Chessistics/chessistics-tests/Rules/TransferResolverTests.cs

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

namespace Chessistics.Tests.Rules;

public class TransferResolverTests
{
    [Fact]
    public void Production_GivesToAdjacentEmptyPiece()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Rook, 3)
            .BuildState();

        // Place a piece at (1,0) — adjacent to production at (0,0)
        var piece = new PieceState(1, PieceKind.Rook, new Coords(1, 0), new Coords(2, 0), 0);
        piece.CurrentCell = new Coords(1, 0);
        board.Pieces.Add(piece);

        // Fill production buffer
        board.ProductionBuffers[new Coords(0, 0)] = CargoType.Wood;

        var events = TransferResolver.ResolveTransfers(board);

        Assert.Contains(events, e => e is CargoTransferredEvent ct
            && ct.From == new Coords(0, 0)
            && ct.To == new Coords(1, 0)
            && ct.Type == CargoType.Wood);

        Assert.Equal(CargoType.Wood, piece.Cargo);
        Assert.Null(board.ProductionBuffers[new Coords(0, 0)]);
    }

    [Fact]
    public void Production_DoesNotGiveToPieceWithCargo()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Rook, 3)
            .BuildState();

        var piece = new PieceState(1, PieceKind.Rook, new Coords(1, 0), new Coords(2, 0), 0);
        piece.CurrentCell = new Coords(1, 0);
        piece.Cargo = CargoType.Wood; // already carrying
        board.Pieces.Add(piece);
        board.ProductionBuffers[new Coords(0, 0)] = CargoType.Wood;

        var events = TransferResolver.ResolveTransfers(board);

        // No transfer from production — piece already has cargo
        Assert.DoesNotContain(events, e => e is CargoTransferredEvent ct && ct.From == new Coords(0, 0));
        Assert.Equal(CargoType.Wood, board.ProductionBuffers[new Coords(0, 0)]);
    }

    [Fact]
    public void Piece_TransfersToAdjacentEmptyPiece()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Rook, 3)
            .BuildState();

        var giver = new PieceState(1, PieceKind.Rook, new Coords(1, 0), new Coords(2, 0), 0);
        giver.CurrentCell = new Coords(1, 0);
        giver.Cargo = CargoType.Wood;

        var receiver = new PieceState(2, PieceKind.Rook, new Coords(2, 0), new Coords(3, 0), 1);
        receiver.CurrentCell = new Coords(2, 0);

        board.Pieces.AddRange([giver, receiver]);

        var events = TransferResolver.ResolveTransfers(board);

        Assert.Contains(events, e => e is CargoTransferredEvent ct
            && ct.GivingPieceId == 1 && ct.ReceivingPieceId == 2);
        Assert.Null(giver.Cargo);
        Assert.Equal(CargoType.Wood, receiver.Cargo);
    }

    [Fact]
    public void Piece_DeliversToDemand()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 3, 99)
            .WithStock(PieceKind.Rook, 3)
            .BuildState();

        var piece = new PieceState(1, PieceKind.Rook, new Coords(2, 0), new Coords(3, 0), 0);
        piece.CurrentCell = new Coords(2, 0); // adjacent to demand at (3,0)
        piece.Cargo = CargoType.Wood;
        board.Pieces.Add(piece);

        var events = TransferResolver.ResolveTransfers(board);

        Assert.Contains(events, e => e is CargoTransferredEvent ct
            && ct.To == new Coords(3, 0) && ct.GivingPieceId == 1);
        Assert.Contains(events, e => e is DemandProgressEvent dp
            && dp.Current == 1 && dp.Required == 3);
        Assert.Null(piece.Cargo);
    }

    [Fact]
    public void Piece_DoesNotDeliverWrongType()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 3, 99) // wants Wood
            .WithStock(PieceKind.Rook, 3)
            .BuildState();

        var piece = new PieceState(1, PieceKind.Rook, new Coords(2, 0), new Coords(3, 0), 0);
        piece.CurrentCell = new Coords(2, 0);
        piece.Cargo = CargoType.Stone; // carrying Stone, demand wants Wood
        board.Pieces.Add(piece);

        var events = TransferResolver.ResolveTransfers(board);

        Assert.DoesNotContain(events, e => e is CargoTransferredEvent ct && ct.To == new Coords(3, 0));
        Assert.Equal(CargoType.Stone, piece.Cargo); // still holding
    }

