398 lines
12 KiB
C#
398 lines
12 KiB
C#
using Gameboard.ShogiUI.BoardState.Pieces;
|
|
using PathFinding;
|
|
using System;
|
|
using System.Collections.Generic;
|
|
using System.Numerics;
|
|
using System.Text;
|
|
|
|
namespace Gameboard.ShogiUI.BoardState
|
|
{
|
|
/// <summary>
|
|
/// Facilitates Shogi board state transitions, cognisant of Shogi rules.
|
|
/// The board is always from Player1's perspective.
|
|
/// [0,0] is the lower-left position, [8,8] is the higher-right position
|
|
/// </summary>
|
|
public class ShogiBoard
|
|
{
|
|
private delegate void MoveSetCallback(Piece piece, Vector2 position);
|
|
private readonly PathFinder2D<Piece> pathFinder;
|
|
public ShogiBoard validationBoard;
|
|
private Vector2 player1King;
|
|
private Vector2 player2King;
|
|
public IReadOnlyDictionary<WhichPlayer, List<Piece>> Hands { get; }
|
|
public Array2D<Piece> Board { get; }
|
|
public List<Move> MoveHistory { get; }
|
|
public WhichPlayer WhoseTurn => MoveHistory.Count % 2 == 0 ? WhichPlayer.Player1 : WhichPlayer.Player2;
|
|
public WhichPlayer? InCheck { get; private set; }
|
|
public bool IsCheckmate { get; private set; }
|
|
|
|
public ShogiBoard()
|
|
{
|
|
Board = new Array2D<Piece>(9, 9);
|
|
MoveHistory = new List<Move>(20);
|
|
Hands = new Dictionary<WhichPlayer, List<Piece>> {
|
|
{ WhichPlayer.Player1, new List<Piece>()},
|
|
{ WhichPlayer.Player2, new List<Piece>()},
|
|
};
|
|
pathFinder = new PathFinder2D<Piece>(Board);
|
|
InitializeBoardState();
|
|
player1King = new Vector2(4, 0);
|
|
player2King = new Vector2(4, 8);
|
|
}
|
|
|
|
public ShogiBoard(IList<Move> moves) : this()
|
|
{
|
|
for (var i = 0; i < moves.Count; i++)
|
|
{
|
|
if (!Move(moves[i]))
|
|
{
|
|
throw new InvalidOperationException($"Unable to construct ShogiBoard with the given move at index {i}.");
|
|
}
|
|
}
|
|
}
|
|
|
|
private ShogiBoard(ShogiBoard toCopy)
|
|
{
|
|
Board = new Array2D<Piece>(9, 9);
|
|
for (var x = 0; x < 9; x++)
|
|
for (var y = 0; y < 9; y++)
|
|
Board[x, y] = toCopy.Board[x, y]?.DeepClone();
|
|
|
|
pathFinder = new PathFinder2D<Piece>(Board);
|
|
MoveHistory = new List<Move>(toCopy.MoveHistory);
|
|
Hands = new Dictionary<WhichPlayer, List<Piece>>
|
|
{
|
|
{ WhichPlayer.Player1, new List<Piece>(toCopy.Hands[WhichPlayer.Player1]) },
|
|
{ WhichPlayer.Player2, new List<Piece>(toCopy.Hands[WhichPlayer.Player2]) }
|
|
};
|
|
player1King = toCopy.player1King;
|
|
player2King = toCopy.player2King;
|
|
}
|
|
|
|
public bool Move(Move move)
|
|
{
|
|
var otherPlayer = WhoseTurn == WhichPlayer.Player1 ? WhichPlayer.Player2 : WhichPlayer.Player1;
|
|
var moveSuccess = TryMove(move);
|
|
|
|
if (!moveSuccess)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
// Evaluate check
|
|
if (EvaluateCheckAfterMove(move, otherPlayer))
|
|
{
|
|
InCheck = otherPlayer;
|
|
IsCheckmate = EvaluateCheckmate();
|
|
}
|
|
return true;
|
|
}
|
|
/// <summary>
|
|
/// Attempts a given move. Returns false if the move is illegal.
