Implement automatic intro skipping

Requires that the client playing media supports remote commands.
Closes #9.

ConfusedPolarBear.Plugin.IntroSkipper/AutoSkip.cs

@@ -0,0 +1,197 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Timers;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Plugins;
+using MediaBrowser.Controller.Session;
+using MediaBrowser.Model.Entities;
+using MediaBrowser.Model.Session;
+using Microsoft.Extensions.Logging;
+
+namespace ConfusedPolarBear.Plugin.IntroSkipper;
+
+/// <summary>
+/// Automatically skip past introduction sequences.
+/// Commands clients to seek to the end of the intro as soon as they start playing it.
+/// </summary>
+public class AutoSkip : IServerEntryPoint
+{
+    private readonly object _sentSeekCommandLock = new();
+
+    private ILogger<AutoSkip> _logger;
+    private IUserDataManager _userDataManager;
+    private ISessionManager _sessionManager;
+    private System.Timers.Timer _playbackTimer = new(1000);
+    private Dictionary<string, bool> _sentSeekCommand;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AutoSkip"/> class.
+    /// </summary>
+    /// <param name="userDataManager">User data manager.</param>
+    /// <param name="sessionManager">Session manager.</param>
+    /// <param name="logger">Logger.</param>
+    public AutoSkip(
+        IUserDataManager userDataManager,
+        ISessionManager sessionManager,
+        ILogger<AutoSkip> logger)
+    {
+        _userDataManager = userDataManager;
+        _sessionManager = sessionManager;
+        _logger = logger;
+        _sentSeekCommand = new Dictionary<string, bool>();
+    }
+
+    /// <summary>
+    /// If introduction auto skipping is enabled, set it up.
+    /// </summary>
+    /// <returns>Task.</returns>
+    public Task RunAsync()
+    {
+        if (!Plugin.Instance!.Configuration.AutoSkip)
+        {
+            _logger.LogDebug("Not setting up automatic skipping");
+            return Task.CompletedTask;
+        }
+
+        _logger.LogDebug("Setting up automatic skipping");
+
+        _userDataManager.UserDataSaved += UserDataManager_UserDataSaved;
+
+        _playbackTimer.AutoReset = true;
+        _playbackTimer.Elapsed += PlaybackTimer_Elapsed;
+        _playbackTimer.Start();
+
+        return Task.CompletedTask;
+    }
+
+    private void UserDataManager_UserDataSaved(object? sender, UserDataSaveEventArgs e)
+    {
+        var itemId = e.Item.Id;
+
+        // Ignore all events except playback start & end
+        if (e.SaveReason != UserDataSaveReason.PlaybackStart && e.SaveReason != UserDataSaveReason.PlaybackFinished)
+        {
+            return;
+        }
+
+        // Lookup the session for this item.
+        SessionInfo? session = null;
+
+        try
+        {
+            foreach (var needle in _sessionManager.Sessions)
+            {
+                if (needle.UserId == e.UserId && needle.NowPlayingItem.Id == itemId)
+                {
+                    session = needle;
+                    break;
+                }
+            }
+
+            if (session == null)
+            {
+                _logger.LogInformation("Unable to find session for {Item}", itemId);
+                return;
+            }
+        }
+        catch (NullReferenceException)
+        {
+            return;
+        }
+
+        // Reset the seek command state for this device.
+        lock (_sentSeekCommandLock)
+        {
+            var device = session.DeviceId;
+
+            _logger.LogDebug("Resetting seek command state for session {Session}", device);
+            _sentSeekCommand[device] = false;
+        }
+    }
+
+    private void PlaybackTimer_Elapsed(object? sender, ElapsedEventArgs e)
+    {
+        foreach (var session in _sessionManager.Sessions)
+        {
+            var deviceId = session.DeviceId;
+            var itemId = session.NowPlayingItem.Id;
+            var position = session.PlayState.PositionTicks / TimeSpan.TicksPerSecond;
+
+            // Don't send the seek command more than once in the same session.
+            lock (_sentSeekCommandLock)
+            {
+                if (_sentSeekCommand[deviceId])
+                {
+                    _logger.LogTrace("Already sent seek command for session {Session}", deviceId);
+                    continue;
+                }
+            }
+
+            // Assert that an intro was detected for this item.
+            if (!Plugin.Instance!.Intros.TryGetValue(itemId, out var intro) || !intro.Valid)
+            {
+                continue;
+            }
+
+            // Seek is unreliable if called at the very start of an episode.
+            var adjustedStart = Math.Max(5, intro.IntroStart);
+
+            _logger.LogTrace(
+                "Playback position is {Position}, intro runs from {Start} to {End}",
+                position,
+                adjustedStart,
+                intro.IntroEnd);
+
+            if (position < adjustedStart || position > intro.IntroEnd)
+            {
+                continue;
+            }
+
+            // Send the seek command
+            _logger.LogDebug("Sending seek command to {Session}", deviceId);
+
+            var seekCommand = new PlaystateRequest
+            {
+                Command = PlaystateCommand.Seek,
+                ControllingUserId = session.UserId.ToString("N"),
+                SeekPositionTicks = (long)intro.IntroEnd * TimeSpan.TicksPerSecond,
+            };
+
+            _sessionManager.SendPlaystateCommand(session.Id, session.Id, seekCommand, CancellationToken.None);
+
+            // Flag that we've sent the seek command so that it's not sent repeatedly
+            lock (_sentSeekCommandLock)
+            {
+                _logger.LogTrace("Setting seek command state for session {Session}", deviceId);
+                _sentSeekCommand[deviceId] = true;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Dispose.
+    /// </summary>
+    public void Dispose()
+    {
+        Dispose(true);
+        GC.SuppressFinalize(this);
+    }
+
+    /// <summary>
+    /// Protected dispose.
+    /// </summary>
+    /// <param name="disposing">Dispose.</param>
+    protected virtual void Dispose(bool disposing)
+    {
+        if (!disposing)
+        {
+            return;
+        }
+
+        _userDataManager.UserDataSaved -= UserDataManager_UserDataSaved;
+        _playbackTimer.Stop();
+        _playbackTimer.Dispose();
+    }
+}

