Expand Settler candidate tile scoring

Author: ajhalme

C7Engine/AI/StrategicAI/ExpansionPriority.cs

@@ -20,7 +20,7 @@ public override void CalculateWeightAndMetadata(Player player) {
 			if (player.cities.Count < 2) {
 				this.calculatedWeight = 1000;
 			} else {
-				int score = UtilityCalculations.CalculateAvailableLandScore(player);
+				float score = UtilityCalculations.CalculateAvailableLandScore(player);
 				score = ApplyEarlyGameMultiplier(score);
 				score = ApplyNationTraitMultiplier(score, player);
 
@@ -58,18 +58,17 @@ public override string ToString() {
 			return "ExpansionPriority";
 		}
 
-		private int ApplyEarlyGameMultiplier(int score) {
+		private float ApplyEarlyGameMultiplier(float score) {
 			//If it's early game, multiply this score.
 			//TODO: We haven't implemented the part for "how many turns does the game have?" yet.  So this is hard-coded.
-			int gameTurn = EngineStorage.gameData.turn;
-			int percentOfGameFinished = (gameTurn * 100) / TEMP_GAME_LENGTH;
-			if (percentOfGameFinished < EARLY_GAME_CUTOFF) {
-				score = score * (EARLY_GAME_CUTOFF - percentOfGameFinished) / 5;
-			}
-			return score;
+			var gameTurn = EngineStorage.gameData.turn;
+			var percentOfGameFinished = (gameTurn * 100) / TEMP_GAME_LENGTH;
+			var isEarlyGame = percentOfGameFinished < EARLY_GAME_CUTOFF;
+			var multiplier = isEarlyGame ? (EARLY_GAME_CUTOFF - percentOfGameFinished) / 5.0f : 1.0f;
+			return score * multiplier;
 		}
 
-		private int ApplyNationTraitMultiplier(int score, Player player) {
+		private float ApplyNationTraitMultiplier(float score, Player player) {
 			// TODO: The "Expansionist" trait should give a higher priority to this strategic priority.
 			return score;
 		}

C7Engine/AI/StrategicAI/UtilityCalculations.cs

@@ -1,5 +1,6 @@
 
 using System.Collections.Generic;
+using System.Linq;
 using C7GameData;
 
 namespace C7Engine.AI.StrategicAI {
@@ -11,16 +12,14 @@ namespace C7Engine.AI.StrategicAI {
 	public class UtilityCalculations {
 
 		private static readonly int PossibleCityLocationScore = 2;   //how much weight to give to each possible city location
-		private static readonly int TileScoreDivider = 10;    //how much to divide each location's tile score by
+		private static readonly float TileScoreDivider = 10f;    //how much to divide each location's tile score by
 
-		public static int CalculateAvailableLandScore(Player player) {
+		public static float CalculateAvailableLandScore(Player player) {
 			//Figure out if there's land to settle, and how much
-			Dictionary<Tile, float> possibleLocations = SettlerLocationAI.GetScoredSettlerCandidates(player.cities[0].location, player);
-			int score = possibleLocations.Count * PossibleCityLocationScore;
-			foreach (int i in possibleLocations.Values) {
-				score += i / TileScoreDivider;
-			}
-			return score;
+			var possibleLocations = SettlerLocationAI.GetScoredSettlerCandidates(player.cities[0].location, player);
+			var availableLand = possibleLocations.Count * PossibleCityLocationScore;
+			var settlementQuality = possibleLocations.Values.Sum(i => i / TileScoreDivider);
+			return settlementQuality + availableLand;
 		}
 	}
 }

C7Engine/AI/StrategicAI/WarPriority.cs

@@ -46,7 +46,7 @@ public override void CalculateWeightAndMetadata(Player player) {
 				}
 			}
 
-			bool outOfLandToExpandTo = UtilityCalculations.CalculateAvailableLandScore(player) == 0;
+			bool outOfLandToExpandTo = UtilityCalculations.CalculateAvailableLandScore(player) < 1;
 
