/**
 * Copyright (c) 2006-2015, JGraph Ltd
 * Copyright (c) 2006-2015, Gaudenz Alder
 */
/**
 * Class: mxConstraintHandler
 *
 * Handles constraints on connection targets. This class is in charge of
 * showing fixed points when the mouse is over a vertex and handles constraints
 * to establish new connections.
 *
 * Constructor: mxConstraintHandler
 *
 * Constructs an new constraint handler.
 * 
 * Parameters:
 * 
 * graph - Reference to the enclosing <mxGraph>.
 * factoryMethod - Optional function to create the edge. The function takes
 * the source and target <mxCell> as the first and second argument and
 * returns the <mxCell> that represents the new edge.
 */
function mxConstraintHandler(graph)
{
	this.graph = graph;
	
	// Adds a graph model listener to update the current focus on changes
	this.resetHandler = mxUtils.bind(this, function(sender, evt)
	{
		if (this.currentFocus != null && this.graph.view.getState(this.currentFocus.cell) == null)
		{
			this.reset();
		}
		else
		{
			this.redraw();
		}
	});
	
	this.graph.model.addListener(mxEvent.CHANGE, this.resetHandler);
	this.graph.view.addListener(mxEvent.SCALE, this.resetHandler);
	this.graph.addListener(mxEvent.ROOT, this.resetHandler);
};

/**
 * Variable: pointImage
 * 
 * <mxImage> to be used as the image for fixed connection points.
 */
mxConstraintHandler.prototype.pointImage = new mxImage(mxClient.imageBasePath + '/point.gif', 5, 5);

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

/**
 * Variable: enabled
 * 
 * Specifies if events are handled. Default is true.
 */
mxConstraintHandler.prototype.enabled = true;

/**
 * Variable: highlightColor
 * 
 * Specifies the color for the highlight. Default is <mxConstants.DEFAULT_VALID_COLOR>.
 */
mxConstraintHandler.prototype.highlightColor = mxConstants.DEFAULT_VALID_COLOR;

/**
 * Function: isEnabled
 * 
 * Returns true if events are handled. This implementation
 * returns <enabled>.
 */
mxConstraintHandler.prototype.isEnabled = function()
{
	return this.enabled;
};
	
/**
 * Function: setEnabled
 * 
 * Enables or disables event handling. This implementation
 * updates <enabled>.
 * 
 * Parameters:
 * 
 * enabled - Boolean that specifies the new enabled state.
 */
mxConstraintHandler.prototype.setEnabled = function(enabled)
{
	this.enabled = enabled;
};

/**
 * Function: reset
 * 
 * Resets the state of this handler.
 */
mxConstraintHandler.prototype.reset = function()
{
	if (this.focusIcons != null)
	{
		for (var i = 0; i < this.focusIcons.length; i++)
		{
			this.focusIcons[i].destroy();
		}
		
		this.focusIcons = null;
	}
	
	if (this.focusHighlight != null)
	{
		this.focusHighlight.destroy();
		this.focusHighlight = null;
	}
	
	this.currentConstraint = null;
	this.currentFocusArea = null;
	this.currentPoint = null;
	this.currentFocus = null;
	this.focusPoints = null;
};

/**
 * Function: getTolerance
 * 
 * Returns the tolerance to be used for intersecting connection points. This
 * implementation returns <mxGraph.tolerance>.
 * 
 * Parameters:
 * 
 * me - <mxMouseEvent> whose tolerance should be returned.
 */
mxConstraintHandler.prototype.getTolerance = function(me)
{
	return this.graph.getTolerance();
};

/**
 * Function: getImageForConstraint
 * 
 * Returns the tolerance to be used for intersecting connection points.
 */
mxConstraintHandler.prototype.getImageForConstraint = function(state, constraint, point)
{
	return this.pointImage;
};

/**
 * Function: isEventIgnored
 * 
 * Returns true if the given <mxMouseEvent> should be ignored in <update>. This
 * implementation always returns false.
 */
mxConstraintHandler.prototype.isEventIgnored = function(me, source)
{
	return false;
};

/**
 * Function: isStateIgnored
 * 
 * Returns true if the given state should be ignored. This always returns false.
 */
mxConstraintHandler.prototype.isStateIgnored = function(state, source)
{
	return false;
};

/**
 * Function: destroyIcons
 * 
 * Destroys the <focusIcons> if they exist.
 */
mxConstraintHandler.prototype.destroyIcons = function()
{
	if (this.focusIcons != null)
	{
		for (var i = 0; i < this.focusIcons.length; i++)
		{
			this.focusIcons[i].destroy();
		}
		
		this.focusIcons = null;
		this.focusPoints = null;
	}
};

/**
 * Function: destroyFocusHighlight
 * 
 * Destroys the <focusHighlight> if one exists.
 */
mxConstraintHandler.prototype.destroyFocusHighlight = function()
{
	if (this.focusHighlight != null)
	{
		this.focusHighlight.destroy();
		this.focusHighlight = null;
	}
};

