Add linked suggestions with synced voting

Contracts/Dtos.cs

@@ -2,8 +2,9 @@ namespace GameList.Contracts;
 
 public record SetNameRequest(string Name);
 public record SuggestionRequest(string Name, string? Genre, string? Description, string? ScreenshotUrl, string? YoutubeUrl, string? GameUrl, int? MinPlayers, int? MaxPlayers);
-public record SuggestionDto(int Id, string Name, string? Genre, string? Description, string? ScreenshotUrl, string? YoutubeUrl, string? GameUrl, int? MinPlayers, int? MaxPlayers);
+public record SuggestionDto(int Id, string Name, string? Genre, string? Description, string? ScreenshotUrl, string? YoutubeUrl, string? GameUrl, int? MinPlayers, int? MaxPlayers, int? ParentSuggestionId = null, IReadOnlyList<int>? LinkedIds = null, IReadOnlyList<string>? LinkedTitles = null);
 public record VoteRequest(int SuggestionId, int Score);
 public record ResultsOpenRequest(bool ResultsOpen);
 public record VoteFinalizeRequest(bool Final);
 public record VoteStatusDto(Guid PlayerId, string Name, bool Finalized);
+public record LinkSuggestionsRequest(int SourceSuggestionId, int TargetSuggestionId);

Data/AppDbContext.cs

@@ -49,6 +49,11 @@ public class AppDbContext : DbContext
             builder.Property(s => s.GameUrl).HasMaxLength(2048);
             builder.Property(s => s.MinPlayers);
             builder.Property(s => s.MaxPlayers);
+            builder.HasOne(s => s.ParentSuggestion)
+                   .WithMany(p => p.LinkedSuggestions)
+                   .HasForeignKey(s => s.ParentSuggestionId)
+                   .OnDelete(DeleteBehavior.SetNull);
+            builder.HasIndex(s => s.ParentSuggestionId);
         });
 
         modelBuilder.Entity<Vote>(builder =>

Data/Migrations/20260205075456_AddSuggestionLinks.Designer.cs

@@ -0,0 +1,241 @@
+// <auto-generated />
+using System;
+using GameList.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace GameList.Data.Migrations
+{
+    [DbContext(typeof(AppDbContext))]
+    [Migration("20260205075456_AddSuggestionLinks")]
+    partial class AddSuggestionLinks
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "10.0.2");
+
+            modelBuilder.Entity("GameList.Domain.AppState", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<bool>("ResultsOpen")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("AppState");
+
+                    b.HasData(
+                        new
+                        {
+                            Id = 1,
+                            ResultsOpen = false,
+                            UpdatedAt = new DateTimeOffset(new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Unspecified), new TimeSpan(0, 0, 0, 0, 0))
+                        });
+                });
+
+            modelBuilder.Entity("GameList.Domain.Player", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("CurrentPhase")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(0);
+
+                    b.Property<string>("DisplayName")
+                        .HasMaxLength(16)
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("IsAdmin")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(false);
+
+                    b.Property<DateTimeOffset?>("LastLoginAt")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("NormalizedUsername")
+                        .IsRequired()
+                        .HasMaxLength(24)
+                        .HasColumnType("TEXT");
+
+                    b.Property<byte[]>("PasswordHash")
+                        .IsRequired()
+                        .HasColumnType("BLOB");
+
+                    b.Property<byte[]>("PasswordSalt")
+                        .IsRequired()
+                        .HasColumnType("BLOB");
+
+                    b.Property<string>("Username")
+                        .IsRequired()
+                        .HasMaxLength(24)
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("VotesFinal")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(false);
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("NormalizedUsername")
+                        .IsUnique();
+
+                    b.ToTable("Players");
+                });
+
+            modelBuilder.Entity("GameList.Domain.Suggestion", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Description")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("GameUrl")
+                        .HasMaxLength(2048)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Genre")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT");
+
+                    b.Property<int?>("MaxPlayers")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int?>("MinPlayers")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT");
+
+                    b.Property<int?>("ParentSuggestionId")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<Guid>("PlayerId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("ScreenshotUrl")
+                        .HasMaxLength(2048)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("YoutubeUrl")
+                        .HasMaxLength(2048)
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ParentSuggestionId");
+
+                    b.HasIndex("PlayerId");
+
+                    b.ToTable("Suggestions");
+                });
+
+            modelBuilder.Entity("GameList.Domain.Vote", b =>
+                {
+                    b.Property<int>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("TEXT");
+
+                    b.Property<Guid>("PlayerId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("Score")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("SuggestionId")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("SuggestionId");
+
+                    b.HasIndex("PlayerId", "SuggestionId")
+                        .IsUnique();
+
+                    b.ToTable("Votes");
+                });
+
+            modelBuilder.Entity("GameList.Domain.Suggestion", b =>
+                {
+                    b.HasOne("GameList.Domain.Suggestion", "ParentSuggestion")
+                        .WithMany("LinkedSuggestions")
+                        .HasForeignKey("ParentSuggestionId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("GameList.Domain.Player", "Player")
+                        .WithMany("Suggestions")
+                        .HasForeignKey("PlayerId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("ParentSuggestion");
+
+                    b.Navigation("Player");
+                });
+
+            modelBuilder.Entity("GameList.Domain.Vote", b =>
+                {
+                    b.HasOne("GameList.Domain.Player", "Player")
+                        .WithMany("Votes")
+                        .HasForeignKey("PlayerId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("GameList.Domain.Suggestion", "Suggestion")
+                        .WithMany("Votes")
+                        .HasForeignKey("SuggestionId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Player");
+
+                    b.Navigation("Suggestion");
+                });
+
+            modelBuilder.Entity("GameList.Domain.Player", b =>
+                {
+                    b.Navigation("Suggestions");
+
+                    b.Navigation("Votes");
+                });
+
+            modelBuilder.Entity("GameList.Domain.Suggestion", b =>
+                {
+                    b.Navigation("LinkedSuggestions");
+
+                    b.Navigation("Votes");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

