Border tile assignment improvements

C7/MapView.cs

@@ -271,7 +271,7 @@ public override void drawObject(LooseView looseView, GameData gameData, Tile til
 			int randomJungleRow = tile.YCoordinate % 2;
 			int randomJungleColumn;
 			ImageTexture jungleTexture;
-			if (tile.getEdgeNeighbors().Any(t => t.IsWater())) {
+			if (tile.GetEdgeNeighbors().Any(t => t.IsWater())) {
 				randomJungleColumn = tile.XCoordinate % 6;
 				jungleTexture = smallJungleTexture;
 			} else {
@@ -298,7 +298,7 @@ public override void drawObject(LooseView looseView, GameData gameData, Tile til
 				}
 			} else {
 				forestRow = tile.YCoordinate % 2;
-				if (tile.getEdgeNeighbors().Any(t => t.IsWater())) {
+				if (tile.GetEdgeNeighbors().Any(t => t.IsWater())) {
 					forestColumn = tile.XCoordinate % 5;
 					if (tile.baseTerrainType.Key == "grassland") {
 						forestTexture = smallForestTexture;
@@ -343,7 +343,7 @@ public override void drawObject(LooseView looseView, GameData gameData, Tile til
 			int randomJungleRow = tile.YCoordinate % 2;
 			int randomMarshColumn;
 			ImageTexture marshTexture;
-			if (tile.getEdgeNeighbors().Any(t => t.IsWater())) {
+			if (tile.GetEdgeNeighbors().Any(t => t.IsWater())) {
 				randomMarshColumn = tile.XCoordinate % 5;
 				marshTexture = smallMarshTexture;
 			} else {

C7Engine/C7GameData/City.cs

@@ -670,8 +670,9 @@ public List<Tile> GetTilesWithinBorders() {
 		private List<Tile> GetTilesOfRank(int rank) {
 			List<Tile> result = new();
 			foreach (Tile t in location.GetTilesWithinRankDistance(rank)) {
+				// Law II
 				// Ocean tiles may only hold claims of rank 2.
-				if (t.baseTerrainType.Key == "ocean" && rank > 2) {
+				if (t.baseTerrainType.Key == "ocean" && t.rankDistanceTo(location) > 2) {
 					continue;
 				}
 				result.Add(t);

C7Engine/C7GameData/GameData.cs

@@ -147,6 +147,26 @@ public void UpdateTileOwners() {
 			foreach (Player player in players) {
 				player.tileKnowledge.RecomputeActiveTiles();
 				player.UpdateResourcesInBorders(map.tiles.Where(t => t.owningCity?.owner == player));
+
+				foreach (Tile t in player.tileKnowledge.knownTiles.Where(t => t.owningCity == null && t.GetEdgeNeighbors().Any(e => e.owningCity != null)).ToList()) {
+					// Law VII
+					if (t.neighbors.TryGetValue(TileDirection.NORTHWEST, out Tile tnw)
+						&& t.neighbors.TryGetValue(TileDirection.SOUTHEAST, out Tile tse)
+						&& tnw.owningCity != null && tse.owningCity != null
+						&& tnw.owningCity.owner == tse.owningCity.owner) {
+						t.owningCity = ResolveTileOwnershipConflict(tnw.owningCity, tse.owningCity, t);
+						t.owningCity.owner.tileKnowledge.AddTilesToKnown(t);
+						continue;
+					}
+					// Law VIII
+					if (t.neighbors.TryGetValue(TileDirection.NORTHEAST, out Tile tne)
+						&& t.neighbors.TryGetValue(TileDirection.SOUTHWEST, out Tile tsw)
+						&& tne.owningCity != null && tsw.owningCity != null
+						&& tne.owningCity.owner == tsw.owningCity.owner) {
+						t.owningCity = ResolveTileOwnershipConflict(tne.owningCity, tsw.owningCity, t);
+						t.owningCity.owner.tileKnowledge.AddTilesToKnown(t);
+					}
+				}
 			}
 		}
 
@@ -256,26 +276,46 @@ public void InvalidateCachedTradeNetwork() {
 
 		// Rules taken from https://forums.civfanatics.com/threads/the-eight-laws-of-border-dynamics.106882/
 		private City ResolveTileOwnershipConflict(City a, City b, Tile t) {
+			if (a.Equals(b)) return a;
+
 			int aRank = a.location.rankDistanceTo(t);
 			int bRank = b.location.rankDistanceTo(t);
 
+			// Law I
+			// Cities can claim tiles of rank n+1, where n is the city's expansion level
+			if (a.GetBorderExpansionLevel() + 1 < aRank && b.GetBorderExpansionLevel() + 1 >= bRank) return b;
+			if (b.GetBorderExpansionLevel() + 1 < bRank && a.GetBorderExpansionLevel() + 1 >= aRank) return a;
+
+			// Law III
 			// The city with the lowest rank claim gets the tile.
-			if (aRank > bRank) {
-				return b;
-			} else if (aRank < bRank) {
-				return a;
-			}
+			if (aRank > bRank) return b;
+			if (aRank < bRank) return a;
 
