// Package fakedb provides an in-memory repository.Querier for tests.
package fakedb

import (
	"cmp"
	"context"
	"math/rand/v2"
	"slices"
	"sync"
	"time"

	"music-server/internal/db/repository"

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

// Store is an in-memory implementation of the queries used by the application.
// Calling a query it does not implement panics through the nil embedded interface.
type Store struct {
	repository.Querier

	mu          sync.Mutex
	nextID      int32
	Soundtracks []repository.Soundtrack
	Songs       []repository.Song
	Sessions    map[string]repository.Session
	Queues      []repository.Queue
	QueueSongs  []repository.QueueSong

	// Err, when set, is returned by every implemented query.
	Err error
}

// New returns an empty Store.
func New() *Store {
	return &Store{Sessions: map[string]repository.Session{}}
}

func (s *Store) lock() func() {
	s.mu.Lock()
	return s.mu.Unlock
}

// AddSoundtrack inserts a soundtrack and returns it with its ID and UUID set.
func (s *Store) AddSoundtrack(st repository.Soundtrack) repository.Soundtrack {
	defer s.lock()()
	s.nextID++
	st.ID = s.nextID
	if st.Uuid == uuid.Nil {
		st.Uuid = uuid.New()
	}
	s.Soundtracks = append(s.Soundtracks, st)
	return st
}

// AddTestSong inserts a song and returns it with its UUID and soundtrack UUID set.
func (s *Store) AddTestSong(song repository.Song) repository.Song {
	defer s.lock()()
	if song.Uuid == uuid.Nil {
		song.Uuid = uuid.New()
	}
	if i := s.soundtrackIndex(song.SoundtrackID); song.SoundtrackUuid == uuid.Nil && i >= 0 {
		song.SoundtrackUuid = s.Soundtracks[i].Uuid
	}
	s.Songs = append(s.Songs, song)
	return song
}

// Soundtrack returns the soundtrack with the given name.
func (s *Store) Soundtrack(name string) (repository.Soundtrack, bool) {
	defer s.lock()()
	for _, st := range s.Soundtracks {
		if st.SoundtrackName == name {
			return st, true
		}
	}
	return repository.Soundtrack{}, false
}

// SongsOf returns the songs of a soundtrack sorted by path.
func (s *Store) SongsOf(soundtrackID int32) []repository.Song {
	defer s.lock()()
	var songs []repository.Song
	for _, song := range s.Songs {
		if song.SoundtrackID == soundtrackID {
			songs = append(songs, song)
		}
	}
	slices.SortFunc(songs, func(a, b repository.Song) int { return cmp.Compare(a.Path, b.Path) })
	return songs
}

func (s *Store) soundtrackIndex(id int32) int {
	return slices.IndexFunc(s.Soundtracks, func(st repository.Soundtrack) bool { return st.ID == id })
}

func (s *Store) updateSoundtrack(id int32, f func(*repository.Soundtrack)) error {
	defer s.lock()()
	if s.Err != nil {
		return s.Err
	}
	if i := s.soundtrackIndex(id); i >= 0 {
		f(&s.Soundtracks[i])
	}
	return nil
}

func sortedByName(soundtracks []repository.Soundtrack) []repository.Soundtrack {
	slices.SortFunc(soundtracks, func(a, b repository.Soundtrack) int { return cmp.Compare(a.SoundtrackName, b.SoundtrackName) })
	return soundtracks
}

func (s *Store) FindAllSoundtracks(context.Context) ([]repository.Soundtrack, error) {
	defer s.lock()()
	if s.Err != nil {
		return nil, s.Err
	}
	var active []repository.Soundtrack
	for _, st := range s.Soundtracks {
		if st.Deleted == nil {
			active = append(active, st)
		}
	}
	return sortedByName(active), nil
}