ConfusedPolarBear.Plugin.IntroSkipper/Configuration/PluginConfiguration.cs

@@ -19,6 +19,11 @@ public class PluginConfiguration : BasePluginConfiguration
     /// </summary>
     public bool CacheFingerprints { get; set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether introductions should be automatically skipped.
+    /// </summary>
+    public bool AutoSkip { get; set; }
+
     /// <summary>
     /// Gets or sets the seconds before the intro starts to show the skip prompt at.
     /// </summary>

ConfusedPolarBear.Plugin.IntroSkipper/Configuration/configPage.html

@@ -12,6 +12,19 @@
         <div data-role="content">
             <div class="content-primary">
                 <form id="FingerprintConfigForm">
+                    <div class="checkboxContainer checkboxContainer-withDescription">
+                        <label class="emby-checkbox-label">
+                            <input id="AutoSkip" type="checkbox" is="emby-checkbox" />
+                            <span>Automatically skip intros</span>
+                        </label>
+
+                        <div class="fieldDescription">
+                            If checked, intros will be automatically skipped. Will only work if web
+                            sockets are configured correctly.<br />
+                            <strong>Jellyfin must be restarted after changing this setting.</strong>
+                        </div>
+                    </div>
+
                     <div class="checkboxContainer checkboxContainer-withDescription">
                         <label class="emby-checkbox-label">
                             <input id="CacheFingerprints" type="checkbox" is="emby-checkbox" />
@@ -34,7 +47,7 @@
                     </div>
 
                     <div class="inputContainer">
-                        <label class="inputLabel inputLabelUnfocused" for="AnInteger">Hide skip prompt at</label>
+                        <label class="inputLabel inputLabelUnfocused" for="AnInteger">Hide skip prompt after</label>
                         <input id="HidePromptAdjustment" type="number" is="emby-input" min="2" />
                         <div class="fieldDescription">
                             Seconds after the introduction starts to hide the skip prompt at.
@@ -53,7 +66,7 @@
 
                         <p>
                             Erasing introduction timestamps is only necessary after upgrading the plugin if specifically
-                            requested to do so in the plugin's changelog.
+                            requested to do so in the plugin's changelog. After the timestamps are erased, run the Analyze episodes scheduled task to re-analyze all media on the server.
                         </p>
                     </div>
                 </form>
@@ -401,6 +414,7 @@
                 .addEventListener('pageshow', function () {
                     Dashboard.showLoadingMsg();
                     ApiClient.getPluginConfiguration("c83d86bb-a1e0-4c35-a113-e2101cf4ee6b").then(function (config) {
+                        document.querySelector('#AutoSkip').checked = config.AutoSkip;
                         document.querySelector('#CacheFingerprints').checked = config.CacheFingerprints;
 
                         document.querySelector('#ShowPromptAdjustment').value = config.ShowPromptAdjustment;
@@ -414,6 +428,7 @@
                 .addEventListener('submit', function (e) {
                     Dashboard.showLoadingMsg();
                     ApiClient.getPluginConfiguration("c83d86bb-a1e0-4c35-a113-e2101cf4ee6b").then(function (config) {
+                        config.AutoSkip = document.querySelector('#AutoSkip').checked;
                         config.CacheFingerprints = document.querySelector('#CacheFingerprints').checked;
 
                         config.ShowPromptAdjustment = document.querySelector("#ShowPromptAdjustment").value;

README.md

@@ -10,7 +10,9 @@ Installing this plugin (along with a modified web interface and `fpcalc`) will r
 
 ![Skip intro button](images/skip-button.png)
 
-This plugin **will not work** until both the modified web interface and `fpcalc` are installed. The easiest way to do this is to follow the steps below.
+If you use Jellyfin clients that do not use the web interface provided by the server, the plugin can be configured to automatically skip intros.
+
+This plugin **will not work** without installing `fpcalc`. The easiest way to do this is to follow the steps below.
 
 ## Introduction requirements