add tests, replace playout items when collections are updated (#1566)

ErsatzTV.Core.Tests/Scheduling/BlockScheduling/BlockPlayoutChangeDetectionTests.cs

@@ -0,0 +1,172 @@
+using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Domain.Scheduling;
+using ErsatzTV.Core.Scheduling;
+using ErsatzTV.Core.Scheduling.BlockScheduling;
+using FluentAssertions;
+using Newtonsoft.Json;
+using NUnit.Framework;
+
+namespace ErsatzTV.Core.Tests.Scheduling.BlockScheduling;
+
+public static class BlockPlayoutChangeDetectionTests
+{
+    [TestFixture]
+    public class FindUpdatedItems
+    {
+        // takes playout items, item block keys and effective blocks
+        // returns blocks to schedule and playout items to remove
+        
+        // test case: nothing has changed
+        
+        // test case: block has moved from one time to another time, nothing after
+        // test case: block has moved from one time to another time, same block after
+        // test case: block has moved from one time to another time, different block with same collection after
+        // test case: block was moved from one time to another time, different block with different collection after        
+        
+        // test case: block was removed, nothing after
+        // test case: block was removed, same block after
+        // test case: block was removed, different block with same collection after
+        // test case: block was removed, different block with different collection after
+        
+        // test case: block was added, nothing after
+        // test case: block was added, same block after
+        // test case: block was added, different block with same collection after
+        // test case: block was added, different block with different collection after
+        
+
+        [Test]
+        public void Should_Work_When_Nothing_Has_Changed()
+        {
+            DateTimeOffset dateUpdated = DateTimeOffset.Now;
+            List<Block> blocks = Blocks(dateUpdated);
+            var template = new Template { Id = 1, DateUpdated = dateUpdated.UtcDateTime };
+            var playoutTemplate = new PlayoutTemplate { Id = 10, DateUpdated = dateUpdated.UtcDateTime };
+
+            Block block1 = blocks[0];
+            Block block2 = blocks[1];
+            var blockKey1 = new BlockKey(block1, template, playoutTemplate);
+            var blockKey2 = new BlockKey(block2, template, playoutTemplate);
+            var collectionKey1 = CollectionKey.ForBlockItem(block1.Items.Head());
+            var collectionKey2 = CollectionKey.ForBlockItem(block2.Items.Head());
+
+            // 9am-9:20am
+            PlayoutItem playoutItem1 = PlayoutItem(blockKey1, collectionKey1, GetLocalDate(2024, 1, 17).AddHours(9));
+            // 1pm-1:20pm
+            PlayoutItem playoutItem2 = PlayoutItem(blockKey2, collectionKey2, GetLocalDate(2024, 1, 17).AddHours(13));
+
+            List<PlayoutItem> playoutItems = [playoutItem1, playoutItem2];
+            Dictionary<PlayoutItem, BlockKey> itemBlockKeys =
+                new()
+                {
+                    { playoutItem1, blockKey1 },
+                    { playoutItem2, blockKey2 }
+                };
+
+            List<EffectiveBlock> effectiveBlocks =
+            [
+                new EffectiveBlock(block1, blockKey1, GetLocalDate(2024, 1, 17).AddHours(9)),
+                new EffectiveBlock(block2, blockKey2, GetLocalDate(2024, 1, 17).AddHours(13)),
+            ];
+
+            Map<CollectionKey, string> collectionEtags = LanguageExt.Map<CollectionKey, string>.Empty;
+            collectionEtags = collectionEtags.Add(collectionKey1, JsonConvert.SerializeObject(collectionKey1));
