class_name PixelStyle
extends ArtStyle
## Pixel art in the manner of classic farming games, drawn in code. A tile
## is 16 by 16 pixels, seen a little from the front: rock shows its face
## toward open ground, and figures, animals and plants stand upright. Every
## graphic is made once as a small image, pixel by pixel from the palette,
## and kept; the camera enlarges each pixel to a crisp square.
##
## The subclasses choose the palette and the outlines.

## Pixels along the edge of a tile.
const TILE := 16
## Rows of the face that rock shows toward open ground below it.
const FACE := 6
## Images of a burst of chips, from the hit to its end.
const HIT_FRAMES := 6
## Size of a figure: a tile wide and one and a half tiles tall.
const FIGURE_SIZE := Vector2i(16, 24)
const CLEAR := Color(0, 0, 0, 0)

## Colours by name; the subclass fills them.
var palette: Dictionary[String, Color] = {}
## The colours of the players, in the order of their numbers.
var players: Array[Color] = []
## True for outlines in a darker shade of what they surround, false for one
## dark outline colour.
var tinted_outlines := false
var _textures: Dictionary[String, Texture2D] = {}


## A small image that the drawings put their pixels on.
class Pixels:
	const SIDES: Array[Vector2i] = [Vector2i(1, 0), Vector2i(-1, 0), Vector2i(0, 1), Vector2i(0, -1)]
	const CLEAR := Color(0, 0, 0, 0)

	var image: Image
	var size: Vector2i

	func _init(width: int, height: int) -> void:
		size = Vector2i(width, height)
		image = Image.create_empty(width, height, false, Image.FORMAT_RGBA8)

	func has(x: int, y: int) -> bool:
		return x >= 0 and y >= 0 and x < size.x and y < size.y

	func put(x: int, y: int, color: Color) -> void:
		if has(x, y):
			image.set_pixel(x, y, color)

	## The colour at x, y, transparent outside the image.
	func at(x: int, y: int) -> Color:
		return image.get_pixel(x, y) if has(x, y) else CLEAR

	func filled(x: int, y: int) -> bool:
		return at(x, y).a > 0.0

	## Lays the translucent `color` over the pixel at x, y.
	func shade(x: int, y: int, color: Color) -> void:
		if has(x, y):
			image.set_pixel(x, y, image.get_pixel(x, y).blend(color))

	func rect(x: int, y: int, width: int, height: int, color: Color) -> void:
		for row in range(y, y + height):
			for column in range(x, x + width):
				put(column, row, color)

	## Fills the ellipse around cx, cy with the half axes rx and ry.
	func ellipse(cx: float, cy: float, rx: float, ry: float, color: Color) -> void:
		for row in range(floori(cy - ry), ceili(cy + ry) + 1):
			for column in range(floori(cx - rx), ceili(cx + rx) + 1):
				var dx := (column + 0.5 - cx) / rx
				var dy := (row + 0.5 - cy) / ry
				if dx * dx + dy * dy <= 1.0:
					put(column, row, color)

	## A line of single pixels from x0, y0 to x1, y1.
	func line(x0: int, y0: int, x1: int, y1: int, color: Color) -> void:
		var dx := absi(x1 - x0)
		var dy := -absi(y1 - y0)
		var sx := 1 if x0 < x1 else -1
		var sy := 1 if y0 < y1 else -1
		var error := dx + dy
		var x := x0
		var y := y0
		while true:
			put(x, y, color)
			if x == x1 and y == y1:
				return
			var twice := 2 * error
			if twice >= dy:
				error += dy
				x += sx
			if twice <= dx:
				error += dx
				y += sy

	## Surrounds everything solid drawn so far with a line one pixel wide: in
	## `color`, or, with `tinted`, in a darker shade of the pixel beside it.
	func outline(color: Color, tinted: bool) -> void:
		var found: Array[Vector3i] = []
		var colors: Array[Color] = []
		for y in size.y:
			for x in size.x:
				if filled(x, y):
					continue
				for side in SIDES:
					var beside := at(x + side.x, y + side.y)
					if beside.a >= 1.0:
						found.append(Vector3i(x, y, 0))
						colors.append(beside.darkened(0.5) if tinted else color)
						break
		for index in found.size():
			put(found[index].x, found[index].y, colors[index])


func player_color(player: int) -> Color:
	return players[maxi(0, player) % players.size()]


func _c(name: String) -> Color:
	return palette[name]


