class_name SeabedDetailTextures
extends RefCounted

## Procedural, seamless detail maps for the seabed shader, built synchronously from
## seeded noise so no texture asset is needed and every build is identical:
## an oriented sand ripple normal map, a rock normal map and the rock grain map
## (height, also read as occlusion and albedo mottling).

const TEXTURE_SIZE := 256
const RIPPLES_PER_TILE := 2.0
const RIPPLE_WARP := 0.22
const ROCK_BUMP_SCALE := 6.0
const SAND_BUMP_SCALE := 3.0

var sand_normal: ImageTexture
var rock_normal: ImageTexture
var rock_grain: ImageTexture


static func build(seed: int) -> SeabedDetailTextures:
	var result := SeabedDetailTextures.new()
	var rock_height := _rock_height_image(seed)
	result.rock_grain = _texture_from(rock_height)
	var rock_bumps := rock_height.duplicate() as Image
	rock_bumps.bump_map_to_normal_map(ROCK_BUMP_SCALE)
	result.rock_normal = _texture_from(rock_bumps)
	var sand_height := _sand_height_image(seed + 1)
	sand_height.bump_map_to_normal_map(SAND_BUMP_SCALE)
	result.sand_normal = _texture_from(sand_height)
	return result


## Ridged fractal noise: sharp crests and pits, seamless across the tile.
static func _rock_height_image(seed: int) -> Image:
	var noise := FastNoiseLite.new()
	noise.noise_type = FastNoiseLite.TYPE_SIMPLEX_SMOOTH
	noise.seed = seed
	noise.frequency = 0.012
	noise.fractal_type = FastNoiseLite.FRACTAL_RIDGED
	noise.fractal_octaves = 5
	return noise.get_seamless_image(TEXTURE_SIZE, TEXTURE_SIZE, false, false, 0.1, true)


## Ripples across the tile's v axis, warped and grained by noise. Asymmetric profile
## (gentle stoss side, steep lee side) as on a swell-built sand bed.
static func _sand_height_image(seed: int) -> Image:
	var warp := FastNoiseLite.new()
	warp.noise_type = FastNoiseLite.TYPE_SIMPLEX_SMOOTH
	warp.seed = seed
	warp.frequency = 0.02
	warp.fractal_octaves = 2
	var warp_image := warp.get_seamless_image(TEXTURE_SIZE, TEXTURE_SIZE, false, false, 0.1, true)
	var grain := FastNoiseLite.new()
	grain.noise_type = FastNoiseLite.TYPE_SIMPLEX_SMOOTH
	grain.seed = seed + 7
	grain.frequency = 0.15
	grain.fractal_octaves = 3
	var grain_image := grain.get_seamless_image(TEXTURE_SIZE, TEXTURE_SIZE, false, false, 0.1, true)
	var image := Image.create(TEXTURE_SIZE, TEXTURE_SIZE, false, Image.FORMAT_L8)
	for y in TEXTURE_SIZE:
		for x in TEXTURE_SIZE:
			var phase := (float(y) / float(TEXTURE_SIZE)) * RIPPLES_PER_TILE
			phase += (warp_image.get_pixel(x, y).r - 0.5) * RIPPLE_WARP
			var fraction := phase - floorf(phase)
			var crest := fraction / 0.7 if fraction < 0.7 else (1.0 - fraction) / 0.3
			var height := crest * 0.8 + grain_image.get_pixel(x, y).r * 0.2
			image.set_pixel(x, y, Color(height, height, height))
	return image


static func _texture_from(image: Image) -> ImageTexture:
	image.generate_mipmaps()
	return ImageTexture.create_from_image(image)