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This commit is contained in:
Lucas Morgan
2021-03-01 20:55:37 -06:00
parent f55716d2ec
commit 3da187be17
5 changed files with 154 additions and 109 deletions
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189
Gameboard.ShogiUI.BoardState/ShogiBoard.cs
View File

@@ -44,11 +44,15 @@ namespace Gameboard.ShogiUI.BoardState
{
for (var i = 0; i < moves.Count; i++)
{
if (!Move(moves[i]))
if (!TryMove(moves[i]))
{
throw new InvalidOperationException($"Unable to construct ShogiBoard with the given move at index {i}.");
}
}
if (EvaluateCheckAfterMove(WhoseTurn))
{
InCheck = WhoseTurn;
}
}
private ShogiBoard(ShogiBoard toCopy)
@@ -72,7 +76,6 @@ namespace Gameboard.ShogiUI.BoardState
public bool Move(Move move)
{
var otherPlayer = WhoseTurn == WhichPlayer.Player1 ? WhichPlayer.Player2 : WhichPlayer.Player1;
var moveSuccess = TryMove(move);
if (!moveSuccess)
@@ -81,11 +84,14 @@ namespace Gameboard.ShogiUI.BoardState
}
// Evaluate check
InCheck = EvaluateCheck(otherPlayer) ? otherPlayer : null;
if (EvaluateCheckAfterMove(WhoseTurn))
{
InCheck = WhoseTurn;
if (InCheck.HasValue)
{
//IsCheckmate = EvaluateCheckmate();
}
}
return true;
}
/// <summary>
@@ -109,47 +115,17 @@ namespace Gameboard.ShogiUI.BoardState
return false;
}
// Assert that this move does not put the moving player in check.
if (validationBoard.EvaluateCheck(WhoseTurn)) return false;
if (validationBoard.EvaluateCheckAfterMove(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;
}
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...
{
if (!isCheckmate) return; // Short circuit
var from = new Vector2(x, y);
if (piece.Owner == InCheck) // Owned by the player in check...
{
var positionsToCheck = new List<Vector2>(10);
//IterateMoveSet(from, (innerPiece, position) =>
//{
// if (innerPiece?.Owner != InCheck) positionsToCheck.Add(position); // Find possible moves...
//});
// And evaluate if any move gets the player out of check.
foreach (var position in positionsToCheck)
{
if (validationBoard == null) validationBoard = new ShogiBoard(this);
var moveSuccess = validationBoard.TryMove(new Move { From = from, To = position });
if (moveSuccess)
{
isCheckmate &= validationBoard.EvaluateCheck(InCheck.Value);
validationBoard = null;
}
}
}
});
return isCheckmate;
}
/// <returns>True if the move was successful.</returns>
private bool PlaceFromHand(Move move)
{
@@ -186,7 +162,7 @@ namespace Gameboard.ShogiUI.BoardState
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, fromPiece) == false) return false; // Invalid move; move not part of move-set.
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)
@@ -227,10 +203,13 @@ namespace Gameboard.ShogiUI.BoardState
return true;
}
private bool IsPathable(Vector2 from, Vector2 to, Piece piece)
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(piece, from, to, (other, position) =>
var isPathable = pathFinder.PathTo(from, to, (other, position) =>
{
if (other.Owner == piece.Owner) isObstructed = true;
});
@@ -272,39 +251,92 @@ namespace Gameboard.ShogiUI.BoardState
Console.WriteLine(builder.ToString());
}
#region Rules Validation
/// <summary>
/// Evaluate if a player is in check given the current board state.
/// </summary>
private bool EvaluateCheck(WhichPlayer whichPlayer)
private bool EvaluateCheckAfterMove(WhichPlayer whichPlayer)
{
var destination = whichPlayer == WhichPlayer.Player1 ? player1King : player2King;
var inCheck = false;
// Iterate every board piece...
Board.ForEachNotNull((piece, x, y) =>
{
var origin = new Vector2(x, y);
// ...that belongs to the opponent within range...
if (piece.Owner != whichPlayer && pathFinder.IsPathable(origin, destination, piece))
{
pathFinder.PathTo(piece, origin, destination, (threatenedPiece, position) =>
{
// ...and threatens the player's king.
inCheck |=
threatenedPiece.WhichPiece == WhichPiece.King
&& threatenedPiece.Owner == whichPlayer;
});
}
});
return inCheck;
}
/// <summary>
/// Iterate through the possible moves of a piece at a given position.
/// </summary>
var isCheck = false;
var kingPosition = whichPlayer == WhichPlayer.Player1 ? player1King : player2King;
/// <summary>
/// Useful for iterating the board for pieces that move many spaces.
/// </summary>
/// <param name="callback">A function that returns true if walking should continue.</param>
// Get last move.
var move = MoveHistory[^1];
// 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 moveSuccess = validationBoard.TryMove(new Move { From = from, To = position });
if (moveSuccess)
{
isCheckmate = false;
}
});
}
});
return isCheckmate;
}
#endregion
#region Initialize
@@ -362,18 +394,5 @@ namespace Gameboard.ShogiUI.BoardState
ResetRearRow(WhichPlayer.Player2);
}
#endregion
//public static ShogiBoard ConstructWithMoves(IList<Move> moves)
//{
// var s = new ShogiBoard();
// for (var i = 0; i < moves.Count; i++)
// {
// if (!s.Move(moves[i]))
// {
// throw new InvalidOperationException($"Unable to construct ShogiBoard with the given move at index {i}.");
// }
// }
// return s;
//}
}
}

