package pkg

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"io"
	"l_szr_go/entity"
	"os"
)

func SaveAsWav(buffer *bytes.Buffer, filename string, config entity.Config) error {
	if buffer.Len() == 0 {
		return fmt.Errorf("缓冲区为空，无法保存")
	}

	file, err := os.Create(filename)
	if err != nil {
		return fmt.Errorf("创建文件失败: %v", err)
	}
	defer file.Close()

	// 写入 WAV 头部
	if err := writeWavHeader(file, config.SampleRate, config.BitDepth, config.Channels, buffer.Len()); err != nil {
		return fmt.Errorf("写入 WAV 头部失败: %v", err)
	}

	// 写入 PCM 数据
	if _, err := buffer.WriteTo(file); err != nil {
		return fmt.Errorf("写入 PCM 数据失败: %v", err)
	}

	return nil
}

func writeWavHeader(w io.Writer, sampleRate, bitDepth, channels, dataSize int) error {
	header := struct {
		ChunkID       [4]byte
		ChunkSize     uint32
		Format        [4]byte
		Subchunk1ID   [4]byte
		Subchunk1Size uint32
		AudioFormat   uint16
		NumChannels   uint16
		SampleRate    uint32
		ByteRate      uint32
		BlockAlign    uint16
		BitsPerSample uint16
		Subchunk2ID   [4]byte
		Subchunk2Size uint32
	}{
		ChunkID:       [4]byte{'R', 'I', 'F', 'F'},
		ChunkSize:     36 + uint32(dataSize),
		Format:        [4]byte{'W', 'A', 'V', 'E'},
		Subchunk1ID:   [4]byte{'f', 'm', 't', ' '},
		Subchunk1Size: 16,
		AudioFormat:   1, // PCM
		NumChannels:   uint16(channels),
		SampleRate:    uint32(sampleRate),
		ByteRate:      uint32(sampleRate * channels * bitDepth / 8),
		BlockAlign:    uint16(channels * bitDepth / 8),
		BitsPerSample: uint16(bitDepth),
		Subchunk2ID:   [4]byte{'d', 'a', 't', 'a'},
		Subchunk2Size: uint32(dataSize),
	}

	return binary.Write(w, binary.LittleEndian, header)
}