package ffmpeg

import (
	"bytes"
	"encoding/binary"
)

// encodeWAV writes float32 PCM samples (range [-1, 1]) as a 16-bit PCM mono
// WAV file, matching how uma-tts-api's soundfile.write step feeds pydub
// (samples get truncated/clamped rather than wrapped on overflow).
func encodeWAV(pcm []float32, sampleRate int) []byte {
	const (
		numChannels   = 1
		bitsPerSample = 16
	)
	byteRate := sampleRate * numChannels * bitsPerSample / 8
	blockAlign := numChannels * bitsPerSample / 8
	dataSize := len(pcm) * 2

	var buf bytes.Buffer
	buf.WriteString("RIFF")
	_ = binary.Write(&buf, binary.LittleEndian, uint32(36+dataSize))
	buf.WriteString("WAVE")

	buf.WriteString("fmt ")
	_ = binary.Write(&buf, binary.LittleEndian, uint32(16)) // PCM fmt chunk size
	_ = binary.Write(&buf, binary.LittleEndian, uint16(1))  // PCM format tag
	_ = binary.Write(&buf, binary.LittleEndian, uint16(numChannels))
	_ = binary.Write(&buf, binary.LittleEndian, uint32(sampleRate))
	_ = binary.Write(&buf, binary.LittleEndian, uint32(byteRate))
	_ = binary.Write(&buf, binary.LittleEndian, uint16(blockAlign))
	_ = binary.Write(&buf, binary.LittleEndian, uint16(bitsPerSample))

	buf.WriteString("data")
	_ = binary.Write(&buf, binary.LittleEndian, uint32(dataSize))
	for _, sample := range pcm {
		_ = binary.Write(&buf, binary.LittleEndian, int16(clampSample(sample)*32767))
	}

	return buf.Bytes()
}

func clampSample(s float32) float32 {
	switch {
	case s > 1:
		return 1
	case s < -1:
		return -1
	default:
		return s
	}
}