WireItLibrary

/**
 * The arrow wire widget
 * @class ArrowWire
 * @namespace WireIt
 * @extends WireIt.Wire
 * @constructor
 * @param  {WireIt.Terminal}    terminal1   Source terminal
 * @param  {WireIt.Terminal}    terminal2   Target terminal
 * @param  {HTMLElement} parentEl    Container of the CANVAS tag
 * @param  {Obj}                options      Wire configuration (see properties)
 */
WireIt.ArrowWire = function( terminal1, terminal2, parentEl, options) {
	WireIt.ArrowWire.superclass.constructor.call(this, terminal1, terminal2, parentEl, options);
};

YAHOO.lang.extend(WireIt.ArrowWire, WireIt.Wire, {
	
	/** 
    * @property xtype
    * @description String representing this class for exporting as JSON
    * @default "WireIt.ArrowWire"
    * @type String
    */
   xtype: "WireIt.ArrowWire",

   /**
    * Drawing methods for arrows
    */
   draw: function() {
		var d = 7; // arrow width/2
      var redim = d+3; //we have to make the canvas a little bigger because of arrows
      var margin=[4+redim,4+redim];

      // Get the positions of the terminals
      var p1 = this.terminal1.getXY();
      var p2 = this.terminal2.getXY();

      var distance=Math.sqrt(Math.pow(p1[0]-p2[0],2)+Math.pow(p1[1]-p2[1],2));

      var min=[ Math.min(p1[0],p2[0])-margin[0], Math.min(p1[1],p2[1])-margin[1]];
      var max=[ Math.max(p1[0],p2[0])+margin[0], Math.max(p1[1],p2[1])+margin[1]];

		// Store the min, max positions to display the label later
		this.min = min;
		this.max = max;      

      // Redimensionnement du canvas
      
      var lw=Math.abs(max[0]-min[0])+redim;
      var lh=Math.abs(max[1]-min[1])+redim;

      p1[0]=p1[0]-min[0];
      p1[1]=p1[1]-min[1];
      p2[0]=p2[0]-min[0];
      p2[1]=p2[1]-min[1];

      this.SetCanvasRegion(min[0],min[1],lw,lh);

      var ctxt=this.getContext();
      
      // Draw the border
      ctxt.lineCap=this.bordercap;
      ctxt.strokeStyle=this.bordercolor;
      ctxt.lineWidth=this.width+this.borderwidth*2;
      ctxt.beginPath();
      ctxt.moveTo(p1[0],p1[1]);
      ctxt.lineTo(p2[0],p2[1]);
      ctxt.stroke();

      // Draw the inner bezier curve
      ctxt.lineCap=this.cap;
      ctxt.strokeStyle=this.color;
      ctxt.lineWidth=this.width;
      ctxt.beginPath();
      ctxt.moveTo(p1[0],p1[1]);
      ctxt.lineTo(p2[0],p2[1]);
      ctxt.stroke();

		/* start drawing arrows */
		var t1 = p1;
		var t2 = p2;

		var z = [0,0]; //point on the wire with constant distance (dlug) from terminal2
		var dlug = 20; //arrow length
		var t = (distance === 0) ? 0 : 1-(dlug/distance);
		z[0] = Math.abs( t1[0] +  t*(t2[0]-t1[0]) );
		z[1] = Math.abs( t1[1] + t*(t2[1]-t1[1]) );	

		//line which connects the terminals: y=ax+b
		var a,b;
		var W = t1[0] - t2[0];
		var Wa = t1[1] - t2[1];
		var Wb = t1[0]*t2[1] - t1[1]*t2[0];
		if (W !== 0) {
			a = Wa/W;
			b = Wb/W;
		}
		else {
			a = 0;
		}
		//line perpendicular to the main line: y = aProst*x + b
		var aProst, bProst;
		if (a === 0) {
			aProst = 0;
		}
		else {
			aProst = -1/a;
		}
		bProst = z[1] - aProst*z[0]; //point z lays on this line

		//we have to calculate coordinates of 2 points, which lay on perpendicular line and have the same distance (d) from point z
		var A = 1 + Math.pow(aProst,2);
		var B = 2*aProst*bProst - 2*z[0] - 2*z[1]*aProst;
		var C = -2*z[1]*bProst + Math.pow(z[0],2) + Math.pow(z[1],2) - Math.pow(d,2) + Math.pow(bProst,2);
		var delta = Math.pow(B,2) - 4*A*C;
		if (delta < 0) { return; }

		var x1 = (-B + Math.sqrt(delta)) / (2*A);
		var x2 = (-B - Math.sqrt(delta)) / (2*A);	 
		var y1 = aProst*x1 + bProst;
		var y2 = aProst*x2 + bProst;

		if(t1[1] == t2[1]) {
			var o = (t1[0] > t2[0]) ? 1 : -1;
			x1 = t2[0]+o*dlug;
			x2 = x1;
			y1 -= d;
			y2 += d;
		}

		//triangle fill
		ctxt.fillStyle = this.color;
		ctxt.beginPath();
		ctxt.moveTo(t2[0],t2[1]);
		ctxt.lineTo(x1,y1);
		ctxt.lineTo(x2,y2);
		ctxt.fill();

		//triangle border	
		ctxt.strokeStyle = this.bordercolor;
		ctxt.lineWidth = this.borderwidth;
		ctxt.beginPath();
		ctxt.moveTo(t2[0],t2[1]);
		ctxt.lineTo(x1,y1);
		ctxt.lineTo(x2,y2);
		ctxt.lineTo(t2[0],t2[1]);
		ctxt.stroke();
   }
	
	
	
});