adding playlist watcher

Selector.CLI/Command/HostCommand.cs

@@ -9,6 +9,7 @@ using Selector.Extensions;
 using System;
 using System.CommandLine;
 using System.CommandLine.Invocation;
+using System.Threading.Tasks;
 
 namespace Selector.CLI
 {
@@ -31,9 +32,14 @@ namespace Selector.CLI
         {
             try
             {
-                CreateHostBuilder(Environment.GetCommandLineArgs(), ConfigureDefault, ConfigureDefaultNlog)
-                    .Build()
-                    .Run();
+                var host = CreateHostBuilder(Environment.GetCommandLineArgs(),ConfigureDefault, ConfigureDefaultNlog)
+                    .Build();
+
+                var logger = host.Services.GetRequiredService<ILogger<HostCommand>>();
+                var env = host.Services.GetRequiredService<IHostEnvironment>();
+                SetupExceptionHandling(logger, env);
+
+                host.Run();
             }
             catch(Exception ex)
             {
@@ -44,6 +50,22 @@ namespace Selector.CLI
             return 0;
         }
 
+        private static void SetupExceptionHandling(ILogger logger, IHostEnvironment env)
+        {
+            AppDomain.CurrentDomain.UnhandledException += (obj, e) =>
+            {
+                if(e.ExceptionObject is Exception ex)
+                {
+                    logger.LogError(ex as Exception, "Unhandled exception thrown");
+
+                    if (env.IsDevelopment())
+                    {
+                        throw ex;
+                    }
+                }
+            };
+        }
+
         public static RootOptions ConfigureOptions(HostBuilderContext context, IServiceCollection services)
         {
             services.Configure<RootOptions>(options =>

Selector.CLI/Services/LocalWatcherService.cs

@@ -95,14 +95,20 @@ namespace Selector.CLI
                         watcher = await WatcherFactory.Get<PlayerWatcher>(spotifyFactory, id: watcherOption.Name, pollPeriod: watcherOption.PollPeriod);
                         break;
                     case WatcherType.Playlist:
-                        throw new NotImplementedException("Playlist watchers not implemented");
-                        // break;
+                        var playlistWatcher = await WatcherFactory.Get<PlaylistWatcher>(spotifyFactory, id: watcherOption.Name, pollPeriod: watcherOption.PollPeriod) as PlaylistWatcher;
+                        playlistWatcher.config = new() { PlaylistId = watcherOption.PlaylistUri };
+
+                        watcher = playlistWatcher;
+                        break;
                 }
 
                 List<IConsumer> consumers = new();
-                foreach(var consumer in watcherOption.Consumers)
+
+                if (watcherOption.Consumers is not null)
                 {
-                    switch(consumer)
+                    foreach (var consumer in watcherOption.Consumers)
+                    {
+                        switch (consumer)
                         {
                             case Consumers.AudioFeatures:
                                 consumers.Add(await ServiceProvider.GetService<AudioFeatureInjectorFactory>().Get(spotifyFactory));
@@ -121,7 +127,7 @@ namespace Selector.CLI
                                 break;
 
                             case Consumers.PlayCounter:
-                            if(!string.IsNullOrWhiteSpace(watcherOption.LastFmUsername))
+                                if (!string.IsNullOrWhiteSpace(watcherOption.LastFmUsername))
                                 {
                                     consumers.Add(await ServiceProvider.GetService<PlayCounterFactory>().Get(creds: new() { Username = watcherOption.LastFmUsername }));
                                 }
@@ -132,6 +138,7 @@ namespace Selector.CLI
                                 break;
                         }
                     }
+                }
 
                 watcherCollection.Add(watcher, consumers);
             }

Selector.CLI/nlog.config

@@ -31,5 +31,6 @@
 		<logger name="*" minlevel="Debug" writeTo="logfile" />
 		<logger name="*" minlevel="Trace" writeTo="tracefile" />
 		<logger name="Selector.*" minlevel="Debug" writeTo="logconsole" />
+		<logger name="Microsoft.*" minlevel="Warning" writeTo="logconsole" />
 	</rules>
 </nlog>

