Chessistics/chessistics-tests/Simulation/GameSimTests.cs

using Chessistics.Engine.Commands;
using Chessistics.Engine.Events;
using Chessistics.Engine.Model;
using Chessistics.Tests.Helpers;
using Xunit;

namespace Chessistics.Tests.Simulation;

public class GameSimTests
{
    private SimHelper CreateLevel1Sim()
    {
        var level = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "Scierie", CargoType.Wood, 2)
            .WithDemand(3, 0, "Depot Royal", CargoType.Wood, 3, 30)
            .WithStock(PieceKind.Rook, 3)
            .Build();
        return SimHelper.FromLevel(level);
    }

    [Fact]
    public void PlacePiece_Succeeds()
    {
        var sim = CreateLevel1Sim();
        var events = sim.Place(PieceKind.Rook, (0, 0), (1, 0));

        Assert.Single(events);
        Assert.IsType<PiecePlacedEvent>(events[0]);
        var placed = (PiecePlacedEvent)events[0];
        Assert.Equal(PieceKind.Rook, placed.Kind);
    }

    [Fact]
    public void PlacePiece_StockExhausted_Rejected()
    {
        var sim = CreateLevel1Sim();
        sim.Place(PieceKind.Rook, (0, 0), (1, 0));
        sim.Place(PieceKind.Rook, (0, 1), (1, 1));
        sim.Place(PieceKind.Rook, (0, 2), (1, 2));

        // 4th rook — only 3 in stock
        var events = sim.Place(PieceKind.Rook, (0, 3), (1, 3));
        Assert.IsType<PlacementRejectedEvent>(events[0]);
    }

    [Fact]
    public void PlaceDuringRunning_Rejected()
    {
        var sim = CreateLevel1Sim();
        sim.Place(PieceKind.Rook, (0, 0), (1, 0));
        sim.Start();

        var events = sim.Place(PieceKind.Rook, (0, 1), (1, 1));
        Assert.IsType<CommandRejectedEvent>(events[0]);
    }

    [Fact]
    public void StartWithNoPieces_Rejected()
    {
        var sim = CreateLevel1Sim();
        var events = sim.Start();
        Assert.IsType<CommandRejectedEvent>(events[0]);
    }

    [Fact]
    public void RemoveDuringRunning_Rejected()
    {
        var sim = CreateLevel1Sim();
        sim.Place(PieceKind.Rook, (0, 0), (1, 0));
        sim.Start();

        var events = sim.Remove(1);
        Assert.IsType<CommandRejectedEvent>(events[0]);
    }

    [Fact]
    public void StopDuringEdit_Rejected()
    {
        var sim = CreateLevel1Sim();
        var events = sim.Stop();
        Assert.IsType<CommandRejectedEvent>(events[0]);
    }

    [Fact]
    public void SinglePiece_Oscillates()
    {
        var sim = CreateLevel1Sim();
        sim.Place(PieceKind.Rook, (0, 0), (2, 0));
        sim.Start();

        // Step 1: piece moves from (0,0) to (2,0)
        var events1 = sim.Step();
        Assert.Contains(events1, e => e is PieceMovedEvent m && m.From == new Coords(0, 0) && m.To == new Coords(2, 0));

        // Step 2: piece moves back from (2,0) to (0,0)
        var events2 = sim.Step();
        Assert.Contains(events2, e => e is PieceMovedEvent m && m.From == new Coords(2, 0) && m.To == new Coords(0, 0));

        // Step 3: piece moves forward again
        var events3 = sim.Step();
        Assert.Contains(events3, e => e is PieceMovedEvent m && m.From == new Coords(0, 0) && m.To == new Coords(2, 0));
    }

    [Fact]
    public void ChainedPieces_TransferCargo()
    {
        var sim = CreateLevel1Sim();
        // Piece A: (0,0) → (1,0), Piece B: (2,0) → (3,0)
        // Adjacent at (1,0)↔(2,0) when A is at end and B is at start
        sim.Place(PieceKind.Rook, (0, 0), (1, 0));
        sim.Place(PieceKind.Rook, (2, 0), (3, 0));
        sim.Start();

        // Run until we see a cargo transfer between pieces
        var allEvents = sim.StepN(20);

        // Should have production events and cargo transfers
        Assert.Contains(allEvents, e => e is CargoProducedEvent);
        Assert.Contains(allEvents, e => e is CargoTransferredEvent);
    }

    [Fact]
    public void Production_GeneratesOnInterval()
    {
        var sim = CreateLevel1Sim();
        // Place rook adjacent to production so it picks up cargo, freeing the buffer
        sim.Place(PieceKind.Rook, (0, 0), (1, 0));

        sim.Start();
        var allEvents = sim.StepN(6);

        var prodEvents = allEvents.OfType<CargoProducedEvent>().ToList();
        // With interval 2, produces on turns 2, 4, 6 (buffer freed each time by adjacent piece)
        Assert.True(prodEvents.Count >= 2, $"Expected at least 2 productions, got {prodEvents.Count}");
    }

    [Fact]
    public void Victory_WhenAllDemandsMet()
    {
        // Tiny level: prod adjacent to demand, just need one piece to relay
        var level = new BoardBuilder(3, 1)
            .WithProduction(0, 0, "P", CargoType.Wood, 1)
            .WithDemand(2, 0, "D", CargoType.Wood, 1, 30)
            .WithStock(PieceKind.Rook, 2)
            .Build();
        var sim = SimHelper.FromLevel(level);

        sim.Place(PieceKind.Rook, (1, 0), (2, 0));
        sim.Start();

        // Run enough turns for production → piece → demand
        var allEvents = sim.StepN(10);

        Assert.Contains(allEvents, e => e is VictoryEvent);
    }

    [Fact]
    public void Defeat_WhenDeadlineExpires()
    {
        // Demand with very tight deadline, piece placed far from demand
        var level = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 3, "D", CargoType.Wood, 10, 3) // need 10 in 3 turns — impossible
            .WithStock(PieceKind.Rook, 3)
            .Build();
        var sim = SimHelper.FromLevel(level);

        sim.Place(PieceKind.Rook, (1, 0), (2, 0));
        sim.Start();

        var allEvents = sim.StepN(5);

        Assert.Contains(allEvents, e => e is DeadlineExpiredEvent);
    }

    [Fact]
    public void StopResetsState()
    {
        var sim = CreateLevel1Sim();
        sim.Place(PieceKind.Rook, (0, 0), (1, 0));
        sim.Start();
        sim.StepN(5);
        sim.Stop();

        var snap = sim.Snapshot;
        Assert.Equal(SimPhase.Edit, snap.Phase);
        Assert.Equal(0, snap.TurnNumber);
        // Pieces should be back at start cells
        Assert.All(snap.Pieces, p => Assert.Equal(p.StartCell, p.CurrentCell));
    }

    [Fact]
    public void ResetClearsEverything()
    {
        var sim = CreateLevel1Sim();
        sim.Place(PieceKind.Rook, (0, 0), (1, 0));
        sim.Reset();

        var snap = sim.Snapshot;
        Assert.Equal(SimPhase.Edit, snap.Phase);
        Assert.Empty(snap.Pieces);
        Assert.Equal(3, snap.RemainingStock[PieceKind.Rook]);
    }
}