extends Node
## 简易音效：用 AudioStreamWAV 程序合成 4 种音效。
## 每次播放 new 一个 AudioStreamPlayer，结束后自动释放。
## 之后要替换成 .wav 素材，把 _generate_xxx() 换成 load() 资源即可。

const SAMPLE_RATE: int = 22050

func play_hit() -> void:
	_play(_make_sin(880.0, 0.05, 0.4))

func play_break() -> void:
	_play(_make_noise(0.18, 0.5))

func play_lost() -> void:
	_play(_make_sweep(440.0, 110.0, 0.4, 0.5))

func play_win() -> void:
	_play(_make_sweep(523.0, 1046.0, 0.5, 0.5))

# ───────── 合成函数 ─────────

func _make_sin(freq: float, duration: float, volume: float) -> AudioStreamWAV:
	return _build(duration, func(t: float, d: float) -> float:
		var env: float = 1.0 - t / d  # 线性衰减
		return sin(TAU * freq * t) * volume * env
	)

func _make_noise(duration: float, volume: float) -> AudioStreamWAV:
	return _build(duration, func(t: float, d: float) -> float:
		var env: float = 1.0 - t / d
		return randf_range(-volume, volume) * env
	)

func _make_sweep(from_freq: float, to_freq: float, duration: float, volume: float) -> AudioStreamWAV:
	return _build(duration, func(t: float, d: float) -> float:
		var progress: float = t / d
		var f: float = lerp(from_freq, to_freq, progress)
		var env: float = (1.0 - progress) * (1.0 - progress)  # 平方衰减
		return sin(TAU * f * t) * volume * env
	)

# 构造一个 AudioStreamWAV；sample_fn(t, duration) 返回 [-1, 1] 的振幅
func _build(duration: float, sample_fn: Callable) -> AudioStreamWAV:
	var sample_count: int = int(SAMPLE_RATE * duration)
	var data := PackedByteArray()
	data.resize(sample_count * 2)  # 16-bit 单声道
	for i in range(sample_count):
		var t: float = float(i) / SAMPLE_RATE
		var s: float = clamp(sample_fn.call(t, duration), -1.0, 1.0)
		# 16-bit: 范围 [-32768, 32767]
		var sample_i: int = int(s * 32767.0)
		data[2 * i] = sample_i & 0xFF
		data[2 * i + 1] = (sample_i >> 8) & 0xFF
	var stream := AudioStreamWAV.new()
	stream.format = AudioStreamWAV.FORMAT_16_BITS
	stream.mix_rate = SAMPLE_RATE
	stream.stereo = false
	stream.data = data
	return stream

func _play(stream: AudioStream) -> void:
	var player := AudioStreamPlayer.new()
	player.stream = stream
	add_child(player)
	player.play()
	player.finished.connect(player.queue_free)