extends Node

## Fog texture state — visibility/exploration/zone tint images updated from GameState.
## Read by fog_shader.gd for shader uniforms. Not a renderer — pure data.
## Architecture: docs/architecture/fog-shader-spec.md | D-059

# Fog texture byte values — visibility and exploration layers.
# Used by fog shader to distinguish visual treatment per tile.
# Test assertions reference these: assert_that(byte).is_equal(FogState.VIS_FORWARD)
const VIS_HIDDEN: int = 0        # Not in LOS — fully fogged
const VIS_PERIPHERAL: int = 180  # In LOS, peripheral sector — light fog dimming
const VIS_FORWARD: int = 255     # In LOS, forward sector — clear vision

const EXP_UNEXPLORED: int = 0   # Never seen — total darkness
const EXP_EXPLORED: int = 128   # Previously seen, now out of LOS — deep fog
const EXP_VISIBLE: int = 255    # Currently in LOS — clear (written each frame)

var map_bounds: Rect2i = Rect2i(0, 0, 1, 1)
var visibility_texture: ImageTexture
var exploration_texture: ImageTexture
var zone_tint_texture: ImageTexture

var _vis_bytes: PackedByteArray
var _exp_bytes: PackedByteArray
var _vis_image: Image
var _exp_image: Image
var _tint_image: Image
var _width: int = 1
var _height: int = 1
var _prev_visible: Dictionary = {}  # Tiles visible last frame (for incremental decay)


func _ready() -> void:
	_resize(Rect2i(0, 0, 64, 64))


func _resize(bounds: Rect2i) -> void:
	map_bounds = bounds
	_width = maxi(bounds.size.x, 1)
	_height = maxi(bounds.size.y, 1)
	var sz := _width * _height

	_vis_bytes = PackedByteArray()
	_vis_bytes.resize(sz)
	_vis_bytes.fill(VIS_HIDDEN)
	_vis_image = Image.create_from_data(_width, _height, false, Image.FORMAT_R8, _vis_bytes)
	visibility_texture = ImageTexture.create_from_image(_vis_image)

	_exp_bytes = PackedByteArray()
	_exp_bytes.resize(sz)
	_exp_bytes.fill(EXP_UNEXPLORED)
	_exp_image = Image.create_from_data(_width, _height, false, Image.FORMAT_R8, _exp_bytes)
	exploration_texture = ImageTexture.create_from_image(_exp_image)

	# Zone tint — neutral dark for Sprint 6 (zone metadata deferred)
	_tint_image = Image.create(_width, _height, false, Image.FORMAT_RGB8)
	_tint_image.fill(Color(0.05, 0.05, 0.08))
	zone_tint_texture = ImageTexture.create_from_image(_tint_image)

	_prev_visible.clear()


func update_from_state() -> void:
	# Resize if map bounds changed
	var tiles := GameState.visible_tiles
	if tiles.size() > 0:
		var new_bounds := _compute_bounds(tiles)
		if new_bounds != map_bounds:
			_resize(new_bounds)

	var ox: int = map_bounds.position.x
	var oy: int = map_bounds.position.y
	var positions: Dictionary = GameState.visible_positions
	var sectors: Dictionary = GameState.visibility_sectors

	# TODO(v0.2): gradual decay over game-time instead of immediate EXP_VISIBLE→EXP_EXPLORED

	# 1. Clear visibility, then write current LOS
	_vis_bytes.fill(VIS_HIDDEN)
	for pos in positions:
		var px: int = pos.x - ox
		var py: int = pos.y - oy
		if px < 0 or py < 0 or px >= _width or py >= _height:
			continue
		var sector: String = sectors.get(pos, "Forward")
		_vis_bytes[py * _width + px] = VIS_FORWARD if sector == "Forward" else VIS_PERIPHERAL
	_vis_image.set_data(_width, _height, false, Image.FORMAT_R8, _vis_bytes)
	visibility_texture.update(_vis_image)

	# 2. Exploration: tiles leaving LOS decay to EXP_EXPLORED, visible tiles stay EXP_VISIBLE
	#    Only touch tiles that changed (O(visible) not O(map_size))
	for pos in _prev_visible:
		if not positions.has(pos):
			var px: int = pos.x - ox
			var py: int = pos.y - oy
			if px >= 0 and py >= 0 and px < _width and py < _height:
				var idx: int = py * _width + px
				if _exp_bytes[idx] > EXP_EXPLORED:
					_exp_bytes[idx] = EXP_EXPLORED

	for pos in positions:
		var px: int = pos.x - ox
		var py: int = pos.y - oy
		if px >= 0 and py >= 0 and px < _width and py < _height:
			_exp_bytes[py * _width + px] = EXP_VISIBLE
	_exp_image.set_data(_width, _height, false, Image.FORMAT_R8, _exp_bytes)
	exploration_texture.update(_exp_image)

	# Shallow copy — correct for Dictionary<Vector2i, bool/String> values
	_prev_visible = positions.duplicate()


func _compute_bounds(tiles: Array) -> Rect2i:
	var min_x := 999999
	var min_y := 999999
	var max_x := -999999
	var max_y := -999999
	for tile in tiles:
		if not tile is Dictionary or not tile.has("x") or not tile.has("y"):
			continue
		min_x = mini(min_x, int(tile.x))
		min_y = mini(min_y, int(tile.y))
		max_x = maxi(max_x, int(tile.x))
		max_y = maxi(max_y, int(tile.y))
	# Guard: all tiles invalid (no x/y) — sentinels would produce negative Rect2i
	if min_x > max_x:
		return Rect2i(0, 0, 1, 1)
	# Margin for fog gradient bleed at edges
	return Rect2i(min_x - 4, min_y - 4, max_x - min_x + 9, max_y - min_y + 9)