package service

import (
	"butterfliu/internal/model"
	"butterfliu/internal/repository"
	"butterfliu/internal/scanner"
	"errors"
	"fmt"
	"log"
	"path/filepath"
	"strings"
)

// ScanReport holds the result of a library scan.
type ScanReport struct {
	TotalFiles  int      `json:"total_files"`
	Processed   int      `json:"processed"`
	Added       int      `json:"added"`
	Skipped     int      `json:"skipped"`
	FailedFiles []string `json:"failed_files"`
}

type ScanProgressFunc func(ScanReport)

type LibraryService struct {
	libRepo    *repository.LibraryRepository
	artistRepo *repository.ArtistRepository
	albumRepo  *repository.AlbumRepository
	songRepo   *repository.SongRepository
	mediaRepo  *repository.MediaRepository
}

func NewLibraryService(
	libRepo *repository.LibraryRepository,
	artistRepo *repository.ArtistRepository,
	albumRepo *repository.AlbumRepository,
	songRepo *repository.SongRepository,
	mediaRepo *repository.MediaRepository,
) *LibraryService {
	return &LibraryService{
		libRepo:    libRepo,
		artistRepo: artistRepo,
		albumRepo:  albumRepo,
		songRepo:   songRepo,
		mediaRepo:  mediaRepo,
	}
}

func (s *LibraryService) GetAll() ([]model.Library, error) {
	return s.libRepo.GetAll()
}

func (s *LibraryService) GetByID(id int) (model.Library, error) {
	return s.libRepo.GetByID(id)
}

func (s *LibraryService) Create(name, path string) (model.Library, error) {
	if name = strings.TrimSpace(name); name == "" {
		return model.Library{}, errors.New("library name cannot be empty")
	}
	if path = strings.TrimSpace(path); path == "" {
		return model.Library{}, errors.New("library path cannot be empty")
	}
	return s.libRepo.Create(name, path)
}

func (s *LibraryService) UpdateName(id int, name string) error {
	if name = strings.TrimSpace(name); name == "" {
		return errors.New("library name cannot be empty")
	}
	return s.libRepo.UpdateName(id, name)
}

func (s *LibraryService) UpdatePath(id int, path string) error {
	if path = strings.TrimSpace(path); path == "" {
		return errors.New("library path cannot be empty")
	}
	return s.libRepo.UpdatePath(id, path)
}

func (s *LibraryService) Delete(id int) error {
	return s.libRepo.Delete(id)
}

func (s *LibraryService) GetSongs(id int) ([]model.SongDetail, error) {
	return s.mediaRepo.GetSongsByLibraryWithDetails(id)
}

func (s *LibraryService) GetSongsByArtist(id int) ([]model.SongDetail, error) {
	return s.mediaRepo.GetSongsByArtistWithDetails(id)
}

func (s *LibraryService) GetSongsByAlbum(id int) ([]model.SongDetail, error) {
	return s.mediaRepo.GetSongsByAlbumWithDetails(id)
}

func (s *LibraryService) GetArtists() ([]model.Artist, error) {
	return s.artistRepo.GetAll()
}

func (s *LibraryService) GetArtist(id int) (model.ArtistDetail, error) {
	artist, err := s.artistRepo.Get(id)
	if err != nil {
		return model.ArtistDetail{}, err
	}
	albums, err := s.albumRepo.GetIDsByArtist(id)
	if err != nil {
		return model.ArtistDetail{}, err
	}
	songs, err := s.artistRepo.GetSongIDsByArtist(id)
	if err != nil {
		return model.ArtistDetail{}, err
	}
	return model.ArtistDetail{
		ID:     artist.ID,
		Name:   artist.Name,
		Songs:  songs,
		Albums: albums,
	}, nil
}

func (s *LibraryService) GetAlbums() ([]model.Album, error) {
	return s.albumRepo.GetAll()
}

func (s *LibraryService) GetAlbumsByArtistWithDetail(artistID int) ([]model.AlbumDetail, error) {
	albums, err := s.albumRepo.GetByArtist(artistID)
	if err != nil {
		return nil, err
	}
	details := []model.AlbumDetail{}
	for _, a := range albums {
		songs, err := s.albumRepo.GetSongIDs(a.ID)
		if err != nil {
			break
		}
		artist, err := s.artistRepo.Get(artistID)
		if err != nil {
			break
		}
		details = append(details, model.AlbumDetail{
			ID:     a.ID,
			Title:  a.Title,
			Artist: artist.Name,
			Songs:  songs,
		})
	}
	return details, nil
}