 			// Don't go to war if there's still land we should be expanding to.
 			if (!outOfLandToExpandTo) {

C7Engine/AI/UnitAI/SettlerLocationAI.cs

@@ -30,12 +30,16 @@ private static Dictionary<Tile, float> AssignTileScores(Tile startTile, Player p
 			candidates = candidates.Where(t => !SettlerAlreadyMovingTowardsTile(t, playerSettlers) && t.IsAllowCities());
 			foreach (Tile t in candidates) {
 				float score = GetTileYieldScore(t, player);
-				//For simplicity's sake, I'm only going to look at immediate neighbors here, but
-				//a lot more things should be considered over time.
+
+				// Consider the immediate neighbors
 				foreach (Tile nt in t.neighbors.Values) {
 					score += GetTileYieldScore(nt, player);
 				}
-				//TODO #802: Also look at the next ring out, with lower weights.
+
+				// Consider the outer ring of the BFC
+				foreach (var ot in t.GetBFCOuterRing()) {
+					score += GetTileYieldScore(ot, player) / 3;
+				}
 
 				//Prefer hills for defense, and coast for boats and such.
 				if (t.baseTerrainType.Key == "hills") {
@@ -45,6 +49,9 @@ private static Dictionary<Tile, float> AssignTileScores(Tile startTile, Player p
 					score += player.civilization.Adjustments.WaterBonus;
 				}
 
+				// Let defensibility play a role
+				score += (float)t.baseTerrainType.defenseBonus.amount * 20.0f;
+
 				//Lower scores if they are far away
 				float preDistanceScore = score;
 				int distance = startTile.distanceTo(t);

C7Engine/C7GameData/Tile.cs

@@ -702,6 +702,42 @@ public List<Tile> GetTilesWithinRankDistance(int rank) {
 			return result;
 		}
 
+		private List<Tile> _outerRing;
+
+		public List<Tile> GetBFCOuterRing() {
+			if (_outerRing != null)
+				return _outerRing;
+
+			// List of all the BFC tiles NOT including direct Neighbors
+			// Essentially, this is every outer tile except North->North, South->South, West->West,East->East
+			(TileDirection direction1, TileDirection direction2)[] outerRingDirections =
+			{
+				(TileDirection.NORTHWEST, TileDirection.NORTH),
+				(TileDirection.NORTHWEST, TileDirection.NORTHWEST),
+				(TileDirection.NORTHWEST, TileDirection.WEST),
+				(TileDirection.SOUTHWEST, TileDirection.WEST),
+				(TileDirection.SOUTHWEST, TileDirection.SOUTHWEST),
+				(TileDirection.SOUTHWEST, TileDirection.SOUTH),
+				(TileDirection.SOUTHEAST, TileDirection.EAST),
+				(TileDirection.SOUTHEAST, TileDirection.SOUTHEAST),
+				(TileDirection.SOUTHEAST, TileDirection.SOUTH),
+				(TileDirection.NORTHEAST, TileDirection.NORTH),
+				(TileDirection.NORTHEAST, TileDirection.NORTHEAST),
+				(TileDirection.NORTHEAST, TileDirection.EAST)
+			};
+
+			Dictionary<(TileDirection,TileDirection), Tile> outerRing = new Dictionary<(TileDirection,TileDirection), Tile>();
+			foreach ((TileDirection dir1, TileDirection dir2) directions in outerRingDirections) {
+				if (!neighbors.TryGetValue(directions.dir1, out var inner))
+					continue;
+
+				if (inner != NONE && inner.neighbors.TryGetValue(directions.dir2, out var outer) && outer != NONE)
+					outerRing[(directions.dir1, directions.dir2)] = outer;
+			}
+			_outerRing = outerRing.Values.ToList();
+			return _outerRing;
+		}
+
 		public MapUnit FindTopDefender(MapUnit opponent) {
 			if (unitsOnTile.Count > 0) {
 				IEnumerable<MapUnit> potentialDefenders = unitsOnTile.Where(u => u.CanDefendAgainst(opponent));