// Package audio normalizes arbitrary audio/video inputs into a whisper.cpp-friendly
// 16 kHz mono PCM WAV file using ffmpeg.
package audio

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

// ExtractWAV runs ffmpeg to convert input (audio or video) into a 16kHz mono
// signed-16-bit PCM WAV file at outPath. ffmpeg must be on PATH.
func ExtractWAV(ctx context.Context, input, outPath string) error {
	if _, err := exec.LookPath("ffmpeg"); err != nil {
		return fmt.Errorf("ffmpeg not found on PATH: %w", err)
	}
	if _, err := os.Stat(input); err != nil {
		return fmt.Errorf("input not readable: %w", err)
	}
	if err := os.MkdirAll(filepath.Dir(outPath), 0o755); err != nil {
		return err
	}

	cmd := exec.CommandContext(ctx, "ffmpeg",
		"-y",
		"-loglevel", "error",
		"-i", input,
		"-vn",
		"-ac", "1",
		"-ar", "16000",
		"-c:a", "pcm_s16le",
		outPath,
	)
	cmd.Stdout = os.Stderr
	cmd.Stderr = os.Stderr
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("ffmpeg: %w", err)
	}
	return nil
}