/**
 * Copyright (c) 2006-2015, JGraph Ltd
 * Copyright (c) 2006-2015, Gaudenz Alder
 */
/**
 * Class: mxPanningHandler
 * 
 * Event handler that pans and creates popupmenus. To use the left
 * mousebutton for panning without interfering with cell moving and
 * resizing, use <isUseLeftButton> and <isIgnoreCell>. For grid size
 * steps while panning, use <useGrid>. This handler is built-into
 * <mxGraph.panningHandler> and enabled using <mxGraph.setPanning>.
 * 
 * Constructor: mxPanningHandler
 * 
 * Constructs an event handler that creates a <mxPopupMenu>
 * and pans the graph.
 *
 * Event: mxEvent.PAN_START
 *
 * Fires when the panning handler changes its <active> state to true. The
 * <code>event</code> property contains the corresponding <mxMouseEvent>.
 *
 * Event: mxEvent.PAN
 *
 * Fires while handle is processing events. The <code>event</code> property contains
 * the corresponding <mxMouseEvent>.
 *
 * Event: mxEvent.PAN_END
 *
 * Fires when the panning handler changes its <active> state to false. The
 * <code>event</code> property contains the corresponding <mxMouseEvent>.
 */
function mxPanningHandler(graph)
{
	if (graph != null)
	{
		this.graph = graph;
		this.graph.addMouseListener(this);

		// Handles force panning event
		this.forcePanningHandler = mxUtils.bind(this, function(sender, evt)
		{
			var evtName = evt.getProperty('eventName');
			var me = evt.getProperty('event');
			
			if (evtName == mxEvent.MOUSE_DOWN && this.isForcePanningEvent(me))
			{
				this.start(me);
				this.active = true;
				this.fireEvent(new mxEventObject(mxEvent.PAN_START, 'event', me));
				me.consume();
			}
		});

		this.graph.addListener(mxEvent.FIRE_MOUSE_EVENT, this.forcePanningHandler);
		
		// Handles pinch gestures
		this.gestureHandler = mxUtils.bind(this, function(sender, eo)
		{
			if (this.isPinchEnabled())
			{
				var evt = eo.getProperty('event');
				
				if (!mxEvent.isConsumed(evt) && evt.type == 'gesturestart')
				{
					this.initialScale = this.graph.view.scale;
				
					// Forces start of panning when pinch gesture starts
					if (!this.active && this.mouseDownEvent != null)
					{
						this.start(this.mouseDownEvent);
						this.mouseDownEvent = null;
					}
				}
				else if (evt.type == 'gestureend' && this.initialScale != null)
				{
					this.initialScale = null;
				}
				
				if (this.initialScale != null)
				{
					var value = Math.round(this.initialScale * evt.scale * 100) / 100;
					
					if (this.minScale != null)
					{
						value = Math.max(this.minScale, value);
					}
					
					if (this.maxScale != null)
					{
						value = Math.min(this.maxScale, value);
					}
	
					if (this.graph.view.scale != value)
					{
						this.graph.zoomTo(value);
						mxEvent.consume(evt);
					}
				}
			}
		});
		
		this.graph.addListener(mxEvent.GESTURE, this.gestureHandler);
		
		this.mouseUpListener = mxUtils.bind(this, function()
		{
		    	if (this.active)
		    	{
		    		this.reset();
		    	}
		});
		
		// Stops scrolling on every mouseup anywhere in the document
		mxEvent.addListener(document, 'mouseup', this.mouseUpListener);
	}
};

/**
 * Extends mxEventSource.
 */
mxPanningHandler.prototype = new mxEventSource();
mxPanningHandler.prototype.constructor = mxPanningHandler;

/**
 * Variable: graph
 * 
 * Reference to the enclosing <mxGraph>.
 */
mxPanningHandler.prototype.graph = null;

/**
 * Variable: useLeftButtonForPanning
 * 
 * Specifies if panning should be active for the left mouse button.
 * Setting this to true may conflict with <mxRubberband>. Default is false.
 */
mxPanningHandler.prototype.useLeftButtonForPanning = false;

/**
 * Variable: usePopupTrigger
 * 
 * Specifies if <mxEvent.isPopupTrigger> should also be used for panning.
 */
mxPanningHandler.prototype.usePopupTrigger = true;