Data/Migrations/20260205075456_AddSuggestionLinks.cs

@@ -0,0 +1,49 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace GameList.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddSuggestionLinks : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<int>(
+                name: "ParentSuggestionId",
+                table: "Suggestions",
+                type: "INTEGER",
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Suggestions_ParentSuggestionId",
+                table: "Suggestions",
+                column: "ParentSuggestionId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Suggestions_Suggestions_ParentSuggestionId",
+                table: "Suggestions",
+                column: "ParentSuggestionId",
+                principalTable: "Suggestions",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.SetNull);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Suggestions_Suggestions_ParentSuggestionId",
+                table: "Suggestions");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Suggestions_ParentSuggestionId",
+                table: "Suggestions");
+
+            migrationBuilder.DropColumn(
+                name: "ParentSuggestionId",
+                table: "Suggestions");
+        }
+    }
+}

Data/Migrations/AppDbContextModelSnapshot.cs

@@ -131,6 +131,9 @@ namespace GameList.Data.Migrations
                         .HasMaxLength(100)
                         .HasColumnType("TEXT");
 
+                    b.Property<int?>("ParentSuggestionId")
+                        .HasColumnType("INTEGER");
+
                     b.Property<Guid>("PlayerId")
                         .HasColumnType("TEXT");
 
@@ -144,6 +147,8 @@ namespace GameList.Data.Migrations
 
                     b.HasKey("Id");
 
+                    b.HasIndex("ParentSuggestionId");
+
                     b.HasIndex("PlayerId");
 
                     b.ToTable("Suggestions");
@@ -179,12 +184,19 @@ namespace GameList.Data.Migrations
 
             modelBuilder.Entity("GameList.Domain.Suggestion", b =>
                 {
+                    b.HasOne("GameList.Domain.Suggestion", "ParentSuggestion")
+                        .WithMany("LinkedSuggestions")
+                        .HasForeignKey("ParentSuggestionId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
                     b.HasOne("GameList.Domain.Player", "Player")
                         .WithMany("Suggestions")
                         .HasForeignKey("PlayerId")
                         .OnDelete(DeleteBehavior.Cascade)
                         .IsRequired();
 
+                    b.Navigation("ParentSuggestion");
+
                     b.Navigation("Player");
                 });
 
@@ -216,6 +228,8 @@ namespace GameList.Data.Migrations
 
             modelBuilder.Entity("GameList.Domain.Suggestion", b =>
                 {
+                    b.Navigation("LinkedSuggestions");
+
                     b.Navigation("Votes");
                 });
 #pragma warning restore 612, 618

Domain/Suggestion.cs

@@ -34,5 +34,9 @@ public class Suggestion
 
     public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
 
+    public int? ParentSuggestionId { get; set; }
+    public Suggestion? ParentSuggestion { get; set; }
+    public ICollection<Suggestion> LinkedSuggestions { get; set; } = new List<Suggestion>();
+
     public ICollection<Vote> Votes { get; set; } = new List<Vote>();
 }