+			// Law IV
 			// If the ranks are equal, the city with more culture gets the tile.
-			if (a.GetCulture() < b.GetCulture()) {
-				return b;
-			} else if (a.GetCulture() > b.GetCulture()) {
-				return a;
-			}
+			if (a.GetCulture() + a.GetCulturePerTurn() < b.GetCulture() + b.GetCulturePerTurn()) return b;
+			if (a.GetCulture() + a.GetCulturePerTurn() > b.GetCulture() + b.GetCulturePerTurn()) return a;
 
+			// Law V
 			// If the cultures are equal the oldest city gets the tile.
-			// TODO: track city age - for now we just return the first.
-			return a;
+			// TODO: track city age - for now we are going to skip this.
+			// return a;
+
+			// Law VI
+			// Starting North of the disputed tile, we go counter-clockwise
+			// trying to find the first tile that has one of the competing cities.
+			// We start at (rank - 1) because the rank distance does not necessarily reflect the actual "ring"
+			// the city tile is in, so a tile at rank 3, could well mean it's in the 2nd ring.
+			for (int r = aRank - 1; r <= aRank; r++) {
+				if (r <= 0) continue;
+				Tile winner = t.FindInRing(r, tile => tile.HasCity && (tile.cityAtTile == a || tile.cityAtTile == b), false);
+				if (winner != null) {
+					return winner.owningCity;
+				}
+			}
+
+			// should never happen, if it does some part of the algorithm has gone wrong
+			throw new Exception($"Failed to resolve ownership of {t} between {a.name} and {b.name}, something went wrong");
 		}
 	}
 }

C7Engine/C7GameData/Tile.cs

@@ -186,9 +186,13 @@ public bool NeighborsOcean() {
 		/// This is used by some graphics algorithms.
 		/// </summary>
 		/// <returns></returns>
-		public Tile[] getEdgeNeighbors() {
-			Tile[] edgeNeighbors =  { neighbors[TileDirection.NORTHEAST], neighbors[TileDirection.NORTHWEST], neighbors[TileDirection.SOUTHEAST], neighbors[TileDirection.SOUTHWEST]};
-			return edgeNeighbors;
+		public Tile[] GetEdgeNeighbors() {
+			List<Tile> edgeNeighbors = new();
+			if (neighbors.TryGetValue(TileDirection.NORTHEAST, out Tile ne)) edgeNeighbors.Add(ne);
+			if (neighbors.TryGetValue(TileDirection.NORTHWEST, out Tile nw)) edgeNeighbors.Add(nw);
+			if (neighbors.TryGetValue(TileDirection.SOUTHEAST, out Tile se)) edgeNeighbors.Add(se);
+			if (neighbors.TryGetValue(TileDirection.SOUTHWEST, out Tile sw)) edgeNeighbors.Add(sw);
+			return edgeNeighbors.ToArray();
 		}
 
 		public override string ToString() {
@@ -612,6 +616,37 @@ public Tile GetTileAtNeighborIndex(int neighborIndex) {
 			return map.tileAt(XCoordinate + xDelta, YCoordinate + yDelta);
 		}
 
+		public Tile FindInRing(int rank, Func<Tile, bool> predicate, bool clockwise = true) {
+			Tile startingTile = map.tileAt(this.XCoordinate, this.YCoordinate - (2 * rank));
+
+			if (predicate(startingTile)) return startingTile;
+
+			int dx = startingTile.XCoordinate;
+			int dy = startingTile.YCoordinate;
+
+			// Going SW(counter-clockwise) or SE(clockwise)
+			for (int _ = 1; _ < (2 * rank) + 1; _++) {
+				if (clockwise) { dx++; dy++; } else { dx--; dy++; }
+				if (predicate(map.tileAt(dx, dy))) return map.tileAt(dx, dy);
+			}
+			// Going SE(counter-clockwise) or SW(clockwise)
+			for (int _ = 1; _ < (2 * rank) + 1; _++) {
+				if (clockwise) { dx--; dy++; } else { dx++; dy++; }
+				if (predicate(map.tileAt(dx, dy))) return map.tileAt(dx, dy);
+			}
+			// Going NE(counter-clockwise) or NW(clockwise)
+			for (int _ = 1; _ < (2 * rank) + 1; _++) {
+				if (clockwise) { dx--; dy--; } else { dx++; dy--; }
+				if (predicate(map.tileAt(dx, dy))) return map.tileAt(dx, dy);
+			}
+			// Going NW(counter-clockwise) or NE(clockwise)
+			for (int _ = 1; _ < (2 * rank); _++) {
+				if (clockwise) { dx++; dy--; } else { dx--; dy--; }
+				if (predicate(map.tileAt(dx, dy))) return map.tileAt(dx, dy);
+			}
+			return null;
+		}
+
 		// Returns the tiles in the spiral ordering defined by
 		// GetTileAtNeighborIndex(i).
 		public List<Tile> GetTilesWithinRankDistance(int rank) {