package backend

import (
	"context"
	"errors"
	"strings"
	"time"

	"music-server/internal/db/repository"

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

// Soundtrack is a soundtrack as returned by the API.
type Soundtrack struct {
	Uuid             uuid.UUID  `json:"uuid"`
	Name             string     `json:"name"`
	AlternativeNames []string   `json:"alternative_names" doc:"Other names the soundtrack is known by"`
	TimesPlayed      int32      `json:"times_played"`
	LastPlayed       *time.Time `json:"last_played,omitempty"`
	Added            time.Time  `json:"added"`
	CoverModified    *int64     `json:"cover_modified,omitempty" doc:"When the cover last changed, in Unix seconds. Missing when there is no cover."`
}

// MaxNameLength is the longest alternative name that can be stored, in bytes.
const MaxNameLength = 200

// 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,
		AlternativeNames: nonNil(s.AlternativeNames),
		TimesPlayed:      s.TimesPlayed,
		LastPlayed:       s.LastPlayed,
		Added:            s.Added,
		CoverModified:    unixSeconds(s.CoverModified),
	}
}

// nonNil returns names, or an empty list for nil, so the JSON is [] and never null.
func nonNil(names []string) []string {
	if names == nil {
		return []string{}
	}
	return names
}

// unixSeconds returns t in Unix seconds, or nil when it is not set.
func unixSeconds(t pgtype.Timestamptz) *int64 {
	if !t.Valid {
		return nil
	}
	seconds := t.Time.Unix()
	return &seconds
}

// SetAlternativeNames replaces the alternative names of an active soundtrack. The names
// are trimmed, and empty names, duplicates and names equal to the soundtrack's own name
// (ignoring case) are dropped.
func (l *LibraryService) SetAlternativeNames(ctx context.Context, id uuid.UUID, names []string) (Soundtrack, error) {
	row, err := l.q.GetSoundtrackByUUID(ctx, id)
	if err != nil {
		return Soundtrack{}, notFound(err)
	}
	row, err = l.q.SetAlternativeNames(ctx, repository.SetAlternativeNamesParams{
		Uuid: id, Names: cleanAlternativeNames(row.SoundtrackName, names),
	})
	if err != nil {
		return Soundtrack{}, notFound(err)
	}
	return toSoundtrack(row), nil
}

func cleanAlternativeNames(name string, names []string) []string {
	cleaned := []string{}
	seen := map[string]bool{strings.ToLower(strings.TrimSpace(name)): true}
	for _, n := range names {
		n = strings.TrimSpace(n)
		key := strings.ToLower(n)
		if n == "" || seen[key] {
			continue
		}
		seen[key] = true
		cleaned = append(cleaned, n)
	}
	return cleaned
}

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
}