function obj_unique_name(name, obj)
{
  name = name.replaceAll('.', '_');
  if (!(name in obj)) return name;
  var t = 1;
  var n = name + t;
  while (n in obj) {
    t++;
    n = name+t;
  }
  return n;
}


var gameobject_impl = {
  get pos() {
    Debug.assert(this.master, `Entity ${this.toString()} has no master.`);
    return this.master.world2this(this.worldpos());
  },

  set pos(x) {
    Debug.assert(this.master, `Entity ${this.toString()} has no master.`);
    this.set_worldpos(this.master.this2world(x));
  },

  get angle() {
    Debug.assert(this.master, `No master set on ${this.toString()}`);
    return this.worldangle() - this.master.worldangle();
  },
  
  set angle(x) {
    var diff = x - this.angle;

    this.objects.forEach(function(x) {
      x.rotate(diff);
      x.pos = Vector.rotate(x.pos, diff);
    });

    this.sworldangle(x-this.master.worldangle());
  },

  get scale() {
    Debug.assert(this.master, `No master set on ${this.toString()}`);
    var pscale = [1,1,1];
    return this.gscale().map((x,i) => x/(this.master.gscale()[i]*pscale[i]));
  },

  set scale(x) {
    if (typeof x === 'number')
      x = [x,x];

    var pct = this.scale.map((s,i) => x[i]/s);
    this.grow(pct);
    
    /* TRANSLATE ALL SUB OBJECTS */
    this.objects.forEach(obj => {
      obj.grow(pct);
      obj.pos = obj.pos.map((x,i)=>x*pct[i]);
    });
  },

  get draw_layer() { return cmd(171, this.body); },
  set draw_layer(x) { cmd(172, this.body, x); },
  set layer(x) { cmd(75,this.body,x); },
  get layer() { return cmd(77,this.body); },
  set warp_layer(x) { cmd(251, this.body,x); },
  get warp_layer() { return cmd(252, this.body); },

  set mass(x) { set_body(7,this.body,x); },
  get mass() {
    if (!(this.phys === physics.dynamic))
      return undefined;

    return q_body(5, this.body);
  },
  get elasticity() { return cmd(107,this.body); },
  set elasticity(x) { cmd(106,this.body,x); },
  get friction() { return cmd(109,this.body); },
  set friction(x) { cmd(108,this.body,x); },
  set timescale(x) { cmd(168,this.body,x); },
  get timescale() { return cmd(169,this.body); },
  set phys(x) { set_body(1, this.body, x); },
  get phys() { return q_body(0,this.body); },
  get velocity() { return q_body(3, this.body); },
  set velocity(x) { set_body(9, this.body, x); },
  get damping() { return cmd(157,this.body); },
  set damping(x) { cmd(156, this.body, x); },
  get angularvelocity() { return Math.rad2turn(q_body(4,this.body)); },
  set angularvelocity(x) { set_body(8, this.body, Math.turn2rad(x)); },
  get max_velocity() { return cmd(152, this.body); },
  set max_velocity(x) { cmd(151, this.body, x); },
  get max_angularvelocity() { return cmd(155,this.body); },
  set max_angularvelocity(x) { cmd(154,this.body,x); },
  get_moi() { return q_body(6, this.body); },
  set_moi(x) {
    if(x <= 0) {
      console.error("Cannot set moment of inertia to 0 or less.");
      return;
    }
    set_body(13, this.body, x);
  },
};

var gameobject = {
  get_comp_by_name(name) {
    var comps = [];
    for (var c of Object.values(this.components))
      if (c.comp === name) comps.push(c);

    if (comps.length) return comps;
    return undefined;
  },
  check_dirty() {
    this._ed.urdiff = this.json_obj();
    this._ed.dirty = !Object.empty(this._ed.urdiff);
    return; // TODO: IMPLEMENT
    var lur = ur[this.master.ur];
    if (!lur) return;
    var lur = lur.objects[this.toString()];
    var d = ediff(this._ed.urdiff,lur);
    if (!d || Object.empty(d))
      this._ed.inst = true;
    else
      this._ed.inst = false;
  },
  _ed: {
    selectable: false,
    dirty: false
  },
  
  namestr() {
    var s = this.toString();
    if (this._ed.dirty)
      if (this._ed.inst) s += "#";
      else s += "*";
    return s;
  },

