yes

Sources/Engine/Board.swift

@@ -1,11 +1,15 @@
 enum Event {
-	case kingInCheck(_ by: Piece)
+	case kingInCheck(_ by: Piece, on: King)
 	case piecePinned(from: Piece, on: Piece)
 }
+
 protocol EventDelegate {
 	func notify(_ event: Event)
 	func movePiece(_ piece: Piece, to dst: Square.Position) throws
+	func addPieceToTarget(_ piece: Piece, target: Square.Position)
+	func getSquareInfo(on pos: Square.Position) -> Square?
 }
+
 public class Board: CustomStringConvertible, EventDelegate {
 	public typealias Grid = [[Square]]
 
@@ -20,16 +24,104 @@ public class Board: CustomStringConvertible, EventDelegate {
 		}
 	}
 
-	func notify(_ event: Event) {
+	public struct TerminalColors: CustomStringConvertible, Hashable {
+		public enum Foreground: String {
+			case def = "39"
+			case black = "30"
+			case red = "31"
+			case green = "32"
+			case yellow = "33"
+			case blue = "34"
+			case magenta = "35"
+			case cyan = "36"
+			case white = "37"
+		}
+		public enum Background: String {
+			case def = "49"
+			case black = "40"
+			case red = "41"
+			case green = "42"
+			case yellow = "43"
+			case blue = "44"
+			case magenta = "45"
+			case cyan = "46"
+			case white = "47"
+		}
+
+		public var foregroundColor: Foreground? = .def
+		public var backgroundColor: Background? = .def
+
+		public init() {}
+
+		public init(fg: Foreground?, bg: Background) {
+			foregroundColor = fg
+			backgroundColor = bg
+		}
+
+		public var description: String {
+			var res = "\u{001B}["
+			if let fc = foregroundColor {
+				res += fc.rawValue
+				if backgroundColor != nil {
+					res += ";"
+				}
+			}
+			if let bc = backgroundColor {
+				res += bc.rawValue
+			}
+			return res + "m"
+		}
 
 	}
 
+	func notify(_ event: Event) {
+		#warning("Not implemented")
+		switch event {
+		case .kingInCheck(let piece, let king):
+			king.insertThreat(piece)
+		case .piecePinned(let p1, let p2):
+			break
+		}
+	}
+
+	internal func addPieceToTarget(_ piece: Piece, target: Square.Position) {
+		guard self[target] != nil else {
+			return
+		}
+		squares[target.index!].targetted.insert(piece)
+	}
+
+	public private(set) var halfMoveClock: UInt8 = 0
+
+	public var fullMoveClock: UInt8 {
+		halfMoveClock / 2
+	}
+
+	public internal(set) var threatenedSquares: [Color: Set<Square.Position>] =
+		[
+			.White: [],
+			.Black: [],
+		]
+
+	public internal(set) var history = History()
+
+	public private(set) var turn: Color = .White
+
 	func movePiece(_ piece: Piece, to dst: Square.Position) throws {
 		let from = piece.position
+		history.add(
+			.pieceMove(
+				from: squares[from.index!],
+				to: squares[dst.index!]))
 		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 {
@@ -47,7 +139,7 @@ public class Board: CustomStringConvertible, EventDelegate {
 			case .destinationSquareUnreachable(let pos):
 				"The destination square given \(pos.rank) \(pos.file) is unreachable."
 			case .squareHasNoPiece(let pos):
-				"The square \(pos.rank) \(pos.file) doesn't have any piece to be moved."
+				"The square \(pos.rank) \(pos.file) doesn't have any piece."
 			case .destinationIsIllegal(let pos):
 				"The destination square given \(pos.rank) \(pos.file) is illegal to be moved to."
 			case .squareANIsTooLong(let an):
@@ -59,38 +151,11 @@ public class Board: CustomStringConvertible, EventDelegate {
 	}
 