|
|
/// </summary>
|
|
private bool TryMove(Move move)
|
|
{
|
|
// Try making the move in a "throw away" board.
|
|
if (validationBoard == null)
|
|
{
|
|
validationBoard = new ShogiBoard(this);
|
|
}
|
|
|
|
var isValid = move.PieceFromCaptured.HasValue
|
|
? validationBoard.PlaceFromHand(move)
|
|
: validationBoard.PlaceFromBoard(move);
|
|
if (!isValid)
|
|
{
|
|
// Invalidate the "throw away" board.
|
|
validationBoard = null;
|
|
return false;
|
|
}
|
|
// If already in check, assert the move that resulted in check no longer results in check.
|
|
if (InCheck == WhoseTurn)
|
|
{
|
|
if (validationBoard.EvaluateCheckAfterMove(MoveHistory[^1], WhoseTurn))
|
|
{
|
|
// Sneakily using this.WhoseTurn instead of validationBoard.WhoseTurn;
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// The move is valid and legal; update board state.
|
|
if (move.PieceFromCaptured.HasValue) PlaceFromHand(move);
|
|
else PlaceFromBoard(move);
|
|
return true;
|
|
}
|
|
/// <returns>True if the move was successful.</returns>
|
|
private bool PlaceFromHand(Move move)
|
|
{
|
|
if (move.PieceFromCaptured.HasValue == false) return false; //Invalid move
|
|
var index = Hands[WhoseTurn].FindIndex(p => p.WhichPiece == move.PieceFromCaptured);
|
|
if (index < 0) return false; // Invalid move
|
|
if (Board[move.To.X, move.To.Y] != null) return false; // Invalid move; cannot capture while playing from the hand.
|
|
|
|
var minimumY = 0;
|
|
switch (move.PieceFromCaptured.Value)
|
|
{
|
|
case WhichPiece.Knight:
|
|
// Knight cannot be placed onto the farthest two ranks from the hand.
|
|
minimumY = WhoseTurn == WhichPlayer.Player1 ? 2 : 6;
|
|
break;
|
|
case WhichPiece.Lance:
|
|
case WhichPiece.Pawn:
|
|
// Lance and Pawn cannot be placed onto the farthest rank from the hand.
|
|
minimumY = WhoseTurn == WhichPlayer.Player1 ? 1 : 7;
|
|
break;
|
|
}
|
|
if (WhoseTurn == WhichPlayer.Player1 && move.To.Y < minimumY) return false;
|
|
if (WhoseTurn == WhichPlayer.Player2 && move.To.Y > minimumY) return false;
|
|
|
|
// Mutate the board.
|
|
Board[move.To.X, move.To.Y] = Hands[WhoseTurn][index];
|
|
Hands[WhoseTurn].RemoveAt(index);
|
|
|
|
return true;
|
|
}
|
|
/// <returns>True if the move was successful.</returns>
|
|
private bool PlaceFromBoard(Move move)
|
|
{
|
|
var fromPiece = Board[move.From.X, move.From.Y];
|
|
if (fromPiece == null) return false; // Invalid move
|
|
if (fromPiece.Owner != WhoseTurn) return false; // Invalid move; cannot move other players pieces.
|
|
if (IsPathable(move.From, move.To) == false) return false; // Invalid move; move not part of move-set.
|
|
|
|
var captured = Board[move.To.X, move.To.Y];
|
|
if (captured != null)
|
|
{
|
|
if (captured.Owner == WhoseTurn) return false; // Invalid move; cannot capture your own piece.
|
|
captured.Capture();
|
|
Hands[captured.Owner].Add(captured);
|
|
}
|
|
|
|
//Mutate the board.
