feat: playlist implementation

octo-fiesta/Services/Common/BaseDownloadService.cs

@@ -4,6 +4,7 @@ using octo_fiesta.Models.Download;
 using octo_fiesta.Models.Search;
 using octo_fiesta.Models.Subsonic;
 using octo_fiesta.Services.Local;
+using octo_fiesta.Services.Subsonic;
 using TagLib;
 using IOFile = System.IO.File;
 
@@ -21,6 +22,7 @@ public abstract class BaseDownloadService : IDownloadService
     protected readonly IMusicMetadataService MetadataService;
     protected readonly SubsonicSettings SubsonicSettings;
     protected readonly ILogger Logger;
+    protected readonly IServiceProvider ServiceProvider;
     
     protected readonly string DownloadPath;
     protected readonly string CachePath;
@@ -38,12 +40,14 @@ public abstract class BaseDownloadService : IDownloadService
         ILocalLibraryService localLibraryService,
         IMusicMetadataService metadataService,
         SubsonicSettings subsonicSettings,
+        IServiceProvider serviceProvider,
         ILogger logger)
     {
         Configuration = configuration;
         LocalLibraryService = localLibraryService;
         MetadataService = metadataService;
         SubsonicSettings = subsonicSettings;
+        ServiceProvider = serviceProvider;
         Logger = logger;
         
         DownloadPath = configuration["Library:DownloadPath"] ?? "./downloads";
@@ -79,6 +83,30 @@ public abstract class BaseDownloadService : IDownloadService
         return info;
     }
     
+    public async Task<string?> GetLocalPathIfExistsAsync(string externalProvider, string externalId)
+    {
+        if (externalProvider != ProviderName)
+        {
+            return null;
+        }
+        
+        // Check local library
+        var localPath = await LocalLibraryService.GetLocalPathForExternalSongAsync(externalProvider, externalId);
+        if (localPath != null && IOFile.Exists(localPath))
+        {
+            return localPath;
+        }
+        
+        // Check cache directory
+        var cachedPath = GetCachedFilePath(externalProvider, externalId);
+        if (cachedPath != null && IOFile.Exists(cachedPath))
+        {
+            return cachedPath;
+        }
+        
+        return null;
+    }
+    
     public abstract Task<bool> IsAvailableAsync();
     
     public void DownloadRemainingAlbumTracksInBackground(string externalProvider, string albumExternalId, string excludeTrackExternalId)
@@ -240,6 +268,25 @@ public abstract class BaseDownloadService : IDownloadService
             
             song.LocalPath = localPath;
             
+            // Check if this track belongs to a playlist and update M3U
+            try
+            {
+                var playlistSyncService = ServiceProvider.GetService(typeof(PlaylistSyncService)) as PlaylistSyncService;
+                if (playlistSyncService != null)
+                {
+                    var playlistId = playlistSyncService.GetPlaylistIdForTrack(songId);
+                    if (playlistId != null)
+                    {
+                        Logger.LogInformation("Track {SongId} belongs to playlist {PlaylistId}, adding to M3U", songId, playlistId);
+                        await playlistSyncService.AddTrackToM3UAsync(playlistId, song, localPath);
+                    }
+                }
+            }
+            catch (Exception ex)
+            {
+                Logger.LogWarning(ex, "Failed to update playlist M3U for track {SongId}", songId);
+            }
+            
             // Only register and scan if NOT in cache mode
             if (!isCache)
             {

octo-fiesta/Services/Common/PlaylistIdHelper.cs

@@ -0,0 +1,76 @@
+namespace octo_fiesta.Services.Common;
+
+/// <summary>
+/// Helper class for handling external playlist IDs.
+/// Playlist IDs use the format: "pl-{provider}-{externalId}"
+/// Example: "pl-deezer-123456", "pl-qobuz-789"
+/// </summary>
+public static class PlaylistIdHelper
+{
+    private const string PlaylistPrefix = "pl-";
+    
+    /// <summary>
+    /// Checks if an ID represents an external playlist.
+    /// </summary>
+    /// <param name="id">The ID to check</param>
+    /// <returns>True if the ID starts with "pl-", false otherwise</returns>
+    public static bool IsExternalPlaylist(string? id)
+    {
+        return !string.IsNullOrEmpty(id) && id.StartsWith(PlaylistPrefix, StringComparison.OrdinalIgnoreCase);
+    }
+    
+    /// <summary>
+    /// Parses a playlist ID to extract provider and external ID.
+    /// </summary>
+    /// <param name="id">The playlist ID in format "pl-{provider}-{externalId}"</param>
+    /// <returns>A tuple containing (provider, externalId)</returns>
+    /// <exception cref="ArgumentException">Thrown if the ID format is invalid</exception>
+    public static (string provider, string externalId) ParsePlaylistId(string id)
+    {
+        if (!IsExternalPlaylist(id))
+        {
+            throw new ArgumentException($"Invalid playlist ID format. Expected 'pl-{{provider}}-{{externalId}}', got '{id}'", nameof(id));
+        }
+        
+        // Remove "pl-" prefix
+        var withoutPrefix = id.Substring(PlaylistPrefix.Length);
+        
+        // Split by first dash to get provider and externalId
+        var dashIndex = withoutPrefix.IndexOf('-');
+        if (dashIndex == -1)
+        {
+            throw new ArgumentException($"Invalid playlist ID format. Expected 'pl-{{provider}}-{{externalId}}', got '{id}'", nameof(id));
+        }
+        
+        var provider = withoutPrefix.Substring(0, dashIndex);
+        var externalId = withoutPrefix.Substring(dashIndex + 1);
+        
+        if (string.IsNullOrEmpty(provider) || string.IsNullOrEmpty(externalId))
+        {
+            throw new ArgumentException($"Invalid playlist ID format. Provider or external ID is empty in '{id}'", nameof(id));
+        }
+        
+        return (provider, externalId);
+    }
+    
+    /// <summary>
+    /// Creates a playlist ID from provider and external ID.
+    /// </summary>
+    /// <param name="provider">The provider name (e.g., "deezer", "qobuz")</param>
+    /// <param name="externalId">The external ID from the provider</param>
+    /// <returns>A playlist ID in format "pl-{provider}-{externalId}"</returns>
+    public static string CreatePlaylistId(string provider, string externalId)
+    {
+        if (string.IsNullOrEmpty(provider))
+        {
+            throw new ArgumentException("Provider cannot be null or empty", nameof(provider));
+        }
+        
+        if (string.IsNullOrEmpty(externalId))
+        {
+            throw new ArgumentException("External ID cannot be null or empty", nameof(externalId));
+        }
+        
+        return $"{PlaylistPrefix}{provider.ToLowerInvariant()}-{externalId}";
+    }
+}