## The dark line around things, or around a thing of colour `fill` when
## outlines are tinted.
func _ink(fill: Color) -> Color:
	return fill.darkened(0.5) if tinted_outlines else _c("outline")


## A number from 0 to 1 that looks random and is the same for the same
## arguments.
static func _noise(x: int, y: int, salt: int) -> float:
	return float(TileShape.variant(Vector2i(x * 31 + salt * 977, y * 17 - salt * 131)) % 1000) / 1000.0


## The texture made by `make` under `key`, made only the first time.
func _image(key: String, make: Callable) -> Texture2D:
	var texture: Texture2D = _textures.get(key)
	if texture == null:
		var pixels: Pixels = make.call()
		texture = ImageTexture.create_from_image(pixels.image)
		_textures[key] = texture
	return texture


## Draws `texture` with its top left corner at `at`, on whole pixels.
static func _put(canvas: CanvasItem, texture: Texture2D, at: Vector2, modulate := Color.WHITE) -> void:
	canvas.draw_texture(texture, at.round(), modulate)


## The neighbours of `mask` that change how a tile looks: the four sides,
## and a corner only where both sides beside it are set.
static func _shape(mask: int) -> int:
	var result := mask & (TileShape.N | TileShape.E | TileShape.S | TileShape.W)
	var corners := [
		[TileShape.NE, TileShape.N | TileShape.E], [TileShape.SE, TileShape.S | TileShape.E],
		[TileShape.SW, TileShape.S | TileShape.W], [TileShape.NW, TileShape.N | TileShape.W],
	]
	for corner: Array in corners:
		var sides: int = corner[1]
		if (mask & corner[0]) != 0 and (mask & sides) == sides:
			result |= corner[0]
	return result


# Terrain.


func _ground(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	var shadow: int = state.get("solid", 0) & (TileShape.N | TileShape.W | TileShape.NW)
	var variant: int = state.get("variant", 0) % 8
	_put(canvas, _image("ground/%d/%d" % [shadow, variant], func() -> Pixels: return _earth(variant, shadow)), rect.position)


## The bare earth of the dead world: up to two soft patches of darker earth,
## a light grain or two, now and then a pebble.
func _earth(variant: int, shadow: int) -> Pixels:
	var pixels := Pixels.new(TILE, TILE)
	pixels.rect(0, 0, TILE, TILE, _c("ground"))
	var patches: int = [0, 1, 2, 1, 0, 1, 1, 2][variant]
	for patch in patches:
		var at := _spot(patch, variant, 2, 11)
		for dy in 2:
			for dx in range(-1, 2):
				if _noise(at.x + dx, at.y + dy, variant + 40) < 0.6:
					pixels.put(at.x + dx, at.y + dy, _c("ground_dark"))
	for grain in 1 + variant % 2:
		var at := _spot(grain + 4, variant, 1, 14)
		pixels.put(at.x, at.y, _c("ground_light"))
	if variant % 4 == 1:
		var at := _spot(9, variant, 3, 9)
		_pebble(pixels, at.x, at.y)
	_cast_shadow(pixels, shadow)
	return pixels


## A point in the tile that is the same for the same `index` and `variant`,
## from `low` to `low + span - 1` on both axes.
static func _spot(index: int, variant: int, low: int, span: int) -> Vector2i:
	return Vector2i(low + int(_noise(index, 1, variant) * span), low + int(_noise(index, 2, variant) * span))


func _pebble(pixels: Pixels, x: int, y: int) -> void:
	pixels.put(x, y, _c("pebble_light"))
	pixels.put(x + 1, y, _c("pebble"))
	pixels.put(x, y + 1, _c("pebble"))
	pixels.put(x + 1, y + 1, _c("pebble_dark"))


## Darkens the ground where rock to the north or west casts its shadow; the
## light falls from the top left.
func _cast_shadow(pixels: Pixels, shadow: int) -> void:
	var deep := Color(0, 0, 0, 0.32)
	var faint := Color(0, 0, 0, 0.16)
	if (shadow & TileShape.N) != 0:
		for x in TILE:
			pixels.shade(x, 0, deep)
			pixels.shade(x, 1, deep if x % 2 == 0 else faint)
			pixels.shade(x, 2, faint if x % 2 == 1 else CLEAR)
	if (shadow & TileShape.W) != 0:
		for y in range(1 if (shadow & TileShape.N) != 0 else 0, TILE):
			pixels.shade(0, y, faint)
	elif (shadow & (TileShape.N | TileShape.NW)) == TileShape.NW:
		pixels.shade(0, 0, deep)


func _soft_rock(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	_rock(canvas, rect, state, "soft")


func _hard_rock(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	_rock(canvas, rect, state, "hard")


func _bedrock(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	_rock(canvas, rect, state, "bed")