|
|
if (move.IsPromotion)
|
|
{
|
|
if (WhoseTurn == WhichPlayer.Player1 && (move.To.Y > 5 || move.From.Y > 5))
|
|
{
|
|
fromPiece.Promote();
|
|
}
|
|
else if (WhoseTurn == WhichPlayer.Player2 && (move.To.Y < 3 || move.From.Y < 3))
|
|
{
|
|
fromPiece.Promote();
|
|
}
|
|
}
|
|
Board[move.To.X, move.To.Y] = fromPiece;
|
|
Board[move.From.X, move.From.Y] = null;
|
|
if (fromPiece.WhichPiece == WhichPiece.King)
|
|
{
|
|
if (fromPiece.Owner == WhichPlayer.Player1)
|
|
{
|
|
player1King.X = move.To.X;
|
|
player1King.Y = move.To.Y;
|
|
}
|
|
else if (fromPiece.Owner == WhichPlayer.Player2)
|
|
{
|
|
player2King.X = move.To.X;
|
|
player2King.Y = move.To.Y;
|
|
}
|
|
}
|
|
MoveHistory.Add(move);
|
|
return true;
|
|
}
|
|
|
|
private bool IsPathable(Vector2 from, Vector2 to)
|
|
{
|
|
var piece = Board[from.X, from.Y];
|
|
if (piece == null) return false;
|
|
|
|
var isObstructed = false;
|
|
var isPathable = pathFinder.PathTo(from, to, (other, position) =>
|
|
{
|
|
if (other.Owner == piece.Owner) isObstructed = true;
|
|
});
|
|
return !isObstructed && isPathable;
|
|
}
|
|
|
|
public void PrintStateAsAscii()
|
|
{
|
|
var builder = new StringBuilder();
|
|
builder.Append(" Player 2");
|
|
builder.AppendLine();
|
|
for (var y = 8; y > -1; y--)
|
|
{
|
|
builder.Append("- ");
|
|
for (var x = 0; x < 8; x++) builder.Append("- - ");
|
|
builder.Append("- -");
|
|
builder.AppendLine();
|
|
builder.Append('|');
|
|
for (var x = 0; x < 9; x++)
|
|
{
|
|
var piece = Board[x, y];
|
|
if (piece == null)
|
|
{
|
|
builder.Append(" ");
|
|
}
|
|
else
|
|
{
|
|
builder.AppendFormat("{0}", piece.ShortName);
|
|
}
|
|
builder.Append('|');
|
|
}
|
|
builder.AppendLine();
|
|
}
|
|
builder.Append("- ");
|
|
for (var x = 0; x < 8; x++) builder.Append("- - ");
|
|
builder.Append("- -");
|
|
builder.AppendLine();
|
|
builder.Append(" Player 1");
|
|
Console.WriteLine(builder.ToString());
|
|
}
|
|
#region Rules Validation
|
|
private bool EvaluateCheckAfterMove(Move move, WhichPlayer whichPlayer)
|
|
{
|
|
var isCheck = false;
|
|
var kingPosition = whichPlayer == WhichPlayer.Player1 ? player1King : player2King;
|
|
|
|
// Check if the move put the king in check.
|
|
if (pathFinder.PathTo(move.To, kingPosition)) return true;
|
|
|
|
// Get line equation from king through the now-unoccupied location.
|
|
var direction = Vector2.Subtract(kingPosition, move.From);
|
|
var slope = Math.Abs(direction.Y / direction.X);
|
|
// If absolute slope is 45°, look for a bishop along the line.
|
|
// If absolute slope is 0° or 90°, look for a rook along the line.
|
|
// if absolute slope is 0°, look for lance along the line.
|
|
if (float.IsInfinity(slope))
|
|
{
|
|
// if slope of the move is also infinity...can skip this?
|
|
pathFinder.LinePathTo(kingPosition, direction, (piece, position) =>
|
|
{
|
|
if (piece.Owner != whichPlayer)
|
|
{
|
|
switch (piece.WhichPiece)
|
|
{
|
|
case WhichPiece.Rook:
|
|
isCheck = true;
|
|
break;
|
|
case WhichPiece.Lance:
|
|
if (!piece.IsPromoted) isCheck = true;
|
|
break;
|
|
}
|
|
}
|
|
});
|
|
}
|
|
else if (slope == 1)
|
|
{
|
|
pathFinder.LinePathTo(kingPosition, direction, (piece, position) =>
|
|
{
|
|
if (piece.Owner != whichPlayer && piece.WhichPiece == WhichPiece.Bishop)
|
|
{
|
|
isCheck = true;
|
|
}
|
|
});
|
|
}
|
|
else if (slope == 0)
|
|
{
|
|
pathFinder.LinePathTo(kingPosition, direction, (piece, position) =>
|
|
{
|
|
if (piece.Owner != whichPlayer && piece.WhichPiece == WhichPiece.Rook)
|
|
{
|
|
isCheck = true;
|
|
}
|
|
});
|
|
}
|
|
|
|
return isCheck;
|
|
}
|
|
private bool EvaluateCheckmate()
|
|
{
|
|
if (!InCheck.HasValue) return false;
|
|
|
|
// Assume true and try to disprove.