+            collectionEtags = collectionEtags.Add(collectionKey2, JsonConvert.SerializeObject(collectionKey2));
+
+            Tuple<List<EffectiveBlock>, List<PlayoutItem>> result = BlockPlayoutChangeDetection.FindUpdatedItems(
+                playoutItems,
+                itemBlockKeys,
+                effectiveBlocks,
+                collectionEtags);
+
+            // nothing to schedule
+            result.Item1.Should().HaveCount(0);
+            
+            // do not need to remove any playout items or history
+            result.Item2.Should().HaveCount(0);
+        }
+
+        private static List<Block> Blocks(DateTimeOffset dateUpdated)
+        {
+            List<Block> blocks =
+            [
+                // SHOW A
+                new Block
+                {
+                    Id = 1,
+                    Items =
+                    [
+                        new BlockItem
+                        {
+                            Id = 1,
+                            Index = 1,
+                            BlockId = 1,
+                            CollectionType = ProgramScheduleItemCollectionType.TelevisionShow,
+                            MediaItemId = 1,
+                            PlaybackOrder = PlaybackOrder.Chronological
+                        }
+                    ],
+                    DateUpdated = dateUpdated.UtcDateTime
+                },
+                // SHOW B
+                new Block
+                {
+                    Id = 2,
+                    Items =
+                    [
+                        new BlockItem
+                        {
+                            Id = 2,
+                            Index = 1,
+                            BlockId = 2,
+                            CollectionType = ProgramScheduleItemCollectionType.TelevisionShow,
+                            MediaItemId = 2,
+                            PlaybackOrder = PlaybackOrder.Chronological
+                        }
+                    ],
+                    DateUpdated = dateUpdated.UtcDateTime
+                },
+                // SHOW C
+                new Block
+                {
+                    Id = 3,
+                    Items =
+                    [
+                        new BlockItem
+                        {
+                            Id = 3,
+                            Index = 1,
+                            BlockId = 3,
+                            CollectionType = ProgramScheduleItemCollectionType.TelevisionShow,
+                            MediaItemId = 3,
+                            PlaybackOrder = PlaybackOrder.Chronological
+                        }
+                    ],
+                    DateUpdated = dateUpdated.UtcDateTime
+                }
+            ];
+
+            foreach (Block block in blocks)
+            {
+                foreach (BlockItem blockItem in block.Items)
+                {
+                    blockItem.Block = block;
+                }
+            }
+
+            return blocks;
+        }
+
+        private static PlayoutItem PlayoutItem(BlockKey blockKey, CollectionKey collectionKey, DateTimeOffset start) =>
+            new()
+            {
+                Start = start.UtcDateTime,
+                Finish = start.UtcDateTime.AddMinutes(20),
+                BlockKey = JsonConvert.SerializeObject(blockKey),
+                CollectionKey = JsonConvert.SerializeObject(collectionKey),
+                CollectionEtag = JsonConvert.SerializeObject(collectionKey)
+            };
+        
+        private static DateTimeOffset GetLocalDate(int year, int month, int day) =>
+            new(year, month, day, 0, 0, 0, TimeSpan.FromHours(-6));
+    }
+}