/**
 * Function: isKeepFocusEvent
 * 
 * Returns true if the current focused state should not be changed for the given event.
 * This returns true if shift and alt are pressed.
 */
mxConstraintHandler.prototype.isKeepFocusEvent = function(me)
{
	return mxEvent.isShiftDown(me.getEvent());
};

/**
 * Function: getCellForEvent
 * 
 * Returns the cell for the given event.
 */
mxConstraintHandler.prototype.getCellForEvent = function(me, point)
{
	var cell = me.getCell();
	
	// Gets cell under actual point if different from event location
	if (cell == null && point != null && (me.getGraphX() != point.x || me.getGraphY() != point.y))
	{
		cell = this.graph.getCellAt(point.x, point.y);
	}
	
	// Uses connectable parent vertex if one exists
	if (cell != null && !this.graph.isCellConnectable(cell))
	{
		var parent = this.graph.getModel().getParent(cell);
		
		if (this.graph.getModel().isVertex(parent) && this.graph.isCellConnectable(parent))
		{
			cell = parent;
		}
	}
	
	return cell;
};

/**
 * Function: update
 * 
 * Updates the state of this handler based on the given <mxMouseEvent>.
 * Source is a boolean indicating if the cell is a source or target.
 */
mxConstraintHandler.prototype.update = function(me, source, existingEdge, point)
{
	if (this.isEnabled() && !this.isEventIgnored(me))
	{
		// Lazy installation of mouseleave handler
		if (this.mouseleaveHandler == null && this.graph.container != null)
		{
			this.mouseleaveHandler = mxUtils.bind(this, function()
			{
				this.reset();
			});

			mxEvent.addListener(this.graph.container, 'mouseleave', this.resetHandler);	
		}
		
		var tol = this.getTolerance(me);
		var x = (point != null) ? point.x : me.getGraphX();
		var y = (point != null) ? point.y : me.getGraphY();
		var grid = new mxRectangle(x - tol, y - tol, 2 * tol, 2 * tol);
		var mouse = new mxRectangle(me.getGraphX() - tol, me.getGraphY() - tol, 2 * tol, 2 * tol);
		var state = this.graph.view.getState(this.getCellForEvent(me, point));

		// Keeps focus icons visible while over vertex bounds and no other cell under mouse or shift is pressed
		if (!this.isKeepFocusEvent(me) && (this.currentFocusArea == null || this.currentFocus == null ||
			(state != null) || !this.graph.getModel().isVertex(this.currentFocus.cell) ||
			!mxUtils.intersects(this.currentFocusArea, mouse)) && (state != this.currentFocus))
		{
			this.currentFocusArea = null;
			this.currentFocus = null;
			this.setFocus(me, state, source);
		}

		this.currentConstraint = null;
		this.currentPoint = null;
		var minDistSq = null;
		
		if (this.focusIcons != null && this.constraints != null &&
			(state == null || this.currentFocus == state))
		{
			var cx = mouse.getCenterX();
			var cy = mouse.getCenterY();
			
			for (var i = 0; i < this.focusIcons.length; i++)
			{
				var dx = cx - this.focusIcons[i].bounds.getCenterX();
				var dy = cy - this.focusIcons[i].bounds.getCenterY();
				var tmp = dx * dx + dy * dy;
				
				if ((this.intersects(this.focusIcons[i], mouse, source, existingEdge) || (point != null &&
					this.intersects(this.focusIcons[i], grid, source, existingEdge))) &&
					(minDistSq == null || tmp < minDistSq))
				{
					this.currentConstraint = this.constraints[i];
					this.currentPoint = this.focusPoints[i];
					minDistSq = tmp;
					
					var tmp = this.focusIcons[i].bounds.clone();
					tmp.grow(mxConstants.HIGHLIGHT_SIZE);
					
					if (mxClient.IS_IE)
					{
						tmp.grow(1);
						tmp.width -= 1;
						tmp.height -= 1;
					}
					
					if (this.focusHighlight == null)
					{
						var hl = this.createHighlightShape();
						hl.dialect = (this.graph.dialect == mxConstants.DIALECT_SVG) ?
								mxConstants.DIALECT_SVG : mxConstants.DIALECT_VML;
						hl.pointerEvents = false;

						hl.init(this.graph.getView().getOverlayPane());
						this.focusHighlight = hl;
						
						var getState = mxUtils.bind(this, function()
						{
							return (this.currentFocus != null) ? this.currentFocus : state;
						});
	
						mxEvent.redirectMouseEvents(hl.node, this.graph, getState);
					}

					this.focusHighlight.bounds = tmp;
					this.focusHighlight.redraw();
				}
			}
		}
		
		if (this.currentConstraint == null)
		{
			this.destroyFocusHighlight();
		}
	}
	else
	{
		this.currentConstraint = null;
		this.currentFocus = null;
		this.currentPoint = null;
	}
};