|
|
var isCheckmate = true;
|
|
Board.ForEachNotNull((piece, x, y) => // For each piece...
|
|
{
|
|
// Short circuit
|
|
if (!isCheckmate) return;
|
|
|
|
var from = new Vector2(x, y);
|
|
if (piece.Owner == InCheck) // ...owned by the player in check...
|
|
{
|
|
// ...evaluate if any move gets the player out of check.
|
|
pathFinder.PathEvery(from, (other, position) =>
|
|
{
|
|
if (validationBoard == null) validationBoard = new ShogiBoard(this);
|
|
var moveToTry = new Move { From = from, To = position };
|
|
var moveSuccess = validationBoard.TryMove(moveToTry);
|
|
if (moveSuccess)
|
|
{
|
|
validationBoard = null;
|
|
if (!EvaluateCheckAfterMove(moveToTry, InCheck.Value))
|
|
{
|
|
isCheckmate = false;
|
|
}
|
|
}
|
|
});
|
|
}
|
|
});
|
|
return isCheckmate;
|
|
}
|
|
#endregion
|
|
|
|
#region Initialize
|
|
private void ResetEmptyRows()
|
|
{
|
|
for (int y = 3; y < 6; y++)
|
|
for (int x = 0; x < 9; x++)
|
|
Board[x, y] = null;
|
|
}
|
|
private void ResetFrontRow(WhichPlayer player)
|
|
{
|
|
int y = player == WhichPlayer.Player1 ? 2 : 6;
|
|
for (int x = 0; x < 9; x++) Board[x, y] = new Pawn(player);
|
|
}
|
|
private void ResetMiddleRow(WhichPlayer player)
|
|
{
|
|
int y = player == WhichPlayer.Player1 ? 1 : 7;
|
|
|
|
Board[0, y] = null;
|
|
for (int x = 2; x < 7; x++) Board[x, y] = null;
|
|
Board[8, y] = null;
|
|
if (player == WhichPlayer.Player1)
|
|
{
|
|
Board[1, y] = new Bishop(player);
|
|
Board[7, y] = new Rook(player);
|
|
}
|
|
else
|
|
{
|
|
Board[1, y] = new Rook(player);
|
|
Board[7, y] = new Bishop(player);
|
|
}
|
|
}
|
|
private void ResetRearRow(WhichPlayer player)
|
|
{
|
|
int y = player == WhichPlayer.Player1 ? 0 : 8;
|
|
|
|
Board[0, y] = new Lance(player);
|
|
Board[1, y] = new Knight(player);
|
|
Board[2, y] = new SilverGeneral(player);
|
|
Board[3, y] = new GoldenGeneral(player);
|
|
Board[4, y] = new King(player);
|
|
Board[5, y] = new GoldenGeneral(player);
|
|
Board[6, y] = new SilverGeneral(player);
|
|
Board[7, y] = new Knight(player);
|
|
Board[8, y] = new Lance(player);
|
|
}
|
|
private void InitializeBoardState()
|
|
{
|
|
ResetRearRow(WhichPlayer.Player1);
|
|
ResetMiddleRow(WhichPlayer.Player1);
|
|
ResetFrontRow(WhichPlayer.Player1);
|
|
ResetEmptyRows();
|
|
ResetFrontRow(WhichPlayer.Player2);
|
|
ResetMiddleRow(WhichPlayer.Player2);
|
|
ResetRearRow(WhichPlayer.Player2);
|
|
}
|
|
#endregion
|
|
}
|
|
}
|