octo-fiesta/Services/Deezer/DeezerDownloadService.cs

@@ -50,8 +50,9 @@ public class DeezerDownloadService : BaseDownloadService
         IMusicMetadataService metadataService,
         IOptions<SubsonicSettings> subsonicSettings,
         IOptions<DeezerSettings> deezerSettings,
+        IServiceProvider serviceProvider,
         ILogger<DeezerDownloadService> logger)
-        : base(configuration, localLibraryService, metadataService, subsonicSettings.Value, logger)
+        : base(configuration, localLibraryService, metadataService, subsonicSettings.Value, serviceProvider, logger)
     {
         _httpClient = httpClientFactory.CreateClient();
         

octo-fiesta/Services/Deezer/DeezerMetadataService.cs

@@ -231,6 +231,12 @@ public class DeezerMetadataService : IMusicMetadataService
             {
                 // Pass the album artist to ensure proper folder organization
                 var song = ParseDeezerTrack(track, trackIndex, album.Artist);
+                
+                // Ensure album metadata is set (tracks in album response may not have full album object)
+                song.Album = album.Title;
+                song.AlbumId = album.Id;
+                song.AlbumArtist = album.Artist;
+                
                 if (ShouldIncludeSong(song))
                 {
                     album.Songs.Add(song);
@@ -511,6 +517,163 @@ public class DeezerMetadataService : IMusicMetadataService
         };
     }
 
+    public async Task<List<ExternalPlaylist>> SearchPlaylistsAsync(string query, int limit = 20)
+    {
+        try
+        {
+            var url = $"{BaseUrl}/search/playlist?q={Uri.EscapeDataString(query)}&limit={limit}";
+            var response = await _httpClient.GetAsync(url);
+            
+            if (!response.IsSuccessStatusCode) return new List<ExternalPlaylist>();
+            
+            var json = await response.Content.ReadAsStringAsync();
+            var result = JsonDocument.Parse(json);
+            
+            var playlists = new List<ExternalPlaylist>();
+            if (result.RootElement.TryGetProperty("data", out var data))
+            {
+                foreach (var playlist in data.EnumerateArray())
+                {
+                    playlists.Add(ParseDeezerPlaylist(playlist));
+                }
+            }
+            
+            return playlists;
+        }
+        catch
+        {
+            return new List<ExternalPlaylist>();
+        }
+    }
+    
+    public async Task<ExternalPlaylist?> GetPlaylistAsync(string externalProvider, string externalId)
+    {
+        if (externalProvider != "deezer") return null;
+        
+        try
+        {
+            var url = $"{BaseUrl}/playlist/{externalId}";
+            var response = await _httpClient.GetAsync(url);
+            
+            if (!response.IsSuccessStatusCode) return null;
+            
+            var json = await response.Content.ReadAsStringAsync();
+            var playlistElement = JsonDocument.Parse(json).RootElement;
+            
+            if (playlistElement.TryGetProperty("error", out _)) return null;
+            
+            return ParseDeezerPlaylist(playlistElement);
+        }
+        catch
+        {
+            return null;
+        }
+    }
+    
+    public async Task<List<Song>> GetPlaylistTracksAsync(string externalProvider, string externalId)
+    {
+        if (externalProvider != "deezer") return new List<Song>();
+        
+        try
+        {
+            var url = $"{BaseUrl}/playlist/{externalId}";
+            var response = await _httpClient.GetAsync(url);
+            
+            if (!response.IsSuccessStatusCode) return new List<Song>();
+            
+            var json = await response.Content.ReadAsStringAsync();
+            var playlistElement = JsonDocument.Parse(json).RootElement;
+            
+            if (playlistElement.TryGetProperty("error", out _)) return new List<Song>();
+            
+            var songs = new List<Song>();
+            
+            // Get playlist name for album field
+            var playlistName = playlistElement.TryGetProperty("title", out var titleEl)
+                ? titleEl.GetString() ?? "Unknown Playlist"
+                : "Unknown Playlist";
+            
+            if (playlistElement.TryGetProperty("tracks", out var tracks) &&
+                tracks.TryGetProperty("data", out var tracksData))
+            {
+                int trackIndex = 1;
+                foreach (var track in tracksData.EnumerateArray())
+                {
+                    // For playlists, use the track's own artist (not a single album artist)
+                    var song = ParseDeezerTrack(track, trackIndex);
+                    
+                    // Override album name to be the playlist name
+                    song.Album = playlistName;
+                    
+                    if (ShouldIncludeSong(song))
+                    {
+                        songs.Add(song);
+                    }
+                    trackIndex++;
+                }
+            }
+            
+            return songs;
+        }
+        catch
+        {
+            return new List<Song>();
+        }
+    }
+
+    private ExternalPlaylist ParseDeezerPlaylist(JsonElement playlist)
+    {
+        var externalId = playlist.GetProperty("id").GetInt64().ToString();
+        
+        // Get curator/creator name
+        string? curatorName = null;
+        if (playlist.TryGetProperty("user", out var user) &&
+            user.TryGetProperty("name", out var userName))
+        {
+            curatorName = userName.GetString();
+        }
+        else if (playlist.TryGetProperty("creator", out var creator) &&
+                 creator.TryGetProperty("name", out var creatorName))
+        {
+            curatorName = creatorName.GetString();
+        }
+        
+        // Get creation date
+        DateTime? createdDate = null;
+        if (playlist.TryGetProperty("creation_date", out var creationDateEl))
+        {
+            var dateStr = creationDateEl.GetString();
+            if (!string.IsNullOrEmpty(dateStr) && DateTime.TryParse(dateStr, out var date))
+            {
+                createdDate = date;
+            }
+        }
+        
+        return new ExternalPlaylist
+        {
+            Id = Common.PlaylistIdHelper.CreatePlaylistId("deezer", externalId),
+            Name = playlist.GetProperty("title").GetString() ?? "",
+            Description = playlist.TryGetProperty("description", out var desc) 
+                ? desc.GetString() 
+                : null,
+            CuratorName = curatorName,
+            Provider = "deezer",
+            ExternalId = externalId,
+            TrackCount = playlist.TryGetProperty("nb_tracks", out var nbTracks) 
+                ? nbTracks.GetInt32() 
+                : 0,
+            Duration = playlist.TryGetProperty("duration", out var duration) 
+                ? duration.GetInt32() 
+                : 0,
+            CoverUrl = playlist.TryGetProperty("picture_medium", out var picture) 
+                ? picture.GetString() 
+                : (playlist.TryGetProperty("picture_big", out var pictureBig) 
+                    ? pictureBig.GetString() 
+                    : null),
+            CreatedDate = createdDate
+        };
+    }
+
     /// <summary>
     /// Determines whether a song should be included based on the explicit content filter setting
     /// </summary>