  urstr() {
    if (this._ed.dirty) return "*"+this.ur;
    return this.ur;
  },
  
  full_path() {
    return this.path_from(world);
  },
  /* pin this object to the to object */
  pin(to) {
    var p = cmd(222,this.body, to.body);
  },
  slide(to, a, b, min, max) {
    a ??= [0,0];
    b ??= [0,0];
    min ??= 0;
    max ??= 50;
    var p = cmd(229,this.body,to.body,a,b,min,max);
    p.max_force = 500;
    p.break();
  },
  pivot(to, piv) {
    piv ??= this.worldpos();
    var p = cmd(221,this.body,to.body,piv);
  },
  /* groove is on to, from local points a and b, anchored to this at local anchor */
  groove(to, a, b, anchor) {
    anchor ??= [0,0];
    var p = cmd(228, to.body, this.body, a, b, anchor);
  },
  damped_spring(to, length, stiffness, damping) {
    length ??= Vector.length(this.worldpos(), to.worldpos());
    stiffness ??= 1;
    damping ??= 1;
    var dc = 2*Math.sqrt(stiffness*this.mass);
    var p = cmd(227, this.body, to.body, [0,0], [0,0], stiffness, damping*dc);
  },
  damped_rotary_spring(to, angle, stiffness, damping) {
    angle ??= 0;
    stiffness ??= 1;
    damping ??= 1;
    /* calculate actual damping value from the damping ratio */
    /* damping = 1 is critical */
    var dc = 2*Math.sqrt(stiffness*this.get_moi()); /* critical damping number */
    /* zeta = actual/critical */
    var p = cmd(226,this.body,to.body,angle,stiffness,damping*dc);
  },
  rotary_limit(to, min, max) {
    var p = cmd(225,this.body,to.body, Math.turn2rad(min),Math.turn2rad(max));
  },
  ratchet(to,ratch) {
    var phase = this.angle - to.angle;
    var p = cmd(230, this.body, to.body, phase, Math.turn2rad(ratch));
  },
  gear(to, ratio) {
    phase ??= 1;
    ratio ??= 1;
    var phase = this.angle - to.angle;
    var p = cmd(223,this.body,to.body,phase,ratio);
  },
  motor(to, rate) {
    var p = cmd(231, this.body, to.body, rate);
  },
  
    path_from(o) {
      var p = this.toString();
      var c = this.master;
      while (c && c !== o && c !== world) {
        p = c.toString() + "." + p;
	c = c.master;
      }
      if (c === world) p = "world." + p;
      return p;
    },
  
    clear() {
      for (var k in this.objects) {
	this.objects[k].kill();
      };
      this.objects = {};
    },
    
    delay(fn, seconds) {
      var t = timer.delay(fn.bind(this), seconds);
      this.timers.push(t);
      return t;
    },

    tween(prop, values, def){
      var t = Tween.make(this, prop, values, def);
      t.play();
      
      var k = function() { t.pause(); }
      this.timers.push(k);
      return k;
    },

    cry(file) {
      this.crying =  audio.sound.play(file, audio.sound.bus.sfx);
      var killfn = () => {this.crying = undefined; console.warn("killed"); }
      this.crying.hook = killfn;
      return killfn;
    },

      set torque(x) { if (!(x >= 0 && x <= Infinity)) return; cmd(153, this.body, x); },
      gscale() { return cmd(103,this.body); },
      sgscale(x) {
        if (typeof x === 'number')
	  x = [x,x];
        cmd(36,this.body,x)
      },
      
      phys_material() {
        var mat = {};
	mat.elasticity = this.elasticity;
	mat.friction = this.friction;
	return mat;
      },

      worldpos() { return q_body(1,this.body); },
      set_worldpos(x) {
        var poses = this.objects.map(x => x.pos);
	set_body(2,this.body,x);
	this.objects.forEach((o,i) => o.set_worldpos(this.this2world(poses[i])));
      },
      screenpos() { return Window.world2screen(this.worldpos()); },

      worldangle() { return Math.rad2turn(q_body(2,this.body)); },
      sworldangle(x) { set_body(0,this.body,Math.turn2rad(x)); },

      get_ur() {
//        if (this.ur === 'empty') return undefined;
	return Object.access(ur,this.ur);
      },

