package gobackend

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"sync"
	"time"
)

const (
	deezerBaseURL     = "https://api.deezer.com/2.0"
	deezerSearchURL   = deezerBaseURL + "/search"
	deezerTrackURL    = deezerBaseURL + "/track/%s"
	deezerAlbumURL    = deezerBaseURL + "/album/%s"
	deezerArtistURL   = deezerBaseURL + "/artist/%s"
	deezerPlaylistURL = deezerBaseURL + "/playlist/%s"

	deezerCacheTTL = 10 * time.Minute

	deezerMaxParallelISRC = 10
)

// DeezerClient handles Deezer API interactions (no auth required)
type DeezerClient struct {
	httpClient  *http.Client
	searchCache map[string]*cacheEntry
	albumCache  map[string]*cacheEntry
	artistCache map[string]*cacheEntry
	isrcCache   map[string]string // trackID -> ISRC cache
	cacheMu     sync.RWMutex
}

var (
	deezerClient     *DeezerClient
	deezerClientOnce sync.Once
)

// GetDeezerClient returns singleton Deezer client
func GetDeezerClient() *DeezerClient {
	deezerClientOnce.Do(func() {
		deezerClient = &DeezerClient{
			httpClient:  NewHTTPClientWithTimeout(15 * time.Second),
			searchCache: make(map[string]*cacheEntry),
			albumCache:  make(map[string]*cacheEntry),
			artistCache: make(map[string]*cacheEntry),
			isrcCache:   make(map[string]string),
		}
	})
	return deezerClient
}

// Deezer API response types
type deezerTrack struct {
	ID            int64             `json:"id"`
	Title         string            `json:"title"`
	Duration      int               `json:"duration"` // in seconds
	TrackPosition int               `json:"track_position"`
	DiskNumber    int               `json:"disk_number"`
	ISRC          string            `json:"isrc"`
	Link          string            `json:"link"`
	ReleaseDate   string            `json:"release_date"` // Sometimes at track level
	Artist        deezerArtist      `json:"artist"`
	Album         deezerAlbumSimple `json:"album"`
	Contributors  []deezerArtist    `json:"contributors"`
}

type deezerArtist struct {
	ID            int64  `json:"id"`
	Name          string `json:"name"`
	Picture       string `json:"picture"`
	PictureMedium string `json:"picture_medium"`
	PictureBig    string `json:"picture_big"`
	PictureXL     string `json:"picture_xl"`
	NbFan         int    `json:"nb_fan"`
}

type deezerAlbumSimple struct {
	ID          int64  `json:"id"`
	Title       string `json:"title"`
	Cover       string `json:"cover"`
	CoverMedium string `json:"cover_medium"`
	CoverBig    string `json:"cover_big"`
	CoverXL     string `json:"cover_xl"`
	ReleaseDate string `json:"release_date"` // Sometimes at album level
	RecordType  string `json:"record_type"`  // album, single, ep, compile
}

func (c *DeezerClient) convertTrack(track deezerTrack) TrackMetadata {
	artistName := track.Artist.Name
	if len(track.Contributors) > 0 {
		names := make([]string, len(track.Contributors))
		for i, a := range track.Contributors {
			names[i] = a.Name
		}
		artistName = strings.Join(names, ", ")
	}

	albumImage := track.Album.CoverXL
	if albumImage == "" {
		albumImage = track.Album.CoverBig
	}
	if albumImage == "" {
		albumImage = track.Album.CoverMedium
	}
	if albumImage == "" {
		albumImage = track.Album.Cover
	}

	releaseDate := track.ReleaseDate
	if releaseDate == "" {
		releaseDate = track.Album.ReleaseDate
	}

	return TrackMetadata{
		SpotifyID:   fmt.Sprintf("deezer:%d", track.ID),
		Artists:     artistName,
		Name:        track.Title,
		AlbumName:   track.Album.Title,
		AlbumArtist: track.Artist.Name,
		DurationMS:  track.Duration * 1000,
		Images:      albumImage,
		ReleaseDate: releaseDate, // Added this
		TrackNumber: track.TrackPosition,
		DiscNumber:  track.DiskNumber,
		ExternalURL: track.Link,
		ISRC:        track.ISRC,
	}
}