octo-fiesta/Services/IDownloadService.cs

@@ -42,6 +42,14 @@ public interface IDownloadService
     /// </summary>
     DownloadInfo? GetDownloadStatus(string songId);
     
+    /// <summary>
+    /// Gets the local path for a song if it has been downloaded already
+    /// </summary>
+    /// <param name="externalProvider">The provider (deezer, qobuz, etc.)</param>
+    /// <param name="externalId">The ID on the external provider</param>
+    /// <returns>The local file path if exists, null otherwise</returns>
+    Task<string?> GetLocalPathIfExistsAsync(string externalProvider, string externalId);
+    
     /// <summary>
     /// Checks if the service is properly configured and functional
     /// </summary>

octo-fiesta/Services/IMusicMetadataService.cs

@@ -54,4 +54,28 @@ public interface IMusicMetadataService
     /// Gets an artist's albums
     /// </summary>
     Task<List<Album>> GetArtistAlbumsAsync(string externalProvider, string externalId);
+    
+    /// <summary>
+    /// Searches for playlists on external providers
+    /// </summary>
+    /// <param name="query">Search term</param>
+    /// <param name="limit">Maximum number of results</param>
+    /// <returns>List of found playlists</returns>
+    Task<List<ExternalPlaylist>> SearchPlaylistsAsync(string query, int limit = 20);
+    
+    /// <summary>
+    /// Gets details of an external playlist (metadata only, not tracks)
+    /// </summary>
+    /// <param name="externalProvider">Provider name (e.g., "deezer", "qobuz")</param>
+    /// <param name="externalId">Playlist ID from the provider</param>
+    /// <returns>Playlist details or null if not found</returns>
+    Task<ExternalPlaylist?> GetPlaylistAsync(string externalProvider, string externalId);
+    
+    /// <summary>
+    /// Gets all tracks from an external playlist
+    /// </summary>
+    /// <param name="externalProvider">Provider name (e.g., "deezer", "qobuz")</param>
+    /// <param name="externalId">Playlist ID from the provider</param>
+    /// <returns>List of songs in the playlist</returns>
+    Task<List<Song>> GetPlaylistTracksAsync(string externalProvider, string externalId);
 }

octo-fiesta/Services/Qobuz/QobuzDownloadService.cs

@@ -43,8 +43,9 @@ public class QobuzDownloadService : BaseDownloadService
         QobuzBundleService bundleService,
         IOptions<SubsonicSettings> subsonicSettings,
         IOptions<QobuzSettings> qobuzSettings,
+        IServiceProvider serviceProvider,
         ILogger<QobuzDownloadService> logger)
-        : base(configuration, localLibraryService, metadataService, subsonicSettings.Value, logger)
+        : base(configuration, localLibraryService, metadataService, subsonicSettings.Value, serviceProvider, logger)
     {
         _httpClient = httpClientFactory.CreateClient();
         _bundleService = bundleService;

octo-fiesta/Services/Qobuz/QobuzMetadataService.cs

@@ -212,6 +212,12 @@ public class QobuzMetadataService : IMusicMetadataService
                 foreach (var track in tracksData.EnumerateArray())
                 {
                     var song = ParseQobuzTrack(track);
+                    
+                    // Ensure album metadata is set (tracks in album response may not have full album object)
+                    song.Album = album.Title;
+                    song.AlbumId = album.Id;
+                    song.AlbumArtist = album.Artist;
+                    
                     if (ShouldIncludeSong(song))
                     {
                         album.Songs.Add(song);
@@ -305,6 +311,180 @@ public class QobuzMetadataService : IMusicMetadataService
         }
     }
 