 	public func move(src: String, dst: String) throws {
-		guard src.count < 3 else {
-			throw MoveFailure.squareANIsTooLong(an: src)
+		if let from = try Square.Position(with: src),
+			let to = try Square.Position(with: dst)
+		{
+			try move(src: from, dst: to)
 		}
-		guard src.count > 1 else {
-			throw MoveFailure.squareANIsTooShort(an: src)
-		}
-		guard dst.count < 3 else {
-			throw MoveFailure.squareANIsTooLong(an: dst)
-		}
-		guard dst.count > 1 else {
-			throw MoveFailure.squareANIsTooShort(an: dst)
-		}
-		guard let f1 = src.first, let r1 = src.last, r1.isWholeNumber else {
-			return
-		}
-		guard let f2 = dst.first, let r2 = src.last, r2.isWholeNumber else {
-			return
-		}
-		guard
-			let srcFile = Square.Position.File.init(rawValue: String(f1))?.value
-		else {
-			return
-		}
-		guard
-			let dstFile = Square.Position.File.init(rawValue: String(f2))?.value
-		else {
-			return
-		}
-
-		try move(
-			src: Square.Position(rank: Int8(String(r1))!, file: srcFile),
-			dst: Square.Position(rank: Int8(String(r2))!, file: dstFile))
 	}
 
 	public func move(src: Square.Position, dst: Square.Position) throws {
@@ -105,6 +170,15 @@ public class Board: CustomStringConvertible, EventDelegate {
 		}
 
 		try piece.move(to: dst)
+		threatenedSquares = [
+			.White: [],
+			.Black: [],
+		]
+		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 +257,6 @@ public class Board: CustomStringConvertible, EventDelegate {
 			file += 1
 			index += 1
 		}
-		#if DEBUG
-			print(b)
-		#endif
 		squares = b
 	}
 
@@ -206,9 +277,14 @@ public class Board: CustomStringConvertible, EventDelegate {
 				rank -= 1
 			}
 		}
-		// TODO: Handle better
+		#warning("Handle better.")
 		do {
 			try setBoard()
+			for square in squares where square.piece != nil {
+				let p = square.piece!
+				p.getLegalPosition()
+				threatenedSquares[p.color]! += Set(p.legalPositions)
+			}
 		} catch Fen.FenError.NotAppropriateLength(let n, let column) {
 			fatalError("Not appropriate length: \(n) on \(column)")
 		} catch {
@@ -216,15 +292,27 @@ public class Board: CustomStringConvertible, EventDelegate {
 		}
 	}
 
-	public var description: String {
+	public func text(with colors: [TerminalColors: [Square.Position]]? = nil)
+		-> String
+	{
 		var boardString =
 			"    A   B   C   D   E   F   G   H \n  \(UnicodeBar.TopHorizontalLine)\n"
 		var _rank: UInt8 = 8
+		let def: TerminalColors = .init()
+		var h1 = def
 		board.forEach { rank in
 			boardString += String(_rank) + " \(UnicodeBar.VerticalBar)"
 			rank.forEach { square in
 				let p = square.piece?.unicodeRepresentation ?? " "
-				boardString += " \(p) \(UnicodeBar.VerticalBar)"
+				h1 = def
+				if let c = colors {
+					for (color, s) in c
+					where (s.contains { $0 == square.position }) {
+						h1 = color
+					}
+				}
+				boardString +=
+					"\(h1) \(p) \(def)\(UnicodeBar.VerticalBar)"
 			}
 			boardString += "\n"
 			_rank -= 1
@@ -236,6 +324,10 @@ public class Board: CustomStringConvertible, EventDelegate {
 		return boardString
 	}
 
+	public var description: String {
+		text()
+	}
+
 	internal subscript(pos: Square.Position) -> Square? {
 		guard let i = pos.index else {
 			return nil

Sources/Engine/Extensions/Set+Union.swift

@@ -0,0 +1,9 @@
+extension Set {
+	static func + (lhs: Set<Element>, rhs: Set<Element>) -> Set<Element> {
+		return lhs.union(rhs)
+	}
+
+	static func += (lhs: inout Set<Element>, rhs: Set<Element>) {
+		lhs.formUnion(rhs)
+	}
+}

Sources/Engine/Extensions/Targets+Unique.swift

@@ -0,0 +1,9 @@
+extension Square.Targets {
+	public mutating func insert(_ piece: Piece) {
+		guard !self.contains(piece) else {
+			return
+		}
+
+		self.append(piece)
+	}
+}