func (s *Store) GetAllSoundtracksIncludingDeleted(context.Context) ([]repository.Soundtrack, error) {
	defer s.lock()()
	if s.Err != nil {
		return nil, s.Err
	}
	return sortedByName(slices.Clone(s.Soundtracks)), nil
}

func (s *Store) InsertSoundtrack(_ context.Context, arg repository.InsertSoundtrackParams) (repository.InsertSoundtrackRow, error) {
	if s.Err != nil {
		return repository.InsertSoundtrackRow{}, s.Err
	}
	st := s.AddSoundtrack(repository.Soundtrack{
		SoundtrackName: arg.SoundtrackName,
		Path:           arg.Path,
		Hash:           arg.Hash,
		Uuid:           arg.Uuid,
		Added:          time.Now(),
	})
	return repository.InsertSoundtrackRow{ID: st.ID, Uuid: st.Uuid}, nil
}

func (s *Store) ResetSoundtrackIdSeq(context.Context) (int64, error) {
	return int64(s.nextID), s.Err
}

func (s *Store) UpdateSoundtrackHash(_ context.Context, arg repository.UpdateSoundtrackHashParams) error {
	return s.updateSoundtrack(arg.ID, func(st *repository.Soundtrack) { st.Hash = arg.Hash })
}

func (s *Store) UpdateSoundtrackName(_ context.Context, arg repository.UpdateSoundtrackNameParams) error {
	return s.updateSoundtrack(arg.ID, func(st *repository.Soundtrack) { st.SoundtrackName, st.Path = arg.Name, arg.Path })
}

func (s *Store) SetSoundtrackFingerprint(_ context.Context, arg repository.SetSoundtrackFingerprintParams) error {
	return s.updateSoundtrack(arg.ID, func(st *repository.Soundtrack) { st.Fingerprint = arg.Fingerprint })
}

func (s *Store) RemoveSoundtrackDeletionDate(_ context.Context, id int32) error {
	return s.updateSoundtrack(id, func(st *repository.Soundtrack) { st.Deleted = nil })
}

func (s *Store) AddSoundtrackPlayedByUUID(_ context.Context, id uuid.UUID) error {
	defer s.lock()()
	now := time.Now()
	for i := range s.Soundtracks {
		if s.Soundtracks[i].Uuid == id {
			s.Soundtracks[i].TimesPlayed++
			s.Soundtracks[i].LastPlayed = &now
		}
	}
	return s.Err
}

func (s *Store) GetSoundtrackById(_ context.Context, id int32) (repository.Soundtrack, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.Soundtrack{}, s.Err
	}
	if i := s.soundtrackIndex(id); i >= 0 && s.Soundtracks[i].Deleted == nil {
		return s.Soundtracks[i], nil
	}
	return repository.Soundtrack{}, pgx.ErrNoRows
}

func (s *Store) GetSoundtrackByUUID(_ context.Context, id uuid.UUID) (repository.Soundtrack, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.Soundtrack{}, s.Err
	}
	for _, st := range s.Soundtracks {
		if st.Uuid == id && st.Deleted == nil {
			return st, nil
		}
	}
	return repository.Soundtrack{}, pgx.ErrNoRows
}

func (s *Store) soundtrackByUUID(id uuid.UUID) int {
	return slices.IndexFunc(s.Soundtracks, func(st repository.Soundtrack) bool { return st.Uuid == id })
}

func (s *Store) updateSoundtrackByUUID(id uuid.UUID, f func(*repository.Soundtrack)) error {
	defer s.lock()()
	if s.Err != nil {
		return s.Err
	}
	if i := s.soundtrackByUUID(id); i >= 0 {
		f(&s.Soundtracks[i])
	}
	return nil
}

func (s *Store) SetAlternativeNames(_ context.Context, arg repository.SetAlternativeNamesParams) (repository.Soundtrack, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.Soundtrack{}, s.Err
	}
	i := s.soundtrackByUUID(arg.Uuid)
	if i < 0 || s.Soundtracks[i].Deleted != nil {
		return repository.Soundtrack{}, pgx.ErrNoRows
	}
	st := &s.Soundtracks[i]
	st.AlternativeNames = slices.Clone(arg.Names)
	if st.CoverFile == nil {
		st.CoverChecked = pgtype.Timestamptz{}
	}
	return *st, nil
}

