class_name Art
extends RefCounted
## Every graphic on the playing field has an id. Art draws it in the chosen
## style, or from a picture whose file name is the id, so that an artist can
## replace a graphic without changing code: res://art/terrain/ground.png
## replaces the drawing of GROUND.

## The style changed, or pictures were loaded. Everything drawn by Art has to
## be drawn again.
signal changed

const GROUND := &"terrain/ground"
const SOFT_ROCK := &"terrain/soft_rock"
const HARD_ROCK := &"terrain/hard_rock"
const BEDROCK := &"terrain/bedrock"
## The cracks of a tile that took hits, drawn over the tile.
const CRACKS := &"terrain/cracks"
## The burst where a pickaxe lands.
const HIT := &"effect/hit"
const FIGURE := &"figure"
## The outline of the tile under the mouse.
const MARKER := &"marker"
## Graphics of later milestones, shown in the showcase of the style samples.
const DEAD_SOIL := &"soil/dead"
const LIVING_SOIL := &"soil/living"
const MOSS := &"plant/moss"
const VINE := &"plant/vine"
const FIBER_PLANT := &"plant/fiber"
const STONE := &"item/stone"
const GRAZER := &"animal/grazer"
const RUIN := &"ruin"

## Every id, in the order the showcase and the checks go through them.
const IDS: Array[StringName] = [
	GROUND, SOFT_ROCK, HARD_ROCK, BEDROCK, CRACKS, HIT, FIGURE, MARKER,
	DEAD_SOIL, LIVING_SOIL, MOSS, VINE, FIBER_PLANT, STONE, GRAZER, RUIN,
]
## The folder where pictures that replace drawings are looked for.
const OVERRIDE_DIR := "res://art"

## The styles to choose from, in the order the game offers them.
var styles: Array[ArtStyle] = [WarmStyle.new(), PastelStyle.new(), GlowStyle.new()]
## The style everything is drawn in.
var style: ArtStyle = styles[0]
var _overrides: Dictionary[StringName, Texture2D] = {}


## The keys of the styles, as LaunchOptions and the settings name them.
static func style_keys() -> Array[StringName]:
	return [WarmStyle.KEY, PastelStyle.KEY, GlowStyle.KEY]


## Draws everything in the style named `key` from now on. Returns false, and
## changes nothing, if no style has that key.
func select(key: StringName) -> bool:
	for candidate in styles:
		if candidate.key() == key:
			if candidate != style:
				style = candidate
				changed.emit()
			return true
	return false


## Switches to the style after the current one, and from the last to the
## first.
func select_next() -> void:
	style = styles[(styles.find(style) + 1) % styles.size()]
	changed.emit()


## Uses the picture `<directory>/<id>.png` instead of the drawing, for every
## id that has one. Pictures loaded earlier are dropped.
func load_overrides(directory: String) -> void:
	_overrides.clear()
	for id in IDS:
		var texture := _load_texture(directory.path_join(String(id) + ".png"))
		if texture != null:
			_overrides[id] = texture
	changed.emit()


## True if a picture replaces the drawing of `id`.
func has_override(id: StringName) -> bool:
	return _overrides.has(id)


## Draws the graphic `id` into `rect` on `canvas`. Call it only while
## `canvas` draws, from its _draw(). `state` carries what the graphic shows,
## for example how far a plant has grown; see the styles for the entries.
func draw(canvas: CanvasItem, id: StringName, rect: Rect2, state: Dictionary = {}) -> void:
	var texture: Texture2D = _overrides.get(id)
	if texture != null:
		canvas.draw_texture_rect(texture, rect, false)
	else:
		style.draw(canvas, id, rect, state)


static func _load_texture(path: String) -> Texture2D:
	if path.begins_with("res://"):
		return load(path) as Texture2D if ResourceLoader.exists(path) else null
	if not FileAccess.file_exists(path):
		return null
	var image := Image.load_from_file(path)
	return ImageTexture.create_from_image(image) if image != null else null