Fix empty merchant NPCs (Christine, Julia, Moss)

src/Persistence/Initialization/Updates/AddMissingMerchantStoresPlugIn.cs

@@ -0,0 +1,86 @@
+// <copyright file="AddMissingMerchantStoresPlugIn.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.Persistence.Initialization.Updates;
+
+using System.Runtime.InteropServices;
+using MUnique.OpenMU.DataModel.Configuration;
+using MUnique.OpenMU.PlugIns;
+
+/// <summary>
+/// This update gives a merchant store to the NPCs which have a merchant window
+/// but no items assigned, so talking to them opens an empty (non-working) shop.
+/// </summary>
+/// <remarks>
+/// Affected NPCs: Christine the General Goods Merchant (545) and Market Union Member Julia (547)
+/// in the Loren Market, and Moss The Merchant (492) in Elvenland. Each one is given a clone of
+/// the general-goods (potion girl) store carried by Thompson the Merchant (231).
+/// </remarks>
+[PlugIn]
+[Display(Name = PlugInName, Description = PlugInDescription)]
+[Guid("f78d6e1d-1cb5-45f7-912d-54b2cb1220eb")]
+public class AddMissingMerchantStoresPlugIn : UpdatePlugInBase
+{
+    /// <summary>
+    /// The plug in name.
+    /// </summary>
+    internal const string PlugInName = "Add missing merchant stores";
+
+    /// <summary>
+    /// The plug in description.
+    /// </summary>
+    internal const string PlugInDescription = "Gives a general-goods store to merchant NPCs which had a shop window but no items (Christine 545, Julia 547, Moss 492), cloned from Thompson the Merchant (231).";
+
+    /// <summary>
+    /// The number of the NPC whose store is cloned for the empty merchants.
+    /// </summary>
+    private const short StoreSourceNpcNumber = 231; // Thompson the Merchant - carries the general-goods (potion girl) store
+
+    /// <summary>
+    /// The numbers of the NPCs which have a merchant window but no store.
+    /// </summary>
+    private static readonly short[] EmptyMerchantNpcNumbers = [545, 547, 492];
+
+    /// <inheritdoc />
+    public override UpdateVersion Version => UpdateVersion.AddMissingMerchantStores;
+
+    /// <inheritdoc />
+    public override string DataInitializationKey => VersionSeasonSix.DataInitialization.Id;
+
+    /// <inheritdoc />
+    public override string Name => PlugInName;
+
+    /// <inheritdoc />
+    public override string Description => PlugInDescription;
+
+    /// <inheritdoc />
+    public override bool IsMandatory => false;
+
+    /// <inheritdoc />
+    public override DateTime CreatedAt => new(2026, 06, 17, 0, 0, 0, DateTimeKind.Utc);
+
+    /// <inheritdoc />
+    protected override ValueTask ApplyAsync(IContext context, GameConfiguration gameConfiguration)
+    {
+        var storeSource = gameConfiguration.Monsters.FirstOrDefault(m => m.Number == StoreSourceNpcNumber);
+        if (storeSource?.MerchantStore is null)
+        {
+            return default;
+        }
+
+        foreach (var number in EmptyMerchantNpcNumbers)
+        {
+            var npc = gameConfiguration.Monsters.FirstOrDefault(m => m.Number == number);
+            if (npc is null || npc.MerchantStore is not null)
+            {
+                continue;
+            }
+
+            npc.MerchantStore = storeSource.MerchantStore.Clone(gameConfiguration);
+            npc.MerchantStore.SetGuid(npc.Number);
+        }
+
+        return default;
+    }
+}

src/Persistence/Initialization/Updates/UpdateVersion.cs

@@ -422,4 +422,9 @@ public enum UpdateVersion
     /// The version of the <see cref="AddRandomExperienceConfigAttributesPlugInSeason6"/>.
     /// </summary>
     AddRandomExperienceConfigAttributesSeason6 = 83,
+
+    /// <summary>
+    /// The version of the <see cref="AddMissingMerchantStoresPlugIn"/>.
+    /// </summary>
+    AddMissingMerchantStores = 84,
 }