1
Gameboard.ShogiUI.UnitTests/BoardState/ShogiBoardShould.cs
View File

@@ -177,7 +177,6 @@ namespace Gameboard.ShogiUI.UnitTests.BoardState
// P1 Bishop puts P2 in check
new Move { From = new Vector2(1, 1), To = new Vector2(6, 6) }
};
//var shogi = new ShogiBoard(moves);
var shogi = new ShogiBoard(moves);
// Prerequisit

4
Gameboard.ShogiUI.UnitTests/PathFinding/PathFinder2DShould.cs
View File

@@ -24,14 +24,14 @@ namespace Gameboard.ShogiUI.UnitTests.PathFinding
var result = finder.IsPathable(
new Vector2(2, 2),
new Vector2(7, 7),
new Vector2(3, 3)
new Vector2(1, 1)
);
result.Should().BeTrue();
result = finder.IsPathable(
new Vector2(2, 2),
new Vector2(7, 7),
new Vector2(2, 2)
new Vector2(0, 0)
);
result.Should().BeFalse();

2
PathFinding/IPlanarCollection.cs
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@@ -4,7 +4,7 @@ namespace PathFinding
{
public interface IPlanarCollection<T> : IEnumerable<T>
{
T this[int x, int y] { get; set; }
T this[float x, float y] { get; set; }
int GetLength(int dimension);
}
}

73
PathFinding/PathFinder2D.cs
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@@ -1,4 +1,5 @@
using System.Collections.Generic;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
@@ -24,46 +25,50 @@ namespace PathFinding
}
/// <summary>
/// Navigate the collection such that each "step" is always towards the destination.
/// Navigate the collection such that each "step" is always towards the destination, respecting the Paths available to the element at origin.
/// </summary>
/// <param name="element">The pathing element.</param>
/// <param name="origin">The starting location.</param>
/// <param name="destination">The destination.</param>
/// <param name="callback">Do cool stuff here.</param>
/// <returns>True if the element reached the destination.</returns>
public bool PathTo(T element, Vector2 origin, Vector2 destination, Callback callback)
public bool PathTo(Vector2 origin, Vector2 destination, Callback callback = null)
{
if (destination.X > width - 1 || destination.Y > height - 1 || destination.X < 0 || destination.Y < 0)
{
return false;
}
var element = collection[origin.X, origin.Y];
var path = FindDirectionTowardsDestination(element.GetPaths(), origin, destination);
var next = Vector2.Add(origin, path.Direction);
if (!IsPathable(origin, destination, next))
if (!IsPathable(origin, destination, path.Direction))
{
// Assumption: if a single best-choice step towards the destination cannot happen, no pathing can happen.
return false;
}
var shouldPath = true;
while (shouldPath)
var next = origin;
while (shouldPath && next != destination)
{
next = Vector2.Add(next, path.Direction);
var collider = collection[(int)next.X, (int)next.Y];
if (collider != null) callback(collider, next);
if (next == destination) return true;
if (path.Distance == Distance.OneStep)
if (collider != null)
{
callback?.Invoke(collider, next);
shouldPath = false;
}
else if (path.Distance == Distance.OneStep)
{
shouldPath = false;
}
next = Vector2.Add(next, path.Direction);
}
return true;
return next == destination;
}
public void PathEvery(IPlanarElement element, Vector2 from, Callback callback)
public void PathEvery(Vector2 from, Callback callback)
{
var element = collection[from.X, from.Y];
foreach (var path in element.GetPaths())
{
var shouldPath = true;
@@ -84,6 +89,22 @@ namespace PathFinding
}
}
/// <summary>
/// Path the line from origin to destination, ignoring any Paths defined by the element at origin.
/// </summary>
public void LinePathTo(Vector2 origin, Vector2 direction, Callback callback)
{
direction = Vector2.Normalize(direction);
var next = Vector2.Add(origin, direction);
while (next.X >= 0 && next.X < width && next.Y >= 0 && next.Y < height)
{
var element = collection[next.X, next.Y];
if (element != null) callback(element, next);
next = Vector2.Add(next, direction);
}
}
public Path FindDirectionTowardsDestination(ICollection<Path> paths, Vector2 origin, Vector2 destination) =>
paths.Aggregate((a, b) => Vector2.Distance(destination, Vector2.Add(origin, a.Direction)) < Vector2.Distance(destination, Vector2.Add(origin, b.Direction)) ? a : b);
@@ -91,20 +112,26 @@ namespace PathFinding
public bool IsPathable(Vector2 origin, Vector2 destination, T element)
{
var path = FindDirectionTowardsDestination(element.GetPaths(), origin, destination);
var next = Vector2.Add(origin, path.Direction);
return IsPathable(origin, destination, next);
return IsPathable(origin, destination, path.Direction);
}
public bool IsPathable(Vector2 origin, Vector2 destination, Vector2 next)
public bool IsPathable(Vector2 origin, Vector2 destination, Vector2 direction)
{
if (Vector2.Distance(next, destination) < Vector2.Distance(origin, destination))
{
// y = mx + b
// b = -mx + y
direction = Vector2.Normalize(direction);
var next = Vector2.Add(origin, direction);
if (Vector2.Distance(next, destination) >= Vector2.Distance(origin, destination)) return false;
var slope = (destination.Y - origin.Y) / (destination.X - origin.X);
var yIntercept = -(slope * origin.X) + origin.Y;
return float.IsInfinity(slope) || next.Y == slope * next.X + yIntercept;
if (float.IsInfinity(slope))
{
return next.X == destination.X;
}
else
{
// b = -mx + y
var yIntercept = -slope * origin.X + origin.Y;
// y = mx + b
return next.Y == slope * next.X + yIntercept;
}
return false;
}
}
}