type deezerAlbumFull struct {
	ID           int64          `json:"id"`
	Title        string         `json:"title"`
	Cover        string         `json:"cover"`
	CoverMedium  string         `json:"cover_medium"`
	CoverBig     string         `json:"cover_big"`
	CoverXL      string         `json:"cover_xl"`
	ReleaseDate  string         `json:"release_date"`
	NbTracks     int            `json:"nb_tracks"`
	RecordType   string         `json:"record_type"` // album, single, ep, compile
	Artist       deezerArtist   `json:"artist"`
	Contributors []deezerArtist `json:"contributors"`
	Tracks       struct {
		Data []deezerTrack `json:"data"`
	} `json:"tracks"`
}

type deezerArtistFull struct {
	ID            int64  `json:"id"`
	Name          string `json:"name"`
	Picture       string `json:"picture"`
	PictureMedium string `json:"picture_medium"`
	PictureBig    string `json:"picture_big"`
	PictureXL     string `json:"picture_xl"`
	NbFan         int    `json:"nb_fan"`
	NbAlbum       int    `json:"nb_album"`
}

type deezerPlaylistFull struct {
	ID            int64  `json:"id"`
	Title         string `json:"title"`
	Picture       string `json:"picture"`
	PictureMedium string `json:"picture_medium"`
	PictureBig    string `json:"picture_big"`
	PictureXL     string `json:"picture_xl"`
	NbTracks      int    `json:"nb_tracks"`
	Creator       struct {
		Name string `json:"name"`
	} `json:"creator"`
	Tracks struct {
		Data []deezerTrack `json:"data"`
	} `json:"tracks"`
}

// SearchAll searches for tracks and artists on Deezer
// NOTE: ISRC is NOT fetched during search for performance - use GetTrackISRC when needed for download
func (c *DeezerClient) SearchAll(ctx context.Context, query string, trackLimit, artistLimit int) (*SearchAllResult, error) {
	GoLog("[Deezer] SearchAll: query=%q, trackLimit=%d, artistLimit=%d\n", query, trackLimit, artistLimit)

	cacheKey := fmt.Sprintf("deezer:all:%s:%d:%d", query, trackLimit, artistLimit)

	c.cacheMu.RLock()
	if entry, ok := c.searchCache[cacheKey]; ok && !entry.isExpired() {
		c.cacheMu.RUnlock()
		GoLog("[Deezer] SearchAll: returning cached result\n")
		return entry.data.(*SearchAllResult), nil
	}
	c.cacheMu.RUnlock()

	result := &SearchAllResult{
		Tracks:  make([]TrackMetadata, 0),
		Artists: make([]SearchArtistResult, 0),
	}

	// Search tracks - NO ISRC fetch for performance
	trackURL := fmt.Sprintf("%s/track?q=%s&limit=%d", deezerSearchURL, url.QueryEscape(query), trackLimit)
	GoLog("[Deezer] Fetching tracks from: %s\n", trackURL)

	var trackResp struct {
		Data  []deezerTrack `json:"data"`
		Error *struct {
			Type    string `json:"type"`
			Message string `json:"message"`
			Code    int    `json:"code"`
		} `json:"error"`
	}
	if err := c.getJSON(ctx, trackURL, &trackResp); err != nil {
		GoLog("[Deezer] Track search failed: %v\n", err)
		return nil, fmt.Errorf("deezer track search failed: %w", err)
	}

	if trackResp.Error != nil {
		GoLog("[Deezer] API error: type=%s, code=%d, message=%s\n", trackResp.Error.Type, trackResp.Error.Code, trackResp.Error.Message)
		return nil, fmt.Errorf("deezer API error: %s (code %d)", trackResp.Error.Message, trackResp.Error.Code)
	}

	GoLog("[Deezer] Got %d tracks from API\n", len(trackResp.Data))

	for _, track := range trackResp.Data {
		// Convert directly without fetching ISRC - much faster
		result.Tracks = append(result.Tracks, c.convertTrack(track))
	}