ErsatzTV.Core.Tests/Scheduling/BlockScheduling/EffectiveBlockTests.cs

@@ -0,0 +1,109 @@
+using ErsatzTV.Core.Domain.Scheduling;
+using ErsatzTV.Core.Scheduling.BlockScheduling;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace ErsatzTV.Core.Tests.Scheduling.BlockScheduling;
+
+public static class EffectiveBlockTests
+{
+    [TestFixture]
+    public class GetEffectiveBlocks
+    {
+        [Test]
+        public void Should_Work_With_No_Matching_Days()
+        {
+            DateTimeOffset now = DateTimeOffset.Now;
+            
+            List<PlayoutTemplate> templates =
+            [
+                new PlayoutTemplate
+                {
+                    Index = 1,
+                    DaysOfWeek = [DayOfWeek.Sunday],
+                    DaysOfMonth = PlayoutTemplate.AllDaysOfMonth(),
+                    MonthsOfYear = PlayoutTemplate.AllMonthsOfYear(),
+                    Template = SingleBlockTemplate(now),
+                    DateUpdated = now.UtcDateTime
+                }
+            ];
+            
+            DateTimeOffset start = GetLocalDate(2024, 1, 15).AddHours(9);
+
+            List<EffectiveBlock> result = EffectiveBlock.GetEffectiveBlocks(templates, start, daysToBuild: 5);
+
+            result.Should().HaveCount(0);
+        }
+        
+        [Test]
+        public void Should_Work_With_Blank_Days()
+        {
+            DateTimeOffset now = DateTimeOffset.Now;
+            
+            List<PlayoutTemplate> templates =
+            [
+                new PlayoutTemplate
+                {
+                    Index = 1,
+                    DaysOfWeek = [DayOfWeek.Monday, DayOfWeek.Wednesday, DayOfWeek.Friday],
+                    DaysOfMonth = PlayoutTemplate.AllDaysOfMonth(),
+                    MonthsOfYear = PlayoutTemplate.AllMonthsOfYear(),
+                    Template = SingleBlockTemplate(now),
+                    DateUpdated = now.UtcDateTime
+                }
+            ];
+
+            DateTimeOffset start = GetLocalDate(2024, 1, 15).AddHours(9);
+
+            List<EffectiveBlock> result = EffectiveBlock.GetEffectiveBlocks(templates, start, daysToBuild: 5);
+
+            result.Should().HaveCount(3);
+            
+            result[0].Start.DayOfWeek.Should().Be(DayOfWeek.Monday);
+            result[0].Start.Date.Should().Be(GetLocalDate(2024, 1, 15).Date);
+            
+            result[1].Start.DayOfWeek.Should().Be(DayOfWeek.Wednesday);
+            result[1].Start.Date.Should().Be(GetLocalDate(2024, 1, 17).Date);
+
+            result[2].Start.DayOfWeek.Should().Be(DayOfWeek.Friday);
+            result[2].Start.Date.Should().Be(GetLocalDate(2024, 1, 19).Date);
+        }
+        
+        // TODO: test when clocks spring forward
+        // TODO: test when clocks fall back
+        
+        // TODO: offset may be incorrect on days with time change, since start offset is re-used
+    }
+
+    private static DateTimeOffset GetLocalDate(int year, int month, int day) =>
+        new(year, month, day, 0, 0, 0, TimeSpan.FromHours(-6));
+
+    private static Template SingleBlockTemplate(DateTimeOffset dateUpdated)
+    {
+        var template = new Template
+        {
+            Id = 1,
+            Items =
+            [
+                new TemplateItem
+                {
+                    Block = new Block
+                    {
+                        Id = 1,
+                        DateUpdated = dateUpdated.UtcDateTime
+                    },
+                    StartTime = TimeSpan.FromHours(9)
+                }
+            ],
+            DateUpdated = dateUpdated.UtcDateTime
+        };
+
+        // this is used for navigation
+        foreach (TemplateItem item in template.Items)
+        {
+            item.Template = template;
+        }
+
+        return template;
+    }
+}

ErsatzTV.Core/Domain/PlayoutItem.cs

@@ -28,6 +28,8 @@ public class PlayoutItem
     public string PreferredSubtitleLanguageCode { get; set; }
     public ChannelSubtitleMode? SubtitleMode { get; set; }
     public string BlockKey { get; set; }
+    public string CollectionKey { get; set; }
+    public string CollectionEtag { get; set; }
     public DateTimeOffset StartOffset => new DateTimeOffset(Start, TimeSpan.Zero).ToLocalTime();
     public DateTimeOffset FinishOffset => new DateTimeOffset(Finish, TimeSpan.Zero).ToLocalTime();
 

ErsatzTV.Core/Interfaces/Metadata/ICollectionEtag.cs

@@ -0,0 +1,8 @@
+using ErsatzTV.Core.Domain;
+
+namespace ErsatzTV.Core.Interfaces.Metadata;
+
+public interface ICollectionEtag
+{
+    string ForCollectionItems(List<MediaItem> items);
+}

ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutBuilder.cs

@@ -2,6 +2,7 @@ using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Domain.Filler;
 using ErsatzTV.Core.Domain.Scheduling;
 using ErsatzTV.Core.Extensions;
+using ErsatzTV.Core.Interfaces.Metadata;
 using ErsatzTV.Core.Interfaces.Repositories;
 using ErsatzTV.Core.Interfaces.Scheduling;
 using Microsoft.Extensions.Logging;
@@ -14,9 +15,15 @@ public class BlockPlayoutBuilder(
     IMediaCollectionRepository mediaCollectionRepository,
     ITelevisionRepository televisionRepository,
     IArtistRepository artistRepository,
+    ICollectionEtag collectionEtag,
     ILogger<BlockPlayoutBuilder> logger)
     : IBlockPlayoutBuilder
 {
+    private static readonly JsonSerializerSettings JsonSettings = new()
+    {
+        NullValueHandling = NullValueHandling.Ignore
+    };
+
     public virtual async Task<Playout> Build(Playout playout, PlayoutBuildMode mode, CancellationToken cancellationToken)
     {
         Logger.LogDebug(
@@ -37,10 +44,12 @@ public class BlockPlayoutBuilder(
         int daysToBuild = await GetDaysToBuild();
 