Sources/Engine/FEN.swift

@@ -64,8 +64,9 @@ public struct Fen: CustomStringConvertible {
 	}
 
 	internal mutating func set(
-		from board: Board.Grid, castling ca: CastlingAvailibility,
-		enPassant: String
+		from board: Board.Grid, activeColor: Color,
+		castling ca: CastlingAvailibility,
+		enPassant: String, halfMoveClock hmc: UInt8, fullMoveClock fmc: UInt8
 	) {
 		#warning(
 			"Determine active color, halfMoveClock, fullMoveClock based on history SAN later passed in arguments"
@@ -95,7 +96,8 @@ public struct Fen: CustomStringConvertible {
 			rankNr += 1
 		}
 
-		value = placement + " w " + ca.rawValue + " " + enPassant + " 0 " + "1"
+		value =
+			"\(placement) \(activeColor) \(ca.rawValue) \(enPassant) \(halfMoveClock) \(fullMoveClock)"
 	}
 
 	public enum FenError: Error {

Sources/Engine/History.swift

@@ -0,0 +1,72 @@
+public struct History {
+	public typealias Array = [(
+		SANMoveDescriptor.Value?, SANMoveDescriptor.Value?
+	)]
+
+	public enum SANMoveDescriptor {
+		public typealias Value = String
+		case pieceMove(from: Square, to: Square)
+		case pawnPush(to: Square, promotion: Piece?)
+
+		public var value: Value {
+			return switch self {
+			#warning("Doesn't work properly")
+			case .pieceMove(let from, let to):
+				{
+					guard let piece = from.piece else {
+						return ""
+					}
+					#warning("Ugly ass code 🤢")
+					var result =
+						piece.kind == .Pawn
+						? ""
+						: "\(piece.kind.fenRepresentation(with: piece.color))"
+					if let ambiguity = (to.targetted.first { $0 ~= piece }) {
+						let file =
+							ambiguity.position.file != from.position.file
+							? Square.Position.File[from.position.file] : nil
+						var rank: Int8? {
+							if file == nil {
+								return ambiguity.position.rank
+									!= from.position.rank
+									? from.position.rank : nil
+							}
+							return nil
+						}
+						if let f = file {
+							result += f.rawValue
+						} else if let r = rank {
+							result += String(r)
+						} else {
+							result +=
+								Square.Position.File[from.position.file]!
+								.rawValue
+								+ String(from.position.rank)
+						}
+					}
+					if to.piece != nil {
+						result += "x"
+					}
+					result +=
+						"\(Square.Position.File[to.position.file]!.rawValue)\(String(to.position.rank))"
+					return result
+				}()
+			case .pawnPush(let to, let promotion):
+				""
+			}
+		}
+	}
+
+	public private(set) var values: Array = []
+
+	internal mutating func add(_ san: SANMoveDescriptor) {
+		#warning("To be tested")
+		if let last = values.last {
+			if last.1 == nil {
+				values[values.count - 1].1 = san.value
+				return
+			}
+		}
+		values.append((san.value, nil))
+	}
+}

Sources/Engine/Pieces/Bishop.swift

@@ -8,12 +8,48 @@ final class Bishop: Piece, DiagonalMoves {
 		return getDiagonalMoves(from: position)
 	}
 
-	override var legalPositions: [Square.Position] {
-		return pseudoLegalPositions.filter { isLegal(on: $0) }
+	override func getLegalPosition() {
+		legalPositions = []
+		var last: Square.Position? = nil
+		for position in pseudoLegalPositions {
+			if !isLegal(on: position) {
+				last = position
+				continue
+			}
+
+			if !DiagonalDirection.isLegal(last: &last, current: position) {
+				last = nil
+			}
+			if last == nil {
+				legalPositions.append(position)
+				if let square = delegate?.getSquareInfo(on: position),
+					let piece = square.piece
+				{
+					if piece.color != color {
+						if let king = piece as? King {
+							delegate?.notify(.kingInCheck(self, on: king))
+							legalPositions.removeLast()
+							last = position
+							return
+						} else {
+							delegate?.notify(
+								.piecePinned(from: self, on: piece))
+							last = position
+						}
+					}
+				}
+				delegate?.addPieceToTarget(self, target: position)
+			}
+		}
 	}
 