## Rock of `kind`: its top, and its face where the ground below is open.
## The ground shows where the outer corners are round.
func _rock(canvas: CanvasItem, rect: Rect2, state: Dictionary, kind: String) -> void:
	var mask := _shape(state.get("solid", 0))
	var variant: int = state.get("variant", 0) % 4
	_ground(canvas, rect, {"variant": state.get("variant", 0)})
	var key := "%s/%d/%d" % [kind, mask, variant]
	_put(canvas, _image(key, func() -> Pixels: return _rock_image(kind, mask, variant)), rect.position)


func _rock_image(kind: String, mask: int, variant: int) -> Pixels:
	var open_n := (mask & TileShape.N) == 0
	var open_e := (mask & TileShape.E) == 0
	var open_s := (mask & TileShape.S) == 0
	var open_w := (mask & TileShape.W) == 0
	var top_rows := TILE - FACE if open_s else TILE
	var ink := _c("outline")
	var pixels := Pixels.new(TILE, TILE)
	for y in TILE:
		for x in TILE:
			var color := _c(kind + "_top")
			if y >= top_rows:
				color = _c(kind + "_face")
				if y == top_rows or ((x + variant) % 4 == 0 and y < TILE - 2):
					color = _c(kind + "_face_dark")
			else:
				if (open_n and y == 1) or (open_w and x == 1):
					color = _c(kind + "_top_light")
				elif open_e and x == TILE - 2:
					color = _c(kind + "_top_dark")
				if open_s and y == top_rows - 1:
					color = _c(kind + "_lip")
			pixels.put(x, y, color)
	_rock_marks(pixels, kind, variant, top_rows)
	if open_n:
		pixels.rect(0, 0, TILE, 1, ink)
	if open_w:
		pixels.rect(0, 0, 1, TILE, ink)
	if open_e:
		pixels.rect(TILE - 1, 0, 1, TILE, ink)
	if open_s:
		pixels.rect(0, TILE - 1, TILE, 1, ink)
	# Inner corners, where the mass turns around open ground.
	if not open_n and not open_w and (mask & TileShape.NW) == 0:
		pixels.put(0, 0, ink)
	if not open_n and not open_e and (mask & TileShape.NE) == 0:
		pixels.put(TILE - 1, 0, ink)
	if not open_s and not open_w and (mask & TileShape.SW) == 0:
		pixels.rect(0, TILE - FACE, 1, FACE, ink)
	if not open_s and not open_e and (mask & TileShape.SE) == 0:
		pixels.rect(TILE - 1, TILE - FACE, 1, FACE, ink)
	# Round outer corners.
	if open_n and open_w:
		_round(pixels, Vector2i(0, 0), Vector2i(1, 1), ink)
	if open_n and open_e:
		_round(pixels, Vector2i(TILE - 1, 0), Vector2i(-1, 1), ink)
	if open_s and open_w:
		_round(pixels, Vector2i(0, TILE - 1), Vector2i(1, -1), ink)
	if open_s and open_e:
		_round(pixels, Vector2i(TILE - 1, TILE - 1), Vector2i(-1, -1), ink)
	return pixels


## Cuts the corner at `corner` and closes the outline one pixel further in,
## in the direction `inward`.
static func _round(pixels: Pixels, corner: Vector2i, inward: Vector2i, ink: Color) -> void:
	pixels.put(corner.x, corner.y, CLEAR)
	pixels.put(corner.x + inward.x, corner.y, CLEAR)
	pixels.put(corner.x, corner.y + inward.y, CLEAR)
	pixels.put(corner.x + inward.x, corner.y + inward.y, ink)


