extends SceneTree

## Photograph every map, for the level select cards.
##
##     godot --path . --windowed --resolution 640x400 \
##         -s res://debug/map_preview_capture.gd
##
## Writes assets/ui/map_previews/<folder>.png, which the menu picks up by
## convention — no map_meta key to add, so a new map that ships a preview gets
## one and a map that does not falls back to its gradient.
##
## The cards used to be a two-stop gradient built from `color1` and `color2` in
## the map's meta file. That tells a player which card they clicked last time and
## nothing whatsoever about the map, which is the entire job of a level select.
##
## ── Framing ─────────────────────────────────────────────────────────────────
##
## The camera stands INSIDE the map, at a spawn point, at eye height, looking
## across it.
##
## The first version framed the whole level from outside by merging every
## VisualInstance3D's AABB and backing off until it fit. Every map came out as a
## tiny diorama floating on a table in the middle of an empty sky — and one came
## out entirely black, because from orbit there was nothing lit in frame. That is
## a minimap, and a minimap is a different thing from a photograph.
##
## What a player wants off a card is the FEEL of a place: its light, its colour,
## how enclosed it is, what the skyline looks like. All of that only exists from
## where a player will actually stand, so that is where the camera goes — and
## spawn points are already authored in every map, so it costs nothing.

const OUT_DIR := "res://assets/ui/map_previews"
const MAPS_DIR := "res://scenes/maps/"
## How long to let a map build itself. The procedural ones generate geometry in
## `_ready` and the neon map streams in props, so a shot taken too early is a
## photograph of an empty skybox.
const SETTLE_FRAMES := 90


func _initialize() -> void:
	_run()


func _run() -> void:
	await process_frame
	DirAccess.make_dir_recursive_absolute(ProjectSettings.globalize_path(OUT_DIR))

	for folder in _map_folders():
		var cfg := ConfigFile.new()
		if cfg.load(MAPS_DIR + folder + "/map_meta.cfg") != OK:
			continue
		var scene_path: String = cfg.get_value("map", "scene_path", "")
		if scene_path == "" or not ResourceLoader.exists(scene_path):
			continue

		var packed: PackedScene = load(scene_path)
		if packed == null:
			print("map_preview: could not load ", scene_path)
			continue
		var level: Node = packed.instantiate()
		root.add_child(level)

		for _i in SETTLE_FRAMES:
			await process_frame

		var shot: Image = await _best_shot(level)
		var path := "%s/%s.png" % [OUT_DIR, folder]
		if shot == null:
			print("map_preview: no usable vantage in ", folder)
		else:
			shot.save_png(ProjectSettings.globalize_path(path))
			print("map_preview: saved ", path)

		level.queue_free()
		for _i in 6:
			await process_frame

	quit(0)


func _map_folders() -> Array:
	var out: Array = []
	var dir := DirAccess.open(MAPS_DIR)
	if dir == null:
		return out
	dir.list_dir_begin()
	var name := dir.get_next()
	while name != "":
		if dir.current_is_dir() and not name.begins_with("."):
			if FileAccess.file_exists(MAPS_DIR + name + "/map_meta.cfg"):
				out.append(name)
		name = dir.get_next()
	out.sort()
	return out


## Try several vantages and keep the one that produces the best PICTURE.
##
## Not the one that satisfies a rule about where cameras should go. Two maps
## defeated every positional rule tried: fps_blockout is a genuinely dark map
## where most spawns face an unlit wall, and procedural_arena builds its geometry
## at runtime so no fixed offset is inside it. Both came out as black rectangles,
## and a black rectangle passes any check that asks "did the camera end up
## somewhere sensible".
##
## So the tool renders each candidate and SCORES the result. The score wants an
## image that is both bright and varied: mean luminance alone picks a shot of the
## empty sky, and variance alone picks a high-contrast corner of a dark room.
## Their product picks a photograph.
func _best_shot(level: Node):
	var bounds := _bounds(level)
	var centre := bounds.get_center() if bounds.size.length() > 0.01 else Vector3.ZERO
	var extent: float = maxf(maxf(bounds.size.x, bounds.size.z), 8.0)

	var cam := Camera3D.new()
	level.add_child(cam)
	cam.far = maxf(bounds.size.length() * 2.0, 800.0)
	# A little wider than the game's own view, so a card shows more of the space
	# than a screenshot of play would.
	cam.fov = 68.0
	cam.current = true

	var best_img: Image = null
	var best_score := -1.0
	for vantage in _vantages(centre, extent):
		cam.global_position = vantage[0]
		var look: Vector3 = vantage[1]
		if cam.global_position.distance_to(look) < 1.0:
			continue
		cam.look_at(look)
		# Two frames: one for the transform, one for the frame drawn with it.
		for _i in 3:
			await process_frame
		var img := root.get_texture().get_image()
		var score := _score(img)
		if score > best_score:
			best_score = score
			best_img = img
	cam.queue_free()
	return best_img


## Candidate camera placements, as `[eye, look_at]` pairs.
##
## Every authored spawn point, plus a raised view from each side of the map for
## the levels that generate themselves and have no spawns by the time this runs.
func _vantages(centre: Vector3, extent: float) -> Array:
	var out: Array = []
	for s in get_nodes_in_group("spawn_points"):
		if s is Node3D:
			var p: Vector3 = (s as Node3D).global_position
			out.append([p + Vector3.UP * 2.2, centre + Vector3.UP * 1.6])
	# Raised corners, looking in. Higher than eye level, because a generated
	# arena's floor is not necessarily at the origin and standing "on" it is a
	# guess where looking down at it is not.
	for dir in [Vector3(1, 0, 1), Vector3(-1, 0, 1), Vector3(1, 0, -1),
			Vector3(-1, 0, -1)]:
		var d: Vector3 = dir.normalized()
		out.append([centre + d * extent * 0.42 + Vector3.UP * extent * 0.22,
			centre + Vector3.UP * extent * 0.04])
	return out


## How good a picture is: bright AND varied. See `_best_shot`.
func _score(img: Image) -> float:
	var small := img.duplicate() as Image
	small.resize(40, 24, Image.INTERPOLATE_BILINEAR)
	var n := 40 * 24
	var mean := 0.0
	for y in 24:
		for x in 40:
			var c := small.get_pixel(x, y)
			mean += 0.2126 * c.r + 0.7152 * c.g + 0.0722 * c.b
	mean /= float(n)
	var variance := 0.0
	for y in 24:
		for x in 40:
			var c := small.get_pixel(x, y)
			var l := 0.2126 * c.r + 0.7152 * c.g + 0.0722 * c.b
			variance += (l - mean) * (l - mean)
	variance /= float(n)
	return mean * sqrt(variance)


func _bounds(node: Node) -> AABB:
	var out := AABB()
	var any := false
	for child in node.find_children("*", "VisualInstance3D", true, false):
		var vi := child as VisualInstance3D
		# Skip anything enormous: a WorldEnvironment's sky or a directional
		# light's own AABB would swallow the map and push the camera to orbit.
		var box := vi.get_aabb()
		if box.size.length() > 100000.0 or box.size.length() < 0.001:
			continue
		box = vi.global_transform * box
		if not any:
			out = box
			any = true
		else:
			out = out.merge(box)
	return out if any else AABB()