 	override func isLegal(on pos: Square.Position) -> Bool {
-		super.isLegal(on: pos)
+		if let s = delegate?.getSquareInfo(on: pos), let p = s.piece,
+			p.color == color
+		{
+			return false
+		}
+		return true
 	}
 
 	init(with color: Color, on position: Square.Position) {

Sources/Engine/Pieces/CommonMoves.swift

@@ -1,4 +1,6 @@
-fileprivate func getDirectionalMoves(from pos: Square.Position, with dir: [(Int8, Int8)]) -> [Square.Position] {
+private func getDirectionalMoves(
+	from pos: Square.Position, with dir: [(Int8, Int8)]
+) -> [Square.Position] {
 	var squares = [Square.Position]()
 	for i: (Int8, Int8) in dir {
 		var currentSquare = pos + i
@@ -9,13 +11,61 @@ fileprivate func getDirectionalMoves(from pos: Square.Position, with dir: [(Int8
 	}
 	return squares
 }
+
 protocol DiagonalMoves {
 	func getDiagonalMoves(from pos: Square.Position) -> [Square.Position]
 }
 
+protocol Direction: CaseIterable {
+	var values: (Int8, Int8) { get }
+	static func isLegal(
+		last: inout Square.Position?,
+		current: Square.Position
+	) -> Bool
+}
+
+public enum DiagonalDirection: Direction {
+	case northWest
+	case northEast
+	case southEast
+	case southWest
+
+	public var values: (Int8, Int8) {
+		return switch self {
+		case .northWest: (1, -1)
+		case .northEast: (1, 1)
+		case .southEast: (-1, 1)
+		case .southWest: (-1, -1)
+		}
+	}
+	public static func isLegal(
+		last: inout Square.Position?,
+		current:
+			Square.Position
+	) -> Bool {
+		var isPred = false
+		for dir in DiagonalDirection.allCases {
+			isPred = last == current - dir.values
+			if isPred {
+				last = current
+				break
+			}
+		}
+
+		return isPred
+	}
+}
+
 extension DiagonalMoves {
 	func getDiagonalMoves(from pos: Square.Position) -> [Square.Position] {
-        getDirectionalMoves(from: pos, with: [(1, -1), (1, 1), (-1, 1), (-1, -1)])
+		getDirectionalMoves(
+			from: pos,
+			with: [
+				DiagonalDirection.northWest.values,
+				DiagonalDirection.northEast.values,
+				DiagonalDirection.southEast.values,
+				DiagonalDirection.southWest.values,
+			])
 	}
 }
 
@@ -23,8 +73,46 @@ protocol LinearMoves {
 	func getLinearMoves(from pos: Square.Position) -> [Square.Position]
 }
 
-extension LinearMoves {
-    func getLinearMoves(from pos: Square.Position) -> [Square.Position] {
-        getDirectionalMoves(from: pos, with: [(1, 0), (0, 1), (-1, 0), (0, -1)])
+public enum LinearDirection: Direction {
+	case north
+	case south
+	case east
+	case west
+
+	public var values: (Int8, Int8) {
+		return switch self {
+		case .north: (1, 0)
+		case .south: (-1, 0)
+		case .east: (0, 1)
+		case .west: (0, -1)
+		}
+	}
+
+	public static func isLegal(
+		last: inout Square.Position?, current: Square.Position
+	) -> Bool {
+		var isPred = false
+		for dir in LinearDirection.allCases {
+			isPred = last == current - dir.values
+			if isPred {
+				last = current
+				break
+			}
+		}
+
+		return isPred
+	}
+}
+
+extension LinearMoves {
+	func getLinearMoves(from pos: Square.Position) -> [Square.Position] {
+		getDirectionalMoves(
+			from: pos,
+			with: [
+				LinearDirection.north.values,
+				LinearDirection.east.values,
+				LinearDirection.south.values,
+				LinearDirection.west.values,
+			])
 	}
 }