/**
 * Variable: ignoreCell
 * 
 * Specifies if panning should be active even if there is a cell under the
 * mousepointer. Default is false.
 */
mxPanningHandler.prototype.ignoreCell = false;

/**
 * Variable: previewEnabled
 * 
 * Specifies if the panning should be previewed. Default is true.
 */
mxPanningHandler.prototype.previewEnabled = true;

/**
 * Variable: useGrid
 * 
 * Specifies if the panning steps should be aligned to the grid size.
 * Default is false.
 */
mxPanningHandler.prototype.useGrid = false;

/**
 * Variable: panningEnabled
 * 
 * Specifies if panning should be enabled. Default is true.
 */
mxPanningHandler.prototype.panningEnabled = true;

/**
 * Variable: pinchEnabled
 * 
 * Specifies if pinch gestures should be handled as zoom. Default is true.
 */
mxPanningHandler.prototype.pinchEnabled = true;

/**
 * Variable: maxScale
 * 
 * Specifies the maximum scale. Default is 8.
 */
mxPanningHandler.prototype.maxScale = 8;

/**
 * Variable: minScale
 * 
 * Specifies the minimum scale. Default is 0.01.
 */
mxPanningHandler.prototype.minScale = 0.01;

/**
 * Variable: dx
 * 
 * Holds the current horizontal offset.
 */
mxPanningHandler.prototype.dx = null;

/**
 * Variable: dy
 * 
 * Holds the current vertical offset.
 */
mxPanningHandler.prototype.dy = null;

/**
 * Variable: startX
 * 
 * Holds the x-coordinate of the start point.
 */
mxPanningHandler.prototype.startX = 0;

/**
 * Variable: startY
 * 
 * Holds the y-coordinate of the start point.
 */
mxPanningHandler.prototype.startY = 0;

/**
 * Function: isActive
 * 
 * Returns true if the handler is currently active.
 */
mxPanningHandler.prototype.isActive = function()
{
	return this.active || this.initialScale != null;
};

/**
 * Function: isPanningEnabled
 * 
 * Returns <panningEnabled>.
 */
mxPanningHandler.prototype.isPanningEnabled = function()
{
	return this.panningEnabled;
};

/**
 * Function: setPanningEnabled
 * 
 * Sets <panningEnabled>.
 */
mxPanningHandler.prototype.setPanningEnabled = function(value)
{
	this.panningEnabled = value;
};

/**
 * Function: isPinchEnabled
 * 
 * Returns <pinchEnabled>.
 */
mxPanningHandler.prototype.isPinchEnabled = function()
{
	return this.pinchEnabled;
};

/**
 * Function: setPinchEnabled
 * 
 * Sets <pinchEnabled>.
 */
mxPanningHandler.prototype.setPinchEnabled = function(value)
{
	this.pinchEnabled = value;
};

/**
 * Function: isPanningTrigger
 * 
 * Returns true if the given event is a panning trigger for the optional
 * given cell. This returns true if control-shift is pressed or if
 * <usePopupTrigger> is true and the event is a popup trigger.
 */
mxPanningHandler.prototype.isPanningTrigger = function(me)
{
	var evt = me.getEvent();
	
	return (this.useLeftButtonForPanning && me.getState() == null &&
			mxEvent.isLeftMouseButton(evt)) || (mxEvent.isControlDown(evt) &&
			mxEvent.isShiftDown(evt)) || (this.usePopupTrigger && mxEvent.isPopupTrigger(evt));
};

/**
 * Function: isForcePanningEvent
 * 
 * Returns true if the given <mxMouseEvent> should start panning. This
 * implementation always returns true if <ignoreCell> is true or for
 * multi touch events.
 */
mxPanningHandler.prototype.isForcePanningEvent = function(me)
{
	return this.ignoreCell || mxEvent.isMultiTouchEvent(me.getEvent());
};

/**
 * Function: mouseDown
 * 
 * Handles the event by initiating the panning. By consuming the event all
 * subsequent events of the gesture are redirected to this handler.
 */
mxPanningHandler.prototype.mouseDown = function(sender, me)
{
	this.mouseDownEvent = me;
	
	if (!me.isConsumed() && this.isPanningEnabled() && !this.active && this.isPanningTrigger(me))
	{
		this.start(me);
		this.consumePanningTrigger(me);
	}
};

