class_name Chunk
extends Node


static var chunks: Array = []

const CHUNK_SIZE := Vector3i(16, 16, 16)

var position := Vector3i.ZERO
var mesh := MeshInstance3D.new()

@export var noise: FastNoiseLite
@export var blocks: Array = []


func generate_block_data(row: int, column: int, depth: int, empty: bool = false):
	position = Vector3i(row, column, depth)
	
	blocks = []
	for x in CHUNK_SIZE.x:
		blocks.append([])
		for y in CHUNK_SIZE.y:
			blocks[x].append([])
			for z in CHUNK_SIZE.z:
				var block_position = Vector3i(
					position.x * CHUNK_SIZE.x + x,
					position.y * CHUNK_SIZE.y + y,
					position.z * CHUNK_SIZE.z + z
				)# * 2
				var value = noise.get_noise_3d(block_position.x, block_position.y, block_position.z) * 100
				
				var type = Block.Type.AIR
				if value > -15:
					type = Block.Type.GRASS
				elif value > -20:
					type = Block.Type.STONE
				
				var block = Block.new()
				block.position = block_position
				block.type = type
				
				if empty:
					block.type = Block.Type.AIR
				
				blocks[x][y].append(block)


func generate_mesh() -> MeshInstance3D:
	var material := preload("res://new_shader_material.tres")
	var st = SurfaceTool.new()
	st.begin(Mesh.PRIMITIVE_TRIANGLES)
	st.set_material(material)
	
	for x in blocks.size():
		for y in blocks[x].size():
			for z in blocks[x][y].size():
				var block: Block = blocks[x][y][z]
				
				var block_front: Block
				if block_exists(x, y, z + 1):
					block_front = blocks[x][y][z + 1]
				elif is_chunk_border(x, y, z) and chunk_exists(position.x, position.y, position.z + 1):
					block_front = chunks[position.x][position.y][position.z + 1].blocks[x][y][0]
				
				var block_back: Block
				if block_exists(x, y, z - 1):
					block_back = blocks[x][y][z - 1]
				elif is_chunk_border(x, y, z) and chunk_exists(position.x, position.y, position.z - 1):
					block_back = chunks[position.x][position.y][position.z - 1].blocks[x][y][CHUNK_SIZE.z - 1]
				
				var block_left: Block
				if block_exists(x - 1, y, z):
					block_left = blocks[x - 1][y][z]
				elif is_chunk_border(x, y, z) and chunk_exists(position.x - 1, position.y, position.z):
					block_left = chunks[position.x - 1][position.y][position.z].blocks[CHUNK_SIZE.x - 1][y][z]
				
				var block_right: Block
				if block_exists(x + 1, y, z):
					block_right = blocks[x + 1][y][z]
				elif is_chunk_border(x, y, z) and chunk_exists(position.x + 1, position.y, position.z):
					block_right = chunks[position.x + 1][position.y][position.z].blocks[0][y][z]
				
				var block_top: Block
				if block_exists(x, y + 1, z):
					block_top = blocks[x][y + 1][z]
				elif is_chunk_border(x, y, z) and chunk_exists(position.x, position.y + 1, position.z):
					block_top = chunks[position.x][position.y + 1][position.z].blocks[x][0][z]
				
				var block_bottom: Block
				if block_exists(x, y - 1, z):
					block_bottom = blocks[x][y - 1][z]
				elif is_chunk_border(x, y, z) and chunk_exists(position.x, position.y - 1, position.z):
					block_bottom = chunks[position.x][position.y - 1][position.z].blocks[x][CHUNK_SIZE.y - 1][z]
				
				if not block.type == Block.Type.AIR:
					if block.type == Block.Type.GRASS:
						if block_top and block_top.type != Block.Type.AIR:
							block.type = Block.Type.DIRT
					
					var rng = RandomNumberGenerator.new()
					rng.seed = randi()
					st.set_color(Color(rng.randf(), rng.randf(), rng.randf()))
					
					st.set_uv(Vector2(0, 0))
					
					if not block_front or block_front.type == Block.Type.AIR:
						block.add_face(st, Block.Face.FRONT)
					
					if not block_right or block_right.type == Block.Type.AIR:
						block.add_face(st, Block.Face.RIGHT)
					
					if not block_back or block_back.type == Block.Type.AIR:
						block.add_face(st, Block.Face.BACK)
					
					if not block_left or block_left.type == Block.Type.AIR:
						block.add_face(st, Block.Face.LEFT)
					
					if not block_top or block_top.type == Block.Type.AIR:
						block.add_face(st, Block.Face.TOP)
					
					if not block_bottom or block_bottom.type == Block.Type.AIR:
						block.add_face(st, Block.Face.BOTTOM)
	
	
	#st.generate_normals()
	#mesh = MeshInstance3D.new()
	mesh.mesh = st.commit()
	
	for child in mesh.get_children():
		child.queue_free()
	mesh.create_trimesh_collision.call_deferred()
	
	mesh.set_meta("chunk", self)
	
	return mesh


func generate_chunk(row: int, column: int, depth: int):
	if blocks.is_empty():
		generate_block_data(row, column, depth)
	
	generate_mesh()


func add_block(block_position: Vector3, block_type: Block.Type = Block.Type.GRASS) -> void:
	var block = Block.new()
	block.position = Vector3i(
		position.x * CHUNK_SIZE.x + block_position.x,
		position.y * CHUNK_SIZE.y + block_position.y,
		position.z * CHUNK_SIZE.z + block_position.z
	)
	block.type = block_type
	
	blocks[block_position.x][block_position.y][block_position.z] = block
	generate_mesh.call_deferred()


func remove_block(block_position: Vector3) -> void:
	blocks[block_position.x][block_position.y][block_position.z].type = Block.Type.AIR
	generate_mesh.call_deferred()


static func chunk_exists(x: int, y: int, z: int):
	return x >= 0 and chunks.size() - 1 >= x and y >= 0 and chunks[x].size() - 1 >= y and z >= 0 and chunks[x][y].size() - 1 >= z

func block_exists(x: int, y: int, z: int):
	return x >= 0 and blocks.size() - 1 >= x and y >= 0 and blocks[x].size() - 1 >= y and z >= 0 and blocks[x][y].size() - 1 >= z

func is_chunk_border(x: int, y: int, z: int):
	return x == 0 or x == CHUNK_SIZE.x - 1 or y == 0 or y == CHUNK_SIZE.y - 1 or z == 0 or z == CHUNK_SIZE.z - 1


static func global_to_chunk(global_position: Vector3) -> Vector3i:
	return floor(global_position / Vector3(CHUNK_SIZE))

static func global_to_chunk_block(global_position: Vector3) -> Vector3i:
	return global_to_block(global_position) - CHUNK_SIZE * global_to_chunk(global_position)

static func global_to_block(global_position: Vector3) -> Vector3i:
	return floor(global_position)