class_name MapGen
extends RefCounted
## Builds a dungeon: generated rooms and corridors around a hand-authored boss
## arena (see [Rooms]).
##
## Deterministic from (seed, depth) alone, so the server can hand a client the
## same two numbers instead of a map, and a failing run can be reproduced from
## its log line.

## The single entry point both server and client use.
##
## Maps are never sent as tile data: they are a pure function of
## (kind, seed, depth), so the server ships three integers and the client
## rebuilds the identical grid. tests/unit/test_map_gen.gd pins the determinism
## that makes that safe, and it keeps a big dungeon free on the wire.
static func build(kind: Protocol.InstanceKind, seed_value: int, depth: int) -> Dictionary:
	if kind == Protocol.InstanceKind.LOBBY:
		return _build_lobby()
	return generate(seed_value, depth)


static func _build_lobby() -> Dictionary:
	var stamp := Rooms.lobby()
	var size := Rooms.size_of(stamp)
	var grid := MapGrid.new(size.x, size.y, MapGrid.Kind.WALL)
	grid.centre_on_origin()
	var markers := Rooms.stamp(grid, stamp, Vector2i.ZERO)
	var spawn := grid.tile_centre(size.x / 2, size.y - 4)
	if not markers["S"].is_empty():
		var m: Vector2i = markers["S"][0]
		spawn = grid.tile_centre(m.x, m.y)
	var portal := grid.tile_centre(size.x / 2, 3)
	if not markers["P"].is_empty():
		var m: Vector2i = markers["P"][0]
		portal = grid.tile_centre(m.x, m.y)
	var target := grid.tile_centre(size.x / 4, size.y / 2)
	if not markers["T"].is_empty():
		var m: Vector2i = markers["T"][0]
		target = grid.tile_centre(m.x, m.y)
	return {
		"grid": grid,
		"rooms": [] as Array[Rect2i],
		"spawn": spawn,
		"portal": portal,
		"dummy": target,
		"boss_pos": Vector2.ZERO,
		"boss_room": Rect2i(),
	}


## Result keys: grid, rooms (Array[Rect2i]), spawn (Vector2), boss_pos
## (Vector2), boss_room (Rect2i).
static func generate(seed_value: int, depth: int) -> Dictionary:
	var rng := RandomNumberGenerator.new()
	rng.seed = seed_value
	var d := maxi(depth, 1)

	# Size grows with depth. Depth 1 is a little under two screens across --
	# enough that fog and exploration mean something without a first run
	# becoming a hike.
	var w := 56 + d * 10
	var h := 36 + d * 7
	var grid := MapGrid.new(w, h, MapGrid.Kind.WALL)
	grid.centre_on_origin()

	# The boss arena is placed first and everything else works around it, so a
	# generated corridor can never carve through the authored fight.
	var stamp := Rooms.warden_hall() if d % 2 == 1 else Rooms.choir_vault()
	var bs := Rooms.size_of(stamp)
	var boss_origin := Vector2i(w - bs.x - 2, (h - bs.y) / 2)
	var markers := Rooms.stamp(grid, stamp, boss_origin)
	var boss_room := Rect2i(boss_origin, bs)

	var boss_pos := grid.tile_centre(
		boss_origin.x + bs.x / 2, boss_origin.y + bs.y / 2)
	if not markers["B"].is_empty():
		var m: Vector2i = markers["B"][0]
		boss_pos = grid.tile_centre(m.x, m.y)

	var door := Vector2i(boss_origin.x, boss_origin.y + bs.y / 2)
	if not markers["D"].is_empty():
		door = markers["D"][0]