         // get blocks to schedule
-        List<EffectiveBlock> blocksToSchedule = EffectiveBlock.GetEffectiveBlocks(playout, start, daysToBuild);
+        List<EffectiveBlock> blocksToSchedule =
+            EffectiveBlock.GetEffectiveBlocks(playout.Templates, start, daysToBuild);
 
         // get all collection items for the playout
         Map<CollectionKey, List<MediaItem>> collectionMediaItems = await GetCollectionMediaItems(blocksToSchedule);
+        Map<CollectionKey, string> collectionEtags = GetCollectionEtags(collectionMediaItems);
 
         Dictionary<PlayoutItem, BlockKey> itemBlockKeys =
             BlockPlayoutChangeDetection.GetPlayoutItemToBlockKeyMap(playout);
@@ -48,8 +57,16 @@ public class BlockPlayoutBuilder(
         // remove items without a block key (shouldn't happen often, just upgrades)
         playout.Items.RemoveAll(i => !itemBlockKeys.ContainsKey(i));
         
+        // remove old items
+        // importantly, this should not remove their history
+        playout.Items.RemoveAll(i => i.FinishOffset < start);
+
         (List<EffectiveBlock> updatedEffectiveBlocks, List<PlayoutItem> playoutItemsToRemove) =
-            BlockPlayoutChangeDetection.FindUpdatedItems(playout, itemBlockKeys, blocksToSchedule);
+            BlockPlayoutChangeDetection.FindUpdatedItems(
+                playout.Items,
+                itemBlockKeys,
+                blocksToSchedule,
+                collectionEtags);
 
         foreach (PlayoutItem playoutItem in playoutItemsToRemove)
         {
@@ -119,6 +136,8 @@ public class BlockPlayoutBuilder(
 
                     TimeSpan itemDuration = DurationForMediaItem(mediaItem);
 
+                    var collectionKey = CollectionKey.ForBlockItem(blockItem);
+                    
                     // create a playout item
                     var playoutItem = new PlayoutItem
                     {
@@ -134,7 +153,9 @@ public class BlockPlayoutBuilder(
                         //PreferredAudioTitle = scheduleItem.PreferredAudioTitle,
                         //PreferredSubtitleLanguageCode = scheduleItem.PreferredSubtitleLanguageCode,
                         //SubtitleMode = scheduleItem.SubtitleMode
-                        BlockKey = JsonConvert.SerializeObject(effectiveBlock.BlockKey)
+                        BlockKey = JsonConvert.SerializeObject(effectiveBlock.BlockKey),
+                        CollectionKey = JsonConvert.SerializeObject(collectionKey, JsonSettings),
+                        CollectionEtag = collectionEtags[collectionKey]
                     };
 
                     if (effectiveBlock.Block.StopScheduling is BlockStopScheduling.BeforeDurationEnd
@@ -299,6 +320,19 @@ public class BlockPlayoutBuilder(
         return LanguageExt.Map.createRange(tuples);
     }
 
+    private Map<CollectionKey, string> GetCollectionEtags(
+        Map<CollectionKey, List<MediaItem>> collectionMediaItems)
+    {
+        var result = new Map<CollectionKey, string>();
+
+        foreach ((CollectionKey key, List<MediaItem> items) in collectionMediaItems)
+        {
+            result = result.Add(key, collectionEtag.ForCollectionItems(items));
+        }
+
+        return result;
+    }
+
     private static TimeSpan DurationForMediaItem(MediaItem mediaItem)
     {
         MediaVersion version = mediaItem.GetHeadVersion();

ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutChangeDetection.cs

@@ -23,22 +23,65 @@ internal static class BlockPlayoutChangeDetection
     }
 
     public static Tuple<List<EffectiveBlock>, List<PlayoutItem>> FindUpdatedItems(
-        Playout playout,
+        List<PlayoutItem> playoutItems,
         Dictionary<PlayoutItem, BlockKey> itemBlockKeys,
-        List<EffectiveBlock> blocksToSchedule)
+        List<EffectiveBlock> blocksToSchedule,
+        Map<CollectionKey, string> collectionEtags)
     {
-        DateTimeOffset lastScheduledItem = playout.Items.Count == 0
+        DateTimeOffset lastScheduledItem = playoutItems.Count == 0
             ? SystemTime.MinValueUtc
-            : playout.Items.Max(i => i.StartOffset);
+            : playoutItems.Max(i => i.StartOffset);
 
         var existingBlockKeys = itemBlockKeys.Values.ToImmutableHashSet();
         var blockKeysToSchedule = blocksToSchedule.Map(b => b.BlockKey).ToImmutableHashSet();
-        var updatedBlocks = new List<EffectiveBlock>();
+        var updatedBlocks = new System.Collections.Generic.HashSet<EffectiveBlock>();
-        var updatedItems = new List<PlayoutItem>();
+        var updatedItemIds = new System.Collections.Generic.HashSet<int>();
 
         var earliestEffectiveBlocks = new Dictionary<BlockKey, DateTimeOffset>();
         var earliestBlocks = new Dictionary<int, DateTimeOffset>();
         
+        // check for changed collections
+        foreach (EffectiveBlock effectiveBlock in blocksToSchedule.OrderBy(b => b.Start))
+        {
+            foreach (PlayoutItem playoutItem in playoutItems)
+            {
+                int blockId = itemBlockKeys[playoutItem].b;
+                if (effectiveBlock.Block.Id != blockId)
+                {
+                    continue;
+                }
+
+                bool isUpdated = string.IsNullOrWhiteSpace(playoutItem.CollectionKey);
+                if (!isUpdated)
+                {
+                    CollectionKey collectionKey = JsonConvert.DeserializeObject<CollectionKey>(playoutItem.CollectionKey);
+
+                    // collection is no longer present or collection has been modified
+                    isUpdated = !collectionEtags.ContainsKey(collectionKey) ||
+                                collectionEtags[collectionKey] != playoutItem.CollectionEtag;
+                }
+                
+                if (isUpdated)
+                {
+                    // playout item needs to be removed/re-added
+                    updatedItemIds.Add(playoutItem.Id);
+                    
+                    // block needs to be scheduled again
+                    updatedBlocks.Add(effectiveBlock);
+
+                    if (!earliestEffectiveBlocks.ContainsKey(effectiveBlock.BlockKey))
+                    {
+                        earliestEffectiveBlocks[effectiveBlock.BlockKey] = effectiveBlock.Start;
+                    }
+
+                    if (!earliestBlocks.ContainsKey(effectiveBlock.Block.Id))
+                    {
+                        earliestBlocks[effectiveBlock.Block.Id] = effectiveBlock.Start;
+                    }
+                }
+            }
+        }
+
         // process in sorted order to simplify checks
         foreach (EffectiveBlock effectiveBlock in blocksToSchedule.OrderBy(b => b.Start))
         {
@@ -80,7 +123,7 @@ internal static class BlockPlayoutChangeDetection
         }
 
         // find affected playout items
-        foreach (PlayoutItem item in playout.Items)
+        foreach (PlayoutItem item in playoutItems)
         {
             BlockKey blockKey = itemBlockKeys[item];
 
@@ -92,11 +135,11 @@ internal static class BlockPlayoutChangeDetection
             
             if (!blockKeysToSchedule.Contains(blockKey) || blockKeyIsAffected || blockIdIsAffected)
             {
-                updatedItems.Add(item);
+                updatedItemIds.Add(item.Id);
             }
         }
 
-        return Tuple(updatedBlocks, updatedItems);
+        return Tuple(updatedBlocks.ToList(), playoutItems.Filter(i => updatedItemIds.Contains(i.Id)).ToList());
     }
 
     public static void RemoveItemAndHistory(Playout playout, PlayoutItem playoutItem)

ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutPreviewBuilder.cs

@@ -1,5 +1,6 @@
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Domain.Scheduling;
+using ErsatzTV.Core.Interfaces.Metadata;
 using ErsatzTV.Core.Interfaces.Repositories;
 using ErsatzTV.Core.Interfaces.Scheduling;
 using Microsoft.Extensions.Logging;
@@ -12,11 +13,13 @@ public class BlockPlayoutPreviewBuilder(
     IMediaCollectionRepository mediaCollectionRepository,
     ITelevisionRepository televisionRepository,
     IArtistRepository artistRepository,
+    ICollectionEtag collectionEtag,
     ILogger<BlockPlayoutBuilder> logger) : BlockPlayoutBuilder(
     configElementRepository,
     mediaCollectionRepository,
     televisionRepository,
     artistRepository,
+    collectionEtag,
     logger), IBlockPlayoutPreviewBuilder
 {
     private readonly Dictionary<Guid, System.Collections.Generic.HashSet<CollectionKey>> _randomizedCollections = [];