    [Fact]
    public void HigherStatus_ReceivesFirst()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Rook, 3)
            .WithStock(PieceKind.Knight, 3)
            .BuildState();

        // Giver piece at (1,0) with cargo
        var giver = new PieceState(1, PieceKind.Rook, new Coords(1, 0), new Coords(2, 0), 0);
        giver.CurrentCell = new Coords(1, 0);
        giver.Cargo = CargoType.Wood;

        // Two receivers: Rook (status 5) and Knight (status 3) both adjacent
        var rookReceiver = new PieceState(2, PieceKind.Rook, new Coords(1, 1), new Coords(2, 1), 1);
        rookReceiver.CurrentCell = new Coords(1, 1); // adjacent to (1,0)

        var knightReceiver = new PieceState(3, PieceKind.Knight, new Coords(2, 0), new Coords(0, 1), 2);
        knightReceiver.CurrentCell = new Coords(2, 0); // adjacent to (1,0)

        board.Pieces.AddRange([giver, rookReceiver, knightReceiver]);

        var events = TransferResolver.ResolveTransfers(board);

        // Rook (status 5) should receive before Knight (status 3)
        var transfer = events.OfType<CargoTransferredEvent>().First(e => e.GivingPieceId == 1);
        Assert.Equal(2, transfer.ReceivingPieceId); // rook receives
    }

    [Fact]
    public void HigherStatus_GivesFirst()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Rook, 3)
            .WithStock(PieceKind.Knight, 3)
            .BuildState();

        // Two givers: Rook (5) at (1,0) and Knight (3) at (1,1), both with cargo
        var rook = new PieceState(1, PieceKind.Rook, new Coords(1, 0), new Coords(2, 0), 0);
        rook.CurrentCell = new Coords(1, 0);
        rook.Cargo = CargoType.Wood;

        var knight = new PieceState(2, PieceKind.Knight, new Coords(1, 1), new Coords(3, 2), 1);
        knight.CurrentCell = new Coords(1, 1);
        knight.Cargo = CargoType.Wood;

        // One receiver adjacent to both: at (2,0) — adjacent to rook at (1,0) but not to knight at (1,1)
        // Let's make receiver at (1,2) — adjacent to knight (1,1) only
        // Actually: receiver at (2,1) — adjacent to nothing. Let me think...
        // Receiver needs to be adjacent to both. (1,0) and (1,1) share neighbor (2,0)? No, (2,0) is adjacent to (1,0) only.
        // Shared neighbor: none directly... Let's change: both givers adjacent to same receiver
        // Put receiver at (0, 0) — but that's production. Put receiver at (0, 1):
        // (0,1) is adjacent to (1,1) [knight] and (0,0) [production], not to (1,0) [rook]
        // Let's use a simpler setup:

        // Rook with cargo at (2,0), Knight with cargo at (2,2), receiver at (2,1) — adjacent to both
        rook.CurrentCell = new Coords(2, 0);
        knight.CurrentCell = new Coords(2, 2);

        var receiver = new PieceState(3, PieceKind.Rook, new Coords(2, 1), new Coords(3, 1), 2);
        receiver.CurrentCell = new Coords(2, 1);

        board.Pieces.AddRange([rook, knight, receiver]);

        var events = TransferResolver.ResolveTransfers(board);

        // Rook (status 5) should give first to the receiver
        var transfer = events.OfType<CargoTransferredEvent>().First();
        Assert.Equal(1, transfer.GivingPieceId); // rook gives first
    }

    [Fact]
    public void TieBreaker_PlacementOrder()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(3, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Knight, 5)
            .BuildState();

        // Two knights (same status 3) with cargo, both adjacent to same empty receiver
        var knight1 = new PieceState(1, PieceKind.Knight, new Coords(2, 0), new Coords(0, 1), 0); // earlier
        knight1.CurrentCell = new Coords(2, 0);
        knight1.Cargo = CargoType.Wood;

        var knight2 = new PieceState(2, PieceKind.Knight, new Coords(2, 2), new Coords(0, 3), 1); // later
        knight2.CurrentCell = new Coords(2, 2);
        knight2.Cargo = CargoType.Wood;

        var receiver = new PieceState(3, PieceKind.Knight, new Coords(2, 1), new Coords(0, 2), 2);
        receiver.CurrentCell = new Coords(2, 1); // adjacent to both (2,0) and (2,2)

        board.Pieces.AddRange([knight1, knight2, receiver]);

        var events = TransferResolver.ResolveTransfers(board);
        var transfer = events.OfType<CargoTransferredEvent>().First();