func (s *Store) ListSoundtracksNeedingCover(
	_ context.Context, checkedBefore pgtype.Timestamptz,
) ([]repository.ListSoundtracksNeedingCoverRow, error) {
	defer s.lock()()
	if s.Err != nil {
		return nil, s.Err
	}
	var rows []repository.ListSoundtracksNeedingCoverRow
	for _, st := range sortedByName(slices.Clone(s.Soundtracks)) {
		if st.Deleted != nil || st.CoverFile != nil || st.CoverManual ||
			(st.CoverChecked.Valid && !st.CoverChecked.Time.Before(checkedBefore.Time)) {
			continue
		}
		rows = append(rows, repository.ListSoundtracksNeedingCoverRow{
			Uuid: st.Uuid, SoundtrackName: st.SoundtrackName, AlternativeNames: st.AlternativeNames,
		})
	}
	return rows, nil
}

func (s *Store) SetCover(_ context.Context, arg repository.SetCoverParams) error {
	return s.updateSoundtrackByUUID(arg.Uuid, func(st *repository.Soundtrack) {
		now := pgtype.Timestamptz{Time: time.Now(), Valid: true}
		st.CoverFile, st.CoverSource, st.CoverExternalID = arg.File, arg.Source, arg.ExternalID
		st.CoverManual, st.CoverModified, st.CoverChecked = arg.Manual, now, now
	})
}

func (s *Store) MarkCoverChecked(_ context.Context, id uuid.UUID) error {
	return s.updateSoundtrackByUUID(id, func(st *repository.Soundtrack) {
		st.CoverChecked = pgtype.Timestamptz{Time: time.Now(), Valid: true}
	})
}

func (s *Store) ClearCover(_ context.Context, id uuid.UUID) error {
	return s.updateSoundtrackByUUID(id, func(st *repository.Soundtrack) {
		st.CoverFile, st.CoverSource, st.CoverExternalID, st.CoverManual = nil, nil, nil, false
		st.CoverModified, st.CoverChecked = pgtype.Timestamptz{}, pgtype.Timestamptz{}
	})
}

func (s *Store) ListCoverFiles(context.Context) ([]string, error) {
	defer s.lock()()
	if s.Err != nil {
		return nil, s.Err
	}
	var files []string
	for _, st := range s.Soundtracks {
		if st.CoverFile != nil {
			files = append(files, *st.CoverFile)
		}
	}
	return files, nil
}

func (s *Store) MarkSoundtracksDeletedExcept(_ context.Context, ids []int32) error {
	defer s.lock()()
	if s.Err != nil {
		return s.Err
	}
	now := time.Now()
	for i := range s.Soundtracks {
		if s.Soundtracks[i].Deleted == nil && !slices.Contains(ids, s.Soundtracks[i].ID) {
			s.Soundtracks[i].Deleted = &now
		}
	}
	return nil
}

func (s *Store) ClearSoundtracks(context.Context) error {
	defer s.lock()()
	s.Soundtracks = nil
	return s.Err
}

func (s *Store) ClearSongs(context.Context) error {
	defer s.lock()()
	s.Songs = nil
	return s.Err
}

func (s *Store) FindSongsFromSoundtrack(_ context.Context, soundtrackID int32) ([]repository.Song, error) {
	if s.Err != nil {
		return nil, s.Err
	}
	return s.SongsOf(soundtrackID), nil
}

func (s *Store) FetchAllSongs(context.Context) ([]repository.Song, error) {
	defer s.lock()()
	return slices.Clone(s.Songs), s.Err
}