Selector.Cache/Consumer/CacheWriterConsumer.cs

@@ -10,7 +10,7 @@ using StackExchange.Redis;
 
 namespace Selector.Cache
 {
-    public class CacheWriter : IConsumer
+    public class CacheWriter : IPlayerConsumer
     {
         private readonly IPlayerWatcher Watcher;
         private readonly IDatabaseAsync Db;

Selector.Cache/Consumer/Factory/AudioInjectorCaching.cs

@@ -22,7 +22,7 @@ namespace Selector.Cache
             Db = db;
         }
 
-        public async Task<IConsumer> Get(ISpotifyConfigFactory spotifyFactory, IPlayerWatcher watcher = null)
+        public async Task<IPlayerConsumer> Get(ISpotifyConfigFactory spotifyFactory, IPlayerWatcher watcher = null)
         {
             var config = await spotifyFactory.GetConfig();
             var client = new SpotifyClient(config);

Selector.Cache/Consumer/Factory/CacheWriterFactory.cs

@@ -9,7 +9,7 @@ using StackExchange.Redis;
 namespace Selector.Cache
 {
     public interface ICacheWriterFactory {
-        public Task<IConsumer> Get(IPlayerWatcher watcher = null);
+        public Task<IPlayerConsumer> Get(IPlayerWatcher watcher = null);
     }
 
     public class CacheWriterFactory: ICacheWriterFactory {
@@ -25,9 +25,9 @@ namespace Selector.Cache
             LoggerFactory = loggerFactory;
         }
 
-        public Task<IConsumer> Get(IPlayerWatcher watcher = null)
+        public Task<IPlayerConsumer> Get(IPlayerWatcher watcher = null)
         {
-            return Task.FromResult<IConsumer>(new CacheWriter(
+            return Task.FromResult<IPlayerConsumer>(new CacheWriter(
                 watcher,
                 Cache,
                 LoggerFactory.CreateLogger<CacheWriter>()

Selector.Cache/Consumer/Factory/PlayCounterCachingFactory.cs

@@ -28,7 +28,7 @@ namespace Selector.Cache
             Creds = creds;
         }
 
-        public Task<IConsumer> Get(LastfmClient fmClient = null, LastFmCredentials creds = null, IPlayerWatcher watcher = null)
+        public Task<IPlayerConsumer> Get(LastfmClient fmClient = null, LastFmCredentials creds = null, IPlayerWatcher watcher = null)
         {
             var client = fmClient ?? Client;
 
@@ -37,7 +37,7 @@ namespace Selector.Cache
                 throw new ArgumentNullException("No Last.fm client provided");
             }
 
-            return Task.FromResult<IConsumer>(new PlayCounterCaching(
+            return Task.FromResult<IPlayerConsumer>(new PlayCounterCaching(
                 watcher,
                 client.Track,
                 client.Album,

Selector.Cache/Consumer/Factory/PublisherFactory.cs

@@ -9,7 +9,7 @@ using StackExchange.Redis;
 namespace Selector.Cache
 {
     public interface IPublisherFactory {
-        public Task<IConsumer> Get(IPlayerWatcher watcher = null);
+        public Task<IPlayerConsumer> Get(IPlayerWatcher watcher = null);
     }
 
     public class PublisherFactory: IPublisherFactory {
@@ -25,9 +25,9 @@ namespace Selector.Cache
             LoggerFactory = loggerFactory;
         }
 
-        public Task<IConsumer> Get(IPlayerWatcher watcher = null)
+        public Task<IPlayerConsumer> Get(IPlayerWatcher watcher = null)
         {
-            return Task.FromResult<IConsumer>(new Publisher(
+            return Task.FromResult<IPlayerConsumer>(new Publisher(
                 watcher,
                 Subscriber,
                 LoggerFactory.CreateLogger<Publisher>()

Selector.Cache/Consumer/PublisherConsumer.cs

@@ -10,7 +10,7 @@ using StackExchange.Redis;
 
 namespace Selector.Cache
 {
-    public class Publisher : IConsumer
+    public class Publisher : IPlayerConsumer
     {
         private readonly IPlayerWatcher Watcher;
         private readonly ISubscriber Subscriber;

