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

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

namespace Game.Blackjack.Tests;

public class PlayTests
{
    private const int StartingChips = 100;
    private const int BetAmount = 10;

    [Fact]
    public void Play_BasicStrategy()
    {
        var (world, group) = TestHelpers.SetupGame(seed: 42);
        var agent = new BasicStrategyAgent();

        var log = RunUntilDone(world, group, agent,
            $"Blackjack: Basic Strategy (seed=42, agent={agent})");

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

    [Fact]
    public void Play_RandomAgent()
    {
        var (world, group) = TestHelpers.SetupGame(seed: 123);
        var agent = new RandomBlackjackAgent();

        var log = RunUntilDone(world, group, agent,
            $"Blackjack: Random Agent (seed=123, agent={agent})");

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

    [Fact]
    public void Play_WeightedPool()
    {
        var (world, group) = TestHelpers.SetupGame(seed: 77);

        var pool = new WeightedAgentPool<BlackjackDecision>();
        pool.Add(new BasicStrategyAgent(), 7);
        pool.Add(new RandomBlackjackAgent(), 3);

        var agent = pool.Pick();
        var log = RunUntilDone(world, group, agent,
            $"Blackjack: Weighted Pool (seed=77, agent={agent})");

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

    // ── Round Runner ──────────────────────────────────────────────────

    /// <summary>
    /// Runs rounds until the player runs out of chips (can't afford minimum bet)
    /// or doubles their starting chips.
    /// </summary>
    private static PlayLog RunUntilDone(World world, SystemGroup group,
        IAgent<BlackjackDecision> agent, string header)
    {
        var log = new PlayLog { Header = header };

        using var capture = new ObservableCapture(world);
        capture.FormatWith<Card>(c => $"{c.Rank} of {c.Suit}");
        capture.FormatWith<GameState>(s => $"{s.Phase} Chips={s.Chips} Bet={s.CurrentBet}");

        int totalRounds = 0;
        int wins = 0;
        int losses = 0;
        int pushes = 0;
        var roundSummaries = new List<string>();
        var decisions = new List<string>();

        while (true)
        {
            var state = world.ReadSingleton<GameState>();
            int chips = state.Chips;

            if (chips < BetAmount)
            {
                log.Header += $" — BUSTED after {totalRounds} rounds";
                break;
            }
            if (chips >= StartingChips * 2)
            {
                log.Header += $" — DOUBLED after {totalRounds} rounds";
                break;
            }
            if (totalRounds >= 200)
            {
                log.Header += $" — MAX ROUNDS ({totalRounds})";
                break;
            }

            world.Commands.Enqueue(new PlaceBetCommand { Amount = BetAmount });
            group.RunLogical();

            int roundHits = 0;
            int playerTurnSafety = 0;
            while (world.ReadSingleton<GameState>().Phase == GamePhase.PlayerTurn && playerTurnSafety < 52)
            {
                playerTurnSafety++;
                var total = HandUtil.CalculateHand(world, new PlayerHand());
                var decision = agent.Decide(world);
                decisions.Add($"R{totalRounds + 1} Hand={total}, Decision={decision}");

                if (decision == BlackjackDecision.Hit)
                {
                    world.Commands.Enqueue(new HitCommand());
                    roundHits++;
                }
                else
                {
                    world.Commands.Enqueue(new StandCommand());
                }

                group.RunLogical();
            }

            state = world.ReadSingleton<GameState>();
            int newChips = state.Chips;
            int delta = newChips - chips;
            roundSummaries.Add($"Round {totalRounds + 1}: {state.Result} | Bet={BetAmount} | Chips: {chips}→{newChips} ({delta:+0;-#}) | Hits: {roundHits}");

            switch (state.Result)
            {
                case RoundResult.PlayerWin:
                case RoundResult.DealerBust:
                    wins++;
                    break;
                case RoundResult.DealerWin:
                case RoundResult.PlayerBust:
                    losses++;
                    break;
                case RoundResult.Push:
                    pushes++;
                    break;
            }

            totalRounds++;

            world.Commands.Enqueue(new NewRoundCommand());
            group.RunLogical();
        }

        log.Header += $" | W:{wins} L:{losses} P:{pushes}";

        log.AddSection("Round Summaries", roundSummaries);
        log.AddSection("Decisions", decisions);
        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("--- Round Summaries ---");
        content.Should().Contain("--- Decisions ---");
        content.Should().Contain("--- Reactivity ---");
        content.Should().Contain("--- Final State ---");
        content.Should().Contain("Result:");
    }

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

    private enum BlackjackDecision { Hit, Stand }

    private sealed class BasicStrategyAgent : IAgent<BlackjackDecision>
    {
        public BlackjackDecision Decide(World world)
        {
            var total = HandUtil.CalculateHand(world, new PlayerHand());
            return total < 17 ? BlackjackDecision.Hit : BlackjackDecision.Stand;
        }
        public override string ToString() => "BasicStrategy";
    }

    private sealed class RandomBlackjackAgent : IAgent<BlackjackDecision>
    {
        private static readonly Random _rng = new();
        public BlackjackDecision Decide(World world)
        {
            var total = HandUtil.CalculateHand(world, new PlayerHand());
            if (total >= 21) return BlackjackDecision.Stand;
            return _rng.Next(2) == 0 ? BlackjackDecision.Hit : BlackjackDecision.Stand;
        }
        public override string ToString() => "Random";
    }
}