## Small details on the top of rock: pores and chips on soft rock, glinting
## crystals in hard rock, layers in bedrock.
func _rock_marks(pixels: Pixels, kind: String, variant: int, top_rows: int) -> void:
	var room := maxi(1, top_rows - 6)
	for pore in 2:
		var spot := Vector2i(3 + int(_noise(pore, 8, variant) * 10.0), 3 + int(_noise(pore, 9, variant) * room))
		pixels.put(spot.x, spot.y, _c(kind + "_top_dark"))
	var at := Vector2i(4 + int(_noise(7, 8, variant) * 7.0), 3 + int(_noise(7, 9, variant) * room))
	match kind:
		"soft":
			if variant % 2 == 0:
				pixels.put(at.x, at.y, _c("soft_top_dark"))
				pixels.put(at.x + 1, at.y, _c("soft_top_dark"))
				pixels.put(at.x + 1, at.y - 1, _c("soft_top_light"))
				pixels.put(at.x + 2, at.y + 1, _c("soft_top_dark"))
		"hard":
			if variant % 2 == 1:
				pixels.put(at.x, at.y, _c("hard_glint"))
				pixels.put(at.x + 1, at.y, _c("hard_top_light"))
				pixels.put(at.x, at.y + 1, _c("hard_top_light"))
		"bed":
			for row in range(4, top_rows - 1, 5):
				for column in range(3, TILE - 3):
					if _noise(column, row, variant) < 0.5:
						pixels.put(column, row, _c("bed_top_dark"))


func _cracks(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	var hits := clampi(state.get("hits", 1), 1, 3)
	var variant: int = state.get("variant", 0) % 4
	_put(canvas, _image("cracks/%d/%d" % [hits, variant], func() -> Pixels: return _crack_image(hits, variant)), rect.position)


func _crack_image(hits: int, variant: int) -> Pixels:
	var pixels := Pixels.new(TILE, TILE)
	var path: Array[Vector2i] = []
	var at := Vector2i(5 + variant, 3)
	for step in 2 + hits * 3:
		path.append(at)
		var turn := _noise(step, hits, variant)
		at += Vector2i(-1 if turn < 0.3 else (1 if turn > 0.65 else 0), 1)
	if hits >= 2:
		var branch: Vector2i = path[path.size() >> 1]
		for step in 3:
			branch += Vector2i(1, 1 if step % 2 == 0 else 0)
			path.append(branch)
	for point in path:
		pixels.put(point.x + 1, point.y, _c("soft_top_light"))
	for point in path:
		pixels.put(point.x, point.y, _c("outline"))
	return pixels


func _hit(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	var frame := clampi(int(float(state.get("age", 0.0)) * HIT_FRAMES), 0, HIT_FRAMES - 1)
	var variant: int = state.get("variant", 0) % 4
	_put(canvas, _image("hit/%d/%d" % [frame, variant], func() -> Pixels: return _hit_image(frame, variant)), rect.position - Vector2(8, 8))


## Chips that fly up and fall, and a puff of dust, in a square of two tiles
## around the tile.
func _hit_image(frame: int, variant: int) -> Pixels:
	var pixels := Pixels.new(TILE * 2, TILE * 2)
	var t := (frame + 1.0) / HIT_FRAMES
	for chip in 5:
		var angle := -PI / 2.0 + (chip - 2) * 0.6 + (variant - 1.5) * 0.15
		var distance := 3.0 + t * 10.0
		var x := roundi(TILE + cos(angle) * distance)
		var y := roundi(TILE - 1 + sin(angle) * distance + t * t * 10.0)
		pixels.put(x, y, _c("soft_top_light"))
		if frame < 3 and chip % 2 == 0:
			pixels.put(x + 1, y, _c("soft_top"))
			pixels.put(x, y + 1, _c("soft_face"))
			pixels.put(x + 1, y + 1, _c("soft_face_dark"))
	if frame < 3:
		pixels.outline(_c("outline"), tinted_outlines)
		var radius := 3.0 + frame * 2.0
		for puff in 8:
			var angle := TAU * puff / 8.0 + variant
			var dust := _c("dust")
			dust.a = 0.75 - frame * 0.2
			pixels.put(roundi(TILE + cos(angle) * radius), roundi(TILE - 1 + sin(angle) * radius * 0.6), dust)
	return pixels


func _marker(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	var reachable: bool = state.get("reachable", false)
	_put(canvas, _image("marker/%s" % reachable, func() -> Pixels: return _marker_image(reachable)), rect.position - Vector2(1, 1))