	// Search artists
	artistURL := fmt.Sprintf("%s/artist?q=%s&limit=%d", deezerSearchURL, url.QueryEscape(query), artistLimit)
	GoLog("[Deezer] Fetching artists from: %s\n", artistURL)

	var artistResp struct {
		Data  []deezerArtist `json:"data"`
		Error *struct {
			Type    string `json:"type"`
			Message string `json:"message"`
			Code    int    `json:"code"`
		} `json:"error"`
	}
	if err := c.getJSON(ctx, artistURL, &artistResp); err == nil {
		if artistResp.Error != nil {
			GoLog("[Deezer] Artist API error: type=%s, code=%d, message=%s\n", artistResp.Error.Type, artistResp.Error.Code, artistResp.Error.Message)
		} else {
			GoLog("[Deezer] Got %d artists from API\n", len(artistResp.Data))
			for _, artist := range artistResp.Data {
				result.Artists = append(result.Artists, SearchArtistResult{
					ID:         fmt.Sprintf("deezer:%d", artist.ID),
					Name:       artist.Name,
					Images:     c.getBestArtistImage(artist),
					Followers:  artist.NbFan,
					Popularity: 0,
				})
			}
		}
	} else {
		GoLog("[Deezer] Artist search failed: %v\n", err)
	}

	GoLog("[Deezer] SearchAll complete: %d tracks, %d artists\n", len(result.Tracks), len(result.Artists))

	// Cache result
	c.cacheMu.Lock()
	c.searchCache[cacheKey] = &cacheEntry{
		data:      result,
		expiresAt: time.Now().Add(deezerCacheTTL),
	}
	c.cacheMu.Unlock()

	return result, nil
}

// GetTrack fetches a single track by Deezer ID
func (c *DeezerClient) GetTrack(ctx context.Context, trackID string) (*TrackResponse, error) {
	trackURL := fmt.Sprintf(deezerTrackURL, trackID)

	var track deezerTrack
	if err := c.getJSON(ctx, trackURL, &track); err != nil {
		return nil, err
	}

	return &TrackResponse{
		Track: c.convertTrack(track),
	}, nil
}

// GetAlbum fetches album with tracks
// ISRC is fetched in parallel for better performance
func (c *DeezerClient) GetAlbum(ctx context.Context, albumID string) (*AlbumResponsePayload, error) {
	c.cacheMu.RLock()
	if entry, ok := c.albumCache[albumID]; ok && !entry.isExpired() {
		c.cacheMu.RUnlock()
		return entry.data.(*AlbumResponsePayload), nil
	}
	c.cacheMu.RUnlock()

	albumURL := fmt.Sprintf(deezerAlbumURL, albumID)

	var album deezerAlbumFull
	if err := c.getJSON(ctx, albumURL, &album); err != nil {
		return nil, err
	}

	albumImage := c.getBestAlbumImage(album)
	artistName := album.Artist.Name
	if len(album.Contributors) > 0 {
		names := make([]string, len(album.Contributors))
		for i, a := range album.Contributors {
			names[i] = a.Name
		}
		artistName = strings.Join(names, ", ")
	}

	info := AlbumInfoMetadata{
		TotalTracks: album.NbTracks,
		Name:        album.Title,
		ReleaseDate: album.ReleaseDate,
		Artists:     artistName,
		Images:      albumImage,
	}

	// Fetch ISRCs in parallel
	isrcMap := c.fetchISRCsParallel(ctx, album.Tracks.Data)

	tracks := make([]AlbumTrackMetadata, 0, len(album.Tracks.Data))
	// Normalize record_type (Deezer uses "compile" instead of "compilation")
	albumType := album.RecordType
	if albumType == "compile" {
		albumType = "compilation"
	}

	for _, track := range album.Tracks.Data {
		trackIDStr := fmt.Sprintf("%d", track.ID)
		isrc := isrcMap[trackIDStr]