+    public async Task<List<ExternalPlaylist>> SearchPlaylistsAsync(string query, int limit = 20)
+    {
+        try
+        {
+            var appId = await _bundleService.GetAppIdAsync();
+            var url = $"{BaseUrl}playlist/search?query={Uri.EscapeDataString(query)}&limit={limit}&app_id={appId}";
+            
+            var response = await GetWithAuthAsync(url);
+            if (!response.IsSuccessStatusCode) return new List<ExternalPlaylist>();
+            
+            var json = await response.Content.ReadAsStringAsync();
+            var result = JsonDocument.Parse(json);
+            
+            var playlists = new List<ExternalPlaylist>();
+            if (result.RootElement.TryGetProperty("playlists", out var playlistsData) &&
+                playlistsData.TryGetProperty("items", out var items))
+            {
+                foreach (var playlist in items.EnumerateArray())
+                {
+                    playlists.Add(ParseQobuzPlaylist(playlist));
+                }
+            }
+            
+            return playlists;
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to search playlists for query: {Query}", query);
+            return new List<ExternalPlaylist>();
+        }
+    }
+    
+    public async Task<ExternalPlaylist?> GetPlaylistAsync(string externalProvider, string externalId)
+    {
+        if (externalProvider != "qobuz") return null;
+        
+        try
+        {
+            var appId = await _bundleService.GetAppIdAsync();
+            var url = $"{BaseUrl}playlist/get?playlist_id={externalId}&app_id={appId}";
+            
+            var response = await GetWithAuthAsync(url);
+            if (!response.IsSuccessStatusCode) return null;
+            
+            var json = await response.Content.ReadAsStringAsync();
+            var playlistElement = JsonDocument.Parse(json).RootElement;
+            
+            if (playlistElement.TryGetProperty("error", out _)) return null;
+            
+            return ParseQobuzPlaylist(playlistElement);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to get playlist {ExternalId}", externalId);
+            return null;
+        }
+    }
+    
+    public async Task<List<Song>> GetPlaylistTracksAsync(string externalProvider, string externalId)
+    {
+        if (externalProvider != "qobuz") return new List<Song>();
+        
+        try
+        {
+            var appId = await _bundleService.GetAppIdAsync();
+            var url = $"{BaseUrl}playlist/get?playlist_id={externalId}&app_id={appId}&extra=tracks";
+            
+            var response = await GetWithAuthAsync(url);
+            if (!response.IsSuccessStatusCode) return new List<Song>();
+            
+            var json = await response.Content.ReadAsStringAsync();
+            var playlistElement = JsonDocument.Parse(json).RootElement;
+            
+            if (playlistElement.TryGetProperty("error", out _)) return new List<Song>();
+            
+            var songs = new List<Song>();
+            
+            // Get playlist name for album field
+            var playlistName = playlistElement.TryGetProperty("name", out var nameEl)
+                ? nameEl.GetString() ?? "Unknown Playlist"
+                : "Unknown Playlist";
+            
+            if (playlistElement.TryGetProperty("tracks", out var tracks) &&
+                tracks.TryGetProperty("items", out var tracksData))
+            {
+                int trackIndex = 1;
+                foreach (var track in tracksData.EnumerateArray())
+                {
+                    // For playlists, use the track's own artist (not a single album artist)
+                    var song = ParseQobuzTrack(track);
+                    
+                    // Override album name to be the playlist name
+                    song.Album = playlistName;
+                    song.Track = trackIndex;
+                    
+                    if (ShouldIncludeSong(song))
+                    {
+                        songs.Add(song);
+                    }
+                    trackIndex++;
+                }
+            }
+            
+            return songs;
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to get playlist tracks for {ExternalId}", externalId);
+            return new List<Song>();
+        }
+    }
+    
+    private ExternalPlaylist ParseQobuzPlaylist(JsonElement playlist)
+    {
+        var externalId = GetIdAsString(playlist.GetProperty("id"));
+        
+        // Get curator/creator name
+        string? curatorName = null;
+        if (playlist.TryGetProperty("owner", out var owner) &&
+            owner.TryGetProperty("name", out var ownerName))
+        {
+            curatorName = ownerName.GetString();
+        }
+        
+        // Get creation date
+        DateTime? createdDate = null;
+        if (playlist.TryGetProperty("created_at", out var createdAtEl))
+        {
+            var timestamp = createdAtEl.GetInt64();
+            createdDate = DateTimeOffset.FromUnixTimeSeconds(timestamp).DateTime;
+        }
+        
+        // Get cover URL from images
+        string? coverUrl = null;
+        if (playlist.TryGetProperty("images300", out var images300))
+        {
+            var imagesArray = images300.EnumerateArray().ToList();
+            if (imagesArray.Count > 0)
+            {
+                coverUrl = imagesArray[0].GetString();
+            }
+        }
+        else if (playlist.TryGetProperty("image_rectangle", out var imageRect))
+        {
+            var imagesArray = imageRect.EnumerateArray().ToList();
+            if (imagesArray.Count > 0)
+            {
+                coverUrl = imagesArray[0].GetString();
+            }
+        }
+        
+        return new ExternalPlaylist
+        {
+            Id = Common.PlaylistIdHelper.CreatePlaylistId("qobuz", externalId),
+            Name = playlist.TryGetProperty("name", out var name)
+                ? name.GetString() ?? ""
+                : "",
+            Description = playlist.TryGetProperty("description", out var desc)
+                ? desc.GetString()
+                : null,
+            CuratorName = curatorName,
+            Provider = "qobuz",
+            ExternalId = externalId,
+            TrackCount = playlist.TryGetProperty("tracks_count", out var tracksCount)
+                ? tracksCount.GetInt32()
+                : 0,
+            Duration = playlist.TryGetProperty("duration", out var duration)
+                ? duration.GetInt32()
+                : 0,
+            CoverUrl = coverUrl,
+            CreatedDate = createdDate
+        };
+    }
+
     /// <summary>
     /// Safely gets an ID value as a string, handling both number and string types from JSON
     /// </summary>