## Four corners around the tile, with a dark rim that shows on any ground.
func _marker_image(reachable: bool) -> Pixels:
	var pixels := Pixels.new(TILE + 2, TILE + 2)
	var color := _c("marker_near") if reachable else _c("marker_far")
	var last := TILE
	for corner: Vector2i in [Vector2i(1, 1), Vector2i(last, 1), Vector2i(1, last), Vector2i(last, last)]:
		var dx := 1 if corner.x == 1 else -1
		var dy := 1 if corner.y == 1 else -1
		for i in 4:
			pixels.put(corner.x + dx * i, corner.y, color)
			pixels.put(corner.x, corner.y + dy * i, color)
	pixels.outline(_c("outline"), false)
	return pixels


# Figures.


func _figure(canvas: CanvasItem, rect: Rect2, state: Dictionary) -> void:
	var frame := 0
	if state.get("moving", false):
		frame = 1 + int(fposmod(float(state.get("step", 0.0)), TAU) / TAU * 4.0) % 4
	var colour := maxi(0, state.get("player", -1)) % players.size()
	var left: bool = float(state.get("facing", 1.0)) < 0.0
	var foot := Vector2(rect.get_center().x, rect.end.y)
	_put(canvas, _image("shadow/12", func() -> Pixels: return _shadow_image(12)), foot - Vector2(6, 2))
	var key := "figure/%d/%d/%s" % [colour, frame, left]
	_put(canvas, _image(key, func() -> Pixels: return _figure_image(colour, frame, left)), foot - Vector2(FIGURE_SIZE.x / 2.0, FIGURE_SIZE.y))


## A soft shadow on the ground, `width` pixels wide.
func _shadow_image(width: int) -> Pixels:
	var pixels := Pixels.new(width, 3)
	pixels.ellipse(width / 2.0, 1.5, width / 2.0, 1.5, Color(0, 0, 0, 0.28))
	return pixels


## A figure in walking frame `frame` (0 standing, 1 to 4 walking), facing
## right or, with `left`, left. The shirt has the colour of the player.
func _figure_image(colour: int, frame: int, left: bool) -> Pixels:
	var pixels := Pixels.new(FIGURE_SIZE.x, FIGURE_SIZE.y)
	var shirt := players[colour]
	# The body sinks a pixel while the legs are apart, so the head always keeps
	# a free row above it for its outline.
	var bob := 1 if frame == 1 or frame == 3 else 0
	# The far leg and the near leg, by frame.
	var legs: Array[Vector2i] = [Vector2i(6, 9), Vector2i(5, 10), Vector2i(7, 8), Vector2i(10, 5), Vector2i(8, 7)]
	for leg in 2:
		var x := legs[frame].x if leg == 0 else legs[frame].y
		var lifted := 1 if frame > 0 and frame % 2 == 1 and leg == 0 else 0
		pixels.rect(x, 18, 2, 4 - lifted, _c("pants_dark") if leg == 0 else _c("pants"))
		pixels.rect(x, 22 - lifted, 3, 2, _c("boots"))
	pixels.rect(5, 11 + bob, 6, 8, shirt)
	pixels.rect(5, 11 + bob, 1, 8, shirt.darkened(0.2))
	pixels.rect(5, 18 + bob, 6, 1, shirt.darkened(0.35))
	var swing: int = [0, 1, 0, -1, 0][frame]
	pixels.rect(8 + swing, 12 + bob, 2, 5, shirt.darkened(0.15))
	pixels.rect(8 + swing, 17 + bob, 2, 1, _c("skin"))
	# The head: hair behind, the face in front, bangs above the eye.
	pixels.ellipse(7.8, 5.8 + bob, 5.2, 5.0, _c("hair"))
	pixels.ellipse(9.6, 7.4 + bob, 3.7, 3.9, _c("skin"))
	pixels.rect(9, 3 + bob, 4, 2, _c("hair"))
	pixels.put(6, 2 + bob, _c("hair_light"))
	pixels.put(7, 2 + bob, _c("hair_light"))
	pixels.put(8, 1 + bob, _c("hair_light"))
	pixels.put(11, 6 + bob, _c("eye"))
	pixels.put(11, 7 + bob, _c("eye"))
	pixels.put(8, 8 + bob, _c("skin_shade"))
	pixels.put(12, 9 + bob, _c("skin_shade"))
	pixels.outline(_ink(shirt), tinted_outlines)
	if left:
		pixels.image.flip_x()
	return pixels