Endpoints/AdminEndpoints.cs

@@ -3,6 +3,7 @@ using GameList.Domain;
 using GameList.Contracts;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
+using System.Collections.Generic;
 
 namespace GameList.Endpoints;
 
@@ -51,6 +52,78 @@ public static class AdminEndpoints
             return Results.Ok(new { voters, ready, waiting });
         });
 
+        admin.MapPost("/link-suggestions", async ([FromBody] LinkSuggestionsRequest request, HttpContext ctx, AppDbContext db, IConfiguration config) =>
+        {
+            var player = await EndpointHelpers.GetAuthenticatedPlayer(ctx, db);
+            if (player is null || !await EndpointHelpers.IsAdmin(ctx, db, config)) return Results.Unauthorized();
+
+            var phase = await EndpointHelpers.GetPhase(db, player.Id);
+            if (phase != Phase.Vote)
+                return EndpointHelpers.PhaseMismatch(Phase.Vote, phase);
+
+            if (request.SourceSuggestionId == request.TargetSuggestionId)
+                return Results.BadRequest(new { error = "Pick two different games to link." });
+
+            var suggestions = await db.Suggestions.ToListAsync();
+            var source = suggestions.FirstOrDefault(s => s.Id == request.SourceSuggestionId);
+            var target = suggestions.FirstOrDefault(s => s.Id == request.TargetSuggestionId);
+            if (source is null || target is null)
+                return Results.NotFound(new { error = "Suggestion not found." });
+
+            var rootIndex = EndpointHelpers.BuildLinkRoots(suggestions.Select(s => (s.Id, s.ParentSuggestionId)));
+            if (!rootIndex.TryGetValue(source.Id, out var sourceRoot) || !rootIndex.TryGetValue(target.Id, out var targetRoot))
+                return Results.NotFound(new { error = "Suggestion not found." });
+
+            if (sourceRoot == targetRoot)
+                return Results.BadRequest(new { error = "These games are already linked." });
+
+            var affectedRootIds = new HashSet<int> { sourceRoot, targetRoot };
+            var affectedIds = rootIndex
+                .Where(kv => affectedRootIds.Contains(kv.Value))
+                .Select(kv => kv.Key)
+                .ToList();
+
+            await using var tx = await db.Database.BeginTransactionAsync();
+
+            foreach (var suggestion in suggestions)
+            {
+                var root = rootIndex.GetValueOrDefault(suggestion.Id);
+                if (root == targetRoot)
+                {
+                    suggestion.ParentSuggestionId = suggestion.Id == targetRoot ? null : targetRoot;
+                }
+                else if (root == sourceRoot)
+                {
+                    suggestion.ParentSuggestionId = targetRoot;
+                }
+            }
+
+            await db.SaveChangesAsync();
+
+            var affectedPlayerIds = await db.Votes
+                .Where(v => affectedIds.Contains(v.SuggestionId))
+                .Select(v => v.PlayerId)
+                .Distinct()
+                .ToListAsync();
+
+            await db.Votes.Where(v => affectedIds.Contains(v.SuggestionId)).ExecuteDeleteAsync();
+
+            if (affectedPlayerIds.Count > 0)
+            {
+                await db.Players.Where(p => affectedPlayerIds.Contains(p.Id))
+                    .ExecuteUpdateAsync(p => p.SetProperty(x => x.VotesFinal, false));
+            }
+
+            await tx.CommitAsync();
+
+            return Results.Ok(new
+            {
+                RootId = targetRoot,
+                LinkedSuggestionIds = affectedIds,
+                UnfinalizedPlayers = affectedPlayerIds.Count
+            });
+        });
+
         admin.MapPost("/reset", async (HttpContext ctx, AppDbContext db, IConfiguration config) =>
         {
             if (!await EndpointHelpers.IsAdmin(ctx, db, config)) return Results.Unauthorized();