      /* spawn an entity
         text can be:
	   the file path of a script
	   an ur object
	   nothing
      */
      spawn(text) {
	var ent = Object.create(gameobject);
	
        if (typeof text === 'object')
	  text = text.name;

        if (typeof text === 'undefined')
	  ent.ur = "empty";
  	else if (typeof text !== 'string') {
	  console.error(`Must pass in an ur type or a string to make an entity.`);
	  return;
	} else {
	  if (Object.access(ur,text))
	    ent.ur = text;
	  else if (io.exists(text))
	    ent.ur = "script";
	  else {
	    console.warn(`Cannot make an entity from '${text}'. Not a valid ur.`);
	    return;
	  }
	}
	    
	Object.mixin(ent,gameobject_impl);
	ent.body = make_gameobject();

	ent.components = {};
	ent.objects = {};
	ent.timers = [];
	 
	ent.reparent(this);

	 ent._ed = {
	   selectable: true,
	   dirty: false,
	   inst: false,
	   urdiff: {},
	 };

	 cmd(113, ent.body, ent); // set the internal obj reference to this obj

	 Object.hide(ent, 'ur', 'body', 'components', 'objects', '_ed', 'timers', 'master');
       if (ent.ur === 'empty') {
         if (!ur.empty.proto) ur.empty.proto = json.decode(json.encode(ent));
         return ent;
       }

       if (ent.ur === 'script')
         eval_env(io.slurp(text), ent, ent.ur);
       else 
         apply_ur(ent.ur, ent);

	 for (var [prop,p] of Object.entries(ent)) {
	   if (!p) continue;
	   if (typeof p !== 'object') continue;
	   if (component.isComponent(p)) continue;
	   if (!p.comp) continue;
	   ent[prop] = component[p.comp].make(ent);
	   Object.merge(ent[prop], p);
	   ent.components[prop] = ent[prop];
	 };

       check_registers(ent);
       ent.components.forEach(function(x) {
	 if (typeof x.collide === 'function')
	   register_collide(1, x.collide.bind(x), ent.body, x.shape);
       });
       
	
        if (typeof ent.load === 'function') ent.load();
	if (Game.playing())
  	  if (typeof ent.start === 'function') ent.start();
	
        var mur = ent.get_ur();
        if (mur && !mur.proto)
	    mur.proto = json.decode(json.encode(ent));
	    
        ent.sync();
	
	 if (!Object.empty(ent.objects)) {
	   var o = ent.objects;
	   delete ent.objects;
	   for (var i in o) {
	     say(`MAKING ${i}`);
	     var n = ent.spawn(ur[o[i].ur]);
	     ent.rename_obj(n.toString(), i);
	     delete o[i].ur;
	     Object.assign(n, o[i]);
	   }
	 }

        return ent;
      },

  /* Reparent 'this' to be 'parent's child */
  reparent(parent) {
    Debug.assert(parent, `Tried to reparent ${this.toString()} to nothing.`);
    if (this.master === parent) {
      console.warn("not reparenting ...");
      console.warn(`${this.master} is the same as ${parent}`);
      return;
    }

    this.master?.remove_obj(this);
    
    this.master = parent;
      
    function unique_name(list, name) {
      name ??= "new_object";
      var str = name.replaceAll('.', '_');
      var n = 1;
      var t = str;
      while (list.indexOf(t) !== -1) {
        t = str + n;
	n++;
      }
      return t;
    };

    var name = unique_name(Object.keys(parent.objects), this.ur);

    parent.objects[name] = this;
    parent[name] = this;
    this.toString = function() { return name; };
  },
  
   remove_obj(obj) {
     if (this[obj.toString()] === this.objects[obj.toString()])
       delete this[obj.toString()];
       
     delete this.objects[obj.toString()];
     delete this[obj.toString()];
   },

  components: {},
  objects: {},
  master: undefined,
  
    pulse(vec) { set_body(4, this.body, vec);},
    shove(vec) { set_body(12,this.body,vec);},
    shove_at(vec, at) { set_body(14,this.body,vec,at); },
    world2this(pos) { return cmd(70, this.body, pos); },
    this2world(pos) { return cmd(71, this.body, pos); },
    this2screen(pos) { return Window.world2screen(this.this2world(pos)); },
    screen2this(pos) { return this.world2this(Window.screen2world(pos)); },
    dir_world2this(dir) { return cmd(160, this.body, dir); },
    dir_this2world(dir) { return cmd(161, this.body, dir); },
      
