/*
 * Ext JS Library 2.0 Copyright(c) 2006-2007, Ext JS, LLC. licensing@extjs.com
 * 
 * http://extjs.com/license
 */

/**
 * @class Ext.dd.ScrollManager Provides automatic scrolling of overflow regions
 *        in the page during drag operations.<br>
 *        <br>
 *        <b>Note: This class uses "Point Mode" and is untested in "Intersect
 *        Mode".</b>
 * @singleton
 */
Ext.dd.ScrollManager = function() {
	var ddm = Ext.dd.DragDropMgr;
	var els = {};
	var dragEl = null;
	var proc = {};

	var onStop = function(e) {
		dragEl = null;
		clearProc();
	};

	var triggerRefresh = function() {
		if (ddm.dragCurrent) {
			ddm.refreshCache(ddm.dragCurrent.groups);
		}
	};

	var doScroll = function() {
		if (ddm.dragCurrent) {
			var dds = Ext.dd.ScrollManager;
			var inc = proc.el.ddScrollConfig
					? proc.el.ddScrollConfig.increment
					: dds.increment;
			if (!dds.animate) {
				if (proc.el.scroll(proc.dir, inc)) {
					triggerRefresh();
				}
			} else {
				proc.el.scroll(proc.dir, inc, true, dds.animDuration,
						triggerRefresh);
			}
		}
	};

	var clearProc = function() {
		if (proc.id) {
			clearInterval(proc.id);
		}
		proc.id = 0;
		proc.el = null;
		proc.dir = "";
	};

	var startProc = function(el, dir) {
		clearProc();
		proc.el = el;
		proc.dir = dir;
		proc.id = setInterval(doScroll, Ext.dd.ScrollManager.frequency);
	};

	var onFire = function(e, isDrop) {
		if (isDrop || !ddm.dragCurrent) {
			return;
		}
		var dds = Ext.dd.ScrollManager;
		if (!dragEl || dragEl != ddm.dragCurrent) {
			dragEl = ddm.dragCurrent;
			// refresh regions on drag start
			dds.refreshCache();
		}

		var xy = Ext.lib.Event.getXY(e);
		var pt = new Ext.lib.Point(xy[0], xy[1]);
		for (var id in els) {
			var el = els[id], r = el._region;
			var c = el.ddScrollConfig ? el.ddScrollConfig : dds;
			if (r && r.contains(pt) && el.isScrollable()) {
				if (r.bottom - pt.y <= c.vthresh) {
					if (proc.el != el) {
						startProc(el, "down");
					}
					return;
				} else if (r.right - pt.x <= c.hthresh) {
					if (proc.el != el) {
						startProc(el, "left");
					}
					return;
				} else if (pt.y - r.top <= c.vthresh) {
					if (proc.el != el) {
						startProc(el, "up");
					}
					return;
				} else if (pt.x - r.left <= c.hthresh) {
					if (proc.el != el) {
						startProc(el, "right");
					}
					return;
				}
			}
		}
		clearProc();
	};

	ddm.fireEvents = ddm.fireEvents.createSequence(onFire, ddm);
	ddm.stopDrag = ddm.stopDrag.createSequence(onStop, ddm);

	return {
		/**
		 * Registers new overflow element(s) to auto scroll
		 * 
		 * @param {Mixed/Array}
		 *            el The id of or the element to be scrolled or an array of
		 *            either
		 */
		register : function(el) {
			if (el instanceof Array) {
				for (var i = 0, len = el.length; i < len; i++) {
					this.register(el[i]);
				}
			} else {
				el = Ext.get(el);
				els[el.id] = el;
			}
		},

		/**
		 * Unregisters overflow element(s) so they are no longer scrolled
		 * 
		 * @param {Mixed/Array}
		 *            el The id of or the element to be removed or an array of
		 *            either
		 */
		unregister : function(el) {
			if (el instanceof Array) {
				for (var i = 0, len = el.length; i < len; i++) {
					this.unregister(el[i]);
				}
			} else {
				el = Ext.get(el);
				delete els[el.id];
			}
		},

		/**
		 * The number of pixels from the top or bottom edge of a container the
		 * pointer needs to be to trigger scrolling (defaults to 25)
		 * 
		 * @type Number
		 */
		vthresh : 25,
		/**
		 * The number of pixels from the right or left edge of a container the
		 * pointer needs to be to trigger scrolling (defaults to 25)
		 * 
		 * @type Number
		 */
		hthresh : 25,

		/**
		 * The number of pixels to scroll in each scroll increment (defaults to
		 * 50)
		 * 
		 * @type Number
		 */
		increment : 100,

		/**
		 * The frequency of scrolls in milliseconds (defaults to 500)
		 * 
		 * @type Number
		 */
		frequency : 500,

		/**
		 * True to animate the scroll (defaults to true)
		 * 
		 * @type Boolean
		 */
		animate : true,

		/**
		 * The animation duration in seconds - MUST BE less than
		 * Ext.dd.ScrollManager.frequency! (defaults to .4)
		 * 
		 * @type Number
		 */
		animDuration : .4,

		/**
		 * Manually trigger a cache refresh.
		 */
		refreshCache : function() {
			for (var id in els) {
				if (typeof els[id] == 'object') { // for people extending the
													// object prototype
					els[id]._region = els[id].getRegion();
				}
			}
		}
	};
}();