var builder = new function(){
	var base = this
	
	var els = []

	base.init = function(){
		base.bind()
	}

	base.bind = function(){
		app.on("clip", rebuild)
	}

	function rebuild(){
		if (window.scene) {
			clear()
			build()
			bind()
		}
	}
	function build (){
		clipper.rooms = sort_rooms_by_id(clipper.rooms)

		clipper.regions.forEach(function(room){
			build_walls(room).forEach(function(el){
				els.push(el)
				scene.add(el)
			})
		})

		clipper.rooms = sort_rooms_by_height(clipper.rooms)
		clipper.rooms.forEach(function(room){
			build_floors(room).forEach(function(el){
				els.push(el)
				scene.add(el)
			})
		})

		clipper.rooms = sort_rooms_by_id(clipper.rooms)
	}
	
	function bind (){
		clipper.rooms.forEach(function(room){
			room.walls = room.group_mx_walls()
			room.walls.forEach(function(wall){
				wall.bind()
				wall.randomize_colors()
			})
		})
	}
	
	function clear (){
		els.forEach(function(el){
			scene.remove(el)
			el.destroy && el.destroy()
		})
		els = []
	}

	function build_walls (region){
		var room = clipper.rooms[ region.id ]
		
		var list = [], el = null
		
		var width = region.x.length()
		var depth = region.y.length()
		var height = room.height

		if (region.sides & FRONT) {
			el = make_wall('.front')
			el.width = width
			el.height = height
			el.rotationY = PI
			el.x = region.x.a + width/2
			el.y = height/2
			el.z = region.y.a
			el.rect = region
			el.side = FRONT
			room.mx_walls.push(el)
			list.push(el)
		}
		if (region.sides & BACK) {
			var el = make_wall('.back')
			el.width = width
			el.height = height
			el.rotationY = 0
			el.x = region.x.b - width/2
			el.y = height/2
			el.z = region.y.b
			el.rect = region
			el.side = BACK
			room.mx_walls.push(el)
			list.push(el)
		}
		if (region.sides & LEFT) {
			el = make_wall('.left')
			el.rotationY = HALF_PI
			el.height = height
			el.width = depth
			el.x = region.x.a
			el.y = height/2
			el.z = region.y.a + depth/2
			el.rect = region
			el.side = LEFT
			room.mx_walls.push(el)
			list.push(el)
		}
		if (region.sides & RIGHT) {
			el = make_wall('.right')
			el.rotationY = -HALF_PI
			el.height = height
			el.width = depth
			el.x = region.x.b
			el.y = height/2
			el.z = region.y.b - depth/2
			el.rect = region
			el.side = RIGHT
			room.mx_walls.push(el)
			list.push(el)
		}

		return list
	}

	function build_floors(room){
		var list = [], el = null
		
		var constructed = room.intersects.filter(function(room){ return room.constructed })
		sort_rooms_by_height(constructed)
		
		if (constructed.length > 0) {
			// render the regions that don't intersect with anything we've already rendered
			// if the height is different, calculate the overlapping sides and render half-walls
			room.regions.forEach(function(region){
				var intersected = false
				for (var i = 0; i < constructed.length; i++) {
					if (constructed[i].rect.contains(region)) {
						intersected = true
						// r.sides = 0xf
						// half_sides
					}
					else if (constructed[i].rect.intersects(region)) {
						intersected = true
						if (room.height < constructed[i].height) {
							list = list.concat( make_ceiling_walls( room, constructed[i], region ) )
						}
					}
				}
				if (! intersected) {
					el = make_floor(room, region) 
					list.push( el )
					room.mx_floor.push(el)

					el = make_ceiling(room, region) 
					list.push( el )
					room.mx_ceiling.push(el)
				}
			})

		}
		else {
			// render floor and ceiling for the entire rectangle
			el = make_floor(room, room.rect) 
			list.push( el )
			room.mx_floor.push(el)

			el = make_ceiling(room, room.rect) 
			list.push( el )
			room.mx_ceiling.push(el)
		}
		
		room.constructed = true
		return list
	}
	
	function make_ceiling_walls( lo, hi, region ){
		var list = []
		
		var width = region.x.length()
		var depth = region.y.length()
		var height = hi.height - lo.height
		
		if (! (region.half_sides & LEFT) && region.x.a == hi.rect.x.a) {
			el = make_wall('.left')
			el.rotationY = HALF_PI
			el.height = height
			el.width = depth
			el.x = region.x.a
			el.y = lo.height + height/2
			el.z = region.y.a + depth/2
			el.rect = region
			list.push(el)
			hi.walls.push(el)
			region.half_sides |= LEFT
		}

		if (! (region.half_sides & RIGHT) && region.x.b == hi.rect.x.b) {
			el = make_wall('.right')
			el.rotationY = -HALF_PI
			el.height = height
			el.width = depth
			el.x = region.x.b
			el.y = lo.height + height/2
			el.z = region.y.b - depth/2
			el.rect = region
			list.push(el)
			hi.walls.push(el)
			region.half_sides |= RIGHT
		}

		if (! (region.half_sides & FRONT) && region.y.a == hi.rect.y.a) {
			el = make_wall('.front')
			el.width = width
			el.height = height
			el.rotationY = PI
			el.x = region.x.a + width/2
			el.y = lo.height + height/2
			el.z = region.y.a
			el.rect = region
			list.push(el)
			hi.walls.push(el)
			region.half_sides |= FRONT
		}

		if (! (region.half_sides & BACK) && region.y.b == hi.rect.y.b) {
			el = make_wall('.back')
			el.width = width
			el.height = height
			el.rotationY = 0
			el.x = region.x.b - width/2
			el.y = lo.height + height/2
			el.z = region.y.b
			el.rect = region
			list.push(el)
			hi.walls.push(el)
			region.half_sides |= BACK
		}
		return list
	}

	function make_floor(room, region){
		var width = region.x.length()
		var depth = region.y.length()
		
		var el = make_wall('.floor')
		el.height = depth
		el.width = width
		el.x = region.x.a + width/2
		el.y = 0
		el.z = region.y.a + depth/2
		el.rotationX = PI/2
		el.rect = region
		el.side = FLOOR
		return el
	}
	function make_ceiling(room, region){
		var width = region.x.length()
		var depth = region.y.length()
		var height = room.height

		var el = make_wall('.ceiling')
		el.height = depth
		el.width = width
		el.x = region.x.a + width/2
		el.y = height
		el.z = region.y.a + depth/2
		el.rotationX = -PI/2
		el.rect = region
		el.side = CEILING
		return el
	}

	function make_wall(klass){
		var el = new MX.Object3D(".face" + (klass || ""))
		el.width = el.height = el.scaleX = el.scaleY = el.scaleZ = 1
		el.z = el.y = el.x = 0
		el.side = 0
		el.type = "Face"
		el.el.style.opacity = 1.0
		el.side = 0
		el.rect = null
		el.destroy = function(){
			this.el = this.rect = this.rect.x = this.rect.y = null
		}

		// possible if walls are opaque
		// el.el.classList.add("backface-hidden")

		return el
	}

}