Selector.Event/Consumers/UserEventFirer.cs

@@ -3,7 +3,7 @@ using Microsoft.Extensions.Logging.Abstractions;
 
 namespace Selector.Events
 {
-    public class UserEventFirer : IConsumer
+    public class UserEventFirer : IPlayerConsumer
     {
         protected readonly IPlayerWatcher Watcher;
         protected readonly ILogger<UserEventFirer> Logger;

Selector.Tests/Helper.cs

@@ -133,5 +133,15 @@ namespace Selector.Tests
                 VolumePercent = volume
             };
         }
+
+        public static FullPlaylist FullPlaylist(string name, string id = null, string snapshotId = null)
+        {
+            return new FullPlaylist()
+            {
+                Name = name,
+                Id = id ?? name,
+                SnapshotId = snapshotId ?? id ?? name
+            };
+        }
     }
 }

Selector.Tests/Watcher/PlaylistWatcher.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Collections.Generic;
+using Xunit;
+using Moq;
+using FluentAssertions;
+using SpotifyAPI.Web;
+
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit.Sdk;
+
+namespace Selector.Tests
+{
+    public class PlaylistWatcherTests
+    {
+        public static IEnumerable<object[]> CurrentPlaylistData =>
+        new List<object[]>
+        {
+            new object[] { new List<FullPlaylist>(){
+                    Helper.FullPlaylist("playlist1"),
+                    Helper.FullPlaylist("playlist1"),
+                    Helper.FullPlaylist("playlist1"),
+                    Helper.FullPlaylist("playlist1")
+                }
+            }
+        };
+
+        [Theory]
+        [MemberData(nameof(CurrentPlaylistData))]
+        public async void CurrentPlaylist(List<FullPlaylist> playing)
+        {
+            var playlistDequeue = new Queue<FullPlaylist>(playing);
+
+            var spotMock = new Mock<ISpotifyClient>();
+
+            spotMock.Setup(s => s.Playlists.Get(It.IsAny<string>()).Result).Returns(playlistDequeue.Dequeue);
+
+            var config = new PlaylistWatcherConfig() { PlaylistId = "spotify:playlist:test" };
+            var watcher = new PlaylistWatcher(config, spotMock.Object);
+
+            for (var i = 0; i < playing.Count; i++)
+            {
+                await watcher.WatchOne();
+                watcher.Live.Should().Be(playing[i]);
+            }
+        }
+
+        public static IEnumerable<object[]> EventsData =>
+        new List<object[]>
+        {
+            // NO CHANGING
+            new object[] { new List<FullPlaylist>(){
+                    Helper.FullPlaylist("Playlist", snapshotId: "snapshot1"),
+                    Helper.FullPlaylist("Playlist", snapshotId: "snapshot1"),
+                    Helper.FullPlaylist("Playlist", snapshotId: "snapshot1"),
+                },
+                // to raise
+                new List<string>(){  },
+                // to not raise
+                new List<string>(){ "SnapshotChange" }
+            },
+            // CHANGING SNAPSHOT
+            new object[] { new List<FullPlaylist>(){
+                    Helper.FullPlaylist("Playlist", snapshotId: "snapshot1"),
+                    Helper.FullPlaylist("Playlist", snapshotId: "snapshot2"),
+                    Helper.FullPlaylist("Playlist", snapshotId: "snapshot2"),
+                },
+                // to raise
+                new List<string>(){ "SnapshotChange" },
+                // to not raise
+                new List<string>(){  }
+            }
+        };
+
+        [Theory]
+        [MemberData(nameof(EventsData))]
+        public async void Events(List<FullPlaylist> playing, List<string> toRaise, List<string> toNotRaise)
+        {
+            var playlistDequeue = new Queue<FullPlaylist>(playing);
+
+            var spotMock = new Mock<ISpotifyClient>();
+
+            spotMock.Setup(s => s.Playlists.Get(It.IsAny<string>()).Result).Returns(playlistDequeue.Dequeue);
+
+            var config = new PlaylistWatcherConfig() { PlaylistId = "spotify:playlist:test" };
+            var watcher = new PlaylistWatcher(config, spotMock.Object);
+
+            using var monitoredWatcher = watcher.Monitor();
+
+            for (var i = 0; i < playing.Count; i++)
+            {
+                await watcher.WatchOne();
+            }
+
+            toRaise.ForEach(r => monitoredWatcher.Should().Raise(r).WithSender(watcher));
+            toNotRaise.ForEach(r => monitoredWatcher.Should().NotRaise(r));
+        }
+    }
+}