        // knight1 is closer to production at (0,0): dist = 2, knight2: dist = 4
        // So knight1 gives first due to proximity (tiebreaker before placement order)
        Assert.Equal(1, transfer.GivingPieceId);
    }

    [Fact]
    public void Cargo_MovesOneHopPerTurn()
    {
        var board = new BoardBuilder(5, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(4, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Rook, 5)
            .BuildState();

        // Chain of 3 pieces: A(0,0→1,0), B(1,0→2,0), C(2,0→3,0)
        // All currently at their start cells with A having cargo
        var a = new PieceState(1, PieceKind.Rook, new Coords(0, 0), new Coords(1, 0), 0);
        a.CurrentCell = new Coords(1, 0); // at end cell, adjacent to B
        a.Cargo = CargoType.Wood;

        var b = new PieceState(2, PieceKind.Rook, new Coords(1, 0), new Coords(2, 0), 1);
        b.CurrentCell = new Coords(2, 0); // at end cell, adjacent to C

        var c = new PieceState(3, PieceKind.Rook, new Coords(2, 0), new Coords(3, 0), 2);
        c.CurrentCell = new Coords(3, 0); // at end cell

        board.Pieces.AddRange([a, b, c]);

        var events = TransferResolver.ResolveTransfers(board);

        // A gives to B (adjacent: (1,0)→(2,0))
        Assert.Contains(events, e => e is CargoTransferredEvent ct && ct.GivingPieceId == 1 && ct.ReceivingPieceId == 2);

        // B should NOT give to C in the same turn (B just received, participated)
        Assert.DoesNotContain(events, e => e is CargoTransferredEvent ct && ct.GivingPieceId == 2 && ct.ReceivingPieceId == 3);
    }

    [Fact]
    public void NoCrossTransfer_NonAdjacent()
    {
        var board = new BoardBuilder(5, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(4, 0, "D", CargoType.Wood, 1, 99)
            .WithStock(PieceKind.Rook, 5)
            .BuildState();

        var giver = new PieceState(1, PieceKind.Rook, new Coords(0, 0), new Coords(1, 0), 0);
        giver.CurrentCell = new Coords(0, 0);
        giver.Cargo = CargoType.Wood;

        var farPiece = new PieceState(2, PieceKind.Rook, new Coords(2, 0), new Coords(3, 0), 1);
        farPiece.CurrentCell = new Coords(2, 0); // 2 cells away, not adjacent

        board.Pieces.AddRange([giver, farPiece]);

        var events = TransferResolver.ResolveTransfers(board);

        // No piece-to-piece transfer — they're not adjacent
        Assert.DoesNotContain(events, e => e is CargoTransferredEvent ct && ct.GivingPieceId == 1 && ct.ReceivingPieceId == 2);
    }

    [Fact]
    public void DemandPriority_OverPieceReceiver()
    {
        var board = new BoardBuilder(4, 4)
            .WithProduction(0, 0, "P", CargoType.Wood, 2)
            .WithDemand(2, 0, "D", CargoType.Wood, 3, 99)
            .WithStock(PieceKind.Rook, 5)
            .BuildState();

        // Piece with cargo at (1,0) adjacent to both demand at (2,0) and empty piece at (1,1)
        var giver = new PieceState(1, PieceKind.Rook, new Coords(1, 0), new Coords(2, 0), 0);
        giver.CurrentCell = new Coords(1, 0);
        giver.Cargo = CargoType.Wood;

        var receiver = new PieceState(2, PieceKind.Rook, new Coords(1, 1), new Coords(2, 1), 1);
        receiver.CurrentCell = new Coords(1, 1); // adjacent to giver

        board.Pieces.AddRange([giver, receiver]);

        var events = TransferResolver.ResolveTransfers(board);

        // Should deliver to demand, not to piece
        Assert.Contains(events, e => e is CargoTransferredEvent ct && ct.To == new Coords(2, 0));
        Assert.DoesNotContain(events, e => e is CargoTransferredEvent ct && ct.ReceivingPieceId == 2);
    }
}