MusicServer/internal/backend/library.go

package backend

import (
	"context"
	"errors"
	"time"

	"music-server/internal/db/repository"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

// Soundtrack is a soundtrack as returned by the API.
type Soundtrack struct {
	Uuid        uuid.UUID  `json:"uuid"`
	Name        string     `json:"name"`
	TimesPlayed int32      `json:"times_played"`
	LastPlayed  *time.Time `json:"last_played,omitempty"`
	Added       time.Time  `json:"added"`
}

// SoundtrackWithSongList is a soundtrack with all its songs.
type SoundtrackWithSongList struct {
	Soundtrack
	Songs []Song `json:"songs"`
}

// Song is a song as returned by the API.
type Song struct {
	Uuid           uuid.UUID `json:"uuid"`
	Name           string    `json:"name"`
	FileName       *string   `json:"file_name,omitempty"`
	TimesPlayed    int32     `json:"times_played"`
	SoundtrackUuid uuid.UUID `json:"soundtrack_uuid"`
	SoundtrackName string    `json:"soundtrack_name"`
}

// LibraryService looks up soundtracks and songs by UUID.
type LibraryService struct {
	q repository.Querier
}

// NewLibraryService creates a LibraryService.
func NewLibraryService(q repository.Querier) *LibraryService {
	return &LibraryService{q: q}
}

func toSoundtrack(s repository.Soundtrack) Soundtrack {
	return Soundtrack{
		Uuid:        s.Uuid,
		Name:        s.SoundtrackName,
		TimesPlayed: s.TimesPlayed,
		LastPlayed:  s.LastPlayed,
		Added:       s.Added,
	}
}

func notFound(err error) error {
	if errors.Is(err, pgx.ErrNoRows) {
		return ErrNotFound
	}
	return err
}

// Soundtracks returns all active soundtracks, sorted by name.
func (l *LibraryService) Soundtracks(ctx context.Context) ([]Soundtrack, error) {
	rows, err := l.q.FindAllSoundtracks(ctx)
	if err != nil {
		return nil, err
	}
	soundtracks := make([]Soundtrack, len(rows))
	for i, row := range rows {
		soundtracks[i] = toSoundtrack(row)
	}
	return soundtracks, nil
}

// Soundtrack returns an active soundtrack with its songs.
func (l *LibraryService) Soundtrack(ctx context.Context, id uuid.UUID) (SoundtrackWithSongList, error) {
	row, err := l.q.GetSoundtrackByUUID(ctx, id)
	if err != nil {
		return SoundtrackWithSongList{}, notFound(err)
	}
	songRows, err := l.q.GetSongsBySoundtrackUUID(ctx, id)
	if err != nil {
		return SoundtrackWithSongList{}, err
	}
	songs := make([]Song, len(songRows))
	for i, song := range songRows {
		songs[i] = toSong(song, row.SoundtrackName)
	}
	return SoundtrackWithSongList{Soundtrack: toSoundtrack(row), Songs: songs}, nil
}

func toSong(s repository.Song, soundtrackName string) Song {
	return Song{
		Uuid:           s.Uuid,
		Name:           s.SongName,
		FileName:       s.FileName,
		TimesPlayed:    s.TimesPlayed,
		SoundtrackUuid: s.SoundtrackUuid,
		SoundtrackName: soundtrackName,
	}
}

// Song returns a song of an active soundtrack.
func (l *LibraryService) Song(ctx context.Context, id uuid.UUID) (Song, error) {
	row, err := l.q.GetActiveSongByUUID(ctx, id)
	if err != nil {
		return Song{}, notFound(err)
	}
	return toSong(row.Song, row.SoundtrackName), nil
}

// SongPath returns the file path of a song of an active soundtrack, if the file can be played.
func (l *LibraryService) SongPath(ctx context.Context, id uuid.UUID) (string, error) {
	row, err := l.q.GetActiveSongByUUID(ctx, id)
	if err != nil {
		return "", notFound(err)
	}
	if !songIsPlayable(row.Song, row.SoundtrackPath) {
		return "", ErrNotFound
	}
	return row.Song.Path, nil
}