Selector.Web/Startup.cs

@@ -38,6 +38,15 @@ namespace Selector.Web
             {
                 OptionsHelper.ConfigureOptions(options, Configuration);
             });
+            services.Configure<RedisOptions>(options =>
+            {
+                Configuration.GetSection(string.Join(':', RootOptions.Key, RedisOptions.Key)).Bind(options);
+            });
+            services.Configure<NowPlayingOptions>(options =>
+            {
+                Configuration.GetSection(string.Join(':', RootOptions.Key, NowPlayingOptions.Key)).Bind(options);
+            });
+
             var config = OptionsHelper.ConfigureOptions(Configuration);
 
             services.Configure<SpotifyAppCredentials>(options =>

Selector/Consumers/AudioFeatureInjector.cs

@@ -9,7 +9,7 @@ using SpotifyAPI.Web;
 
 namespace Selector
 {
-    public class AudioFeatureInjector : IConsumer
+    public class AudioFeatureInjector : IPlayerConsumer
     {
         protected readonly IPlayerWatcher Watcher;
         protected readonly ITracksClient TrackClient;

Selector/Consumers/Factory/AudioFeatureInjectorFactory.cs

@@ -10,7 +10,7 @@ namespace Selector
 {
     public interface IAudioFeatureInjectorFactory
     {
-        public Task<IConsumer> Get(ISpotifyConfigFactory spotifyFactory, IPlayerWatcher watcher = null);
+        public Task<IPlayerConsumer> Get(ISpotifyConfigFactory spotifyFactory, IPlayerWatcher watcher = null);
     }
     
     public class AudioFeatureInjectorFactory: IAudioFeatureInjectorFactory {
@@ -22,7 +22,7 @@ namespace Selector
             LoggerFactory = loggerFactory;
         }
 
-        public async Task<IConsumer> Get(ISpotifyConfigFactory spotifyFactory, IPlayerWatcher watcher = null)
+        public async Task<IPlayerConsumer> Get(ISpotifyConfigFactory spotifyFactory, IPlayerWatcher watcher = null)
         {
             var config = await spotifyFactory.GetConfig();
             var client = new SpotifyClient(config);

Selector/Consumers/Factory/PlayCounterFactory.cs

@@ -10,7 +10,7 @@ namespace Selector
 {
     public interface IPlayCounterFactory
     {
-        public Task<IConsumer> Get(LastfmClient fmClient = null, LastFmCredentials creds = null, IPlayerWatcher watcher = null);
+        public Task<IPlayerConsumer> Get(LastfmClient fmClient = null, LastFmCredentials creds = null, IPlayerWatcher watcher = null);
     }
     
     public class PlayCounterFactory: IPlayCounterFactory {
@@ -26,7 +26,7 @@ namespace Selector
             Creds = creds;
         }
 
-        public Task<IConsumer> Get(LastfmClient fmClient = null, LastFmCredentials creds = null, IPlayerWatcher watcher = null)
+        public Task<IPlayerConsumer> Get(LastfmClient fmClient = null, LastFmCredentials creds = null, IPlayerWatcher watcher = null)
         {
             var client = fmClient ?? Client;
 
@@ -35,7 +35,7 @@ namespace Selector
                 throw new ArgumentNullException("No Last.fm client provided");
             }
 
-            return Task.FromResult<IConsumer>(new PlayCounter(
+            return Task.FromResult<IPlayerConsumer>(new PlayCounter(
                 watcher,
                 client.Track,
                 client.Album,

