }

            });

            this.validDrops = vdrops;

        },

        /**

        * Get a valid Drop instance back from a Node or a selector string, false otherwise

        * @method getDrop

        * @param {String/Object} node The Node instance or Selector string to check for a valid Drop Object

        * @return {Object}

        */

        getDrop: function(node) {

            var drop = false,

                n = Y.one(node);

            if (n instanceof Y.Node) {

                Y.Array.each(this.targets, function(v) {

                    if (n.compareTo(v.get('node'))) {

                        drop = v;

                    }

                });

            }

            return drop;

        }

    }, true);