func (s *LibraryService) GetAlbum(id int) (model.AlbumDetail, error) {
	album, err := s.albumRepo.Get(id)
	if err != nil {
		return model.AlbumDetail{}, err
	}
	songs, err := s.albumRepo.GetSongIDs(id)
	if err != nil {
		return model.AlbumDetail{}, err
	}
	artist, err := s.artistRepo.Get(album.ArtistID)
	if err != nil {
		return model.AlbumDetail{}, err
	}
	return model.AlbumDetail{
		ID:     id,
		Title:  album.Title,
		Songs:  songs,
		Artist: artist.Name,
	}, nil
}

func (s *LibraryService) Scan(id int, onProgress ScanProgressFunc) (*ScanReport, error) {
	lib, err := s.libRepo.GetByID(id)
	if err != nil {
		return nil, fmt.Errorf("library %d not found: %w", id, err)
	}

	paths, err := scanner.ListAudioFiles(lib.Path)
	if err != nil {
		return nil, fmt.Errorf("scan directory %s: %w", lib.Path, err)
	}

	existingFiles, err := s.mediaRepo.ListExistingByLibrary(lib.ID)
	if err != nil {
		return nil, fmt.Errorf("load existing media files: %w", err)
	}

	existingByPath := make(map[string]repository.ExistingMediaFile, len(existingFiles))
	for _, existing := range existingFiles {
		existingByPath[existing.Path] = existing
	}

	report := &ScanReport{TotalFiles: len(paths)}
	notifyProgress(report, onProgress)

	for _, path := range paths {
		existing, found := existingByPath[path]
		if found && existing.HasSong {
			report.Skipped++
			report.Processed++
			notifyProgress(report, onProgress)
			continue
		}

		song, err := scanner.ProbeAudioFile(path)
		if err != nil {
			log.Printf("Failed to probe %s: %v", filepath.Base(path), err)
			report.FailedFiles = append(report.FailedFiles, path)
			report.Processed++
			notifyProgress(report, onProgress)
			continue
		}

		if err := s.addScannedSong(song, lib.ID, report, found, existing.MediaFileID); err != nil {
			log.Printf("Failed to add %s: %v", filepath.Base(song.Path), err)
			report.FailedFiles = append(report.FailedFiles, song.Path)
		}

		report.Processed++
		notifyProgress(report, onProgress)
	}

	log.Printf("Scan complete for library %d: %+v", id, report)
	return report, nil
}

func notifyProgress(report *ScanReport, onProgress ScanProgressFunc) {
	if onProgress == nil {
		return
	}

	copyReport := ScanReport{
		TotalFiles: report.TotalFiles,
		Processed:  report.Processed,
		Added:      report.Added,
		Skipped:    report.Skipped,
	}
	copyReport.FailedFiles = append([]string(nil), report.FailedFiles...)
	onProgress(copyReport)
}

// addScannedSong upserts a scanned song and its related artist, album, and media file.
func (s *LibraryService) addScannedSong(song scanner.ScannedSong, libraryID int, report *ScanReport, hasExistingMedia bool, mediaFileID int) error {
	mediaFile := model.MediaFile{ID: mediaFileID, Path: song.Path, LibraryID: libraryID}
	if !hasExistingMedia {
		var err error
		mediaFile, err = s.getOrCreateMediaFile(song.Path, libraryID)
		if err != nil {
			return fmt.Errorf("media file: %w", err)
		}
	}

	if hasSong, err := s.songRepo.HasByMediaFileID(mediaFile.ID); err != nil {
		return fmt.Errorf("song lookup: %w", err)
	} else if hasSong {
		report.Skipped++
		return nil
	}

	artist, err := s.getOrCreateArtist(song.Artist)
	if err != nil {
		return fmt.Errorf("artist: %w", err)
	}

	album, err := s.getOrCreateAlbum(song.Album, artist.ID)
	if err != nil {
		return fmt.Errorf("album: %w", err)
	}

	if _, err := s.songRepo.Create(song.Title, artist.ID, album.ID, song.Duration, mediaFile.ID); err != nil {
		return fmt.Errorf("song: %w", err)
	}

	report.Added++
	return nil
}

func (s *LibraryService) getOrCreateMediaFile(path string, libraryID int) (model.MediaFile, error) {
	mf, err := s.mediaRepo.GetByPath(path)
	if err == nil {
		return mf, nil
	}
	return s.mediaRepo.Create(path, libraryID)
}

func (s *LibraryService) getOrCreateArtist(name string) (model.Artist, error) {
	a, err := s.artistRepo.GetByName(name)
	if err == nil {
		return a, nil
	}
	return s.artistRepo.Create(name)
}

func (s *LibraryService) getOrCreateAlbum(title string, artistID int) (model.Album, error) {
	al, err := s.albumRepo.GetByTitleAndArtist(title, artistID)
	if err == nil {
		return al, nil
	}
	return s.albumRepo.Create(title, artistID)
}