Selector/Consumers/IConsumer.cs

@@ -5,8 +5,18 @@ namespace Selector
 {
     public interface IConsumer
     {
-        public void Callback(object sender, ListeningChangeEventArgs e);
         public void Subscribe(IWatcher watch = null);
         public void Unsubscribe(IWatcher watch = null);
     }
+
+    public interface IConsumer<T>: IConsumer
+    {
+        public void Callback(object sender, T e);
+    }
+
+    public interface IPlayerConsumer: IConsumer<ListeningChangeEventArgs>
+    { }
+
+    public interface IPlaylistConsumer : IConsumer<PlaylistChangeEventArgs>
+    { }
 }

Selector/Consumers/PlayCounter.cs

@@ -13,7 +13,7 @@ using IF.Lastfm.Core.Api.Helpers;
 
 namespace Selector
 {
-    public class PlayCounter : IConsumer
+    public class PlayCounter : IPlayerConsumer
     {
         protected readonly IPlayerWatcher Watcher;
         protected readonly ITrackApi TrackClient;

Selector/Consumers/WebHook.cs

@@ -30,7 +30,7 @@ namespace Selector
         }
     }
 
-    public class WebHook : IConsumer
+    public class WebHook : IPlayerConsumer
     {
         protected readonly IPlayerWatcher Watcher;
         protected readonly HttpClient HttpClient;

Selector/Equality/PlayableItemEqualityComparer.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using SpotifyAPI.Web;
+
+namespace Selector.Equality
+{
+    public class PlayableItemEqualityComparer: IEqualityComparer<PlaylistTrack<IPlayableItem>>
+    {
+        public bool Equals(PlaylistTrack<IPlayableItem> x, PlaylistTrack<IPlayableItem> y)
+        {
+            return x.GetUri().Equals(y.GetUri());
+        }
+
+        public int GetHashCode([DisallowNull] PlaylistTrack<IPlayableItem> obj)
+        {
+            return obj.GetUri().GetHashCode();
+        }
+    }
+}
+

Selector/Extensions/SpotifyExtensions.cs

@@ -9,6 +9,8 @@ namespace Selector
 {
     public static class SpotifyExtensions
     {
+        public static string DisplayString(this FullPlaylist playlist) => $"{playlist.Name}";
+
         public static string DisplayString(this FullTrack track) => $"{track.Name} / {track.Album?.Name} / {track.Artists?.DisplayString()}";
         public static string DisplayString(this SimpleAlbum album) => $"{album.Name} / {album.Artists?.DisplayString()}";
         public static string DisplayString(this SimpleArtist artist) => artist.Name;
@@ -48,5 +50,37 @@ namespace Selector
         public static bool IsSpokenWord(this TrackAudioFeatures feature) => feature.Speechiness > 0.66f;
         public static bool IsSpeechAndMusic(this TrackAudioFeatures feature) => feature.Speechiness is >= 0.33f and <= 0.66f;
         public static bool IsNotSpeech(this TrackAudioFeatures feature) => feature.Speechiness < 0.33f;
+
+        public static string GetUri(this IPlayableItem y)
+        {
+            if (y is FullTrack track)
+            {
+                return track.Uri;
+            }
+            else if (y is FullEpisode episode)
+            {
+                return episode.Uri;
+            }
+            else
+            {
+                throw new ArgumentException(nameof(y));
+            }
+        }
+
+        public static string GetUri(this PlaylistTrack<IPlayableItem> y)
+        {
+            if (y.Track is FullTrack track)
+            {
+                return track.Uri;
+            }
+            else if (y.Track is FullEpisode episode)
+            {
+                return episode.Uri;
+            }
+            else
+            {
+                throw new ArgumentException(nameof(y.Track));
+            }
+        }
     }
 }

Selector/Selector.csproj

@@ -10,6 +10,10 @@
     <PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0" />
     <PackageReference Include="SpotifyAPI.Web" Version="6.2.2" />
     <PackageReference Include="Inflatable.Lastfm" Version="1.2.0" />
+    <PackageReference Include="System.Linq.Async" Version="6.0.1" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Remove="System.Linq.Async" />
+  </ItemGroup>
 </Project>

