feat: enforce buffer-zone non-overlap on /claimlink link

ClaimLink/ClaimLinkBuffer.cs

@@ -0,0 +1,64 @@
+using System.Collections.Generic;
+using Vintagestory.API.Common;
+using Vintagestory.API.MathTools;
+
+namespace ClaimLink;
+
+internal static class ClaimLinkBuffer
+{
+    internal static List<Cuboidi> GetBuffer(int groupId)
+    {
+        List<Cuboidi> cuboids = new();
+
+        foreach (string uid in ClaimLinkModSystem.Registry.MemberUidsForGroup(groupId))
+        {
+            foreach (
+                int claimIndex in ClaimLinkModSystem.Registry.ClaimsForPlayerInGroup(uid, groupId)
+            )
+            {
+                if (
+                    !ClaimLinkModSystem.TryResolveOwnedClaim(uid, claimIndex, out LandClaim? claim)
+                    || claim == null
+                )
+                    continue;
+
+                foreach (Cuboidi area in claim.Areas)
+                {
+                    int bufferSize = ClaimLinkModSystem.Config.BufferSize;
+                    cuboids.Add(area.Clone().GrowBy(bufferSize, bufferSize, bufferSize));
+                }
+            }
+        }
+
+        return cuboids;
+    }
+
+    internal static bool TryFindOverlappingClaimLink(
+        List<Cuboidi> areas,
+        int? excludeGroupId,
+        out int violatingGroupId
+    )
+    {
+        int bufferSize = ClaimLinkModSystem.Config.BufferSize;
+        List<Cuboidi> grownAreas = new();
+        foreach (Cuboidi area in areas)
+            grownAreas.Add(area.Clone().GrowBy(bufferSize, bufferSize, bufferSize));
+
+        foreach (int groupId in ClaimLinkModSystem.Registry.All)
+        {
+            if (groupId == excludeGroupId)
+                continue;
+
+            foreach (Cuboidi bufferCuboid in GetBuffer(groupId))
+                foreach (Cuboidi grownArea in grownAreas)
+                    if (grownArea.Intersects(bufferCuboid))
+                    {
+                        violatingGroupId = groupId;
+                        return true;
+                    }
+        }
+
+        violatingGroupId = -1;
+        return false;
+    }
+}

ClaimLink/ClaimLinkChatCommand.cs

@@ -375,12 +375,34 @@ public static class ClaimLinkChatCommand
         int groupId = group.Uid;
         string groupName = group.Name;
 
-        if (!ClaimLinkModSystem.TryResolveOwnedClaim(playerUid, claimIndex, out _))
+        if (
+            !ClaimLinkModSystem.TryResolveOwnedClaim(playerUid, claimIndex, out LandClaim? claim)
+            || claim == null
+        )
             return TextCommandResult.Error("You do not own that claim.");
 
         if (ClaimLinkModSystem.Registry.IsClaimLinked(playerUid, claimIndex))
             return TextCommandResult.Error("That claim is already part of a claim link.");
 
+        if (
+            ClaimLinkBuffer.TryFindOverlappingClaimLink(
+                claim.Areas,
+                groupId,
+                out int violatingGroupId
+            )
+        )
+        {
+            string violatingName = ClaimLinkModSystem.Groups.PlayerGroupsById.TryGetValue(
+                violatingGroupId,
+                out PlayerGroup? violatingGroup
+            )
+                ? violatingGroup!.Name
+                : "another claim link";
+            return TextCommandResult.Error(
+                $"Cannot link that claim, it overlaps the protected buffer of '{violatingName}'."
+            );
+        }
+
         string claimDesc = DescribeClaim(playerUid, claimIndex);
         return Stage(
             playerUid,