/*
Creates or augments an object with Moving functionality.

args may contain x, y, speed, maxSpeed, angle.
*/
function MovingObject(someObj, args){
  // Default arguments
  var id = args.id;
  var x = args.x || 0;
  var y = args.y || 0;
  var speed = args.speed || 0;
  var maxSpeed = args.maxSpeed || 10000;
  var viewAngle = args.viewAngle || args.angle || 0;

  var prevX = args.prevX || x;
  var prevY = args.prevY || y;

  var obj = someObj || {};
  var speedAngle = args.speedAngle || viewAngle;



  var move = function(delta){
    //console.log("parent move " + x + "," + y + "," + speed + "," + speedAngle);
    var k = delta / 1000;
    
    obj.setX(x + Math.cos(speedAngle) * speed * k);
    obj.setY(y + -Math.sin(speedAngle) * speed * k); //-ve, since axis is inverted.
  }



  var adjustSpeed = function(ds){
    // Current speed vector
    var sx = Math.cos(speedAngle * speed);
    var sy = Math.sin(-(speedAngle * speed));
    
    // Add vectors
    sx += Math.cos(viewAngle) * ds;
    sy += Math.sin(-viewAngle) * ds;
    
    var ts = Math.sqrt(sx*sx + sy*sy); // New Magnitude
    speedAngle = Math.atan2(-sy, sx); //atan2??
    speed = Math.max(0, Math.min(ts, maxSpeed));
  };



  var adjustAngle = function(da){
    viewAngle += da;
    
    if(viewAngle < 0) viewAngle += 2*Math.PI;
    if(viewAngle > 2*Math.PI) viewAngle -= 2*Math.PI;
  };



  var equals = function (o){
    return o.getX && Math.abs(obj.getX() - o.getX()) < 0.0001 &&
          o.getY && Math.abs(obj.getY() - o.getY()) < 0.0001 &&
          o.getSpeed && Math.abs(obj.getSpeed() - o.getSpeed()) < 0.0001 &&
          o.getViewAngle && Math.abs(obj.getViewAngle() - o.getViewAngle()) < 0.0001 &&
          o.getObjectType() == obj.getObjectType();
  };
  
  
  
  var toObject = function(){
    return {id: id,
            x: x,
            y: y,
            prevX: prevX,
            prevY: prevY,
            speed: speed,
            maxSpeed: maxSpeed,
            viewAngle: viewAngle,
            speedAngle: speedAngle};
  };



  obj.setX = function(nx){ prevX = x; x = nx; };
  obj.getX = function(){ return x; };
  obj.getPreviousX = function(){ return prevX; };
  obj.setY = function(ny){ prevY = y; y = ny; };
  obj.getY = function(){ return y; };
  obj.getPreviousY = function(){ return prevY; };
  obj.setSpeed = function(ns){ speed = ns; };
  obj.getSpeed = function(){ return speed; };
  obj.getViewAngle = function(){ return viewAngle; };

  obj.accelerate = function(ds){ adjustSpeed(ds || 150); };
  obj.decelerate = function(ds){ adjustSpeed(-ds || -100); };

  obj.turnLeft = function(da){ adjustAngle(da || (Math.PI / 18)); };
  obj.turnRight = function(da){ adjustAngle(-da || (-Math.PI / 18)); };

  obj.move = move;
  obj.equals = equals;
  obj.toObject = toObject;
  obj.getObjectType = function(){ return -1; };

  return obj;
}






global.MovingObject = MovingObject;