Selector/Watcher/Interfaces/Events.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using SpotifyAPI.Web;
 
 namespace Selector
@@ -29,4 +30,38 @@ namespace Selector
             };
         }
     }
+
+    public class PlaylistChangeEventArgs : EventArgs
+    {
+        public FullPlaylist Previous { get; set; }
+        public FullPlaylist Current { get; set; }
+        /// <summary>
+        /// Spotify Username
+        /// </summary>
+        public string SpotifyUsername { get; set; }
+        /// <summary>
+        /// String Id for watcher, used to hold user Db Id
+        /// </summary>
+        /// <value></value>
+        public string Id { get; set; }
+        Timeline<FullPlaylist> Timeline { get; set; }
+        ICollection<PlaylistTrack<IPlayableItem>> CurrentTracks { get; set; }
+        ICollection<PlaylistTrack<IPlayableItem>> AddedTracks { get; set; }
+        ICollection<PlaylistTrack<IPlayableItem>> RemovedTracks { get; set; }
+
+        public static PlaylistChangeEventArgs From(FullPlaylist previous, FullPlaylist current, Timeline<FullPlaylist> timeline, ICollection<PlaylistTrack<IPlayableItem>> tracks = null, ICollection<PlaylistTrack<IPlayableItem>> addedTracks = null, ICollection<PlaylistTrack<IPlayableItem>> removedTracks = null, string id = null, string username = null)
+        {
+            return new PlaylistChangeEventArgs()
+            {
+                Previous = previous,
+                Current = current,
+                Timeline = timeline,
+                CurrentTracks = tracks,
+                AddedTracks = addedTracks,
+                RemovedTracks = removedTracks,
+                Id = id,
+                SpotifyUsername = username
+            };
+        }
+    }
 }

Selector/Watcher/Interfaces/IPlaylistWatcher.cs

@@ -0,0 +1,20 @@
+using System;
+using SpotifyAPI.Web;
+
+namespace Selector
+{
+    public interface IPlaylistWatcher: IWatcher
+    {
+        public event EventHandler<PlaylistChangeEventArgs> NetworkPoll;
+        public event EventHandler<PlaylistChangeEventArgs> SnapshotChange;
+
+        public event EventHandler<PlaylistChangeEventArgs> TracksAdded;
+        public event EventHandler<PlaylistChangeEventArgs> TracksRemoved;
+
+        public event EventHandler<PlaylistChangeEventArgs> NameChanged;
+        public event EventHandler<PlaylistChangeEventArgs> DescriptionChanged;
+
+        public FullPlaylist Live { get; }
+        public Timeline<FullPlaylist> Past { get; }
+    }
+}

