package speech

import (
	"bytes"
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"

	"github.com/google/uuid"
)

type FFmpegConverter struct {
	ffmpegPath string
	tempDir    string
}

func NewFFmpegConverter(ffmpegPath, tempDir string) *FFmpegConverter {
	if ffmpegPath == "" {
		ffmpegPath = "ffmpeg"
	}
	if tempDir == "" {
		tempDir = os.TempDir()
	}
	return &FFmpegConverter{ffmpegPath: ffmpegPath, tempDir: tempDir}
}

// Convert converts audio bytes between formats and returns the converted bytes.
// Intermediate temp files are cleaned up automatically — use ConvertFile when
// you need to keep the output on disk.
func (c *FFmpegConverter) Convert(ctx context.Context, input []byte, fromMime, toMime string) ([]byte, error) {
	id := uuid.New().String()
	inFile := filepath.Join(c.tempDir, id+".input")
	outFile := filepath.Join(c.tempDir, id+".wav")

	defer os.Remove(inFile)
	defer os.Remove(outFile)

	if err := os.WriteFile(inFile, input, 0600); err != nil {
		return nil, fmt.Errorf("write temp input: %w", err)
	}

	if err := c.runFFmpeg(ctx, inFile, outFile); err != nil {
		return nil, err
	}

	out, err := os.ReadFile(outFile)
	if err != nil {
		return nil, fmt.Errorf("read converted file: %w", err)
	}
	return out, nil
}

// ConvertFile converts audio bytes and writes the WAV output to outPath.
// The caller is responsible for deleting outPath when no longer needed.
func (c *FFmpegConverter) ConvertFile(ctx context.Context, input []byte, outPath string) error {
	id := uuid.New().String()
	inFile := filepath.Join(c.tempDir, id+".input")

	defer os.Remove(inFile)

	if err := os.WriteFile(inFile, input, 0600); err != nil {
		return fmt.Errorf("write temp input: %w", err)
	}
	return c.runFFmpeg(ctx, inFile, outPath)
}

func (c *FFmpegConverter) runFFmpeg(ctx context.Context, inFile, outFile string) error {
	cmd := exec.CommandContext(ctx, c.ffmpegPath,
		"-i", inFile,
		"-ar", "16000",
		"-ac", "1",
		"-f", "wav",
		"-y",
		outFile,
	)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("ffmpeg conversion: %w: %s", err, stderr.String())
	}
	return nil
}