public static IEnumerable<Move> EnumerateLegalMoves(Board Board)
{
for (byte t = 0; t < 19; ++t)
{
var tile = Board.GetTile(t);
if (tile.IsOutOfPlay()) continue;
for (byte x = 0; x < 6; ++x)
foreach (var move in EnumerateLegalPieceMoves(new Coordinate(t, x), Board))
yield return move;
}
}
public static IEnumerable<Move> EnumerateLegalPieceMoves(Coordinate Piece, Board Board)
{
if (Piece.Triangle % 2 != Board.Header.WhoseTurnNext)
{
if (Board.GetTriangle(Piece) != 0)
{
for (byte x = 0; x < 6; ++x)
{
var neighbor = FindMoveNeighbor(Piece, x);
if (neighbor.Invalid || Board.GetTile(neighbor.Tile).IsOutOfPlay())
continue;
if (Board.GetTriangle(neighbor) == 0)
yield return new Move(Piece, x, MoveType.MovePiece);
}
}
}
else
{
if (Board.GetTriangle(Piece) != 0)
{
var canSnipe = Board.Tiles.Count(t => t.IsHeldBy(Board.Header.WhoseTurnNext)) >= 2;
if (canSnipe)
yield return new Move(Piece, 0, MoveType.Trade);
}
}
}
public static Board ApplyMove(Board Board, Move Move)
{
var checkForSurrounded = new List<Coordinate>();
var checkForEmpty = new List<byte>();
var sniping = false;
switch ((MoveType)Move.Type)
{
case MoveType.Trade:
{
/*
// Verify move is legal.
// Reject move if attempting to snipe own piece.
if (Move.Triangle % 2 != Board.Header.WhoseTurnNext) throw new InvalidOperationException();
// Reject move if player does not hold at least two tiles.
var heldTileCount = Board.Tiles.Count(t => t.IsHeldBy(Board.Header.WhoseTurnNext));
if (heldTileCount < 2) throw new InvalidOperationException();
// Reject move if there is no enemy piece at the location.
if (Board.GetTriangle(Move.Coordinate) == 0) throw new InvalidOperationException();
*/
// Turn is legal, mutate board.
foreach (var tile in Board.Tiles.Where(t => t.IsHeldBy(Board.Header.WhoseTurnNext)).Take(2))
Board = Board.WithTile(tile.ID, tile.WithStatus(0x03));
Board = Board.WithTile(Move.Tile, Board.GetTile(Move.Tile).WithTriangle(Move.Triangle, 0));
checkForEmpty.Add(Move.Tile);
sniping = true;
}
break;
case MoveType.MovePiece:
{
/*
// Verify move is legal.
// Reject move if attempting to move opponent piece.
if (Move.Triangle % 2 == Board.Header.WhoseTurnNext) throw new InvalidOperationException();
// Reject move if there is no piece at the location.
if (Board.GetTriangle(Move.Coordinate) == 0) throw new InvalidOperationException();
// Find destination triangle coordinate.
*/
var dest = FindMoveNeighbor(Move.Coordinate, Move.Direction);
/*
// Reject move if player attempted to move off board.
if (dest.Invalid) throw new InvalidOperationException();
if (Board.GetTile(dest.Tile).IsOutOfPlay()) throw new InvalidOperationException();
// Reject move if destination triangle is occupied.
if (Board.GetTriangle(dest) != 0) throw new InvalidOperationException();
*/
// Move is legal, mutate board.
Board = Board.WithTile(Move.Tile, Board.GetTile(Move.Tile).WithTriangle(Move.Triangle, 0));
Board = Board.WithTile(dest.Tile, Board.GetTile(dest.Tile).WithTriangle(dest.Triangle, 1));
checkForEmpty.Add(Move.Tile);
for (byte x = 0; x < 3; ++x)
{
var neighbor = FindSurroundNeighbor(dest, x);
if (!neighbor.Invalid && !Board.GetTile(neighbor.Tile).IsOutOfPlay())
checkForSurrounded.Add(neighbor);
}
}
break;
}
while (checkForSurrounded.Count > 0 || checkForEmpty.Count > 0)
{
while (checkForSurrounded.Count > 0)
{
var piece = checkForSurrounded[0];
checkForSurrounded.RemoveAt(0);
var sum = 0;
for (byte x = 0; x < 3; ++x)
{
var neighbor = FindSurroundNeighbor(piece, x);
if (neighbor.Invalid || Board.GetTile(neighbor.Tile).IsOutOfPlay())
sum += 1;
else
sum += Board.GetTriangle(neighbor);
}
if (sum == 3)
{
Board = Board.WithTile(piece.Tile, Board.GetTile(piece.Tile).WithTriangle(piece.Triangle, 0));
checkForEmpty.Add(piece.Tile);
}
}
while (checkForEmpty.Count > 0)
{
var tileID = checkForEmpty[0];
checkForEmpty.RemoveAt(0);
if (!Board.GetTile(tileID).IsEmpty())
continue;
// Tile is empty - if it has 3 or less adjacent tiles in a row, it can be removed.
var runs = new AdjacentRun[3];
var runsCount = 0;
for (var x = 0; x < 6; ++x)
{
var neighbor = Tables.TileAdjacency[tileID][x];
if (neighbor != 0xFF && !Board.GetTile(neighbor).IsOutOfPlay())
{
if (runsCount == 0)
{
runs[0] = new AdjacentRun(x, x, 1);
runsCount += 1;
}
else if (runs[runsCount - 1].End == x - 1)
runs[runsCount - 1] = new AdjacentRun(runs[runsCount - 1].Start, x, runs[runsCount - 1].Count + 1);
else
{
runs[runsCount] = new AdjacentRun(x, x, 1);
runsCount += 1;
}
}
}
if (runsCount > 1 && runs[0].Start == 0 && runs[runsCount - 1].End == 5)
{
runs[0] = new AdjacentRun(runs[runsCount - 1].Start, runs[0].End, runs[0].Count + runs[runsCount - 1].Count);
runsCount -= 1;
}
if (runsCount == 1 && runs[0].Count <= 3)
{
if (sniping)
Board = Board.WithTile(tileID, Board.GetTile(tileID).WithStatus(0x03));
else
Board = Board.WithTile(tileID, Board.GetTile(tileID).WithStatus((byte)(Board.Header.WhoseTurnNext + 1)));
// Mark adjacent triangles for surround consideration.
for (var x = 0; x < 6; ++x)
{
// Don't check own pieces for surround
if (Tables.ExposedAdjacency[x] % 2 != Board.Header.WhoseTurnNext) continue;
// Don't check tiles that don't exist.
var neighbor = Tables.TileAdjacency[tileID][x];
if (neighbor == 0xFF || Board.GetTile(neighbor).IsOutOfPlay()) continue;
checkForSurrounded.Add(new Coordinate(neighbor, Tables.ExposedAdjacency[x]));
}
// Check neighboring tiles to see if they can be removed.
for (var x = 0; x < 6; ++x)
{
var neighbor = Tables.TileAdjacency[tileID][x];
if (neighbor == 0xFF || Board.GetTile(neighbor).IsOutOfPlay()) continue;
checkForEmpty.Add(neighbor);
}
}
}
}
if (Board.Header.WhoseTurnNext == 0)
Board = Board.WithHeader(new StateHeader(0x80));
else
Board = Board.WithHeader(new StateHeader(0x00));
return Board;
}
