butterfliu/internal/scanner/scanner.go

package scanner

import (
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"slices"
	"strconv"
	"strings"
)

type DiscoveredAudioFile struct {
	Path        string
	FileSize    int64
	FileMtimeNs int64
}

type ScannedSong struct {
	Title      string
	Artist     string
	Album      string
	Duration   int
	Path       string
	Format     string
	BitRate    int
	SampleRate int
}

// ffprobeFormat holds the JSON output from ffprobe format section
type ffprobeFormat struct {
	Tags       map[string]string `json:"tags"`
	Duration   string            `json:"duration"`
	BitRate    string            `json:"bit_rate"`
	FormatName string            `json:"format_name"`
}

type ffprobeStream struct {
	CodecType  string `json:"codec_type"`
	SampleRate string `json:"sample_rate"`
}

// ffprobeOutput holds the full ffprobe JSON output
type ffprobeOutput struct {
	Format  ffprobeFormat  `json:"format"`
	Streams []ffprobeStream `json:"streams"`
}

func ScanDirectory(dirPath string) ([]ScannedSong, error) {
	files, err := ListAudioFiles(dirPath)
	if err != nil {
		return nil, err
	}

	songs := make([]ScannedSong, 0, len(files))
	for _, file := range files {
		song, err := ProbeAudioFile(file.Path)
		if err != nil {
			continue
		}
		songs = append(songs, song)
	}

	return songs, nil
}

func ListAudioFiles(dirPath string) ([]DiscoveredAudioFile, error) {
	files := []DiscoveredAudioFile{}

	err := filepath.Walk(dirPath, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		if info.IsDir() {
			return nil
		}

		if !isAudioFile(path) {
			return nil
		}

		files = append(files, DiscoveredAudioFile{
			Path:        path,
			FileSize:    info.Size(),
			FileMtimeNs: info.ModTime().UnixNano(),
		})
		return nil
	})

	return files, err
}

func ProbeAudioFile(filePath string) (ScannedSong, error) {
	if _, err := exec.LookPath("ffprobe"); err != nil {
		return ScannedSong{}, fmt.Errorf("ffprobe not found in PATH: %v", err)
	}

	return processAudioFile(filePath)
}

func processAudioFile(filePath string) (ScannedSong, error) {
	cmd := exec.Command("ffprobe", "-v", "quiet", "-print_format", "json", "-show_format", "-show_streams", filePath)
	output, err := cmd.Output()
	if err != nil {
		return ScannedSong{}, fmt.Errorf("ffprobe failed for %s: %v", filePath, err)
	}

	var probeOutput ffprobeOutput
	if err := json.Unmarshal(output, &probeOutput); err != nil {
		return ScannedSong{}, fmt.Errorf("failed to parse ffprobe output for %s: %v", filePath, err)
	}

	tags := probeOutput.Format.Tags
	if tags == nil {
		tags = make(map[string]string)
	}

	title := tags["title"]
	if title == "" {
		title = filepath.Base(filePath)
	}

	artist := tags["artist"]
	if artist == "" {
		artist = "Unknown Artist"
	}

	album := tags["album"]
	if album == "" {
		album = "Unknown Album"
	}

	duration := 0
	if probeOutput.Format.Duration != "" {
		if d, err := strconv.ParseFloat(probeOutput.Format.Duration, 64); err == nil {
			duration = int(d)
		}
	}

	bitRate := 0
	if probeOutput.Format.BitRate != "" {
		if value, err := strconv.Atoi(probeOutput.Format.BitRate); err == nil {
			bitRate = value
		}
	}

	sampleRate := 0
	for _, stream := range probeOutput.Streams {
		if stream.CodecType != "audio" || stream.SampleRate == "" {
			continue
		}
		if value, err := strconv.Atoi(stream.SampleRate); err == nil {
			sampleRate = value
			break
		}
	}

	format := probeOutput.Format.FormatName
	if format == "" {
		format = strings.TrimPrefix(strings.ToLower(filepath.Ext(filePath)), ".")
	}

	return ScannedSong{
		Title:      title,
		Artist:     artist,
		Album:      album,
		Duration:   duration,
		Path:       filePath,
		Format:     format,
		BitRate:    bitRate,
		SampleRate: sampleRate,
	}, nil
}

func isAudioFile(path string) bool {
	ext := strings.ToLower(filepath.Ext(path))
	audioExtensions := []string{".mp3", ".flac", ".m4a", ".wav", ".ogg"}
	return slices.Contains(audioExtensions, ext)
}