    alive() { return this.body >= 0; },
    in_air() { return q_body(7, this.body);},

  hide() { this.components.forEach(x=>x.hide?.()); this.objects.forEach(x=>x.hide?.());},
  show() { this.components.forEach(function(x) { x.show?.(); }); this.objects.forEach(function(x) { x.show?.(); }); },

  width() {
    var bb = this.boundingbox();
    return bb.r - bb.l;
  },

  height() {
    var bb = this.boundingbox();
    return bb.t-bb.b;
  },

  /* Moving, rotating, scaling functions, world relative */
  move(vec) { this.set_worldpos(this.worldpos().add(vec)); },
  rotate(x) { this.sworldangle(this.worldangle()+x); },
  grow(vec) { this.sgscale(this.gscale().map((x,i)=>x*vec[i])); },

  /* Make a unique object the same as its prototype */
  revert() {
    var jobj = this.json_obj();
    var lobj = this.master.__proto__.objects[this.toString()];
    delete jobj.objects;
    Object.keys(jobj).forEach(function(x) {
      if (lobj && x in lobj)
        this[x] = lobj[x];
      else
        this[x] = this.__proto__[x];
    }, this);
    this.sync();
  },

  toString() { return "new_object"; },
  
  flipx() { return this.scale.x < 0; },
  flipy() { return this.scale.y < 0; },
  
  mirror(plane) {
    this.scale = Vector.reflect(this.scale, plane);
  },
  
    save:true,
    selectable:true,
    ed_locked:false,
    
    disable() { this.components.forEach(function(x) { x.disable(); });},
    enable() { this.components.forEach(function(x) { x.enable(); });},
    sync() {
     this.components.forEach(function(x) { x.sync?.(); });
     this.objects.forEach(function(x) { x.sync?.(); });
    },

      /* Bounding box of the object in world dimensions */
      boundingbox() {
	var boxes = [];
	boxes.push({
	  t:0,
	  r:0,
	  b:0,
	  l:0
	});

	for (var key in this.components) {
	  if ('boundingbox' in this.components[key])
	    boxes.push(this.components[key].boundingbox());
	}
	for (var key in this.objects)
	  boxes.push(this.objects[key].boundingbox());

	var bb = boxes.shift();

	boxes.forEach(function(x) { bb = bbox.expand(bb, x); });
	
	bb = bbox.move(bb, this.pos);

	return bb ? bb : bbox.fromcwh([0,0], [0,0]);
      },

      /* The unique components of this object. Its diff. */
      json_obj() {
        var u = this.get_ur();
	if (!u) return {};
	var proto = u.proto;
	var thiso = json.decode(json.encode(this)); // TODO: SLOW. Used to ignore properties in toJSON of components.
	
        var d = ediff(thiso,proto);
	
	d ??= {};
 
	var objects = {};
	proto.objects ??= {};
	var curobjs = {};
	for (var o in this.objects)
	  curobjs[o] = this.objects[o].instance_obj();

        var odiff = ediff(curobjs, proto.objects);
	if (odiff)
	  d.objects = curobjs;

	delete d.pos;
	delete d.angle;
	delete d.scale;
	delete d.velocity;
	delete d.angularvelocity;
        return d;
      },

      /* The object needed to store an object as an instance of a master */
      instance_obj() {
        var t = this.transform();
	t.ur = this.ur;
	return t;
      },

      proto() {
        var u = this.get_ur();
	if (!u) return {};
	return u.proto;
      },

      transform() {
        var t = {};
	t.pos = this.pos;
	if (t.pos.every(x=>x===0)) delete t.pos;
	t.angle = Math.places(this.angle,4);
	if (t.angle === 0) delete t.angle;
	t.scale = this.scale;
	t.scale = t.scale.map((x,i) => x/this.proto().scale[i]);
	t.scale = t.scale.map(x => Math.places(x,3));
	if (t.scale.every(x=>x===1)) delete t.scale;
	return t;
      },