octo-fiesta/Services/Subsonic/PlaylistSyncService.cs

@@ -0,0 +1,375 @@
+using System.Collections.Concurrent;
+using System.Text;
+using Microsoft.Extensions.Options;
+using octo_fiesta.Models.Domain;
+using octo_fiesta.Models.Settings;
+using octo_fiesta.Models.Subsonic;
+using octo_fiesta.Services.Common;
+using IOFile = System.IO.File;
+
+namespace octo_fiesta.Services.Subsonic;
+
+/// <summary>
+/// Service responsible for downloading playlist tracks and creating M3U files
+/// </summary>
+public class PlaylistSyncService
+{
+    private readonly IMusicMetadataService _deezerMetadataService;
+    private readonly IMusicMetadataService _qobuzMetadataService;
+    private readonly IEnumerable<IDownloadService> _downloadServices;
+    private readonly IConfiguration _configuration;
+    private readonly SubsonicSettings _subsonicSettings;
+    private readonly ILogger<PlaylistSyncService> _logger;
+    
+    // In-memory cache to track which playlist a track belongs to
+    // Key: trackId (format: ext-{provider}-{externalId}), Value: playlistId
+    // TTL: 5 minutes (tracks expire automatically)
+    private readonly ConcurrentDictionary<string, (string PlaylistId, DateTime ExpiresAt)> _trackPlaylistCache = new();
+    private static readonly TimeSpan CacheTTL = TimeSpan.FromMinutes(5);
+    
+    private readonly string _musicDirectory;
+    private readonly string _playlistDirectory;
+    
+    public PlaylistSyncService(
+        IEnumerable<IMusicMetadataService> metadataServices,
+        IEnumerable<IDownloadService> downloadServices,
+        IConfiguration configuration,
+        IOptions<SubsonicSettings> subsonicSettings,
+        ILogger<PlaylistSyncService> logger)
+    {
+        // Get Deezer and Qobuz metadata services
+        _deezerMetadataService = metadataServices.FirstOrDefault(s => s.GetType().Name.Contains("Deezer"))
+            ?? throw new InvalidOperationException("Deezer metadata service not found");
+        _qobuzMetadataService = metadataServices.FirstOrDefault(s => s.GetType().Name.Contains("Qobuz"))
+            ?? throw new InvalidOperationException("Qobuz metadata service not found");
+        
+        _downloadServices = downloadServices;
+        _configuration = configuration;
+        _subsonicSettings = subsonicSettings.Value;
+        _logger = logger;
+        
+        _musicDirectory = configuration["Library:DownloadPath"] ?? "./downloads";
+        _playlistDirectory = Path.Combine(_musicDirectory, _subsonicSettings.PlaylistsDirectory ?? "playlists");
+        
+        // Ensure playlists directory exists
+        if (!Directory.Exists(_playlistDirectory))
+        {
+            Directory.CreateDirectory(_playlistDirectory);
+        }
+        
+        // Start background cleanup task for expired cache entries
+        _ = Task.Run(CleanupExpiredCacheEntriesAsync);
+    }
+    
+    /// <summary>
+    /// Adds a track to the playlist context cache.
+    /// This allows the download service to know which playlist a track belongs to.
+    /// </summary>
+    public void AddTrackToPlaylistCache(string trackId, string playlistId)
+    {
+        var expiresAt = DateTime.UtcNow.Add(CacheTTL);
+        _trackPlaylistCache[trackId] = (playlistId, expiresAt);
+        _logger.LogDebug("Added track {TrackId} to playlist cache with playlistId {PlaylistId}", trackId, playlistId);
+    }
+    
+    /// <summary>
+    /// Gets the playlist ID for a given track ID from cache.
+    /// Returns null if not found or expired.
+    /// </summary>
+    public string? GetPlaylistIdForTrack(string trackId)
+    {
+        if (_trackPlaylistCache.TryGetValue(trackId, out var entry))
+        {
+            if (entry.ExpiresAt > DateTime.UtcNow)
+            {
+                return entry.PlaylistId;
+            }
+            
+            // Expired, remove it
+            _trackPlaylistCache.TryRemove(trackId, out _);
+        }
+        
+        return null;
+    }
+    
+    /// <summary>
+    /// Downloads all tracks from a playlist and creates an M3U file.
+    /// This is triggered when a user stars a playlist.
+    /// </summary>
+    public async Task DownloadFullPlaylistAsync(string playlistId, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            _logger.LogInformation("Starting download for playlist {PlaylistId}", playlistId);
+            
+            // Parse playlist ID
+            if (!PlaylistIdHelper.IsExternalPlaylist(playlistId))
+            {
+                _logger.LogWarning("Invalid playlist ID format: {PlaylistId}", playlistId);
+                return;
+            }
+            
+            var (provider, externalId) = PlaylistIdHelper.ParsePlaylistId(playlistId);
+            
+            // Get playlist metadata
+            var metadataService = provider.ToLower() switch
+            {
+                "deezer" => _deezerMetadataService,
+                "qobuz" => _qobuzMetadataService,
+                _ => throw new NotSupportedException($"Provider '{provider}' not supported for playlists")
+            };
+            
+            var playlist = await metadataService.GetPlaylistAsync(provider, externalId);
+            if (playlist == null)
+            {
+                _logger.LogWarning("Playlist not found: {PlaylistId}", playlistId);
+                return;
+            }
+            
+            var tracks = await metadataService.GetPlaylistTracksAsync(provider, externalId);
+            if (tracks == null || tracks.Count == 0)
+            {
+                _logger.LogWarning("No tracks found in playlist {PlaylistId}", playlistId);
+                return;
+            }
+            
+            _logger.LogInformation("Found {TrackCount} tracks in playlist '{PlaylistName}'", tracks.Count, playlist.Name);
+            
+            // Get the appropriate download service for this provider
+            var downloadService = _downloadServices.FirstOrDefault(s => 
+                s.GetType().Name.Contains(provider, StringComparison.OrdinalIgnoreCase));
+            
+            if (downloadService == null)
+            {
+                _logger.LogError("No download service found for provider '{Provider}'", provider);
+                return;
+            }
+            
+            // Download all tracks
+            var downloadedTracks = new List<(Song Song, string LocalPath)>();
+            
+            foreach (var track in tracks)
+            {
+                try
+                {
+                    if (string.IsNullOrEmpty(track.ExternalId))
+                    {
+                        _logger.LogWarning("Track has no external ID, skipping: {Title}", track.Title);
+                        continue;
+                    }
+                    
+                    // Add track to playlist cache BEFORE downloading
+                    var trackId = $"ext-{provider}-{track.ExternalId}";
+                    AddTrackToPlaylistCache(trackId, playlistId);
+                    
+                    _logger.LogInformation("Downloading track '{Artist} - {Title}'", track.Artist, track.Title);
+                    var localPath = await downloadService.DownloadSongAsync(provider, track.ExternalId, cancellationToken);
+                    
+                    downloadedTracks.Add((track, localPath));
+                    _logger.LogDebug("Downloaded: {Path}", localPath);
+                }
+                catch (Exception ex)
+                {
+                    _logger.LogWarning(ex, "Failed to download track '{Artist} - {Title}'", track.Artist, track.Title);
+                }
+            }
+            
+            if (downloadedTracks.Count == 0)
+            {
+                _logger.LogWarning("No tracks were successfully downloaded for playlist '{PlaylistName}'", playlist.Name);
+                return;
+            }
+            
+            // Create M3U file