/**
 * Function: start
 * 
 * Starts panning at the given event.
 */
mxPanningHandler.prototype.start = function(me)
{
	this.dx0 = -this.graph.container.scrollLeft;
	this.dy0 = -this.graph.container.scrollTop;

	// Stores the location of the trigger event
	this.startX = me.getX();
	this.startY = me.getY();
	this.dx = null;
	this.dy = null;
	
	this.panningTrigger = true;
};

/**
 * Function: consumePanningTrigger
 * 
 * Consumes the given <mxMouseEvent> if it was a panning trigger in
 * <mouseDown>. The default is to invoke <mxMouseEvent.consume>. Note that this
 * will block any further event processing. If you haven't disabled built-in
 * context menus and require immediate selection of the cell on mouseDown in
 * Safari and/or on the Mac, then use the following code:
 * 
 * (code)
 * mxPanningHandler.prototype.consumePanningTrigger = function(me)
 * {
 *   if (me.evt.preventDefault)
 *   {
 *     me.evt.preventDefault();
 *   }
 *   
 *   // Stops event processing in IE
 *   me.evt.returnValue = false;
 *   
 *   // Sets local consumed state
 *   if (!mxClient.IS_SF && !mxClient.IS_MAC)
 *   {
 *     me.consumed = true;
 *   }
 * };
 * (end)
 */
mxPanningHandler.prototype.consumePanningTrigger = function(me)
{
	me.consume();
};

/**
 * Function: mouseMove
 * 
 * Handles the event by updating the panning on the graph.
 */
mxPanningHandler.prototype.mouseMove = function(sender, me)
{
	this.dx = me.getX() - this.startX;
	this.dy = me.getY() - this.startY;
	
	if (this.active)
	{
		if (this.previewEnabled)
		{
			// Applies the grid to the panning steps
			if (this.useGrid)
			{
				this.dx = this.graph.snap(this.dx);
				this.dy = this.graph.snap(this.dy);
			}
			
			this.graph.panGraph(this.dx + this.dx0, this.dy + this.dy0);
		}

		this.fireEvent(new mxEventObject(mxEvent.PAN, 'event', me));
	}
	else if (this.panningTrigger)
	{
		var tmp = this.active;

		// Panning is activated only if the mouse is moved
		// beyond the graph tolerance
		this.active = Math.abs(this.dx) > this.graph.tolerance || Math.abs(this.dy) > this.graph.tolerance;

		if (!tmp && this.active)
		{
			this.fireEvent(new mxEventObject(mxEvent.PAN_START, 'event', me));
		}
	}
	
	if (this.active || this.panningTrigger)
	{
		me.consume();
	}
};

/**
 * Function: mouseUp
 * 
 * Handles the event by setting the translation on the view or showing the
 * popupmenu.
 */
mxPanningHandler.prototype.mouseUp = function(sender, me)
{
	if (this.active)
	{
		if (this.dx != null && this.dy != null)
		{
			// Ignores if scrollbars have been used for panning
			if (!this.graph.useScrollbarsForPanning || !mxUtils.hasScrollbars(this.graph.container))
			{
				var scale = this.graph.getView().scale;
				var t = this.graph.getView().translate;
				this.graph.panGraph(0, 0);
				this.panGraph(t.x + this.dx / scale, t.y + this.dy / scale);
			}
			
			me.consume();
		}
		
		this.fireEvent(new mxEventObject(mxEvent.PAN_END, 'event', me));
	}
	
	this.reset();
};

/**
 * Function: mouseUp
 * 
 * Handles the event by setting the translation on the view or showing the
 * popupmenu.
 */
mxPanningHandler.prototype.reset = function()
{
	this.panningTrigger = false;
	this.mouseDownEvent = null;
	this.active = false;
	this.dx = null;
	this.dy = null;
};

/**
 * Function: panGraph
 * 
 * Pans <graph> by the given amount.
 */
mxPanningHandler.prototype.panGraph = function(dx, dy)
{
	this.graph.getView().setTranslate(dx, dy);
};

/**
 * Function: destroy
 * 
 * Destroys the handler and all its resources and DOM nodes.
 */
mxPanningHandler.prototype.destroy = function()
{
	this.graph.removeMouseListener(this);
	this.graph.removeListener(this.forcePanningHandler);
	this.graph.removeListener(this.gestureHandler);
	mxEvent.removeListener(document, 'mouseup', this.mouseUpListener);
};
