3 files changed, 126 insertions, 0 deletions
diff --git a/MediaBrowser.Controller/Library/IUserDataManager.cs b/MediaBrowser.Controller/Library/IUserDataManager.cs
index 798812bf1f..2ee8845346 100644
--- a/MediaBrowser.Controller/Library/IUserDataManager.cs
+++ b/MediaBrowser.Controller/Library/IUserDataManager.cs
@@ -63,6 +63,24 @@ namespace MediaBrowser.Controller.Library
         Dictionary<Guid, UserItemData> GetUserDataBatch(IReadOnlyList<BaseItem> items, User user);
 
         /// <summary>
+        /// Gets the user data that should drive resume for a multi-version item: the data of the most
+        /// recently played alternate version (including the item itself) that has a resume point.
+        /// </summary>
+        /// <param name="user">The user.</param>
+        /// <param name="item">The item.</param>
+        /// <returns>The resume version's data, or <c>null</c> when the item has no versions or none has a resume point.</returns>
+        VersionResumeData? GetResumeUserData(User user, BaseItem item);
+
+        /// <summary>
+        /// Gets the resume-driving user data for multiple items in a single batch operation.
+        /// See <see cref="GetResumeUserData(User, BaseItem)"/>.
+        /// </summary>
+        /// <param name="items">The items to get resume data for.</param>
+        /// <param name="user">The user.</param>
+        /// <returns>A dictionary mapping item ids to their resume version's data; items without one are omitted.</returns>
+        IReadOnlyDictionary<Guid, VersionResumeData> GetResumeUserDataBatch(IReadOnlyList<BaseItem> items, User user);
+
+        /// <summary>
         /// Gets the user data dto.
         /// </summary>
         /// <param name="item">Item to use.</param>
@@ -80,5 +98,13 @@ namespace MediaBrowser.Controller.Library
         /// <param name="reportedPositionTicks">New playstate.</param>
         /// <returns>True if playstate was updated.</returns>
         bool UpdatePlayState(BaseItem item, UserItemData data, long? reportedPositionTicks);
+
+        /// <summary>
+        /// Clears any stored audio and subtitle stream selections for the given user/item pair.
+        /// Used when the user has opted out of remembering selections.
+        /// </summary>
+        /// <param name="user">The user.</param>
+        /// <param name="item">The item.</param>
+        void ResetPlaybackStreamSelections(User user, BaseItem item);
     }
 }
diff --git a/MediaBrowser.Controller/Library/VersionPlaybackSelector.cs b/MediaBrowser.Controller/Library/VersionPlaybackSelector.cs
new file mode 100644
index 0000000000..1766c50141
--- /dev/null
+++ b/MediaBrowser.Controller/Library/VersionPlaybackSelector.cs
@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using MediaBrowser.Controller.Entities;
+
+namespace MediaBrowser.Controller.Library
+{
+    /// <summary>
+    /// Single definition of "which alternate version was most recently played" shared by the resume tile
+    /// (<see cref="IUserDataManager.GetResumeUserData"/>), the media-source default ordering and Next Up.
+    /// Each call site declares its own eligibility rule so the intentional differences (resumable-only vs.
+    /// resumable-or-completed) are visible in one place instead of being re-implemented divergently.
+    /// The SQL resume query keeps its own translation of the same rule.
+    /// </summary>
+    public static class VersionPlaybackSelector
+    {
+        /// <summary>
+        /// Selects the entry whose user data has the greatest <see cref="UserItemData.LastPlayedDate"/>,
+        /// considering only entries that satisfy <paramref name="isEligible"/>. On an exact tie the first
+        /// encountered entry wins.
+        /// </summary>
+        /// <typeparam name="T">The candidate type (e.g. a version item or a media source).</typeparam>
+        /// <param name="items">The candidates to choose from.</param>
+        /// <param name="dataSelector">Resolves the user data for a candidate, or <c>null</c> when it has none.</param>
+        /// <param name="isEligible">Whether a candidate's user data makes it a valid winner.</param>
+        /// <returns>The most recently played eligible candidate, or <c>default</c> when none qualify.</returns>
+        public static T? SelectMostRecentlyPlayed<T>(
+            IEnumerable<T> items,
+            Func<T, UserItemData?> dataSelector,
+            Func<UserItemData, bool> isEligible)
+        {
+            ArgumentNullException.ThrowIfNull(items);
+            ArgumentNullException.ThrowIfNull(dataSelector);
+            ArgumentNullException.ThrowIfNull(isEligible);
+
+            T? winner = default;
+            var winnerDate = DateTime.MinValue;
+            var hasWinner = false;
+
+            foreach (var item in items)
+            {
+                var data = dataSelector(item);
+                if (data is null || !isEligible(data))
+                {
+                    continue;
+                }
+
+                var date = data.LastPlayedDate ?? DateTime.MinValue;
+                if (!hasWinner || date > winnerDate)
+                {
+                    winner = item;
+                    winnerDate = date;
+                    hasWinner = true;
+                }
+            }
+
+            return winner;
+        }
+    }
+}
diff --git a/MediaBrowser.Controller/Library/VersionResumeData.cs b/MediaBrowser.Controller/Library/VersionResumeData.cs
new file mode 100644
index 0000000000..772e2bf3a7
--- /dev/null
+++ b/MediaBrowser.Controller/Library/VersionResumeData.cs
@@ -0,0 +1,41 @@
+using System;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Model.Dto;
+
+namespace MediaBrowser.Controller.Library
+{
+    /// <summary>
+    /// The user data of the most recently played alternate version that should drive the completion state of a multi-version item.
+    /// </summary>
+    /// <param name="VersionId">The id of the version that owns <paramref name="UserData"/>.</param>
+    /// <param name="UserData">The resume version's user data.</param>
+    public record VersionResumeData(Guid VersionId, UserItemData UserData)
+    {
+        /// <summary>
+        /// Merges the most recently played version's completion state into the supplied user data dto.
+        /// Completion (played) propagates to the primary. An in-progress resume position stays on the version
+        /// that owns it, which is surfaced directly (e.g. in resume queries) so that playback always targets
+        /// the correct version rather than resuming the primary at another version's offset. When the movie was
+        /// finished on a different version, the primary's own stale resume position is cleared so it does not
+        /// render as "watched and resumable" at the same time.
+        /// </summary>
+        /// <param name="dto">The user data dto to update.</param>
+        public void ApplyTo(UserItemDataDto dto)
+        {
+            dto.Played = dto.Played || UserData.Played;
+
+            if ((UserData.LastPlayedDate ?? DateTime.MinValue) > (dto.LastPlayedDate ?? DateTime.MinValue))
+            {
+                dto.LastPlayedDate = UserData.LastPlayedDate;
+            }
+
+            // A different version was finished (played, no resume position of its own) and is the most
+            // recently played: the whole movie is watched.
+            if (!VersionId.Equals(dto.ItemId) && UserData.Played && UserData.PlaybackPositionTicks <= 0)
+            {
+                dto.PlaybackPositionTicks = 0;
+                dto.PlayedPercentage = null;
+            }
+        }
+    }
+}