oecs-sharp/Game.TicTacToe.Tests/PlayTests.cs

using FluentAssertions;
using Game.TicTacToe;
using OECS;
using OECS.PlayTest;
using Xunit;

namespace Game.TicTacToe.Tests;

public class PlayTests
{
    [Fact]
    public void Play_GreedyVsRandom()
    {
        var (world, group) = TestHelpers.SetupGame();
        var agentX = new GreedyTicTacToeAgent(GreedyTicTacToeAgent.Strategy.WinOrBlock);
        var agentO = new RandomTicTacToeAgent();

        var log = RunGame(world, group, agentX, agentO, "TicTacToe: Greedy X vs Random O");

        var path = log.SaveTo("tic_tac_toe_greedy_vs_random.playlog");
        ReadAndVerify(path);
    }

    [Fact]
    public void Play_RandomVsRandom()
    {
        var (world, group) = TestHelpers.SetupGame();
        var agentX = new RandomTicTacToeAgent();
        var agentO = new RandomTicTacToeAgent();

        var log = RunGame(world, group, agentX, agentO, "TicTacToe: Random X vs Random O");

        var path = log.SaveTo("tic_tac_toe_random_vs_random.playlog");
        ReadAndVerify(path);
    }

    [Fact]
    public void Play_GreedyVsGreedy()
    {
        var (world, group) = TestHelpers.SetupGame();
        var agentX = new GreedyTicTacToeAgent(GreedyTicTacToeAgent.Strategy.WinOrBlock);
        var agentO = new GreedyTicTacToeAgent(GreedyTicTacToeAgent.Strategy.WinOrBlock);

        var log = RunGame(world, group, agentX, agentO, "TicTacToe: Greedy X vs Greedy O");

        var path = log.SaveTo("tic_tac_toe_greedy_vs_greedy.playlog");
        ReadAndVerify(path);
    }

    // ── Game Runner ───────────────────────────────────────────────────

    private static PlayLog RunGame(World world, SystemGroup group,
        IAgent<PlaceMarkCommand> agentX, IAgent<PlaceMarkCommand> agentO, string header)
    {
        var log = new PlayLog { Header = header };

        using var capture = new ObservableCapture(world);
        capture.FormatWith<Mark>(m => m.Player.ToString());

        var moves = new List<string>();
        while (world.ReadSingleton<GameState>().Status == GameStatus.Playing)
        {
            var state = world.ReadSingleton<GameState>();
            var agent = state.CurrentPlayer == Player.X ? agentX : agentO;
            var cmd = agent.Decide(world);

            world.Commands.Enqueue(cmd);
            group.RunLogical();

            moves.Add($"{state.CurrentPlayer} → ({cmd.Row},{cmd.Col})");
        }

        var final = world.ReadSingleton<GameState>();
        log.Header += $" — Result: {final.Status}";

        log.AddSection("Moves", moves.Select((m, i) => $"{i + 1}. {m}"));
        log.AddSection("Reactivity", capture.GetLogLines());
        log.FinalSnapshot = TestHelpers.SnapshotWorld(world);

        return log;
    }

    // ── File I/O ──────────────────────────────────────────────────────

    private static void ReadAndVerify(string path)
    {
        var content = File.ReadAllText(path);

        content.Should().Contain("--- Moves ---");
        content.Should().Contain("--- Reactivity ---");
        content.Should().Contain("--- Final State ---");
        content.Should().Contain("Result:");
        content.Should().NotContain("Result: Playing");
    }

    // ── Agents ────────────────────────────────────────────────────────

    private sealed class RandomTicTacToeAgent : GreedyAgent<PlaceMarkCommand>
    {
        protected override List<PlaceMarkCommand> GetLegalActions(World world)
        {
            return TestHelpers.GetEmptyCells(world)
                .Select(c => new PlaceMarkCommand { Row = c.Row, Col = c.Col })
                .ToList();
        }
    }

    private sealed class GreedyTicTacToeAgent : GreedyAgent<PlaceMarkCommand>
    {
        public enum Strategy { WinOrBlock }
        private readonly Strategy _strategy;
        private static readonly Random _rng = new();

        public GreedyTicTacToeAgent(Strategy strategy) => _strategy = strategy;

        protected override List<PlaceMarkCommand> GetLegalActions(World world)
        {
            return TestHelpers.GetEmptyCells(world)
                .Select(c => new PlaceMarkCommand { Row = c.Row, Col = c.Col })
                .ToList();
        }

        protected override float ScoreAction(World world, PlaceMarkCommand action)
        {
            if (_strategy != Strategy.WinOrBlock)
                return 0f;

            var state = world.ReadSingleton<GameState>();
            var me = state.CurrentPlayer;
            var opponent = me == Player.X ? Player.O : Player.X;

            if (TestHelpers.WouldWin(world, action.Row, action.Col, me))
                return 100f;
            if (TestHelpers.WouldWin(world, action.Row, action.Col, opponent))
                return 50f;
            if (action.Row == 1 && action.Col == 1)
                return 10f;

            return 0f;
        }
    }
}