Started to work on king threats

Sources/Engine/Pieces/Bishop.swift

@@ -8,10 +8,6 @@ final class Bishop: Piece, DiagonalMoves {
 		return getDiagonalMoves(from: position)
 	}
 
-	override var legalPositions: [Square.Position] {
-		return pseudoLegalPositions.filter { isLegal(on: $0) }
-	}
-
 	override func isLegal(on pos: Square.Position) -> Bool {
 		super.isLegal(on: pos)
 	}

Sources/Engine/Pieces/King.swift

@@ -1,5 +1,6 @@
 final class King: Piece {
-
+	typealias Threats = (Piece?, Piece?)
+	var threats: Threats = (nil, nil)
 	override var unicodeRepresentation: String {
 		return color == .Black ? "♛" : "♕"
 	}
@@ -17,12 +18,12 @@ final class King: Piece {
 		].filter { $0.index != nil }
 	}
 
-	override var legalPositions: [Square.Position] {
-		return pseudoLegalPositions.filter { isLegal(on: $0) }
-	}
-
 	override func isLegal(on pos: Square.Position) -> Bool {
-		super.isLegal(on: pos)
+		guard super.isLegal(on: pos) else {
+			return false
+		}
+		// Do stuff
+		return true
 	}
 
 	init(with color: Color, on position: Square.Position) {

Sources/Engine/Pieces/Knight.swift

@@ -16,10 +16,6 @@ final class Knight: Piece {
 		].filter { $0.index != nil }
 	}
 
-	override var legalPositions: [Square.Position] {
-		return pseudoLegalPositions.filter { isLegal(on: $0) }
-	}
-
 	override func isLegal(on pos: Square.Position) -> Bool {
 		super.isLegal(on: pos)
 	}

Sources/Engine/Pieces/Pawn.swift

@@ -9,10 +9,6 @@ final class Pawn: Piece {
 		].filter { $0.index != nil }
 	}
 
-	override var legalPositions: [Square.Position] {
-		pseudoLegalPositions.filter { isLegal(on: $0) }
-	}
-
 	override var unicodeRepresentation: String {
 		color == .Black ? "♟" : "♙"
 	}

Sources/Engine/Pieces/Piece.swift

@@ -54,9 +54,10 @@ public enum Kind: String, CaseIterable {
 }
 
 public class Piece {
-	#warning("TODO: TO be removed, handle everything through the delegate")
+	#warning("TODO: To be removed, handle everything through the delegate")
 	internal weak var board: Board?
 	public internal(set) var color: Color
+	public internal(set) var halfMoveCount: UInt8 = 0
 	public var unicodeRepresentation: String {
 		return ""
 	}
@@ -65,25 +66,29 @@ public class Piece {
 	internal var pseudoLegalPositions: [Square.Position] {
 		return []
 	}
-	internal var legalPositions: [Square.Position] {
-		return []
+	internal var legalPositions = [Square.Position]()
+	internal func getLegalPosition() {
+		legalPositions = pseudoLegalPositions.filter { isLegal(on: $0) }
 	}
 	internal var delegate: EventDelegate?
+
 	internal func move(to dst: Square.Position) throws {
 		if !(legalPositions.contains { $0 == dst }) {
 			throw Board.MoveFailure.destinationIsIllegal(pos: dst)
 		}
 
 		try delegate?.movePiece(self, to: dst)
+		halfMoveCount += 1
 	}
-	internal func isLegal(on pos: Square.Position) -> Bool {
 
+	#warning("This method should be better thought out.")
+	internal func isLegal(on pos: Square.Position) -> Bool {
 		if let board = board, let s = board[pos] {
 			if let p = s.piece {
 				if p.color == color { return false }
-				if p.kind == .King {
-					// TODO: Notify board of check
-					delegate?.notify(.kingInCheck(self))
+				if let king = p as? King {
+					#warning("It could be in check or behind another piece.")
+					delegate?.notify(.kingInCheck(self, on: king))
 					return false
 				}
 			}

Sources/Engine/Pieces/Queen.swift

@@ -7,10 +7,6 @@ final class Queen: Piece, LinearMoves, DiagonalMoves {
 		return getDiagonalMoves(from: position) + getLinearMoves(from: position)
 	}
 
-	override var legalPositions: [Square.Position] {
-		return pseudoLegalPositions.filter { isLegal(on: $0) }
-	}
-
 	override func isLegal(on pos: Square.Position) -> Bool {
 		super.isLegal(on: pos)
 	}

Sources/Engine/Pieces/Rook.swift

@@ -8,10 +8,6 @@ final class Rook: Piece, LinearMoves {
 		return getLinearMoves(from: position)
 	}
 
-	override var legalPositions: [Square.Position] {
-		return pseudoLegalPositions.filter { isLegal(on: $0) }
-	}
-
 	override func isLegal(on pos: Square.Position) -> Bool {
 		super.isLegal(on: pos)
 	}