/**
 * Function: redraw
 * 
 * Transfers the focus to the given state as a source or target terminal. If
 * the handler is not enabled then the outline is painted, but the constraints
 * are ignored.
 */
mxConstraintHandler.prototype.redraw = function()
{
	if (this.currentFocus != null && this.constraints != null && this.focusIcons != null)
	{
		var state = this.graph.view.getState(this.currentFocus.cell);
		this.currentFocus = state;
		this.currentFocusArea = new mxRectangle(state.x, state.y, state.width, state.height);
		
		for (var i = 0; i < this.constraints.length; i++)
		{
			var cp = this.graph.getConnectionPoint(state, this.constraints[i]);
			var img = this.getImageForConstraint(state, this.constraints[i], cp);

			var bounds = new mxRectangle(Math.round(cp.x - img.width / 2),
				Math.round(cp.y - img.height / 2), img.width, img.height);
			this.focusIcons[i].bounds = bounds;
			this.focusIcons[i].redraw();
			this.currentFocusArea.add(this.focusIcons[i].bounds);
			this.focusPoints[i] = cp;
		}
	}	
};

/**
 * Function: setFocus
 * 
 * Transfers the focus to the given state as a source or target terminal. If
 * the handler is not enabled then the outline is painted, but the constraints
 * are ignored.
 */
mxConstraintHandler.prototype.setFocus = function(me, state, source)
{
	this.constraints = (state != null && !this.isStateIgnored(state, source) &&
		this.graph.isCellConnectable(state.cell)) ? ((this.isEnabled()) ?
		(this.graph.getAllConnectionConstraints(state, source) || []) : []) : null;

	// Only uses cells which have constraints
	if (this.constraints != null)
	{
		this.currentFocus = state;
		this.currentFocusArea = new mxRectangle(state.x, state.y, state.width, state.height);
		
		if (this.focusIcons != null)
		{
			for (var i = 0; i < this.focusIcons.length; i++)
			{
				this.focusIcons[i].destroy();
			}
			
			this.focusIcons = null;
			this.focusPoints = null;
		}
		
		this.focusPoints = [];
		this.focusIcons = [];
		
		for (var i = 0; i < this.constraints.length; i++)
		{
			var cp = this.graph.getConnectionPoint(state, this.constraints[i]);
			var img = this.getImageForConstraint(state, this.constraints[i], cp);

			var src = img.src;
			var bounds = new mxRectangle(Math.round(cp.x - img.width / 2),
				Math.round(cp.y - img.height / 2), img.width, img.height);
			var icon = new mxImageShape(bounds, src);
			icon.dialect = (this.graph.dialect != mxConstants.DIALECT_SVG) ?
					mxConstants.DIALECT_MIXEDHTML : mxConstants.DIALECT_SVG;
			icon.preserveImageAspect = false;
			icon.init(this.graph.getView().getDecoratorPane());
			
			// Fixes lost event tracking for images in quirks / IE8 standards
			if (mxClient.IS_QUIRKS || document.documentMode == 8)
			{
				mxEvent.addListener(icon.node, 'dragstart', function(evt)
				{
					mxEvent.consume(evt);
					
					return false;
				});
			}
			
			// Move the icon behind all other overlays
			if (icon.node.previousSibling != null)
			{
				icon.node.parentNode.insertBefore(icon.node, icon.node.parentNode.firstChild);
			}

			var getState = mxUtils.bind(this, function()
			{
				return (this.currentFocus != null) ? this.currentFocus : state;
			});
			
			icon.redraw();

			mxEvent.redirectMouseEvents(icon.node, this.graph, getState);
			this.currentFocusArea.add(icon.bounds);
			this.focusIcons.push(icon);
			this.focusPoints.push(cp);
		}
		
		this.currentFocusArea.grow(this.getTolerance(me));
	}
	else
	{
		this.destroyIcons();
		this.destroyFocusHighlight();
	}
};

/**
 * Function: createHighlightShape
 * 
 * Create the shape used to paint the highlight.
 * 
 * Returns true if the given icon intersects the given point.
 */
mxConstraintHandler.prototype.createHighlightShape = function()
{
	var hl = new mxRectangleShape(null, this.highlightColor, this.highlightColor, mxConstants.HIGHLIGHT_STROKEWIDTH);
	hl.opacity = mxConstants.HIGHLIGHT_OPACITY;
	
	return hl;
};

/**
 * Function: intersects
 * 
 * Returns true if the given icon intersects the given rectangle.
 */
mxConstraintHandler.prototype.intersects = function(icon, mouse, source, existingEdge)
{
	return mxUtils.intersects(icon.bounds, mouse);
};

/**
 * Function: destroy
 * 
 * Destroy this handler.
 */
mxConstraintHandler.prototype.destroy = function()
{
	this.reset();
	
	if (this.resetHandler != null)
	{
		this.graph.model.removeListener(this.resetHandler);
		this.graph.view.removeListener(this.resetHandler);
		this.graph.removeListener(this.resetHandler);
		this.resetHandler = null;
	}
	
	if (this.mouseleaveHandler != null && this.graph.container != null)
	{
		mxEvent.removeListener(this.graph.container, 'mouseleave', this.mouseleaveHandler);
		this.mouseleaveHandler = null;
	}
};