		tracks = append(tracks, AlbumTrackMetadata{
			SpotifyID:   fmt.Sprintf("deezer:%d", track.ID),
			Artists:     track.Artist.Name,
			Name:        track.Title,
			AlbumName:   album.Title,
			AlbumArtist: artistName,
			DurationMS:  track.Duration * 1000,
			Images:      albumImage,
			ReleaseDate: album.ReleaseDate,
			TrackNumber: track.TrackPosition,
			TotalTracks: album.NbTracks,
			DiscNumber:  track.DiskNumber,
			ExternalURL: track.Link,
			ISRC:        isrc,
			AlbumID:     fmt.Sprintf("deezer:%d", album.ID),
			AlbumType:   albumType,
		})
	}

	result := &AlbumResponsePayload{
		AlbumInfo: info,
		TrackList: tracks,
	}

	c.cacheMu.Lock()
	c.albumCache[albumID] = &cacheEntry{
		data:      result,
		expiresAt: time.Now().Add(deezerCacheTTL),
	}
	c.cacheMu.Unlock()

	return result, nil
}

// GetArtist fetches artist with albums
func (c *DeezerClient) GetArtist(ctx context.Context, artistID string) (*ArtistResponsePayload, error) {
	c.cacheMu.RLock()
	if entry, ok := c.artistCache[artistID]; ok && !entry.isExpired() {
		c.cacheMu.RUnlock()
		return entry.data.(*ArtistResponsePayload), nil
	}
	c.cacheMu.RUnlock()

	// Fetch artist info
	artistURL := fmt.Sprintf(deezerArtistURL, artistID)
	var artist deezerArtistFull
	if err := c.getJSON(ctx, artistURL, &artist); err != nil {
		return nil, err
	}

	artistInfo := ArtistInfoMetadata{
		ID:         fmt.Sprintf("deezer:%d", artist.ID),
		Name:       artist.Name,
		Images:     c.getBestArtistImageFull(artist),
		Followers:  artist.NbFan,
		Popularity: 0,
	}

	// Fetch artist albums
	albumsURL := fmt.Sprintf("%s/albums?limit=100", fmt.Sprintf(deezerArtistURL, artistID))
	var albumsResp struct {
		Data []struct {
			ID          int64  `json:"id"`
			Title       string `json:"title"`
			ReleaseDate string `json:"release_date"`
			NbTracks    int    `json:"nb_tracks"`
			Cover       string `json:"cover"`
			CoverMedium string `json:"cover_medium"`
			CoverBig    string `json:"cover_big"`
			CoverXL     string `json:"cover_xl"`
			RecordType  string `json:"record_type"` // album, single, ep, compile
		} `json:"data"`
	}

	albums := make([]ArtistAlbumMetadata, 0)
	if err := c.getJSON(ctx, albumsURL, &albumsResp); err == nil {
		for _, album := range albumsResp.Data {
			albumType := album.RecordType
			if albumType == "compile" {
				albumType = "compilation"
			}

			coverURL := album.CoverXL
			if coverURL == "" {
				coverURL = album.CoverBig
			}
			if coverURL == "" {
				coverURL = album.CoverMedium
			}
			if coverURL == "" {
				coverURL = album.Cover
			}

			albums = append(albums, ArtistAlbumMetadata{
				ID:          fmt.Sprintf("deezer:%d", album.ID),
				Name:        album.Title,
				ReleaseDate: album.ReleaseDate,
				TotalTracks: album.NbTracks,
				Images:      coverURL,
				AlbumType:   albumType,
				Artists:     artist.Name,
			})
		}
	}

	result := &ArtistResponsePayload{
		ArtistInfo: artistInfo,
		Albums:     albums,
	}

	c.cacheMu.Lock()
	c.artistCache[artistID] = &cacheEntry{
		data:      result,
		expiresAt: time.Now().Add(deezerCacheTTL),
	}
	c.cacheMu.Unlock()

	return result, nil
}

// GetPlaylist fetches playlist with tracks
// ISRC is fetched in parallel for better performance
func (c *DeezerClient) GetPlaylist(ctx context.Context, playlistID string) (*PlaylistResponsePayload, error) {
	playlistURL := fmt.Sprintf(deezerPlaylistURL, playlistID)

	var playlist deezerPlaylistFull
	if err := c.getJSON(ctx, playlistURL, &playlist); err != nil {
		return nil, err
	}

	playlistImage := playlist.PictureXL
	if playlistImage == "" {
		playlistImage = playlist.PictureBig
	}
	if playlistImage == "" {
		playlistImage = playlist.PictureMedium
	}

	var info PlaylistInfoMetadata
	info.Tracks.Total = playlist.NbTracks
	info.Owner.DisplayName = playlist.Creator.Name
	info.Owner.Name = playlist.Title
	info.Owner.Images = playlistImage