+            await CreateM3UPlaylistAsync(playlist.Name, downloadedTracks);
+            
+            _logger.LogInformation("Playlist download completed: {DownloadedCount}/{TotalCount} tracks for '{PlaylistName}'",
+                downloadedTracks.Count, tracks.Count, playlist.Name);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to download playlist {PlaylistId}", playlistId);
+            throw;
+        }
+    }
+    
+    /// <summary>
+    /// Creates an M3U playlist file with relative paths to downloaded tracks
+    /// </summary>
+    private async Task CreateM3UPlaylistAsync(string playlistName, List<(Song Song, string LocalPath)> tracks)
+    {
+        try
+        {
+            // Sanitize playlist name for file system
+            var fileName = PathHelper.SanitizeFileName(playlistName) + ".m3u";
+            var playlistPath = Path.Combine(_playlistDirectory, fileName);
+            
+            var m3uContent = new StringBuilder();
+            m3uContent.AppendLine("#EXTM3U");
+            
+            foreach (var (song, localPath) in tracks)
+            {
+                // Calculate relative path from playlist directory to track
+                var relativePath = Path.GetRelativePath(_playlistDirectory, localPath);
+                
+                // Convert backslashes to forward slashes for M3U compatibility
+                relativePath = relativePath.Replace('\\', '/');
+                
+                // Add EXTINF line with duration and artist - title
+                var duration = song.Duration ?? 0;
+                m3uContent.AppendLine($"#EXTINF:{duration},{song.Artist} - {song.Title}");
+                m3uContent.AppendLine(relativePath);
+            }
+            
+            await IOFile.WriteAllTextAsync(playlistPath, m3uContent.ToString());
+            _logger.LogInformation("Created M3U playlist: {Path}", playlistPath);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to create M3U playlist for '{PlaylistName}'", playlistName);
+            throw;
+        }
+    }
+    
+    /// <summary>
+    /// Adds a track to an existing M3U playlist or creates it if it doesn't exist.
+    /// This is called progressively as tracks are downloaded.
+    /// The M3U is rebuilt in the correct playlist order each time.
+    /// </summary>
+    public async Task AddTrackToM3UAsync(string playlistId, Song track, string localPath)
+    {
+        try
+        {
+            // Get playlist metadata to get the name and track order
+            if (!PlaylistIdHelper.IsExternalPlaylist(playlistId))
+            {
+                _logger.LogWarning("Invalid playlist ID format: {PlaylistId}", playlistId);
+                return;
+            }
+            
+            var (provider, externalId) = PlaylistIdHelper.ParsePlaylistId(playlistId);
+            
+            var metadataService = provider.ToLower() switch
+            {
+                "deezer" => _deezerMetadataService,
+                "qobuz" => _qobuzMetadataService,
+                _ => null
+            };
+            
+            if (metadataService == null)
+            {
+                _logger.LogWarning("No metadata service found for provider '{Provider}'", provider);
+                return;
+            }
+            
+            var playlist = await metadataService.GetPlaylistAsync(provider, externalId);
+            if (playlist == null)
+            {
+                _logger.LogWarning("Playlist not found: {PlaylistId}", playlistId);
+                return;
+            }
+            
+            // Get all tracks from the playlist to maintain order
+            var allPlaylistTracks = await metadataService.GetPlaylistTracksAsync(provider, externalId);
+            if (allPlaylistTracks == null || allPlaylistTracks.Count == 0)
+            {
+                _logger.LogWarning("No tracks found in playlist: {PlaylistId}", playlistId);
+                return;
+            }
+            
+            // Sanitize playlist name for file system
+            var fileName = PathHelper.SanitizeFileName(playlist.Name) + ".m3u";
+            var playlistPath = Path.Combine(_playlistDirectory, fileName);
+            
+            // Build M3U content in the correct order
+            var m3uContent = new StringBuilder();
+            m3uContent.AppendLine("#EXTM3U");
+            
+            int addedCount = 0;
+            foreach (var playlistTrack in allPlaylistTracks)
+            {
+                // Check if this track has been downloaded locally
+                string? trackLocalPath = null;
+                
+                // If this is the track we just downloaded
+                if (playlistTrack.Id == track.Id)
+                {
+                    trackLocalPath = localPath;
+                }
+                else
+                {
+                    // Check if track was previously downloaded
+                    var trackProvider = playlistTrack.ExternalProvider;
+                    var trackExternalId = playlistTrack.ExternalId;
+                    
+                    if (!string.IsNullOrEmpty(trackProvider) && !string.IsNullOrEmpty(trackExternalId))
+                    {
+                        // Try to find the download service for this provider
+                        var downloadService = _downloadServices.FirstOrDefault(s => 
+                            s.GetType().Name.Contains(trackProvider, StringComparison.OrdinalIgnoreCase));
+                        
+                        if (downloadService != null)
+                        {
+                            trackLocalPath = await downloadService.GetLocalPathIfExistsAsync(trackProvider, trackExternalId);
+                        }
+                    }
+                }
+                
+                // If track is downloaded, add it to M3U
+                if (!string.IsNullOrEmpty(trackLocalPath) && IOFile.Exists(trackLocalPath))
+                {
+                    var relativePath = Path.GetRelativePath(_playlistDirectory, trackLocalPath);
+                    relativePath = relativePath.Replace('\\', '/');
+                    
+                    var duration = playlistTrack.Duration ?? 0;
+                    m3uContent.AppendLine($"#EXTINF:{duration},{playlistTrack.Artist} - {playlistTrack.Title}");
+                    m3uContent.AppendLine(relativePath);
+                    addedCount++;
+                }
+            }
+            
+            // Write the M3U file (overwrites existing)
+            await IOFile.WriteAllTextAsync(playlistPath, m3uContent.ToString());
+            _logger.LogInformation("Updated M3U playlist '{PlaylistName}' with {Count} tracks (in correct order)", 
+                playlist.Name, addedCount);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to add track to M3U playlist");
+        }
+    }
+    
+    /// <summary>
+    /// Background task to clean up expired cache entries every minute
+    /// </summary>
+    private async Task CleanupExpiredCacheEntriesAsync()
+    {
+        while (true)
+        {
+            try
+            {
+                await Task.Delay(TimeSpan.FromMinutes(1));
+                
+                var now = DateTime.UtcNow;
+                var expiredKeys = _trackPlaylistCache
+                    .Where(kvp => kvp.Value.ExpiresAt <= now)
+                    .Select(kvp => kvp.Key)
+                    .ToList();
+                
+                foreach (var key in expiredKeys)
+                {
+                    _trackPlaylistCache.TryRemove(key, out _);
+                }
+                
+                if (expiredKeys.Count > 0)
+                {
+                    _logger.LogDebug("Cleaned up {Count} expired playlist cache entries", expiredKeys.Count);
+                }
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex, "Error during playlist cache cleanup");
+            }
+        }
+    }
+}