Endpoints/EndpointHelpers.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using GameList.Data;
 using GameList.Domain;
 using Microsoft.AspNetCore.Mvc;
@@ -163,4 +164,35 @@ internal static class EndpointHelpers
         ResultsOpen = false,
         UpdatedAt = DateTimeOffset.UnixEpoch
     };
+
+    public static Dictionary<int, int> BuildLinkRoots(IEnumerable<(int Id, int? ParentId)> items)
+    {
+        var parentMap = items.ToDictionary(x => x.Id, x => x.ParentId);
+        var roots = new Dictionary<int, int>();
+        foreach (var id in parentMap.Keys)
+        {
+            roots[id] = FindRootId(id, parentMap);
+        }
+        return roots;
+    }
+
+    public static int FindRootId(int suggestionId, IReadOnlyDictionary<int, int?> parentMap)
+    {
+        var current = suggestionId;
+        var visited = new HashSet<int>();
+
+        while (parentMap.TryGetValue(current, out var parent) && parent is int p && !visited.Contains(p))
+        {
+            visited.Add(current);
+            current = p;
+        }
+
+        return current;
+    }
+
+    public static List<int> LinkedIdsFor(int suggestionId, IReadOnlyDictionary<int, int> rootIndex)
+    {
+        if (!rootIndex.TryGetValue(suggestionId, out var root)) return new();
+        return rootIndex.Where(kv => kv.Value == root).Select(kv => kv.Key).ToList();
+    }
 }

Endpoints/ResultsEndpoints.cs

@@ -46,11 +46,47 @@ public static class ResultsEndpoints
                         s.GameUrl,
                         s.Description,
                         s.Genre,
+                        s.ParentSuggestionId
                     })
                     .OrderByDescending(r => r.Average)
                     .ToListAsync();
 
-                return Results.Ok(results);
+                var rootIndex = EndpointHelpers.BuildLinkRoots(results.Select(r => (r.Id, r.ParentSuggestionId)));
+                var nameLookup = results.ToDictionary(r => r.Id, r => r.Name);
+
+                var shaped = results.Select(r =>
+                {
+                    var linkedIds = EndpointHelpers.LinkedIdsFor(r.Id, rootIndex)
+                        .Where(id => id != r.Id)
+                        .ToList();
+
+                    return new
+                    {
+                        r.Id,
+                        r.Name,
+                        r.Author,
+                        r.MinPlayers,
+                        r.MaxPlayers,
+                        r.Total,
+                        r.Count,
+                        r.Average,
+                        r.Votes,
+                        r.MyVote,
+                        r.ScreenshotUrl,
+                        r.YoutubeUrl,
+                        r.GameUrl,
+                        r.Description,
+                        r.Genre,
+                        r.ParentSuggestionId,
+                        LinkedIds = linkedIds,
+                        LinkedTitles = linkedIds
+                            .Where(id => nameLookup.ContainsKey(id))
+                            .Select(id => nameLookup[id])
+                            .ToList()
+                    };
+                });
+
+                return Results.Ok(shaped);
             }
         );
     }

Endpoints/SuggestEndpoints.cs

@@ -28,13 +28,14 @@ public static class SuggestEndpoints
                     s.GameUrl,
                     s.CreatedAt,
                     s.MinPlayers,
-                    s.MaxPlayers
+                    s.MaxPlayers,
+                    s.ParentSuggestionId
                 })
                 .ToListAsync();
 
             var ordered = mine
                 .OrderBy(s => s.CreatedAt)
-                .Select(s => new SuggestionDto(s.Id, s.Name, s.Genre, s.Description, s.ScreenshotUrl, s.YoutubeUrl, s.GameUrl, s.MinPlayers, s.MaxPlayers));
+                .Select(s => new SuggestionDto(s.Id, s.Name, s.Genre, s.Description, s.ScreenshotUrl, s.YoutubeUrl, s.GameUrl, s.MinPlayers, s.MaxPlayers, s.ParentSuggestionId));
 
             return Results.Ok(ordered);
         });
@@ -206,13 +207,23 @@ public static class SuggestEndpoints
                     s.MinPlayers,
                     s.MaxPlayers,
                     Author = s.Player!.DisplayName,
-                    s.CreatedAt
+                    s.CreatedAt,
+                    s.ParentSuggestionId
                 })
                 .ToListAsync();
 
+            var rootIndex = EndpointHelpers.BuildLinkRoots(all.Select(s => (s.Id, s.ParentSuggestionId)));
+            var nameLookup = all.ToDictionary(s => s.Id, s => s.Name);
+
             var ordered = all
                 .OrderBy(s => s.CreatedAt)
-                .Select(s => new
+                .Select(s =>
+                {
+                    var linkedIds = EndpointHelpers.LinkedIdsFor(s.Id, rootIndex)
+                        .Where(id => id != s.Id)
+                        .ToList();
+
+                    return new
                     {
                         s.Id,
                         s.PlayerId,
@@ -224,7 +235,14 @@ public static class SuggestEndpoints
                         s.GameUrl,
                         s.MinPlayers,
                         s.MaxPlayers,
-                    s.Author
+                        s.Author,
+                        s.ParentSuggestionId,
+                        LinkedIds = linkedIds,
+                        LinkedTitles = linkedIds
+                            .Where(id => nameLookup.ContainsKey(id))
+                            .Select(id => nameLookup[id])
+                            .ToList()
+                    };
                 });
 
             return Results.Ok(ordered);

