class_name EditableTerrain extends Node

##
## Blank sample value.
##
const BLANK := Color(0.0, 0.0, 0.0, 0.0)

var _image := Image.create(1, 1, false, Image.FORMAT_RGBAF)

##
## Tracked [TerrainInstance3D] to echo all terrain editing changes to.
##
var instance: TerrainInstance3D = null:
	get:
		return instance

	set(value):
		if (value != null) and (value != instance):
			value.terrain_map = ImageTexture.create_from_image(_image)

		instance = value

##
## Width and height of the editable terrain in units.
##
var size := Vector2i.ZERO:
	get:
		return size

	set(value):
		_image.resize(value.x, value.y)

		if instance != null:
			instance.size = value
			instance.terrain_map = ImageTexture.create_from_image(_image)

		size = value

func _get_draw_area(point: Vector2i, mask: Image, scale: float) -> Rect2i:
	# Convert worldspace point to image-space coordinates for brush and calculate drawable area.
	var mask_size := mask.get_size()
	var scaled_mask_size := mask_size * scale

	return Rect2i(Vector2i.ZERO, size).intersection(
		Rect2i((point - Vector2i(scaled_mask_size * 0.5)) + Vector2i(size * 0.5), scaled_mask_size))

func _init() -> void:
	clear(BLANK)

##
## Clears the image to the value of [code]clear_color[/code].
##
func clear(clear_color: Color) -> void:
	_image.fill(clear_color)

##
##
##
func erase(point: Vector2i, mask: Image, scale: float, intensity: float, delta: float) -> void:
	var draw_area := _get_draw_area(point, mask, scale)

	if draw_area.has_area():
		var mask_ratio := mask.get_size() / draw_area.size

		for y in draw_area.size.y:
			var brush_mask_y := int(y * mask_ratio.y)

			for x in draw_area.size.x:
				var terrain_map_coord := draw_area.position + Vector2i(x, y)
				var pixel := _image.get_pixelv(terrain_map_coord)

				var mask_intensity_delta := intensity *\
					delta * mask.get_pixel(int(x * mask_ratio.x), brush_mask_y).a

				_image.set_pixelv(terrain_map_coord, Color(
					lerpf(pixel.r, 0.0, mask_intensity_delta),
						lerpf(pixel.g, 0.0, mask_intensity_delta),
							lerpf(pixel.b, 0.0, mask_intensity_delta),
								pixel.a))

		instance.terrain_map.update(_image)

##
##
##
func lower(point: Vector2i, mask: Image, scale: float, intensity: float, delta: float) -> void:
	var draw_area := _get_draw_area(point, mask, scale)

	if draw_area.has_area():
		var mask_ratio := mask.get_size() / draw_area.size

		for y in draw_area.size.y:
			var brush_mask_y := int(y * mask_ratio.y)

			for x in draw_area.size.x:
				var terrain_map_coord := draw_area.position + Vector2i(x, y)
				var pixel := _image.get_pixelv(terrain_map_coord)

				_image.set_pixelv(terrain_map_coord, Color(pixel.r, pixel.g, pixel.b,
					lerpf(pixel.a, pixel.a - (intensity *
						mask.get_pixel(int(x * mask_ratio.x), brush_mask_y).a), delta)))

		instance.terrain_map.update(_image)

##
##
##
func paint_blue(point: Vector2i, mask: Image, scale: float, intensity: float, delta: float) -> void:
	var draw_area := _get_draw_area(point, mask, scale)

	if draw_area.has_area():
		var mask_ratio := mask.get_size() / draw_area.size

		for y in draw_area.size.y:
			var brush_mask_y := int(y * mask_ratio.y)

			for x in draw_area.size.x:
				var terrain_map_coord := draw_area.position + Vector2i(x, y)
				var pixel := _image.get_pixelv(terrain_map_coord)

