fix: persisting portal linkages

Minecraft.World/PortalForcer.cpp

@@ -101,14 +101,77 @@ bool PortalForcer::findPortal(shared_ptr<Entity> e, double xOriginal, double yOr
 	{
 		PortalPosition *pos = it->second;
 
-		closest = 0;
-		xTarget = pos->x;
-		yTarget = pos->y;
-		zTarget = pos->z;
-		pos->lastUsed = level->getGameTime();
-		updateCache = false;
+		if (level->getTile(pos->x, pos->y, pos->z) == Tile::portal_Id)
+		{
+			closest = 0;
+			xTarget = pos->x;
+			yTarget = pos->y;
+			zTarget = pos->z;
+			pos->lastUsed = level->getGameTime();
+			updateCache = false;
+		}
+		else
+		{
+			delete pos;
+			cachedPortals.erase(it);
+			for (auto keyIt = cachedPortalKeys.begin(); keyIt != cachedPortalKeys.end(); ++keyIt)
+			{
+				if (*keyIt == hash)
+				{
+					cachedPortalKeys.erase(keyIt);
+					break;
+				}
+			}
+		}
 	}
-	else
+
+	if (updateCache)
+	{
+		const int localRadius = 16;
+		double localClosest = -1;
+		int localX = 0;
+		int localY = 0;
+		int localZ = 0;
+
+		for (int x = xc - localRadius; x <= xc + localRadius; x++)
+		{
+			double xd = (x + 0.5) - e->x;
+			for (int z = zc - localRadius; z <= zc + localRadius; z++)
+			{
+				double zd = (z + 0.5) - e->z;
+				for (int y = level->getHeight() - 1; y >= 0; y--)
+				{
+					if (level->getTile(x, y, z) == Tile::portal_Id)
+					{
+						while (level->getTile(x, y - 1, z) == Tile::portal_Id)
+						{
+							y--;
+						}
+
+						double yd = (y + 0.5) - e->y;
+						double dist = xd * xd + yd * yd + zd * zd;
+						if (localClosest < 0 || dist < localClosest)
+						{
+							localClosest = dist;
+							localX = x;
+							localY = y;
+							localZ = z;
+						}
+					}
+				}
+			}
+		}
+
+		if (localClosest >= 0)
+		{
+			closest = localClosest;
+			xTarget = localX;
+			yTarget = localY;
+			zTarget = localZ;
+		}
+	}
+
+	if (closest < 0)
 	{
 		for (int x = xc - r; x <= xc + r; x++)
 		{