	// Fetch ISRCs in parallel
	isrcMap := c.fetchISRCsParallel(ctx, playlist.Tracks.Data)

	tracks := make([]AlbumTrackMetadata, 0, len(playlist.Tracks.Data))
	for _, track := range playlist.Tracks.Data {
		albumImage := track.Album.CoverXL
		if albumImage == "" {
			albumImage = track.Album.CoverBig
		}
		if albumImage == "" {
			albumImage = track.Album.CoverMedium
		}

		trackIDStr := fmt.Sprintf("%d", track.ID)
		isrc := isrcMap[trackIDStr]

		tracks = append(tracks, AlbumTrackMetadata{
			SpotifyID:   fmt.Sprintf("deezer:%d", track.ID),
			Artists:     track.Artist.Name,
			Name:        track.Title,
			AlbumName:   track.Album.Title,
			AlbumArtist: track.Artist.Name,
			DurationMS:  track.Duration * 1000,
			Images:      albumImage,
			ReleaseDate: "",
			TrackNumber: track.TrackPosition,
			DiscNumber:  track.DiskNumber,
			ExternalURL: track.Link,
			ISRC:        isrc,
			AlbumID:     fmt.Sprintf("deezer:%d", track.Album.ID),
		})
	}

	return &PlaylistResponsePayload{
		PlaylistInfo: info,
		TrackList:    tracks,
	}, nil
}

// SearchByISRC searches for a track by ISRC using direct endpoint
func (c *DeezerClient) SearchByISRC(ctx context.Context, isrc string) (*TrackMetadata, error) {
	// Use direct ISRC endpoint (API 2.0)
	// https://api.deezer.com/2.0/track/isrc:{ISRC}
	directURL := fmt.Sprintf("%s/track/isrc:%s", deezerBaseURL, isrc)

	var track deezerTrack
	if err := c.getJSON(ctx, directURL, &track); err != nil {
		// Fallback to search if direct endpoint fails
		searchURL := fmt.Sprintf("%s/track?q=isrc:%s&limit=1", deezerSearchURL, isrc)
		var resp struct {
			Data []deezerTrack `json:"data"`
		}
		if err := c.getJSON(ctx, searchURL, &resp); err != nil {
			return nil, err
		}
		if len(resp.Data) == 0 {
			return nil, fmt.Errorf("no track found for ISRC: %s", isrc)
		}
		result := c.convertTrack(resp.Data[0])
		return &result, nil
	}

	if track.ID == 0 {
		return nil, fmt.Errorf("no track found for ISRC: %s", isrc)
	}

	result := c.convertTrack(track)
	return &result, nil
}

func (c *DeezerClient) fetchFullTrack(ctx context.Context, trackID string) (*deezerTrack, error) {
	trackURL := fmt.Sprintf(deezerTrackURL, trackID)
	var track deezerTrack
	if err := c.getJSON(ctx, trackURL, &track); err != nil {
		return nil, err
	}
	return &track, nil
}

// fetchISRCsParallel fetches ISRCs for multiple tracks in parallel with caching
func (c *DeezerClient) fetchISRCsParallel(ctx context.Context, tracks []deezerTrack) map[string]string {
	result := make(map[string]string)
	var resultMu sync.Mutex

	var tracksToFetch []deezerTrack
	c.cacheMu.RLock()
	for _, track := range tracks {
		trackIDStr := fmt.Sprintf("%d", track.ID)
		if isrc, ok := c.isrcCache[trackIDStr]; ok {
			result[trackIDStr] = isrc
		} else {
			tracksToFetch = append(tracksToFetch, track)
		}
	}
	c.cacheMu.RUnlock()

	if len(tracksToFetch) == 0 {
		return result
	}

	// Use semaphore to limit concurrent requests
	sem := make(chan struct{}, deezerMaxParallelISRC)
	var wg sync.WaitGroup

	for _, track := range tracksToFetch {
		wg.Add(1)
		go func(t deezerTrack) {
			defer wg.Done()