Endpoints/VoteEndpoints.cs

@@ -41,28 +41,40 @@ public static class VoteEndpoints
             if (string.IsNullOrWhiteSpace(player.DisplayName))
                 return Results.BadRequest(new { error = "Set a display name before voting." });
 
-            var suggestionExists = await db.Suggestions.AnyAsync(s => s.Id == request.SuggestionId);
+            var linkMap = await db.Suggestions.AsNoTracking()
-            if (!suggestionExists)
+                .Select(s => new { s.Id, s.ParentSuggestionId })
+                .ToListAsync();
+            var rootIndex = EndpointHelpers.BuildLinkRoots(linkMap.Select(s => (s.Id, s.ParentSuggestionId)));
+            if (!rootIndex.ContainsKey(request.SuggestionId))
                 return Results.BadRequest(new { error = "Suggestion not found." });
+            var linkedIds = EndpointHelpers.LinkedIdsFor(request.SuggestionId, rootIndex);
+            if (linkedIds.Count == 0)
+                linkedIds.Add(request.SuggestionId);
 
-            var vote = await db.Votes.FirstOrDefaultAsync(v => v.PlayerId == player.Id && v.SuggestionId == request.SuggestionId);
+            var existingVotes = await db.Votes
+                .Where(v => v.PlayerId == player.Id && linkedIds.Contains(v.SuggestionId))
+                .ToListAsync();
+
+            foreach (var suggestionId in linkedIds)
+            {
+                var vote = existingVotes.FirstOrDefault(v => v.SuggestionId == suggestionId);
                 if (vote == null)
                 {
-                vote = new Vote
+                    db.Votes.Add(new Vote
                     {
                         PlayerId = player.Id,
-                    SuggestionId = request.SuggestionId,
+                        SuggestionId = suggestionId,
                         Score = request.Score
-                };
+                    });
-                db.Votes.Add(vote);
                 }
                 else
                 {
                     vote.Score = request.Score;
                 }
+            }
 
             await db.SaveChangesAsync();
-            return Results.Ok(new { vote.Id, vote.Score });
+            return Results.Ok(new { SuggestionIds = linkedIds, request.Score });
         });
 
         app.MapPost("/api/votes/finalize", async ([FromBody] VoteFinalizeRequest request, HttpContext ctx, AppDbContext db) =>

wwwroot/app.js

@@ -177,6 +177,24 @@ function setupHandlers() {
       }
     });
   }
+
+  const linkApply = $("link-apply");
+  if (linkApply) {
+    linkApply.addEventListener("click", async () => {
+      const source = Number($("link-source")?.value);
+      const target = Number($("link-target")?.value);
+      if (!source || !target || source === target) {
+        return toast(t("admin.linkValidation"), true);
+      }
+      try {
+        await adminApi.linkSuggestions(source, target);
+        toast(t("admin.linkDone"));
+        await refreshPhaseData();
+      } catch (err) {
+        toast(err.message, true);
+      }
+    });
+  }
 }
 
 async function adminAction(fn, successMessage) {

wwwroot/css/admin.css

@@ -29,3 +29,11 @@
     justify-content: space-between;
     align-items: center;
 }
+
+#admin-linker select {
+    width: 100%;
+    padding: 8px;
+    border-radius: 8px;
+    border: 1px solid #e3d4bd;
+    background: #fffaf3;
+}

wwwroot/css/components.css

@@ -99,6 +99,11 @@ button .chip {
     width: 30px;
     font-size: 18px;
 }
+.chip.link-chip {
+    background: #d7e7ff;
+    border: 1px solid #b9d1ff;
+    color: #1b3d75;
+}
 .chip.danger-chip {
     background: #e0564f;
     border: 1px solid #c54740;