func (s *Store) AddSong(_ context.Context, arg repository.AddSongParams) error {
	if s.Err != nil {
		return s.Err
	}
	s.AddTestSong(repository.Song{
		SoundtrackID:   arg.SoundtrackID,
		SongName:       arg.SongName,
		Path:           arg.Path,
		FileName:       arg.FileName,
		Hash:           arg.Hash,
		Uuid:           arg.Uuid,
		SoundtrackUuid: arg.SoundtrackUuid,
	})
	return nil
}

func (s *Store) UpdateSongByUUID(_ context.Context, arg repository.UpdateSongByUUIDParams) error {
	defer s.lock()()
	for i := range s.Songs {
		if s.Songs[i].Uuid == arg.Uuid {
			s.Songs[i].SongName, s.Songs[i].FileName, s.Songs[i].Path, s.Songs[i].Hash = arg.SongName, arg.FileName, arg.Path, arg.Hash
		}
	}
	return s.Err
}

func (s *Store) AddSongPlayedByUUID(_ context.Context, id uuid.UUID) error {
	defer s.lock()()
	for i := range s.Songs {
		if s.Songs[i].Uuid == id {
			s.Songs[i].TimesPlayed++
		}
	}
	return s.Err
}

func (s *Store) GetSongsBySoundtrackUUID(_ context.Context, id uuid.UUID) ([]repository.Song, error) {
	defer s.lock()()
	if s.Err != nil {
		return nil, s.Err
	}
	var songs []repository.Song
	for _, song := range s.Songs {
		if song.SoundtrackUuid == id {
			songs = append(songs, song)
		}
	}
	slices.SortFunc(songs, func(a, b repository.Song) int { return cmp.Compare(a.SongName, b.SongName) })
	return songs, nil
}

func (s *Store) GetActiveSongByUUID(_ context.Context, id uuid.UUID) (repository.GetActiveSongByUUIDRow, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.GetActiveSongByUUIDRow{}, s.Err
	}
	for _, song := range s.Songs {
		if song.Uuid != id {
			continue
		}
		if i := s.soundtrackIndex(song.SoundtrackID); i >= 0 && s.Soundtracks[i].Deleted == nil {
			st := s.Soundtracks[i]
			return repository.GetActiveSongByUUIDRow{Song: song, SoundtrackName: st.SoundtrackName, SoundtrackPath: st.Path}, nil
		}
	}
	return repository.GetActiveSongByUUIDRow{}, pgx.ErrNoRows
}

func (s *Store) RemoveBrokenSongs(_ context.Context, uuids []uuid.UUID) error {
	defer s.lock()()
	s.Songs = slices.DeleteFunc(s.Songs, func(song repository.Song) bool { return slices.Contains(uuids, song.Uuid) })
	return s.Err
}

func (s *Store) GetRandomActiveSong(context.Context) (repository.GetRandomActiveSongRow, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.GetRandomActiveSongRow{}, s.Err
	}
	var rows []repository.GetRandomActiveSongRow
	for _, song := range s.Songs {
		if i := s.soundtrackIndex(song.SoundtrackID); i >= 0 && s.Soundtracks[i].Deleted == nil {
			rows = append(rows, repository.GetRandomActiveSongRow{Song: song, SoundtrackPath: s.Soundtracks[i].Path})
		}
	}
	if len(rows) == 0 {
		return repository.GetRandomActiveSongRow{}, pgx.ErrNoRows
	}
	return rows[rand.IntN(len(rows))], nil
}

func (s *Store) CreateSession(_ context.Context, arg repository.CreateSessionParams) (repository.Session, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.Session{}, s.Err
	}
	session := repository.Session{
		Token:      arg.Token,
		IpAddress:  arg.IpAddress,
		UserAgent:  arg.UserAgent,
		ClientType: arg.ClientType,
		ExpiresAt:  arg.ExpiresAt,
	}
	s.Sessions[arg.Token] = session
	return session, nil
}