	# Generated rooms, confined to the space left of the arena.
	var rooms: Array[Rect2i] = []
	var usable_w := boss_origin.x - 2
	var attempts := 0
	var wanted := 5 + d
	while rooms.size() < wanted and attempts < wanted * 40:
		attempts += 1
		var rw := rng.randi_range(6, 12)
		var rh := rng.randi_range(5, 10)
		var rx := rng.randi_range(1, maxi(usable_w - rw - 1, 2))
		var ry := rng.randi_range(1, maxi(h - rh - 2, 2))
		var candidate := Rect2i(rx, ry, rw, rh)
		# One tile of padding so two rooms never share a wall and merge into an
		# ambiguous blob.
		var padded := candidate.grow(1)
		var clash := false
		for existing in rooms:
			if padded.intersects(existing.grow(1)):
				clash = true
				break
		if clash:
			continue
		rooms.append(candidate)
		grid.fill_rect(candidate, MapGrid.Kind.FLOOR)

	# Connect each room to the previous one, then the last to the arena door,
	# so every room is reachable by construction rather than by luck.
	for i in range(1, rooms.size()):
		_carve_corridor(grid, _centre_of(rooms[i - 1]), _centre_of(rooms[i]))
	if not rooms.is_empty():
		_carve_corridor(grid, _centre_of(rooms[rooms.size() - 1]), door)
		# The door tile itself, and the tile outside it, must be floor.
		grid.set_tile(door.x, door.y, MapGrid.Kind.FLOOR)
		grid.set_tile(door.x - 1, door.y, MapGrid.Kind.FLOOR)

	_scatter_cover(grid, rooms, rng)

	var spawn := boss_pos
	if not rooms.is_empty():
		var c := _centre_of(rooms[0])
		# Cover is scattered before the spawn is chosen, so the spawn tile can
		# have had a pillar dropped on it. Clear it rather than hunting for a
		# free tile: this is the one tile in the map that must be standable.
		grid.set_tile(c.x, c.y, MapGrid.Kind.FLOOR)
		spawn = grid.tile_centre(c.x, c.y)

	return {
		"grid": grid,
		"rooms": rooms,
		"spawn": spawn,
		"portal": Vector2.ZERO,
		"dummy": Vector2.ZERO,
		"boss_pos": boss_pos,
		"boss_room": boss_room,
	}


static func _centre_of(r: Rect2i) -> Vector2i:
	return Vector2i(r.position.x + r.size.x / 2, r.position.y + r.size.y / 2)


## L-shaped, with the corner order chosen by parity so corridors do not all
## bend the same way.
static func _carve_corridor(grid: MapGrid, from: Vector2i, to: Vector2i) -> void:
	if (from.x + from.y) % 2 == 0:
		_carve_h(grid, from.x, to.x, from.y)
		_carve_v(grid, from.y, to.y, to.x)
	else:
		_carve_v(grid, from.y, to.y, from.x)
		_carve_h(grid, from.x, to.x, to.y)


static func _carve_h(grid: MapGrid, x0: int, x1: int, y: int) -> void:
	for x in range(mini(x0, x1), maxi(x0, x1) + 1):
		grid.set_tile(x, y, MapGrid.Kind.FLOOR)


static func _carve_v(grid: MapGrid, y0: int, y1: int, x: int) -> void:
	for y in range(mini(y0, y1), maxi(y0, y1) + 1):
		grid.set_tile(x, y, MapGrid.Kind.FLOOR)


## A few pillars and pits inside generated rooms, so open rooms still have
## something to fight around. Never placed on a room's edge, where they could
## seal a corridor mouth.
static func _scatter_cover(grid: MapGrid, rooms: Array[Rect2i], rng: RandomNumberGenerator) -> void:
	for r in rooms:
		if r.size.x < 7 or r.size.y < 6:
			continue
		var centre := _centre_of(r)
		var count := rng.randi_range(1, 3)
		for _i in count:
			var tx := rng.randi_range(r.position.x + 2, r.end.x - 3)
			var ty := rng.randi_range(r.position.y + 2, r.end.y - 3)
			# Room centres are where corridors meet and where the spawn goes;
			# blocking one can pinch a junction shut.
			if tx == centre.x and ty == centre.y:
				continue
			var kind := MapGrid.Kind.PILLAR if rng.randf() < 0.6 else MapGrid.Kind.PIT
			grid.set_tile(tx, ty, kind)