//==========================================================================================
//			arc_point.txt
//	Author: Clif Collins			Date: Jan 2010
//==========================================================================================

//==========================================================================================
//				arcToPoint
//==========================================================================================
function arcToPoint(arc)
{
	var points,x,y,cos,sin,p,angle;

	points = new Array();
	
	x = arc.radius;
	y = 0;

//---------- First Point -----------
	
	angle = (arc.start / 180) * Math.PI;
	cos = Math.cos(angle);
	sin = Math.sin(angle);

	p = new Object();
	p.x = ((x * cos) - (y * sin)) + arc.cx;
	p.y = ((x * sin) + (y * cos)) + arc.cy;

	points[0] = p
	
//---------- Mid Point -----------

	angle = ((arc.start + (arc.sweep / 2)) / 180) * Math.PI;
	cos = Math.cos(angle);
	sin = Math.sin(angle);

	p = new Object();
	p.x = ((x * cos) - (y * sin)) + arc.cx;
	p.y = ((x * sin) + (y * cos)) + arc.cy;

	points[1] = p

//---------- End Point -----------

	angle = ((arc.start + arc.sweep) / 180) * Math.PI;
	cos = Math.cos(angle);
	sin = Math.sin(angle);

	p = new Object();
	p.x = ((x * cos) - (y * sin)) + arc.cx;
	p.y = ((x * sin) + (y * cos)) + arc.cy;

	points[2] = p

	return points;
}
//======================================================================
//			pointToArc
//======================================================================
function pointToArc(pnt)
{
	var arc,b1,b2,y2,aline,bline,dx,dy,pnt;
	var sdir,cdir,edir;
	var x1,y1,x2,y2,x3,y3;
	var ts,tc,te,rev;

	x1 = pnt[0].x;
	y1 = pnt[0].y;
	x2 = pnt[1].x;
	y2 = pnt[1].y;
	x3 = pnt[2].x;
	y3 = pnt[2].y;

	arc = new Object();

	arc.start  	= 0;
	arc.sweep  	= 360;
	arc.radius	= 0.0;	
	arc.rev		= true;

//---------------------- Arc Center / Radius ------------------

	b1 = bisectLine(x1,y1,x2,y2)			// PERPENDICULAR BISECT
	if (b1 == null) return arc;

	b2 = bisectLine(x2,y2,x3,y3)			// PERPENDICULAR BISECT
	if (b2 == null) return arc;

	pnt =  isectLineLine(b1,b2);
	if (pnt == null) return arc;			// lines do not intersect

	arc.cx		= pnt.x;
	arc.cy		= pnt.y
	
	dx = arc.cx - x1;
	dy = arc.cy - y1;
	arc.radius = Math.sqrt(dx*dx + dy*dy);

//--------------------- Arc Angles ------------------------

	sdir = lineAngle(arc.cx,arc.cy,x1,y1);
	cdir = lineAngle(arc.cx,arc.cy,x2,y2);
	edir = lineAngle(arc.cx,arc.cy,x3,y3);

	sdir = (sdir + 360) % 360;
	cdir = (cdir + 360) % 360;
	edir = (edir + 360) % 360;

	ts = Math.max(sdir,edir);
	te = Math.min(sdir,edir);
	tc = cdir;

	sdir = ts;
	edir = te;

	ts = ts - te
	tc = tc - te			// ASSUME ORDERED
	ts = (ts + 360) % 360;
	tc = (tc + 360) % 360;

	if (ts > tc)
	{
		arc.rev = false;
		ts  = sdir;
		sdir = (edir + 360) % 360;
		edir = ts;
	}

//-------------- Set  Arc ------------------

	arc.start = sdir;
	arc.sweep = edir - sdir;
	if (arc.sweep > 360) arc.sweep = (360 - arc.sweep) % 360;

	return arc;
}
//======================================================================
//				bisectLine
//======================================================================
function bisectLine(x1,y1,x2,y2)
{
	var A,B,C,length;
	var dx,dy,x,y,lin;

	dx = x2 - x1;
	dy = y2 - y1;
	length = Math.sqrt(dx*dx + dy*dy);
	if (length < 0.000001) return null;

	A = (y2 - y1) / length;
	B = (x1 - x2) / length;
	C = (-A * x1) - (B * y1)

	x = (x1 + x2) / 2.0;
	y = (y1 + y2) / 2.0;

	lin = new Object();
	lin.A =  B
	lin.B = -A
	lin.C = ((-lin.A) * x) - (lin.B * y)

	return lin;
}
//======================================================================
//				isectLineLine
//======================================================================
function isectLineLine(L1,L2)
{
	var d,pnt;

	d = (L1.A * L2.B) - (L2.A * L1.B)
	if (Math.abs(d) < 0.00001) return null;

	pnt = new Object();
	pnt.x = ((L1.B * L2.C) - (L2.B * L1.C)) / d
	pnt.y = ((L1.A * L2.C) - (L2.A * L1.C)) / (-d)

	return pnt;
}
//======================================================================
//			   	lineAngle
//======================================================================
function lineAngle(x1,y1,x2,y2)
{
	var dir,dx,dy;

	dir = 0;
	dx = x2 - x1
	dy = y2 - y1

	if (Math.abs(dx) > 0.00001)
	{
	   d = dy / dx
	   dir = Math.atan(d);
	   if (isNaN(dir)) dir = 0;
	   if (Math.abs(dir) < 0.00001) dir = 0;

	   if (dx < 0 && dy < 0)  dir = dir + Math.PI;
	   if (dx < 0 && dy >= 0) dir = dir + Math.PI;
	}
	else
	{
		dir = 270 / 180 * Math.PI;
		if (y2 > y1) dir = 90 / 180 * Math.PI;
		if (Math.abs(y2-y1) < 0.00001) dir = 0;
	}

	dir = dir * 180 / Math.PI;
	dir = (dir + 360) % 360;
	
	return dir;	
}