Selector/Watcher/PlaylistWatcher.cs

@@ -0,0 +1,256 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using SpotifyAPI.Web;
+
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Logging.Abstractions;
+using System.Linq;
+using Selector.Equality;
+
+namespace Selector
+{
+    public class PlaylistWatcherConfig
+    {
+        public string PlaylistId { get; set; }
+        public bool PullTracks { get; set; } = true;
+    }
+
+    public class PlaylistWatcher: BaseWatcher, IPlaylistWatcher
+    {
+        new private readonly ILogger<PlaylistWatcher> Logger;
+        private readonly ISpotifyClient spotifyClient;
+
+        public PlaylistWatcherConfig config { get; set; }
+
+        public event EventHandler<PlaylistChangeEventArgs> NetworkPoll;
+        public event EventHandler<PlaylistChangeEventArgs> SnapshotChange;
+
+        public event EventHandler<PlaylistChangeEventArgs> TracksAdded;
+        public event EventHandler<PlaylistChangeEventArgs> TracksRemoved;
+
+        public event EventHandler<PlaylistChangeEventArgs> NameChanged;
+        public event EventHandler<PlaylistChangeEventArgs> DescriptionChanged;
+
+        public FullPlaylist Live { get; private set; }
+        private List<PlaylistTrack<IPlayableItem>> CurrentTracks { get; set; }
+        private ICollection<PlaylistTrack<IPlayableItem>> LastAddedTracks { get; set; }
+        private ICollection<PlaylistTrack<IPlayableItem>> LastRemovedTracks { get; set; }
+
+        private FullPlaylist Previous { get; set; }
+        public Timeline<FullPlaylist> Past { get; set; } = new();
+
+        private IEqualityComparer<PlaylistTrack<IPlayableItem>> EqualityComparer = new PlayableItemEqualityComparer();
+
+        public PlaylistWatcher(PlaylistWatcherConfig config,
+                ISpotifyClient spotifyClient,
+                ILogger<PlaylistWatcher> logger = null,
+                int pollPeriod = 3000
+        ) : base(logger) {
+
+            this.spotifyClient = spotifyClient;
+            this.config = config;
+            Logger = logger ?? NullLogger<PlaylistWatcher>.Instance;
+            PollPeriod = pollPeriod;
+        }
+
+        public override Task Reset()
+        {
+            Previous = null;
+            Live = null;
+            Past = new();
+
+            return Task.CompletedTask;
+        }
+
+        public override async Task WatchOne(CancellationToken token = default) 
+        {
+            token.ThrowIfCancellationRequested();
+
+            using var logScope = Logger.BeginScope(new Dictionary<string, object> { { "playlist_id", config.PlaylistId } });
+            
+            try{
+                string id;
+
+                if(config.PlaylistId.Contains(':'))
+                {
+                    id = config.PlaylistId.Split(':').Last();
+                }
+                else
+                {
+                    id = config.PlaylistId;
+                }
+
+                Logger.LogTrace("Making Spotify call");
+                var polledCurrent = await spotifyClient.Playlists.Get(id);
+                Logger.LogTrace("Received Spotify call [{context}]", polledCurrent?.DisplayString());
+
+                if (polledCurrent != null) StoreCurrentPlaying(polledCurrent);
+
+                // swap new item into live and bump existing down to previous
+                Previous = Live;
+                Live = polledCurrent;
+
+                OnNetworkPoll(GetEvent());
+
+                await CheckSnapshot();
+                CheckStringValues();
+            }
+            catch(APIUnauthorizedException e)
+            {
+                Logger.LogDebug($"Unauthorised error: [{e.Message}] (should be refreshed and retried?)");
+                //throw e;
+            }
+            catch(APITooManyRequestsException e)
+            {
+                Logger.LogDebug($"Too many requests error: [{e.Message}]");
+                await Task.Delay(e.RetryAfter, token);
+                // throw e;
+            }
+            catch(APIException e)
+            {
+                Logger.LogDebug($"API error: [{e.Message}]");
+                // throw e;
+            }
+        }
+
+        private async Task CheckSnapshot()
+        {
+            switch(Previous, Live)
+            {
+                case (null, not null): // gone null
+                    await PageLiveTracks();
+                    break;
+                case (not null, null): // went non-null
+                    break;
+                case (not null, not null): // continuing non-null
+
+                    if (Live.SnapshotId != Previous.SnapshotId)
+                    {
+                        Logger.LogDebug("Snapshot Id changed: {previous} -> {current}", Previous.SnapshotId, Live.SnapshotId);
+                        await PageLiveTracks();
+                        OnSnapshotChange(GetEvent());
+                    }
+
+                    break;
+            }   
+        }
+
+        private async Task PageLiveTracks()
+        {
+            if (config.PullTracks)