func (s *Store) GetSession(_ context.Context, token string) (repository.Session, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.Session{}, s.Err
	}
	session, ok := s.Sessions[token]
	if !ok {
		return repository.Session{}, pgx.ErrNoRows
	}
	return session, nil
}

func (s *Store) DeleteSession(ctx context.Context, token string) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	defer s.lock()()
	delete(s.Sessions, token)
	return s.Err
}

func (s *Store) DeleteExpiredSessions(context.Context) error {
	defer s.lock()()
	for token, session := range s.Sessions {
		if session.ExpiresAt.Time.Before(time.Now()) {
			delete(s.Sessions, token)
		}
	}
	return s.Err
}

// HasSession reports whether a session with the given token exists.
func (s *Store) HasSession(token string) bool {
	defer s.lock()()
	_, ok := s.Sessions[token]
	return ok
}

func (s *Store) queueIndex(id uuid.UUID) int {
	return slices.IndexFunc(s.Queues, func(q repository.Queue) bool { return q.Uuid == id })
}

func (s *Store) updateQueue(id uuid.UUID, f func(*repository.Queue)) error {
	defer s.lock()()
	if s.Err != nil {
		return s.Err
	}
	if i := s.queueIndex(id); i >= 0 {
		f(&s.Queues[i])
	}
	return nil
}

func (s *Store) CreateQueue(context.Context) (repository.Queue, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.Queue{}, s.Err
	}
	queue := repository.Queue{Uuid: uuid.New(), CurrentSong: -1, StartedAt: pgtype.Timestamptz{Time: time.Now(), Valid: true}}
	s.Queues = append(s.Queues, queue)
	return queue, nil
}

func (s *Store) GetQueue(_ context.Context, id uuid.UUID) (repository.Queue, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.Queue{}, s.Err
	}
	if i := s.queueIndex(id); i >= 0 {
		return s.Queues[i], nil
	}
	return repository.Queue{}, pgx.ErrNoRows
}

func endQueue(q *repository.Queue) {
	if !q.EndedAt.Valid {
		q.EndedAt = pgtype.Timestamptz{Time: time.Now(), Valid: true}
	}
}

func (s *Store) EndQueue(_ context.Context, id uuid.UUID) error {
	return s.updateQueue(id, endQueue)
}

func (s *Store) EndActiveQueues(context.Context) error {
	defer s.lock()()
	for i := range s.Queues {
		endQueue(&s.Queues[i])
	}
	return s.Err
}

func (s *Store) SetQueueLastFetched(_ context.Context, arg repository.SetQueueLastFetchedParams) error {
	return s.updateQueue(arg.Uuid, func(q *repository.Queue) {
		q.LastFetchedSongUuid, q.LastFetchedMode = arg.LastFetchedSongUuid, arg.LastFetchedMode
	})
}

func (s *Store) SetQueueCurrentSong(_ context.Context, arg repository.SetQueueCurrentSongParams) error {
	return s.updateQueue(arg.Uuid, func(q *repository.Queue) { q.CurrentSong = arg.CurrentSong })
}

func (s *Store) AddLastFetchedToQueue(_ context.Context, id uuid.UUID) error {
	defer s.lock()()
	if s.Err != nil {
		return s.Err
	}
	i := s.queueIndex(id)
	if i < 0 {
		return nil
	}
	queue := &s.Queues[i]
	songIndex := slices.IndexFunc(s.Songs, func(song repository.Song) bool { return song.Uuid == queue.LastFetchedSongUuid })
	if songIndex < 0 {
		return nil
	}
	song := s.Songs[songIndex]
	var soundtrackName string
	if st := s.soundtrackIndex(song.SoundtrackID); st >= 0 {
		soundtrackName = s.Soundtracks[st].SoundtrackName
	}
	mode := "unknown"
	if queue.LastFetchedMode != nil {
		mode = *queue.LastFetchedMode
	}
	songNo := int32(0)
	for _, qs := range s.QueueSongs {
		if qs.QueueUuid == id {
			songNo = max(songNo, qs.SongNo+1)
		}
	}
	s.QueueSongs = append(s.QueueSongs, repository.QueueSong{
		QueueUuid: id, SongNo: songNo, SongUuid: song.Uuid, SoundtrackName: soundtrackName, SongName: song.SongName,
		Mode: mode,
	})
	queue.CurrentSong = songNo
	queue.LastFetchedSongUuid, queue.LastFetchedMode = uuid.Nil, nil
	return nil
}