				_image.set_pixelv(terrain_map_coord, Color(
					pixel.r, pixel.g, lerpf(pixel.b, intensity, delta *\
						mask.get_pixel(int(x * mask_ratio.x), brush_mask_y).a),
							pixel.a))

		instance.terrain_map.update(_image)

##
##
##
func paint_green(point: Vector2i, mask: Image, scale: float, intensity: float, delta: float) -> void:
	var draw_area := _get_draw_area(point, mask, scale)

	if draw_area.has_area():
		var mask_ratio := mask.get_size() / draw_area.size

		for y in draw_area.size.y:
			var brush_mask_y := int(y * mask_ratio.y)

			for x in draw_area.size.x:
				var terrain_map_coord := draw_area.position + Vector2i(x, y)
				var pixel := _image.get_pixelv(terrain_map_coord)

				_image.set_pixelv(terrain_map_coord, Color(
					pixel.r, lerpf(pixel.g, intensity, delta *\
						mask.get_pixel(int(x * mask_ratio.x), brush_mask_y).a),
							pixel.b, pixel.a))

		instance.terrain_map.update(_image)

##
##
##
func paint_red(point: Vector2i, mask: Image, scale: float, intensity: float, delta: float) -> void:
	var draw_area := _get_draw_area(point, mask, scale)

	if draw_area.has_area():
		var mask_ratio := mask.get_size() / draw_area.size

		for y in draw_area.size.y:
			var brush_mask_y := int(y * mask_ratio.y)

			for x in draw_area.size.x:
				var terrain_map_coord := draw_area.position + Vector2i(x, y)
				var pixel := _image.get_pixelv(terrain_map_coord)

				_image.set_pixelv(terrain_map_coord, Color(
					lerpf(pixel.r, intensity, delta *\
						mask.get_pixel(int(x * mask_ratio.x), brush_mask_y).a),
							pixel.g, pixel.b, pixel.a))

		instance.terrain_map.update(_image)

##
##
##
func raise(point: Vector2i, mask: Image, scale: float, intensity: float, delta: float) -> void:
	var draw_area := _get_draw_area(point, mask, scale)

	if draw_area.has_area():
		var mask_ratio := mask.get_size() / draw_area.size

		for y in draw_area.size.y:
			var brush_mask_y := int(y * mask_ratio.y)

			for x in draw_area.size.x:
				var terrain_map_coord := draw_area.position + Vector2i(x, y)
				var pixel := _image.get_pixelv(terrain_map_coord)

				_image.set_pixelv(terrain_map_coord, Color(pixel.r, pixel.g, pixel.b,
					lerpf(pixel.a, pixel.a + (intensity *
						mask.get_pixel(int(x * mask_ratio.x), brush_mask_y).a), delta)))

		instance.terrain_map.update(_image)

##
## Samples the color value in the editable terrain at the worldspace [code]point[/code], returning
## its respective [Color] value.
##
## For sample coordinates outside of the terrain map worldspace, [code]BLANK[/code] is returned
## instead.
##
func sample(point: Vector2i) -> Color:
	var image_point := point + Vector2i(size * 0.5)

	if Rect2i(Vector2i.ZERO, size).has_point(image_point):
		return _image.get_pixelv(image_point)

	return BLANK

##
##
##
func smooth(point: Vector2i, mask: Image, scale: float, level: float, delta: float) -> void:
	var draw_area := _get_draw_area(point, mask, scale)

	if draw_area.has_area():
		var mask_ratio := mask.get_size() / draw_area.size

		for y in draw_area.size.y:
			var brush_mask_y := int(y * mask_ratio.y)

			for x in draw_area.size.x:
				var terrain_map_coord := draw_area.position + Vector2i(x, y)
				var pixel := _image.get_pixelv(terrain_map_coord)

				_image.set_pixelv(terrain_map_coord, Color(pixel.r, pixel.g, pixel.b,
					lerpf(pixel.a, level, delta * mask.get_pixel(
						int(x * mask_ratio.x), brush_mask_y).a)))

		instance.terrain_map.update(_image)