+            {
+                Logger.LogDebug("Paging current tracks");
+
+                var newCurrentTracks = await spotifyClient.Paginate(Live.Tracks).ToListAsync();
+
+                Logger.LogTrace("Completed paging current tracks");
+
+                if (CurrentTracks is not null)
+                {
+                    Logger.LogDebug("Identifying diffs");
+
+                    LastAddedTracks = newCurrentTracks.Except(CurrentTracks, EqualityComparer).ToArray();
+                    LastRemovedTracks = CurrentTracks.Except(newCurrentTracks, EqualityComparer).ToArray();
+
+                    if (LastAddedTracks.Count > 0)
+                    {
+                        OnTracksAdded(GetEvent());
+                    }
+
+                    if (LastRemovedTracks.Count > 0)
+                    {
+                        OnTracksRemoved(GetEvent());
+                    }
+
+                    Logger.LogTrace("Completed identifying diffs");
+                }
+
+                CurrentTracks = newCurrentTracks;
+            }
+        }
+
+        private PlaylistChangeEventArgs GetEvent() => PlaylistChangeEventArgs.From(Previous, Live, Past, tracks: CurrentTracks, addedTracks: LastAddedTracks, removedTracks: LastRemovedTracks, id: Id, username: SpotifyUsername);
+
+        private void CheckStringValues()
+        {
+            switch (Previous, Live)
+            {
+                case (null, not null): // gone null
+                    break;
+                case (not null, null): // went non-null
+                    break;
+                case (not null, not null): // continuing non-null
+
+                    if (!Live.Name.Equals(Previous.Name))
+                    {
+                        Logger.LogDebug("Name changed: {previous} -> {current}", Previous.SnapshotId, Live.SnapshotId);
+                        OnNameChanged(GetEvent());
+                    }
+
+                    if (!Live.Description.Equals(Previous.Description))
+                    {
+                        Logger.LogDebug("Description changed: {previous} -> {current}", Previous.SnapshotId, Live.SnapshotId);
+                        OnDescriptionChanged(GetEvent());
+                    }
+
+                    break;
+            }
+        }
+
+        /// <summary>
+        /// Store currently playing in last plays. Determine whether new list or appending required
+        /// </summary>
+        /// <param name="current">New currently playing to store</param>
+        private void StoreCurrentPlaying(FullPlaylist current) 
+        {
+            Past?.Add(current);
+        }
+
+        #region Event Firers
+        protected virtual void OnNetworkPoll(PlaylistChangeEventArgs args)
+        {
+            Logger.LogTrace("Firing network poll event");
+
+            NetworkPoll?.Invoke(this, args);
+        }
+
+        protected virtual void OnSnapshotChange(PlaylistChangeEventArgs args)
+        {
+            Logger.LogTrace("Firing snapshot change event");
+
+            SnapshotChange?.Invoke(this, args); 
+        }
+
+        protected virtual void OnTracksAdded(PlaylistChangeEventArgs args)
+        {
+            Logger.LogTrace("Firing tracks added event");
+
+            TracksAdded?.Invoke(this, args);
+        }
+
+        protected virtual void OnTracksRemoved(PlaylistChangeEventArgs args)
+        {
+            Logger.LogTrace("Firing tracks removed event");
+
+            TracksRemoved?.Invoke(this, args);
+        }
+
+        protected virtual void OnNameChanged(PlaylistChangeEventArgs args)
+        {
+            Logger.LogTrace("Firing name changed event");
+
+            NameChanged?.Invoke(this, args);
+        }
+
+        protected virtual void OnDescriptionChanged(PlaylistChangeEventArgs args)
+        {
+            Logger.LogTrace("Firing description changed event");
+
+            DescriptionChanged?.Invoke(this, args);
+        }
+
+        #endregion
+    }
+}

Selector/Watcher/WatcherFactory.cs

@@ -40,10 +40,25 @@ namespace Selector
                     Id = id
                 };
             }
-            //else if (typeof(T).IsAssignableFrom(typeof(PlaylistWatcher)))
-            //{
+            else if (typeof(T).IsAssignableFrom(typeof(PlaylistWatcher)))
+            {
+                var config = await spotifyFactory.GetConfig();
+                var client = new SpotifyClient(config);
 
-            //}
+                // TODO: catch spotify exceptions
+                var user = await client.UserProfile.Current();
+
+                return new PlaylistWatcher(
+                    new(),
+                    client,
+                    LoggerFactory?.CreateLogger<PlaylistWatcher>() ?? NullLogger<PlaylistWatcher>.Instance,
+                    pollPeriod: pollPeriod
+                )
+                {
+                    SpotifyUsername = user.DisplayName,
+                    Id = id
+                };
+            }
             else
             {
                 throw new ArgumentException("Type unsupported");