      /* Velocity and angular velocity of the object */
      phys_obj() {
        var phys = {};
	phys.velocity = this.velocity;
	phys.angularvelocity = this.angularvelocity;
	return phys;
     },

      dup(diff) {
        var n = this.master.spawn(this.__proto__);
	Object.totalmerge(n, this.instance_obj());
	return n;
      },

  kill() {
    if (this.__kill) return;
    this.__kill = true;
    
    this.timers.forEach(t => t());
    this.timers = [];
    Event.rm_obj(this);
    Player.do_uncontrol(this);
    register_collide(2, undefined, this.body);
    
    if (this.master) {
      this.master.remove_obj(this);
      this.master = undefined;
    }
    
    if (this.__proto__.instances)
      delete this.__proto__.instances[this.toString()];

    for (var key in this.components) {
      this.components[key].kill();
      this.components[key].gameobject = undefined;
      delete this.components[key];
    }

    this.clear();
    this.objects = undefined;
    
    if (typeof this.stop === 'function') this.stop();
    if (typeof this.die === 'function') this.die();
  },

  up() { return [0,1].rotate(this.angle);},
  down() { return [0,-1].rotate(this.angle);},
  right() { return [1,0].rotate(this.angle);},
  left() { return [-1,0].rotate(this.angle); },

  make_objs(objs) {
    for (var prop in objs) {
      say(`spawning ${json.encode(objs[prop])}`);
      var newobj = this.spawn(objs[prop]);
    }
  },

  rename_obj(name, newname) {
    if (!this.objects[name]) {
      console.warn(`No object with name ${name}. Could not rename to ${newname}.`);
      return;
    }
    if (name === newname) {
      Object.hide(this, name);
      return;
    }
    if (this.objects[newname])
      return;

    this.objects[newname] = this.objects[name];
    this[newname] = this[name];
    this[newname].toString = function() { return newname; };
    Object.hide(this, newname);
    delete this.objects[name];
    delete this[name];
    return this.objects[newname];
  },

  add_component(comp, data, name) {
    data ??= undefined;
    if (typeof comp.make !== 'function') return;
    name ??= comp.toString();
    name = obj_unique_name(name, this);
    this[name] = comp.make(this);
    this[name].comp = comp.toString();
    this.components[name] = this[name];
    if (data)
      Object.assign(this[name], data);
    return this[name];
  },

  obj_descend(fn) {
    fn(this);
    for (var o in this.objects)
      this.objects[o].obj_descend(fn);
  },
}
Object.mixin(gameobject,gameobject_impl);

gameobject.spawn.doc = `Spawn an entity of type 'ur' on this entity. Returns the spawned entity.`;

