# Audio —— BGM 交叉淡入淡出 + UI 音效池 + 3D 定位音效。
# 对标客户端 AudioLib：BGM（`bgm/*.mp3`）、UI wav（`**/sound/ui/`）、
# 3D wav（`**/sound/<rel>`）。纯资产接线，无解码器移植（`.mss` 不用）。
# 用 preload("res://audio.gd").new() 造一个，add_child，再 setup()。
extends Node

var _assets: String
var _bgm_root: String
var _sound_roots: PackedStringArray = []
var _cache := {}                       # 绝对路径 -> AudioStream

var _bgm := [null, null]               # 两个 AudioStreamPlayer 交叉淡
var _bgm_cur := 0
var _bgm_name := ""
var _ui_pool: Array[AudioStreamPlayer] = []
var _ui_next := 0

var master_bgm := 0.6
var master_sfx := 0.9
var _queued_bgm := ""

# §9.2 前后台音量存/恢复，字段名对齐参考 CSoundManager 的
# m_fBackupMusicVolume / m_fBackupSoundVolume（REF/MilesLib/SoundManager.h:31）。
var _backup_music_volume := -1.0
var _backup_sound_volume := -1.0
var _volume_saved := false

func _ready() -> void:
	if _queued_bgm != "":
		var n := _queued_bgm
		_queued_bgm = ""
		_bgm_name = ""
		play_bgm(n)

func setup(assets_root: String) -> void:
	_assets = assets_root
	# bgm/ 与 assets/ 同级（<repo>/bgm，见 AssetRoot）
	_bgm_root = _assets.get_base_dir().path_join("bgm")
	# 已知声音根 + 各 patch 的 sound/
	for r in ["Sound/sound", "sound2/sound", "sound_m/sound"]:
		var p := _assets.path_join(r)
		if DirAccess.dir_exists_absolute(p):
			_sound_roots.append(p)
	var da := DirAccess.open(_assets)
	if da:
		for sub in da.get_directories():
			var p := _assets.path_join(sub).path_join("sound")
			if DirAccess.dir_exists_absolute(p):
				_sound_roots.append(p)

	for i in 2:
		var pl := AudioStreamPlayer.new()
		pl.bus = "Master"
		add_child(pl)
		_bgm[i] = pl
	for i in 8:
		var pl := AudioStreamPlayer.new()
		add_child(pl)
		_ui_pool.append(pl)

# --- resolution -----------------------------------------------------------

func _load_stream(path: String) -> AudioStream:
	if _cache.has(path):
		return _cache[path]
	var s: AudioStream = null
	var ext := path.get_extension().to_lower()
	if ext == "mp3":
		var m := AudioStreamMP3.new()
		m.data = FileAccess.get_file_as_bytes(path)
		s = m if m.data.size() > 0 else null
	elif ext == "ogg":
		s = AudioStreamOggVorbis.load_from_file(path)
	elif ext == "wav":
		s = AudioStreamWAV.load_from_file(path)
	_cache[path] = s
	return s

func _find_sound(rel: String) -> String:
	rel = rel.replace("\\", "/")
	var cands := PackedStringArray([rel])
	if rel.get_extension().is_empty():
		cands = PackedStringArray([rel + ".wav", rel + ".ogg"])
	for root in _sound_roots:
		for c in cands:
			var p := root.path_join(c)
			if FileAccess.file_exists(p):
				return p
		# also try under sound/ui/ and sound/common/ for bare names
		if not rel.contains("/"):
			for d in ["ui", "common"]:
				for c in cands:
					var p := root.path_join(d).path_join(c)
					if FileAccess.file_exists(p):
						return p
	return ""

# --- BGM ---------------------------------------------------------------

func play_bgm(name: String, fade := 1.2) -> void:
	if name == _bgm_name:
		return
	if not is_node_ready() or not is_inside_tree():
		_queued_bgm = name   # flushed in _ready()
		return
	_bgm_name = name
	var path := name
	if path.get_extension().is_empty():
		path = _bgm_root.path_join(name + ".mp3")
	elif not path.is_absolute_path():
		path = _bgm_root.path_join(name)
	var stream := _load_stream(path)
	if stream == null:
		push_warning("[audio] bgm not found: " + path)
		return
	if stream is AudioStreamMP3:
		stream.loop = true
	var nxt := 1 - _bgm_cur
	_bgm[nxt].stream = stream
	_bgm[nxt].volume_db = -40.0
	_bgm[nxt].play()
	_fade(_bgm[nxt], linear_to_db(master_bgm), fade)
	_fade(_bgm[_bgm_cur], -40.0, fade, true)
	_bgm_cur = nxt

func stop_bgm(fade := 1.0) -> void:
	_bgm_name = ""
	_fade(_bgm[_bgm_cur], -40.0, fade, true)

func _fade(pl: AudioStreamPlayer, to_db: float, dur: float, stop_after := false) -> void:
	var tw := create_tween()
	tw.tween_property(pl, "volume_db", to_db, dur)
	if stop_after:
		tw.tween_callback(pl.stop)

# 立即把 master_bgm 应用到当前正在播放的 BGM 声道（无淡入）。
# 对标 CSoundManager::SetMusicVolume：改的是「当前音乐实例」的音量。
func set_music_volume(v: float) -> void:
	master_bgm = clampf(v, 0.0, 1.0)
	var pl: AudioStreamPlayer = _bgm[_bgm_cur]
	if pl and pl.playing:
		pl.volume_db = linear_to_db(master_bgm) if master_bgm > 0.0 else -80.0

# §9.2：进入后台前保存音量（CSoundManager::SaveVolume）。
func save_volume() -> void:
	_backup_music_volume = master_bgm
	_backup_sound_volume = master_sfx
	_volume_saved = true

# §9.2：回到前台后恢复音量（CSoundManager::RestoreVolume）。
# 不碰 _bgm_name / _bgm[]，同一首继续播，只把音量拉回来。
func restore_volume() -> void:
	if not _volume_saved:
		return
	master_bgm = _backup_music_volume
	master_sfx = _backup_sound_volume
	_volume_saved = false
	var pl: AudioStreamPlayer = _bgm[_bgm_cur]
	if pl and pl.playing:
		pl.volume_db = linear_to_db(master_bgm) if master_bgm > 0.0 else -80.0

# --- SFX -------------------------------------------------------------------

func play_ui(name: String) -> void:
	var path := _find_sound(name if name.contains("/") else "ui/" + name)
	if path.is_empty():
		path = _find_sound(name)
	if path.is_empty():
		push_warning("[audio] ui sfx not found: " + name)
		return
	var s := _load_stream(path)
	if s == null:
		return
	var pl := _ui_pool[_ui_next]
	_ui_next = (_ui_next + 1) % _ui_pool.size()
	pl.stream = s
	pl.volume_db = linear_to_db(master_sfx)
	pl.play()

func play_at(rel: String, world_pos: Vector3, parent: Node = null) -> void:
	var path := _find_sound(rel)
	if path.is_empty():
		return
	var s := _load_stream(path)
	if s == null:
		return
	var pl := AudioStreamPlayer3D.new()
	pl.stream = s
	pl.unit_size = 6.0
	pl.max_distance = 60.0
	pl.volume_db = linear_to_db(master_sfx)
	(parent if parent else self).add_child(pl)
	pl.global_position = world_pos
	pl.play()
	pl.finished.connect(pl.queue_free)