ErsatzTV.Core/Scheduling/BlockScheduling/EffectiveBlock.cs

@@ -1,11 +1,13 @@
-using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Domain.Scheduling;
 
 namespace ErsatzTV.Core.Scheduling.BlockScheduling;
 
 internal record EffectiveBlock(Block Block, BlockKey BlockKey, DateTimeOffset Start)
 {
-    public static List<EffectiveBlock> GetEffectiveBlocks(Playout playout, DateTimeOffset start, int daysToBuild)
+    public static List<EffectiveBlock> GetEffectiveBlocks(
+        ICollection<PlayoutTemplate> templates,
+        DateTimeOffset start,
+        int daysToBuild)
     {
         DateTimeOffset finish = start.AddDays(daysToBuild);
 
@@ -13,31 +15,21 @@ internal record EffectiveBlock(Block Block, BlockKey BlockKey, DateTimeOffset St
         DateTimeOffset current = start.Date;
         while (current < finish)
         {
-            foreach (PlayoutTemplate playoutTemplate in PlayoutTemplateSelector.GetPlayoutTemplateFor(
+            Option<PlayoutTemplate> maybeTemplate = PlayoutTemplateSelector.GetPlayoutTemplateFor(templates, current);
-                         playout.Templates,
+            foreach (PlayoutTemplate playoutTemplate in maybeTemplate)
-                         current))
             {
                 // logger.LogDebug(
                 //     "Will schedule day {Date} using template {Template}",
                 //     current,
                 //     playoutTemplate.Template.Name);
 
-                foreach (TemplateItem templateItem in playoutTemplate.Template.Items)
+                DateTimeOffset today = current;
-                {
+                
-                    var effectiveBlock = new EffectiveBlock(
+                var newBlocks = playoutTemplate.Template.Items
-                        templateItem.Block,
+                    .Map(i => ToEffectiveBlock(playoutTemplate, i, today, start))
-                        new BlockKey(templateItem.Block, templateItem.Template, playoutTemplate),
+                    .ToList();
-                        new DateTimeOffset(
+
-                            current.Year,
+                effectiveBlocks.AddRange(newBlocks);
-                            current.Month,
-                            current.Day,
-                            templateItem.StartTime.Hours,
-                            templateItem.StartTime.Minutes,
-                            0,
-                            start.Offset));
-
-                    effectiveBlocks.Add(effectiveBlock);
-                }
             }
 
             current = current.AddDays(1);
@@ -48,4 +40,21 @@ internal record EffectiveBlock(Block Block, BlockKey BlockKey, DateTimeOffset St
 
         return effectiveBlocks;
     }
+
+    private static EffectiveBlock ToEffectiveBlock(
+        PlayoutTemplate playoutTemplate,
+        TemplateItem templateItem,
+        DateTimeOffset current,
+        DateTimeOffset start) =>
+        new(
+            templateItem.Block,
+            new BlockKey(templateItem.Block, templateItem.Template, playoutTemplate),
+            new DateTimeOffset(
+                current.Year,
+                current.Month,
+                current.Day,
+                templateItem.StartTime.Hours,
+                templateItem.StartTime.Minutes,
+                0,
+                start.Offset));
 }

ErsatzTV.Core/Scheduling/BlockScheduling/HistoryDetails.cs

@@ -92,6 +92,7 @@ internal static class HistoryDetails
                 maybeMatchedItem = fakeItem;
             }
         }
+        // TODO: match media item
         
         foreach (MediaItem matchedItem in maybeMatchedItem)
         {

ErsatzTV.Infrastructure.MySql/Migrations/20240122152005_Add_PlayoutItemCollectionKey.cs