wwwroot/index.html

@@ -151,6 +151,19 @@
       <input type="checkbox" id="results-open" />
       <span data-i18n="admin.resultsOpenToggle">Allow results phase</span>
     </label>
+    <div class="stack hidden" id="admin-linker">
+      <h4 data-i18n="admin.linkTitle">Link games</h4>
+      <p class="muted small" data-i18n="admin.linkHint">Use during voting to merge duplicates. Linking clears votes and unfinalizes voters.</p>
+      <label class="stack">
+        <span class="label" data-i18n="admin.linkSource">Game to link</span>
+        <select id="link-source"></select>
+      </label>
+      <label class="stack">
+        <span class="label" data-i18n="admin.linkTarget">Link to (parent)</span>
+        <select id="link-target"></select>
+      </label>
+      <button id="link-apply" class="secondary" type="button" data-i18n="admin.linkAction">Link & clear votes</button>
+    </div>
     <div class="stack horizontal">
       <button id="reset" class="danger" data-i18n="admin.reset">Reset (keep players)</button>
       <button id="factory-reset" class="danger" data-i18n="admin.factoryReset">Factory reset</button>

wwwroot/js/api.js

@@ -56,4 +56,6 @@ export const adminApi = {
   voteStatus: () => request("/api/admin/vote-status"),
   reset: () => request("/api/admin/reset", { method: "POST" }),
   factoryReset: () => request("/api/admin/factory-reset", { method: "POST" }),
+  linkSuggestions: (sourceSuggestionId, targetSuggestionId) =>
+    request("/api/admin/link-suggestions", { method: "POST", body: { sourceSuggestionId, targetSuggestionId } }),
 };

wwwroot/js/data.js

@@ -91,6 +91,7 @@ export function signatureSuggestions(list) {
             s.gameUrl,
             s.minPlayers,
             s.maxPlayers,
+            s.parentSuggestionId,
         ]),
     );
 }

wwwroot/js/i18n.js

@@ -75,6 +75,8 @@ const translations = {
     "card.site": "Site ↗",
     "card.youtube": "YouTube ↗",
     "card.openScreenshot": "Open screenshot",
+    "card.linked": "Votes linked",
+    "card.linkedWith": "Linked with: {names}",
 
     "vote.saved": "Saved vote",
     "vote.missing": "Missing",
@@ -107,6 +109,15 @@ const translations = {
     "admin.factoryResetDone": "Factory reset complete",
     "admin.readyForResults": "Ready for results",
     "admin.waitingForPlayers": "Waiting for players: {names}",
+    "admin.linkTitle": "Link games",
+    "admin.linkHint": "Use during voting to merge duplicates. Linking clears votes and unfinalizes voters.",
+    "admin.linkSource": "Game to link",
+    "admin.linkTarget": "Link to (parent)",
+    "admin.linkAction": "Link & clear votes",
+    "admin.linkSourcePlaceholder": "Select game A",
+    "admin.linkTargetPlaceholder": "Select game B (parent)",
+    "admin.linkValidation": "Choose two different games to link.",
+    "admin.linkDone": "Games linked. Votes cleared.",
 
     "toast.unexpected": "Unexpected error",
     "toast.registered": "Registered",
@@ -204,6 +215,8 @@ const translations = {
     "card.site": "Webseite ↗",
     "card.youtube": "YouTube ↗",
     "card.openScreenshot": "Screenshot öffnen",
+    "card.linked": "Verknüpfte Stimmen",
+    "card.linkedWith": "Verknüpft mit: {names}",
 
     "vote.saved": "Stimme gespeichert",
     "vote.missing": "Fehlt",
@@ -236,6 +249,15 @@ const translations = {
     "admin.factoryResetDone": "Werkseinstellung abgeschlossen",
     "admin.readyForResults": "Bereit für Ergebnisse",
     "admin.waitingForPlayers": "Warten auf: {names}",
+    "admin.linkTitle": "Spiele verknüpfen",
+    "admin.linkHint": "Nutze dies in der Bewertungsphase, um Duplikate zu verbinden. Das löscht die Stimmen der verknüpften Spiele und hebt Finalisierungen auf.",
+    "admin.linkSource": "Spiel verknüpfen",
+    "admin.linkTarget": "Verknüpfen mit (Eltern)",
+    "admin.linkAction": "Verknüpfen & Stimmen löschen",
+    "admin.linkSourcePlaceholder": "Spiel A wählen",
+    "admin.linkTargetPlaceholder": "Spiel B (Eltern) wählen",
+    "admin.linkValidation": "Wähle zwei verschiedene Spiele aus.",
+    "admin.linkDone": "Spiele verknüpft. Stimmen gelöscht.",
 