func (s *Store) ListQueueSongs(_ context.Context, id uuid.UUID) ([]repository.ListQueueSongsRow, error) {
	defer s.lock()()
	if s.Err != nil {
		return nil, s.Err
	}
	var rows []repository.ListQueueSongsRow
	for _, qs := range s.QueueSongs {
		if qs.QueueUuid != id {
			continue
		}
		row := repository.ListQueueSongsRow{
			SongNo: qs.SongNo, SongUuid: qs.SongUuid, SoundtrackName: qs.SoundtrackName, SongName: qs.SongName, Mode: qs.Mode,
		}
		if i := slices.IndexFunc(s.Songs, func(song repository.Song) bool { return song.Uuid == qs.SongUuid }); i >= 0 {
			song := s.Songs[i]
			row.Path, row.TimesPlayed, row.SoundtrackUuid = &song.Path, &song.TimesPlayed, song.SoundtrackUuid
		}
		rows = append(rows, row)
	}
	slices.SortFunc(rows, func(a, b repository.ListQueueSongsRow) int { return cmp.Compare(a.SongNo, b.SongNo) })
	return rows, nil
}

func (s *Store) CountLibrary(context.Context) (repository.CountLibraryRow, error) {
	defer s.lock()()
	if s.Err != nil {
		return repository.CountLibraryRow{}, s.Err
	}
	var count repository.CountLibraryRow
	for _, st := range s.Soundtracks {
		if st.Deleted != nil {
			continue
		}
		count.Soundtracks++
		for _, song := range s.Songs {
			if song.SoundtrackID == st.ID {
				count.Songs++
			}
		}
	}
	return count, nil
}

// Statistics queries return empty results; tests that need data use their own fakes.

func (s *Store) GetMostPlayedSoundtracksWithSongs(context.Context, int32) ([]repository.GetMostPlayedSoundtracksWithSongsRow, error) {
	return nil, s.Err
}

func (s *Store) GetLeastPlayedSoundtracksWithSongs(context.Context, int32) ([]repository.GetLeastPlayedSoundtracksWithSongsRow, error) {
	return nil, s.Err
}

func (s *Store) GetLastPlayedSoundtracks(context.Context, int32) ([]repository.GetLastPlayedSoundtracksRow, error) {
	return nil, s.Err
}

func (s *Store) GetOldestPlayedSoundtracks(context.Context, int32) ([]repository.GetOldestPlayedSoundtracksRow, error) {
	return nil, s.Err
}

func (s *Store) GetAllSoundtracksWithSongs(context.Context) ([]repository.GetAllSoundtracksWithSongsRow, error) {
	return nil, s.Err
}

func (s *Store) GetNeverPlayedSoundtracks(context.Context) ([]repository.GetNeverPlayedSoundtracksRow, error) {
	return nil, s.Err
}

func (s *Store) GetMostPlayedSongsWithSoundtrack(context.Context, int32) ([]repository.GetMostPlayedSongsWithSoundtrackRow, error) {
	return nil, s.Err
}

func (s *Store) GetLeastPlayedSongsWithSoundtrack(context.Context, int32) ([]repository.GetLeastPlayedSongsWithSoundtrackRow, error) {
	return nil, s.Err
}

func (s *Store) GetStatisticsSummary(context.Context) (repository.GetStatisticsSummaryRow, error) {
	return repository.GetStatisticsSummaryRow{}, s.Err
}