@@ -0,0 +1,40 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ErsatzTV.Infrastructure.MySql.Migrations
+{
+    /// <inheritdoc />
+    public partial class Add_PlayoutItemCollectionKey : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "CollectionEtag",
+                table: "PlayoutItem",
+                type: "longtext",
+                nullable: true)
+                .Annotation("MySql:CharSet", "utf8mb4");
+
+            migrationBuilder.AddColumn<string>(
+                name: "CollectionKey",
+                table: "PlayoutItem",
+                type: "longtext",
+                nullable: true)
+                .Annotation("MySql:CharSet", "utf8mb4");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "CollectionEtag",
+                table: "PlayoutItem");
+
+            migrationBuilder.DropColumn(
+                name: "CollectionKey",
+                table: "PlayoutItem");
+        }
+    }
+}

ErsatzTV.Infrastructure.MySql/Migrations/TvContextModelSnapshot.cs

@@ -1443,6 +1443,12 @@ namespace ErsatzTV.Infrastructure.MySql.Migrations
                     b.Property<string>("ChapterTitle")
                         .HasColumnType("longtext");
 
+                    b.Property<string>("CollectionEtag")
+                        .HasColumnType("longtext");
+
+                    b.Property<string>("CollectionKey")
+                        .HasColumnType("longtext");
+
                     b.Property<string>("CustomTitle")
                         .HasColumnType("longtext");
 

ErsatzTV.Infrastructure.Sqlite/Migrations/20240122144648_Add_PlayoutItemCollectionKey.cs

@@ -0,0 +1,38 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ErsatzTV.Infrastructure.Sqlite.Migrations
+{
+    /// <inheritdoc />
+    public partial class Add_PlayoutItemCollectionKey : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "CollectionEtag",
+                table: "PlayoutItem",
+                type: "TEXT",
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "CollectionKey",
+                table: "PlayoutItem",
+                type: "TEXT",
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "CollectionEtag",
+                table: "PlayoutItem");
+
+            migrationBuilder.DropColumn(
+                name: "CollectionKey",
+                table: "PlayoutItem");
+        }
+    }
+}

ErsatzTV.Infrastructure.Sqlite/Migrations/TvContextModelSnapshot.cs

@@ -1441,6 +1441,12 @@ namespace ErsatzTV.Infrastructure.Sqlite.Migrations
                     b.Property<string>("ChapterTitle")
                         .HasColumnType("TEXT");
 
+                    b.Property<string>("CollectionEtag")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("CollectionKey")
+                        .HasColumnType("TEXT");
+
                     b.Property<string>("CustomTitle")
                         .HasColumnType("TEXT");
 

ErsatzTV.Infrastructure/Metadata/CollectionEtag.cs

@@ -0,0 +1,31 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Security.Cryptography;
+using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Interfaces.Metadata;
+using Microsoft.IO;
+
+namespace ErsatzTV.Infrastructure.Metadata;
+
+[SuppressMessage("Security", "CA5350:Do Not Use Weak Cryptographic Algorithms")]
+public class CollectionEtag : ICollectionEtag
+{
+    private readonly RecyclableMemoryStreamManager _recyclableMemoryStreamManager;
+
+    public CollectionEtag(RecyclableMemoryStreamManager recyclableMemoryStreamManager) =>
+        _recyclableMemoryStreamManager = recyclableMemoryStreamManager;
+
+    public string ForCollectionItems(List<MediaItem> items)
+    {
+        using MemoryStream ms = _recyclableMemoryStreamManager.GetStream();
+        using var bw = new BinaryWriter(ms);
+
+        foreach (MediaItem item in items.OrderBy(i => i.Id))
+        {
+            bw.Write(item.Id);
+        }
+
+        ms.Position = 0;
+        byte[] hash = SHA1.Create().ComputeHash(ms);
+        return BitConverter.ToString(hash).Replace("-", string.Empty);
+    }
+}

ErsatzTV/Startup.cs

@@ -602,6 +602,7 @@ public class Startup
         services.AddScoped<ILibraryRepository, LibraryRepository>();
         services.AddScoped<IMetadataRepository, MetadataRepository>();
         services.AddScoped<IArtworkRepository, ArtworkRepository>();
+        services.AddScoped<ICollectionEtag, CollectionEtag>();
         services.AddScoped<IFFmpegLocator, FFmpegLocator>();
         services.AddScoped<IFallbackMetadataProvider, FallbackMetadataProvider>();
         services.AddScoped<ILocalStatisticsProvider, LocalStatisticsProvider>();