			// Acquire semaphore
			select {
			case sem <- struct{}{}:
				defer func() { <-sem }()
			case <-ctx.Done():
				return
			}

			trackIDStr := fmt.Sprintf("%d", t.ID)
			fullTrack, err := c.fetchFullTrack(ctx, trackIDStr)
			if err != nil || fullTrack == nil {
				return
			}

			// Store in result and cache
			resultMu.Lock()
			result[trackIDStr] = fullTrack.ISRC
			resultMu.Unlock()

			c.cacheMu.Lock()
			c.isrcCache[trackIDStr] = fullTrack.ISRC
			c.cacheMu.Unlock()
		}(track)
	}

	wg.Wait()
	return result
}

// GetTrackISRC fetches ISRC for a single track (with caching)
// Use this when you need ISRC for download
func (c *DeezerClient) GetTrackISRC(ctx context.Context, trackID string) (string, error) {
	c.cacheMu.RLock()
	if isrc, ok := c.isrcCache[trackID]; ok {
		c.cacheMu.RUnlock()
		return isrc, nil
	}
	c.cacheMu.RUnlock()

	// Fetch from API
	fullTrack, err := c.fetchFullTrack(ctx, trackID)
	if err != nil {
		return "", err
	}

	// Cache the result
	c.cacheMu.Lock()
	c.isrcCache[trackID] = fullTrack.ISRC
	c.cacheMu.Unlock()

	return fullTrack.ISRC, nil
}

func (c *DeezerClient) getBestArtistImage(artist deezerArtist) string {
	if artist.PictureXL != "" {
		return artist.PictureXL
	}
	if artist.PictureBig != "" {
		return artist.PictureBig
	}
	if artist.PictureMedium != "" {
		return artist.PictureMedium
	}
	return artist.Picture
}

func (c *DeezerClient) getBestArtistImageFull(artist deezerArtistFull) string {
	if artist.PictureXL != "" {
		return artist.PictureXL
	}
	if artist.PictureBig != "" {
		return artist.PictureBig
	}
	if artist.PictureMedium != "" {
		return artist.PictureMedium
	}
	return artist.Picture
}

func (c *DeezerClient) getBestAlbumImage(album deezerAlbumFull) string {
	if album.CoverXL != "" {
		return album.CoverXL
	}
	if album.CoverBig != "" {
		return album.CoverBig
	}
	if album.CoverMedium != "" {
		return album.CoverMedium
	}
	return album.Cover
}

func (c *DeezerClient) getJSON(ctx context.Context, endpoint string, dst interface{}) error {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return err
	}

	req.Header.Set("Accept", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return err
	}

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("deezer API returned status %d: %s", resp.StatusCode, string(body))
	}

	return json.Unmarshal(body, dst)
}

// parseDeezerURL is internal function, returns type and ID
func parseDeezerURL(input string) (string, string, error) {
	trimmed := strings.TrimSpace(input)
	if trimmed == "" {
		return "", "", fmt.Errorf("empty URL")
	}

	parsed, err := url.Parse(trimmed)
	if err != nil {
		return "", "", err
	}

	if parsed.Host != "www.deezer.com" && parsed.Host != "deezer.com" && parsed.Host != "deezer.page.link" {
		return "", "", fmt.Errorf("not a Deezer URL")
	}

	parts := strings.Split(strings.Trim(parsed.Path, "/"), "/")

	// Skip language prefix if present (e.g., /en/, /fr/)
	if len(parts) > 0 && len(parts[0]) == 2 {
		parts = parts[1:]
	}

	if len(parts) < 2 {
		return "", "", fmt.Errorf("invalid Deezer URL format")
	}

	resourceType := parts[0]
	resourceID := parts[1]

	switch resourceType {
	case "track", "album", "artist", "playlist":
		return resourceType, resourceID, nil
	default:
		return "", "", fmt.Errorf("unsupported Deezer resource type: %s", resourceType)
	}
}