gameobject.doc = {
  doc: "All objects in the game created through spawning have these attributes.",
  pos: "Position of the object, relative to its master.",
  angle: "Rotation of this object, relative to its master.",
  velocity: "Velocity of the object, relative to world.",
  angularvelocity: "Angular velocity of the object, relative to the world.",
  scale: "Scale of the object, relative to its master.",
  flipx: "Check if the object is flipped on its x axis.",
  flipy: "Check if the object is flipped on its y axis.",
  elasticity: `When two objects collide, their elasticities are multiplied together. Their velocities are then multiplied by this value to find their resultant velocities.`,
  friction: `When one object touches another, friction slows them down.`,
  mass: `The higher the mass of the object, the less forces will affect it.`,
  phys: `Set to 0, 1, or 2, representing static, kinematic, and dynamic.`,
  worldpos: `Function returns the world position of the object.`,
  set_worldpos: `Function to set the position of the object in world coordinates.`,
  worldangle: `Function to get the angle of the entity in the world.`,
  rotate: `Function to rotate this object by x degrees.`,
  move: 'Move an object by x,y,z. If the first parameter is an array, uses up to the first three array values.',
  pulse: `Apply an impulse to this body in world coordinates. Impulse is a short force.`,
  shove: `Apply a force to this body in world coordinates. Should be used over many frames.`,
  shove_at: 'Apply a force to this body, at a position relative to itself.',
  max_velocity: 'The max linear velocity this object can travel.',
  max_angularvelocity: 'The max angular velocity this object can rotate.',
  in_air: `Return true if the object is in the air.`,
  on_ground: `Return true if the object is on the ground.`,
  spawn: `Create an instance of a supplied ur-type on this object. Optionally provide a data object to modify the created entity.`,
  hide: `Make this object invisible.`,
  show: `Make this object visible.`,
  width: `The total width of the object and all its components.`,
  height: `The total height of the object.`,
  move: `Move this object the given amount.`,
  boundingbox: `The boundingbox of the object.`,
  dup: `Make an exact copy of this object.`,
  transform: `Return an object representing the transform state of this object.`,
  kill: `Remove this object from the world.`,
  master: "The entity this entity belongs to.",
  delay: 'Run the given function after the given number of seconds has elapsed.',
  cry: 'Make a sound. Can only make one at a time.',
  add_component: 'Add a component to the object by name.',
  pin: 'Pin joint to another object. Acts as if a rigid rod is between the two objects.',
  slide: 'Slide joint, similar to a pin but with min and max allowed distances.',
  pivot: 'Pivot joint to an object, with the pivot given in world coordinates.',
  groove: 'Groove joint. The groove is on to, from to local coordinates a and b, with this object anchored at anchor.',
  damped_spring: 'Damped spring to another object. Length is the distance it wants to be, stiffness is the spring constant, and damping is the damping ratio. 1 is critical, < 1 is underdamped, > 1 is overdamped.',
  damped_rotary_spring: 'Similar to damped spring but for rotation. Rest angle is the attempted angle.',
  rotary_limit: 'Limit the angle relative to the to body between min and max.',
  ratchet: 'Like a socket wrench, relative to to. ratch is the distance between clicks.',
  gear: 'Keeps the angular velocity ratio of this body and to constant. Ratio is the gear ratio.',
  motor: 'Keeps the relative angular velocity of this body to to at a constant rate. The most simple idea is for one of the bodies to be static, to the other is kept at rate.',
  layer: 'Bitmask for collision layers.',
  draw_layer: 'Layer for drawing. Higher numbers draw above lower ones.',
  warp_layer: 'Bitmask for selecting what warps should affect this entity.',
};

global.ur = {};

if (io.exists(".prosperon/ur.json"))
  ur = json.decode(io.slurp(".prosperon/ur.json"));
else {
  ur = {};
  ur._list = [];
}

/* UR OBJECT
ur {
  name: fully qualified name of ur
  text: file path to the script
  data: file path to data
  proto: resultant object of a freshly made entity
}
*/

/* Apply an ur u to an entity e */
/* u is given as */
function apply_ur(u, e)
{
  if (typeof u !== 'string') {
    console.warn("Must give u as a string.");
    return;
  }
  
  var urs = u.split('.');
  var config = {};
  var topur = ur;
  for (var i = 0; i < urs.length; i++) {
    topur = topur[urs[i]];
    if (!topur) {
      console.warn(`Ur given by ${u} does not exist. Stopped at ${urs[i]}.`);
      return;
    }

    if (topur.text) {
      var script = Resources.replstrs(topur.text);
      eval_env(script, e, topur.text);
    }
      
    if (topur.data) {
      var jss = Resources.replstrs(topur.data);
      Object.merge(config, json.decode(jss));
    }
  }

  Object.merge(e, config);
}

function file2fqn(file)
{
  var fqn = file.strip_ext();
  if (fqn.folder_same_name())
    fqn = fqn.up_path();

  fqn = fqn.replace('/','.');
  var topur;
  if (topur = Object.access(ur,fqn)) return topur;

  var fqnlast = fqn.split('.').last();

  if (topur = Object.access(ur,fqn.tolast('.'))) {
    topur[fqnlast] = {
      name: fqn
    };
    ur._list.push(fqn);
    return Object.access(ur,fqn);
  }
  
  fqn = fqnlast;
  
  ur[fqn] = {
    name: fqn
  };
  ur._list.push(fqn);
  return ur[fqn];
}

Game.loadurs = function() {
  ur = {};
  ur._list = [];
  /* FIND ALL URS IN A PROJECT */
  for (var file of io.glob("**.jso")) {
    if (file[0] === '.' || file[0] === '_') continue;
    var topur = file2fqn(file);
    topur.text = file;
  }

  for (var file of io.glob("**.json")) {
    if (file[0] === '.' || file[0] === '_') continue;
    var topur = file2fqn(file);
    topur.data = file;
  }

  ur.empty = {
    name: "empty"
  };
};

return {
  gameobject
}