class_name Shape
# FIXME: Potential incompatibility between different game versions that have different shapes.

static var REGISTRY: Array[Shape]
static func lookup(id: int) -> Shape:
	return REGISTRY[id] if (id >= 0) and (id < REGISTRY.size()) else EMPTY

# Initialized in `Base._static_init`.
static var EMPTY : Shape
static var FULL  : Shape

## Default shape to return when chunk or layer is not found.
static var DEFAULT : Shape

var id     : int
var base   : Base
var mirror : bool
var angle  : int
var shape  : Shape2D
var points : PackedVector2Array
var uvs    : PackedVector2Array

func _init(base: Base, mirror: bool, angle: int, shape: Shape2D, points: PackedVector2Array) -> void:
	id = REGISTRY.size()
	REGISTRY.append(self)

	self.base   = base
	self.mirror = mirror
	self.angle  = angle
	self.shape  = shape
	self.points = points

	# TODO: Define UVs properly.
	for point in points:
		uvs.append((Vector2.ONE / 2) + point)


## Represents a base shape, before it has been rotated and mirrored
## (if applicable) to create a number of variants based on that shape.
class Base:
	static var EMPTY          := Base.new("empty")
	static var FULL           := Base.new("full"          , _rect())
	static var HALF           := Base.new("half"          , [ 0,1, 2,1, 2,2, 0,2 ], true)
	static var SLOPE          := Base.new("slope"         , [ 0,1, 1,0, 1,1      ], true)
	static var HALF_SLOPE     := Base.new("half_slope"    , [ 0,2, 1,0, 2,2      ], true, true)
	static var HALF_SLOPE_BIG := Base.new("half_slope_big", [ 0,1, 2,0, 2,2, 0,2 ], true, true)

	static func _static_init() -> void:
		Shape.EMPTY = EMPTY.variants[0]
		Shape.FULL  = FULL .variants[0]
		Shape.DEFAULT = Shape.EMPTY

	var name     : String
	var variants : Array[Shape]

	func _init(name: String, shape = null, rotated := false, mirrored := false) -> void:
		self.name = name
		if shape == null:
			variants.append(Shape.new(self, false, 0, null, PackedVector2Array()))
		elif shape is RectangleShape2D:
			variants.append(Shape.new(self, false, 0, shape, _points(shape)))
			if rotated:
				shape = _rotate(shape) # rotate by 90 degrees (swap x and y components)
				variants.append(Shape.new(self, false, 0, shape, _points(shape)))
		elif shape is Array:
			# Convert points (pairs of `int`s) in `Array` to convex shape.
			var factor := float(shape.max())
			var points_orig := PackedVector2Array() # untransformed points
			for i in range(0, shape.size(), 2):
				var point := Vector2(shape[i] / factor, shape[i + 1] / factor)
				points_orig.append(point - (Vector2.ONE / 2)) # ensure shape is centered

			# Add variations of the shape (rotated, mirrored), including the standard shape.
			for mirror in [ false, true ] if mirrored else [ false ]:
				for angle in [ 0, 90, 180, 270 ] if rotated else [ 0 ]:
					var points := points_orig.duplicate() # transformed points
					# Technically we could skip `duplicate()` if not mirrored and not rotated, but eh.

					if mirror: # Mirror (flip) points along the X axis.
						for i in points.size(): points[i] *= Transform2D.FLIP_X

					if angle != 0: # Rotate points around the center.
						var transform := Transform2D(deg_to_rad(angle), Vector2.ZERO)
						for i in points.size(): points[i] *= transform

					var shape_points: PackedVector2Array
					for point in points: shape_points.append(point * Block.SIZE)
					shape = ConvexPolygonShape2D.new()
					shape.points = shape_points

					variants.append(Shape.new(self, mirror, angle, shape, points))
		else:
			breakpoint

	static func _rect(w := 1.0, h := 1.0) -> RectangleShape2D:
		var rect := RectangleShape2D.new()
		rect.size = Vector2(w, h) * Block.SIZE
		return rect
	static func _rotate(rect: RectangleShape2D) -> RectangleShape2D:
		return _rect(rect.size.y, rect.size.x)
	static func _points(rect: RectangleShape2D) -> PackedVector2Array:
		var w := rect.size.x / Block.SIZE / 2
		var h := rect.size.y / Block.SIZE / 2
		return [ Vector2(-w, -h), Vector2(w, -h), Vector2(w, h), Vector2(-w, h) ]


class Layer extends StaticBody2D:
	var data: PackedByteArray

	var chunk: Chunk:
		get: return get_parent()

	func _init() -> void:
		data.resize(Chunk.SIZE * Chunk.SIZE)

	static func load(buffer: StreamBuffer) -> Layer:
		var result := Layer.new()
		buffer.read_raw_buffer_into(result.data)
		return result

	func save(buffer: StreamBuffer) -> void:
		buffer.write_raw_buffer(data)

	func get_at(pos: Vector2i) -> Shape:
		var index := Chunk.array_index(pos)
		return Shape.lookup(data[index])

	func set_at(pos: Vector2i, value: Shape) -> void:
		set_id_at(pos, value.id)
	@rpc("reliable")
	func set_id_at(pos: Vector2i, id: int) -> void:
		var index := Chunk.array_index(pos)
		if data[index] == id: return

		# TODO: Keep track of how many non-air blocks are present, to allow for cleaning empty chunks.
		data[index] = id
		chunk.dirty = true

		if multiplayer.is_server():
			# Send change to every player tracking this chunk.
			for player in chunk.get_players_tracking():
				if player.network.is_local: continue # skip server player
				set_id_at.rpc_id(player.network.peer_id, pos, id)


	func _ready() -> void:
		# TODO: Only update if shapes have been changed.
		chunk.clean.connect(_update_shapes)
		_update_shapes()

	func _update_shapes() -> void:
		const CHUNK_HALF_SIZE := (Vector2.ONE * Chunk.SIZE * Block.SIZE) / 2

		# FIXME: Updating the shape like this is not ideal.
		for child in get_children():
			if child is CollisionShape2D:
				child.queue_free()

		for pos in BlockRegion.LOCAL_CHUNK:
			var shape := get_at(pos)
			if shape.shape == null: continue

			var shape2d := CollisionShape2D.new()
			shape2d.name     = "Block %s" % pos
			shape2d.position = (Vector2(pos) + (Vector2.ONE / 2)) * Block.SIZE - CHUNK_HALF_SIZE
			shape2d.shape    = shape.shape
			add_child(shape2d)