extends SceneTree

const MAP_SIZE := 512
const HALF_SIZE := MAP_SIZE / 2
const HEIGHT_SCALE := 40.0
const DATA_DIRECTORY := "res://terrain/jajce/data"
const TEXTURE_DIRECTORY := "res://terrain/jajce/textures"
const Watercourse := preload("res://world/jajce/JajceWatercourse.gd")


func _initialize() -> void:
	call_deferred("_generate")


func _generate() -> void:
	DirAccess.make_dir_recursive_absolute(ProjectSettings.globalize_path(TEXTURE_DIRECTORY))
	_generate_texture("grass_albedo.png", Color("#516f36"), Color("#79924c"), 17)
	_generate_texture("soil_albedo.png", Color("#65513b"), Color("#92734d"), 29)
	_generate_texture("rock_albedo.png", Color("#55534f"), Color("#89847b"), 43)
	_generate_neutral_normal()

	var terrain := Terrain3D.new()
	terrain.region_size = 256
	root.add_child(terrain)
	await process_frame

	var height_map := Image.create_empty(MAP_SIZE, MAP_SIZE, false, Image.FORMAT_RF)
	var noise := FastNoiseLite.new()
	noise.seed = 1943
	noise.frequency = 0.018
	noise.fractal_octaves = 4
	noise.fractal_gain = 0.45

	for image_z in MAP_SIZE:
		for image_x in MAP_SIZE:
			var world_x := float(image_x - HALF_SIZE)
			var world_z := float(image_z - HALF_SIZE)
			var distance := Vector2(world_x, world_z).length()
			var outside_play_area := smoothstep(20.0, 52.0, distance)
			var ridge := 28.0 * _elliptical_peak(world_x, world_z, -72.0, 18.0, 72.0, 48.0)
			var eastern_hill := 15.0 * _elliptical_peak(world_x, world_z, 105.0, 65.0, 110.0, 90.0)
			var southern_hill := (
				11.0 * _elliptical_peak(world_x, world_z, -35.0, -125.0, 130.0, 85.0)
			)
			var broad_slope := maxf(0.0, (-world_x - 30.0) * 0.035)
			var detail := noise.get_noise_2d(world_x, world_z) * 2.4
			var height := (
				(ridge + eastern_hill + southern_hill + broad_slope + detail) * outside_play_area
			)
			height = _shape_waterfall_shelf(height, world_x, world_z, detail)
			height = _shape_upper_stream(height, world_x, world_z)
			height = _shape_plunge_pool(height, world_x, world_z)
			height = _shape_downstream_channel(height, world_x, world_z)
			height_map.set_pixel(image_x, image_z, Color(height / HEIGHT_SCALE, 0.0, 0.0, 1.0))

	terrain.data.import_images(
		[height_map, null, null], Vector3(-HALF_SIZE, 0.0, -HALF_SIZE), 0.0, HEIGHT_SCALE
	)
	terrain.data.save_directory(DATA_DIRECTORY)
	print("[TerrainGenerator] Generated bounded Jajce terrain and textures")
	quit(0)


func _elliptical_peak(
	x: float, z: float, center_x: float, center_z: float, width: float, depth: float
) -> float:
	return exp(-(pow((x - center_x) / width, 2.0) + pow((z - center_z) / depth, 2.0)))


func _shape_waterfall_shelf(height: float, x: float, z: float, detail: float) -> float:
	var horizontal_mask := 1.0 - smoothstep(10.0, 28.0, absf(x - Watercourse.WATERFALL_CENTER.x))
	var upstream_mask := smoothstep(-76.0, -54.0, z)
	var drop_mask := 1.0 - smoothstep(-25.0, -21.0, z)
	var shelf_mask := horizontal_mask * upstream_mask * drop_mask
	var shelf_height := Watercourse.SHELF_TOP_HEIGHT + detail * 0.08
	return lerpf(height, maxf(height, shelf_height), shelf_mask)


func _shape_upper_stream(height: float, x: float, z: float) -> float:
	if z < Watercourse.UPPER_STREAM_START_Z or z > Watercourse.UPPER_STREAM_END_Z:
		return height
	var center_x := Watercourse.upper_stream_center_x(z)
	var half_width := Watercourse.upper_stream_half_width(z)
	var channel_mask := 1.0 - smoothstep(half_width, half_width + 3.2, absf(x - center_x))
	var target_height := minf(height, Watercourse.upper_stream_bed_height(z))
	return lerpf(height, target_height, channel_mask)


func _shape_plunge_pool(height: float, x: float, z: float) -> float:
	var offset := Vector2(x, z) - Watercourse.PLUNGE_POOL_CENTER
	var elliptical_distance := Vector2(offset.x / 10.5, offset.y / 7.8).length()
	var basin_mask := 1.0 - smoothstep(0.68, 1.15, elliptical_distance)
	var cliff_front_mask := smoothstep(-25.0, -20.5, z)
	var target_height := minf(height, Watercourse.PLUNGE_POOL_BED_HEIGHT)
	return lerpf(height, target_height, basin_mask * cliff_front_mask)


func _shape_downstream_channel(height: float, x: float, z: float) -> float:
	if z < Watercourse.DOWNSTREAM_START_Z or z > Watercourse.DOWNSTREAM_END_Z:
		return height
	var center_x := Watercourse.downstream_center_x(z)
	var half_width := Watercourse.downstream_half_width(z)
	var bank_mask := 1.0 - smoothstep(half_width, half_width + 4.5, absf(x - center_x))
	var target_height := minf(height, Watercourse.downstream_bed_height(z))
	return lerpf(height, target_height, bank_mask)


func _generate_texture(
	file_name: String, dark_color: Color, light_color: Color, seed_value: int
) -> void:
	var noise := FastNoiseLite.new()
	noise.seed = seed_value
	noise.frequency = 0.035
	noise.fractal_octaves = 3
	var image := Image.create_empty(256, 256, false, Image.FORMAT_RGBA8)
	for y in image.get_height():
		for x in image.get_width():
			var value := noise.get_noise_2d(x, y) * 0.5 + 0.5
			var color := dark_color.lerp(light_color, value)
			color.a = value
			image.set_pixel(x, y, color)
	image.generate_mipmaps()
	var path := TEXTURE_DIRECTORY.path_join(file_name)
	var error := image.save_png(path)
	if error != OK:
		push_error("Could not write terrain texture: " + path)


func _generate_neutral_normal() -> void:
	var image := Image.create_empty(256, 256, false, Image.FORMAT_RGBA8)
	image.fill(Color(0.5, 0.5, 1.0, 0.86))
	image.generate_mipmaps()
	var path := TEXTURE_DIRECTORY.path_join("neutral_normal.png")
	var error := image.save_png(path)
	if error != OK:
		push_error("Could not write terrain normal texture: " + path)