octo-fiesta/Services/Subsonic/SubsonicModelMapper.cs

@@ -2,6 +2,7 @@ using System.Text;
 using System.Text.Json;
 using System.Xml.Linq;
 using octo_fiesta.Models.Search;
+using octo_fiesta.Models.Subsonic;
 
 namespace octo_fiesta.Services.Subsonic;
 
@@ -97,22 +98,23 @@ public class SubsonicModelMapper
     }
 
     /// <summary>
-    /// Merges local search results with external search results, deduplicating by name.
+    /// Merges local and external search results (songs, albums, artists, playlists).
     /// </summary>
     public (List<object> MergedSongs, List<object> MergedAlbums, List<object> MergedArtists) MergeSearchResults(
         List<object> localSongs,
         List<object> localAlbums,
         List<object> localArtists,
         SearchResult externalResult,
+        List<ExternalPlaylist> externalPlaylists,
         bool isJson)
     {
         if (isJson)
         {
-            return MergeSearchResultsJson(localSongs, localAlbums, localArtists, externalResult);
+            return MergeSearchResultsJson(localSongs, localAlbums, localArtists, externalResult, externalPlaylists);
         }
         else
         {
-            return MergeSearchResultsXml(localSongs, localAlbums, localArtists, externalResult);
+            return MergeSearchResultsXml(localSongs, localAlbums, localArtists, externalResult, externalPlaylists);
         }
     }
 
@@ -120,14 +122,17 @@ public class SubsonicModelMapper
         List<object> localSongs,
         List<object> localAlbums,
         List<object> localArtists,
-        SearchResult externalResult)
+        SearchResult externalResult,
+        List<ExternalPlaylist> externalPlaylists)
     {
         var mergedSongs = localSongs
             .Concat(externalResult.Songs.Select(s => _responseBuilder.ConvertSongToJson(s)))
             .ToList();
         
+        // Merge albums with playlists (playlists appear as albums with genre "Playlist")
         var mergedAlbums = localAlbums
             .Concat(externalResult.Albums.Select(a => _responseBuilder.ConvertAlbumToJson(a)))
+            .Concat(externalPlaylists.Select(p => ConvertPlaylistToAlbumJson(p)))
             .ToList();
         
         // Deduplicate artists by name - prefer local artists over external ones
@@ -157,7 +162,8 @@ public class SubsonicModelMapper
         List<object> localSongs,
         List<object> localAlbums,
         List<object> localArtists,
-        SearchResult externalResult)
+        SearchResult externalResult,
+        List<ExternalPlaylist> externalPlaylists)
     {
         var ns = XNamespace.Get("http://subsonic.org/restapi");
         
@@ -196,6 +202,11 @@ public class SubsonicModelMapper
         {
             mergedAlbums.Add(_responseBuilder.ConvertAlbumToXml(album, ns));
         }
+        // Add playlists as albums
+        foreach (var playlist in externalPlaylists)
+        {
+            mergedAlbums.Add(ConvertPlaylistToAlbumXml(playlist, ns));
+        }
         
         // Songs
         var mergedSongs = new List<object>();
@@ -211,4 +222,81 @@ public class SubsonicModelMapper
 
