From bfb987c7584946183f97c136617af2d15583fbb2 Mon Sep 17 00:00:00 2001
From: Kamron Batman <3953314+kamronbatman@users.noreply.github.com>
Date: Mon, 5 Dec 2022 20:16:31 -0800
Subject: [PATCH] fix: Fixes client crash while selling items to NPC (#1296)

---
 .../Network/Packets/Outgoing/VendorSellPacketTests.cs  |  5 +++--
 Projects/Server/Mobiles/BaseVendor.cs                  |  8 ++++++++
 .../Network/Packets/OutgoingVendorSellPackets.cs       | 10 ++++------
 Projects/UOContent/Mobiles/Vendors/BaseVendor.cs       |  8 ++++----
 4 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/Projects/Server.Tests/Tests/Network/Packets/Outgoing/VendorSellPacketTests.cs b/Projects/Server.Tests/Tests/Network/Packets/Outgoing/VendorSellPacketTests.cs
index 4c9e9aff1..89aee42a7 100644
--- a/Projects/Server.Tests/Tests/Network/Packets/Outgoing/VendorSellPacketTests.cs
+++ b/Projects/Server.Tests/Tests/Network/Packets/Outgoing/VendorSellPacketTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Server.Network;
 using Xunit;
 
@@ -18,14 +19,14 @@ namespace Server.Tests.Network
             var item2 = new Item(World.NewItem) { Name = "Second Item" };
             var item3 = new Item(World.NewItem);
 
-            var sellStates = new List<SellItemState>
+            var sellStates = new HashSet<SellItemState>
             {
                 new(item1, 100, "Item 1"),
                 new(item2, 100000, "Item 2"),
                 new(item3, 1, "Item 3")
             };
 
-            var expected = new VendorSellList(vendor, sellStates).Compile();
+            var expected = new VendorSellList(vendor, sellStates.ToList()).Compile();
 
             var ns = PacketTestUtilities.CreateTestNetState();
             ns.SendVendorSellList(vendor.Serial, sellStates);
diff --git a/Projects/Server/Mobiles/BaseVendor.cs b/Projects/Server/Mobiles/BaseVendor.cs
index fe6230d65..7e28ea765 100644
--- a/Projects/Server/Mobiles/BaseVendor.cs
+++ b/Projects/Server/Mobiles/BaseVendor.cs
@@ -51,6 +51,14 @@ public class SellItemResponse
     public int Amount { get; }
 }
 
+public class SellItemStateComparer : IEqualityComparer<SellItemState>
+{
+    public bool Equals(SellItemState l, SellItemState r) =>
+        l == null && r == null || l != null && r != null && l.Item == r.Item;
+
+    public int GetHashCode(SellItemState obj) => obj.Item.GetHashCode();
+}
+
 public class SellItemState
 {
     public SellItemState(Item item, int price, string name)
diff --git a/Projects/Server/Network/Packets/OutgoingVendorSellPackets.cs b/Projects/Server/Network/Packets/OutgoingVendorSellPackets.cs
index 116734bf1..b76485efc 100644
--- a/Projects/Server/Network/Packets/OutgoingVendorSellPackets.cs
+++ b/Projects/Server/Network/Packets/OutgoingVendorSellPackets.cs
@@ -22,7 +22,7 @@ namespace Server.Network;
 
 public static class OutgoingVendorSellPackets
 {
-    public static void SendVendorSellList(this NetState ns, Serial vendor, List<SellItemState> list)
+    public static void SendVendorSellList(this NetState ns, Serial vendor, HashSet<SellItemState> set)
     {
         if (ns.CannotSendPackets())
         {
@@ -30,9 +30,8 @@ public static class OutgoingVendorSellPackets
         }
 
         var maxLength = 9;
-        for (int i = 0; i < list.Count; i++)
+        foreach (var sis in set)
         {
-            var sis = list[i];
             var item = sis.Item;
             maxLength += 14 + Math.Max(item.Name?.Length ?? 0, sis.Name?.Length ?? 0);
         }
@@ -42,11 +41,10 @@ public static class OutgoingVendorSellPackets
         writer.Seek(2, SeekOrigin.Current);
 
         writer.Write(vendor);
-        writer.Write((ushort)list.Count);
+        writer.Write((ushort)set.Count);
 
-        for (var i = 0; i < list.Count; i++)
+        foreach (var sis in set)
         {
-            var sis = list[i];
             var item = sis.Item;
             writer.Write(item.Serial);
             writer.Write((ushort)item.ItemID);
diff --git a/Projects/UOContent/Mobiles/Vendors/BaseVendor.cs b/Projects/UOContent/Mobiles/Vendors/BaseVendor.cs
index 5bd8f5fa0..ea80e0c9e 100644
--- a/Projects/UOContent/Mobiles/Vendors/BaseVendor.cs
+++ b/Projects/UOContent/Mobiles/Vendors/BaseVendor.cs
@@ -1042,7 +1042,7 @@ namespace Server.Mobiles
 
             var info = GetSellInfo();
 
-            var list = new List<SellItemState>();
+            var set = new HashSet<SellItemState>(new SellItemStateComparer());
 
             foreach (var ssi in info)
             {
@@ -1055,16 +1055,16 @@ namespace Server.Mobiles
 
                     if (item.IsStandardLoot() && item.Movable && ssi.IsSellable(item))
                     {
-                        list.Add(new SellItemState(item, ssi.GetSellPriceFor(item), ssi.GetNameFor(item)));
+                        set.Add(new SellItemState(item, ssi.GetSellPriceFor(item), ssi.GetNameFor(item)));
                     }
                 }
             }
 
-            if (list.Count > 0)
+            if (set.Count > 0)
             {
                 SendPacksTo(from);
 
-                from.NetState.SendVendorSellList(Serial, list);
+                from.NetState.SendVendorSellList(Serial, set);
             }
             else
             {