refactor: decouple game participants from human players

OpenPolytopia.Common/Gameplay/Game.cs

@@ -102,7 +102,7 @@ public partial class Game {
   /// than once, or a player's tribe isn't registered in <paramref name="tribeManager"/>
   /// </exception>
   public Game(Grid grid, CityManager cityManager, TroopManager troopManager, TribeManager tribeManager,
-    BuildingManager buildingManager, TechTreeDefinition techTreeDefinition, IReadOnlyList<Player> players,
+    BuildingManager buildingManager, TechTreeDefinition techTreeDefinition, IReadOnlyList<IPlayer> players,
     GameSettings? settings = null) {
     ArgumentNullException.ThrowIfNull(grid);
     ArgumentNullException.ThrowIfNull(cityManager);

OpenPolytopia.Common/Player.cs

@@ -1,4 +1,12 @@
 namespace OpenPolytopia.Common;
 
-public record Player(TribeType Tribe, int Id) {
+/// <summary>A participant independent of its human or future bot controller.</summary>
+public interface IPlayer {
+  /// <summary>The participant's tribe.</summary>
+  TribeType Tribe { get; }
+  /// <summary>The participant's id within a game.</summary>
+  int Id { get; }
 }
+
+/// <summary>A human participant in a game.</summary>
+public record Player(TribeType Tribe, int Id) : IPlayer;

OpenPolytopia.Common/TerrainGeneration.cs

@@ -28,7 +28,7 @@ public class TerrainGeneration(
   Grid grid,
   CityManager cityManager,
   TribeManager tribeManager,
-  Player[] players,
+  IPlayer[] players,
   int? seed = null) {
   // base terrain rates, multiplied by every tribe's TerrainRate
   private const float BASE_FOREST_RATE = 0.38f;

OpenPolytopia.UnitTest/PlayerAbstractionTest.cs

@@ -0,0 +1,27 @@
+namespace OpenPolytopia;
+
+using Common;
+using Common.Gameplay;
+using Shouldly;
+using Xunit;
+
+public class PlayerAbstractionTest {
+  private sealed record TestBot(TribeType Tribe, int Id) : IPlayer;
+
+  [Fact]
+  public async System.Threading.Tasks.Task AlternateParticipantCanGenerateAndPlay() {
+    var pieces = GameTestFixture.BuildPieces();
+    IPlayer[] players = [new Player(TribeType.Imperius, 1), new TestBot(TribeType.Imperius, 2)];
+    var grid = new Grid(16);
+    var cities = new CityManager(grid);
+    await new TerrainGeneration(grid, cities, pieces.Tribes, players, 42).GenerateMapAsync();
+    var troops = new TroopManager(16);
+    troops.RegisterTroops(EmbeddedResources.LoadTroops()!);
+    var game = new Common.Gameplay.Game(grid, cities, troops, pieces.Tribes, pieces.Buildings,
+      pieces.TechTree, players);
+    game.Start();
+    game.EndTurn(1).Result.ShouldBe(GameActionResult.Ok);
+    game.CurrentPlayer.ShouldBe(2);
+    game.EndTurn(2).Result.ShouldBe(GameActionResult.Ok);
+  }
+}