         return (mergedSongs, mergedAlbums, mergedArtists);
     }
+    
+    /// <summary>
+    /// Converts an ExternalPlaylist to a JSON object representing an album.
+    /// Playlists are represented as albums with genre "Playlist" and artist "🎵 {Provider} {Curator}".
+    /// </summary>
+    private Dictionary<string, object> ConvertPlaylistToAlbumJson(ExternalPlaylist playlist)
+    {
+        var artistName = $"🎵 {char.ToUpper(playlist.Provider[0])}{playlist.Provider.Substring(1)}";
+        if (!string.IsNullOrEmpty(playlist.CuratorName))
+        {
+            artistName += $" {playlist.CuratorName}";
+        }
+        
+        var artistId = $"curator-{playlist.Provider}-{playlist.CuratorName?.ToLowerInvariant().Replace(" ", "-") ?? "unknown"}";
+        
+        var album = new Dictionary<string, object>
+        {
+            ["id"] = playlist.Id,
+            ["name"] = playlist.Name,
+            ["artist"] = artistName,
+            ["artistId"] = artistId,
+            ["genre"] = "Playlist",
+            ["songCount"] = playlist.TrackCount,
+            ["duration"] = playlist.Duration
+        };
+        
+        if (playlist.CreatedDate.HasValue)
+        {
+            album["year"] = playlist.CreatedDate.Value.Year;
+            album["created"] = playlist.CreatedDate.Value.ToString("yyyy-MM-ddTHH:mm:ss");
+        }
+        
+        if (!string.IsNullOrEmpty(playlist.CoverUrl))
+        {
+            album["coverArt"] = playlist.Id;
+        }
+        
+        return album;
+    }
+    
+    /// <summary>
+    /// Converts an ExternalPlaylist to an XML element representing an album.
+    /// Playlists are represented as albums with genre "Playlist" and artist "🎵 {Provider} {Curator}".
+    /// </summary>
+    private XElement ConvertPlaylistToAlbumXml(ExternalPlaylist playlist, XNamespace ns)
+    {
+        var artistName = $"🎵 {char.ToUpper(playlist.Provider[0])}{playlist.Provider.Substring(1)}";
+        if (!string.IsNullOrEmpty(playlist.CuratorName))
+        {
+            artistName += $" {playlist.CuratorName}";
+        }
+        
+        var artistId = $"curator-{playlist.Provider}-{playlist.CuratorName?.ToLowerInvariant().Replace(" ", "-") ?? "unknown"}";
+        
+        var album = new XElement(ns + "album",
+            new XAttribute("id", playlist.Id),
+            new XAttribute("name", playlist.Name),
+            new XAttribute("artist", artistName),
+            new XAttribute("artistId", artistId),
+            new XAttribute("genre", "Playlist"),
+            new XAttribute("songCount", playlist.TrackCount),
+            new XAttribute("duration", playlist.Duration)
+        );
+        
+        if (playlist.CreatedDate.HasValue)
+        {
+            album.Add(new XAttribute("year", playlist.CreatedDate.Value.Year));
+            album.Add(new XAttribute("created", playlist.CreatedDate.Value.ToString("yyyy-MM-ddTHH:mm:ss")));
+        }
+        
+        if (!string.IsNullOrEmpty(playlist.CoverUrl))
+        {
+            album.Add(new XAttribute("coverArt", playlist.Id));
+        }
+        
+        return album;
+    }
 }

octo-fiesta/Services/Subsonic/SubsonicResponseBuilder.cs

@@ -2,6 +2,7 @@ using Microsoft.AspNetCore.Mvc;
 using System.Xml.Linq;
 using System.Text.Json;
 using octo_fiesta.Models.Domain;
+using octo_fiesta.Models.Subsonic;
 
 namespace octo_fiesta.Services.Subsonic;
 
@@ -137,6 +138,81 @@ public class SubsonicResponseBuilder
         );
         return new ContentResult { Content = doc.ToString(), ContentType = "application/xml" };
     }
+    
+    /// <summary>
+    /// Creates a Subsonic response for a playlist represented as an album.
+    /// Playlists appear as albums with genre "Playlist".
+    /// </summary>
+    public IActionResult CreatePlaylistAsAlbumResponse(string format, ExternalPlaylist playlist, List<Song> tracks)
+    {
+        var totalDuration = tracks.Sum(s => s.Duration ?? 0);
+        
+        // Build artist name with emoji and curator
+        var artistName = $"🎵 {char.ToUpper(playlist.Provider[0])}{playlist.Provider.Substring(1)}";
+        if (!string.IsNullOrEmpty(playlist.CuratorName))
+        {
+            artistName += $" {playlist.CuratorName}";
+        }
+        
+        var artistId = $"curator-{playlist.Provider}-{playlist.CuratorName?.ToLowerInvariant().Replace(" ", "-") ?? "unknown"}";
+        
+        if (format == "json")
+        {
+            return CreateJsonResponse(new 
+            { 
+                status = "ok", 
+                version = SubsonicVersion,
+                album = new
+                {
+                    id = playlist.Id,
+                    name = playlist.Name,
+                    artist = artistName,
+                    artistId = artistId,
+                    coverArt = playlist.Id,
+                    songCount = tracks.Count,
+                    duration = totalDuration,
+                    year = playlist.CreatedDate?.Year ?? 0,
+                    genre = "Playlist",
+                    isCompilation = false,
+                    created = playlist.CreatedDate?.ToString("yyyy-MM-ddTHH:mm:ss"),
+                    song = tracks.Select(s => ConvertSongToJson(s)).ToList()
+                }
+            });
+        }
+        
+        var ns = XNamespace.Get(SubsonicNamespace);
+        var albumElement = new XElement(ns + "album",
+            new XAttribute("id", playlist.Id),
+            new XAttribute("name", playlist.Name),
+            new XAttribute("artist", artistName),
+            new XAttribute("artistId", artistId),
+            new XAttribute("songCount", tracks.Count),
+            new XAttribute("duration", totalDuration),
+            new XAttribute("genre", "Playlist"),
+            new XAttribute("coverArt", playlist.Id)
+        );
+        
+        if (playlist.CreatedDate.HasValue)
+        {
+            albumElement.Add(new XAttribute("year", playlist.CreatedDate.Value.Year));
+            albumElement.Add(new XAttribute("created", playlist.CreatedDate.Value.ToString("yyyy-MM-ddTHH:mm:ss")));
+        }
+        
+        // Add songs
+        foreach (var song in tracks)
+        {
+            albumElement.Add(ConvertSongToXml(song, ns));
+        }
+        
+        var doc = new XDocument(
+            new XElement(ns + "subsonic-response",
+                new XAttribute("status", "ok"),
+                new XAttribute("version", SubsonicVersion),
+                albumElement
+            )
+        );
+        return new ContentResult { Content = doc.ToString(), ContentType = "application/xml" };
+    }
 
     /// <summary>
     /// Creates a Subsonic response containing an artist with albums.