     "toast.unexpected": "Unerwarteter Fehler",
     "toast.registered": "Registriert",

wwwroot/js/ui.js

@@ -115,6 +115,7 @@ export function renderMySuggestions() {
 }
 
 export function renderAllSuggestions() {
+    renderAdminLinker();
     const list = $("all-suggestions");
     if (!list) return;
     list.innerHTML = "";
@@ -147,12 +148,14 @@ export function renderVotes() {
         const current = hasVote ? votesMap[s.id] : 5; // start neutral when no prior vote
         const displayScore = hasVote ? current : "—";
         const displayEmoji = hasVote ? scoreToEmoji(current) : "⚠️";
+        const linkedIds = linkedPeerIds(s);
+        const rootId = linkRootId(s);
         const footer = document.createElement("div");
         footer.className = "vote-controls";
         footer.innerHTML = `
       <div class="warning-text ${hasVote ? "hidden" : ""}" id="warn-${s.id}">${state.votesFinal ? t("vote.missingFinalWarn") : t("vote.missingWarn")}</div>
       <div class="vote-row">
-        <input class="full-slider" type="range" min="0" max="10" value="${current}" data-id="${s.id}" ${state.votesFinal ? "disabled" : ""}>
+        <input class="full-slider" type="range" min="0" max="10" value="${current}" data-id="${s.id}" data-root="${rootId}" data-linked="${linkedIds.join(",")}" ${state.votesFinal ? "disabled" : ""}>
         <span class="score" id="score-${s.id}">${displayScore}</span>
         <span class="score-emoji" id="emoji-${s.id}">${displayEmoji}</span>
       </div>`;
@@ -169,6 +172,7 @@ export function renderVotes() {
             if (emojiEl) emojiEl.textContent = scoreToEmoji(val);
             const warn = $("warn-" + e.target.dataset.id);
             if (warn) warn.classList.add("hidden");
+            syncLinkedSliders(e.target, val);
         });
         input.addEventListener("change", async (e) => {
             if (state.votesFinal) return;
@@ -244,7 +248,7 @@ export function renderResults() {
       <td class="game-cell">
          ${r.screenshotUrl ? `<img class="thumb clickable-thumb" src="${r.screenshotUrl}" alt="${r.name}">` : ''}
          <div class="game-meta">
-           <div class="title-line">${r.name}</div>
+           <div class="title-line">${r.name} ${renderLinkBadge(r)}</div>
            ${buildResultMeta(r)}
          </div>
       </td>
@@ -296,6 +300,14 @@ export function buildCard(
     const card = document.createElement("article");
     card.className = "game-card";
     const hasImage = !!s.screenshotUrl;
+    const linkedTitles = linkedPeerTitles(s);
+    const linked = isLinked(s);
+    const linkTooltip = linked
+        ? linkedTitles.length > 0
+            ? t("card.linkedWith", { names: linkedTitles.join(", ") })
+            : t("card.linked")
+        : "";
+    const linkChip = linked ? `<span class="chip icon link-chip" title="${linkTooltip}">🔗</span>` : "";
     const visual = hasImage
         ? `<button class="card-visual" data-img="${s.screenshotUrl}" aria-label="${t("card.openScreenshot")}" style="background-image:url('${s.screenshotUrl}')"></button>`
         : `<div class="card-visual"></div>`;
@@ -320,6 +332,7 @@ export function buildCard(
       <div class="card-title-row">
         <h3 class="card-title" title="${s.name}">${s.name}</h3>
         <div class="title-meta">
+          ${linkChip}
           ${showAuthor && s.author ? `<span class="chip">${s.author}</span>` : ""}
           ${allowEdit ? `<button class="chip icon" data-edit="${s.id}" type="button" title="${t("card.edit")}">✏️</button>` : ""}
           ${allowDelete ? `<button class="chip icon danger-chip" data-delete="${s.id}" type="button" title="${t("card.delete")}">✕</button>` : ""}
@@ -681,6 +694,63 @@ function renderAdminVoteStatus() {
     status.className = ready ? "badge" : "badge warning";
 }
 
