Started to work on king threats

Sources/Engine/Board.swift

@@ -1,5 +1,5 @@
 enum Event {
-	case kingInCheck(_ by: Piece)
+	case kingInCheck(_ by: Piece, on: King)
 	case piecePinned(from: Piece, on: Piece)
 }
 protocol EventDelegate {
@@ -24,12 +24,30 @@ public class Board: CustomStringConvertible, EventDelegate {
 
 	}
 
+	public private(set) var halfMoveClock: UInt8 = 0
+
+	public var fullMoveClock: UInt8 {
+		halfMoveClock / 2
+	}
+
+	internal var threatenedSquares: [Color: Set<Square.Position>] = [
+		.White: [],
+		.Black: [],
+	]
+
+	public private(set) var turn: Color = .White
+
 	func movePiece(_ piece: Piece, to dst: Square.Position) throws {
 		let from = piece.position
 		piece.position = dst
 		squares[dst.index!].piece = piece
 		squares[from.index!].piece = nil
-		fen.set(from: board, castling: .All, enPassant: fen.enPassant)
+		halfMoveClock += 1
+		turn = !turn
+		fen.set(
+			from: board, activeColor: turn, castling: .All,
+			enPassant: fen.enPassant,
+			halfMoveClock: halfMoveClock, fullMoveClock: fullMoveClock)
 	}
 
 	public enum MoveFailure: Error, CustomStringConvertible {
@@ -105,6 +123,12 @@ public class Board: CustomStringConvertible, EventDelegate {
 		}
 
 		try piece.move(to: dst)
+		#warning("May need to clear threatenedSquares before hand.")
+		for square in squares where square.piece != nil {
+			let p = square.piece!
+			p.getLegalPosition()
+			threatenedSquares[p.color]! += Set(p.legalPositions)
+		}
 	}
 
 	public func getSquareInfo(on pos: Square.Position) -> Square? {
@@ -183,9 +207,6 @@ public class Board: CustomStringConvertible, EventDelegate {
 			file += 1
 			index += 1
 		}
-		#if DEBUG
-			print(b)
-		#endif
 		squares = b
 	}
 
@@ -206,7 +227,7 @@ public class Board: CustomStringConvertible, EventDelegate {
 				rank -= 1
 			}
 		}
-		// TODO: Handle better
+		#warning("Handle better.")
 		do {
 			try setBoard()
 		} catch Fen.FenError.NotAppropriateLength(let n, let column) {