+function renderAdminLinker() {
+    const wrap = $("admin-linker");
+    const source = $("link-source");
+    const target = $("link-target");
+    if (!wrap || !source || !target) return;
+
+    const visible = state.me?.isAdmin && state.phase === "Vote";
+    wrap.classList.toggle("hidden", !visible);
+    if (!visible) return;
+
+    const previousSource = source.value;
+    const previousTarget = target.value;
+
+    const options = (state.allSuggestions ?? []).slice().sort((a, b) => a.name.localeCompare(b.name));
+
+    const fillSelect = (select, placeholderKey) => {
+        select.innerHTML = "";
+        const placeholder = document.createElement("option");
+        placeholder.value = "";
+        placeholder.textContent = t(placeholderKey);
+        placeholder.disabled = true;
+        placeholder.selected = true;
+        select.appendChild(placeholder);
+
+        options.forEach((s) => {
+            const opt = document.createElement("option");
+            opt.value = s.id;
+            opt.textContent = buildLinkOptionLabel(s);
+            opt.dataset.root = linkRootId(s);
+            select.appendChild(opt);
+        });
+    };
+
+    fillSelect(source, "admin.linkSourcePlaceholder");
+    fillSelect(target, "admin.linkTargetPlaceholder");
+
+    if (previousSource && options.some((s) => String(s.id) === previousSource)) source.value = previousSource;
+    if (previousTarget && options.some((s) => String(s.id) === previousTarget)) target.value = previousTarget;
+
+    const preventSameSelection = () => {
+        const sourceVal = source.value;
+        const targetVal = target.value;
+        Array.from(target.options).forEach((opt) => {
+            if (!opt.value) return;
+            opt.disabled = opt.value === sourceVal;
+        });
+        Array.from(source.options).forEach((opt) => {
+            if (!opt.value) return;
+            opt.disabled = opt.value === targetVal;
+        });
+    };
+
+    source.onchange = preventSameSelection;
+    target.onchange = preventSameSelection;
+    preventSameSelection();
+}
+
 function openDeleteConfirmModal(s) {
     const overlay = document.createElement("div");
     overlay.className = "edit-modal";
@@ -754,6 +824,72 @@ function isValidImageUrl(url) {
     }
 }
 
+function linkRootId(s) {
+    return s?.parentSuggestionId ?? s?.id;
+}
+
+function linkedPeerIds(s) {
+    if (!s) return [];
+    if (Array.isArray(s.linkedIds) && s.linkedIds.length > 0) {
+        return s.linkedIds.filter((id) => id !== s.id);
+    }
+    if (!state.allSuggestions?.length) return [];
+    const root = linkRootId(s);
+    return state.allSuggestions
+        .filter((other) => linkRootId(other) === root && other.id !== s.id)
+        .map((other) => other.id);
+}
+
+function linkedPeerTitles(s) {
+    if (!s) return [];
+    if (Array.isArray(s.linkedTitles) && s.linkedTitles.length > 0) {
+        return s.linkedTitles;
+    }
+    if (!state.allSuggestions?.length) return [];
+    const root = linkRootId(s);
+    return state.allSuggestions
+        .filter((other) => linkRootId(other) === root && other.id !== s.id)
+        .map((other) => other.name);
+}
+
+function isLinked(s) {
+    return !!s?.parentSuggestionId || linkedPeerIds(s).length > 0;
+}
+
+function linkTooltip(s) {
+    const peers = linkedPeerTitles(s);
+    if (peers.length === 0) return t("card.linked");
+    return t("card.linkedWith", { names: peers.join(", ") });
+}
+
+function renderLinkBadge(s) {
+    if (!isLinked(s)) return "";
+    return `<span class="chip icon link-chip" title="${linkTooltip(s)}">🔗</span>`;
+}
+
+function buildLinkOptionLabel(s) {
+    const author = s.author ? ` — ${s.author}` : "";
+    const linked = isLinked(s) ? " 🔗" : "";
+    return `${s.name}${author}${linked}`;
+}
+
+function syncLinkedSliders(sourceEl, value) {
+    const linkedAttr = sourceEl?.dataset?.linked;
+    if (!linkedAttr) return;
+    const ids = linkedAttr.split(",").filter(Boolean);
+    ids.forEach((id) => {
+        const slider = document.querySelector(`input[type=range][data-id="${id}"]`);
+        if (!slider || slider === sourceEl) return;
+        slider.value = value;
+        const scoreLabel = $("score-" + id);
+        if (scoreLabel) scoreLabel.textContent = value;
+        const emojiEl = $("emoji-" + id);
+        if (emojiEl) emojiEl.textContent = scoreToEmoji(Number(value));
+        const warn = $("warn-" + id);
+        if (warn) warn.classList.add("hidden");
+    });
+}
+
 export function updatePhaseNav() {
     const isAdmin = !!state.me?.isAdmin;
     const phase = state.phase;
@@ -791,6 +927,7 @@ export function updatePhaseNav() {
     }
 
     renderAdminVoteStatus();
+    renderAdminLinker();
 
     // Toggle admin-only back buttons
     const backButtons = ["nav-vote-prev"];