Sources/Engine/Pieces/King.swift

@@ -1,7 +1,21 @@
 final class King: Piece {
+	typealias Threats = (Piece?, Piece?)
+	internal private(set) var threats: Threats = (nil, nil)
+
+	func insertThreat(_ piece: Piece) {
+		if threats.0 == nil {
+			threats.0 = piece
+			return
+		}
+
+		if threats.1 == nil {
+			threats.1 = piece
+			return
+		}
+	}
 
 	override var unicodeRepresentation: String {
-		return color == .Black ? "♛" : "♕"
+		return color == .Black ? "♚" : "♔"
 	}
 
 	override var pseudoLegalPositions: [Square.Position] {
@@ -17,12 +31,12 @@ 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

@@ -1,6 +1,8 @@
 final class Pawn: Piece {
+	private var sign: Int8 {
+		color == .Black ? -1 : 1
+	}
 	override var pseudoLegalPositions: [Square.Position] {
-		let sign: Int8 = color == .Black ? -1 : 1
 		return [
 			position + (1 * sign, 0),
 			position + (2 * sign, 0),
@@ -9,16 +11,30 @@ final class Pawn: Piece {
 		].filter { $0.index != nil }
 	}
 
-	override var legalPositions: [Square.Position] {
-		pseudoLegalPositions.filter { isLegal(on: $0) }
-	}
-
 	override var unicodeRepresentation: String {
 		color == .Black ? "♟" : "♙"
 	}
 
 	override func isLegal(on pos: Square.Position) -> Bool {
-		super.isLegal(on: pos)
+		#warning("Handle en-passant")
+		if pos == position + (2 * sign, 0) && halfMoveCount > 0 {
+			return false
+		}
+		if (pos == position + (1 * sign, 0) || pos == position + (2 * sign, 0))
+			&& delegate?.getSquareInfo(on: pos)?.piece != nil
+		{
+			return false
+		}
+		guard super.isLegal(on: pos) else {
+			return false
+		}
+		if (pos == position + (1 * sign, 1) || pos == position + (1 * sign, -1))
+			&& delegate?.getSquareInfo(on: pos)?.piece == nil
+		{
+			return false
+		}
+
+		return true
 	}
 
 	init(with color: Color, on position: Square.Position) {

Sources/Engine/Pieces/Piece.swift

@@ -53,10 +53,9 @@ public enum Kind: String, CaseIterable {
 	}
 }
 
-public class Piece {
-	#warning("TODO: TO be removed, handle everything through the delegate")
-	internal weak var board: Board?
+public class Piece: Hashable {
 	public internal(set) var color: Color
+	public internal(set) var halfMoveCount: UInt8 = 0
 	public var unicodeRepresentation: String {
 		return ""
 	}
@@ -65,30 +64,34 @@ public class Piece {
 	internal var pseudoLegalPositions: [Square.Position] {
 		return []
 	}
-	internal var legalPositions: [Square.Position] {
-		return []
+	package internal(set) 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 }) {
+		guard (legalPositions.contains { $0 == dst }) else {
 			throw Board.MoveFailure.destinationIsIllegal(pos: dst)
 		}
 
 		try delegate?.movePiece(self, to: dst)
+		halfMoveCount += 1
 	}
-	internal func isLegal(on pos: Square.Position) -> Bool {
 
-		if let board = board, let s = board[pos] {
+	#warning("This method should be better thought out.")
+	internal func isLegal(on pos: Square.Position) -> Bool {
+		if let s = delegate?.getSquareInfo(on: 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 {
+					delegate?.notify(.kingInCheck(self, on: king))
 					return false
 				}
 			}
 
 		}
+		delegate?.addPieceToTarget(self, target: pos)
 		return true
 	}
 
@@ -97,4 +100,30 @@ public class Piece {
 		self.position = pos
 		self.color = col
 	}
+
+	/// Two pieces are equal when they share the same kind, color and position
+	public static func == (lhs: Piece, rhs: Piece) -> Bool {
+		return lhs.kind == rhs.kind && lhs.color == rhs.color
+			&& lhs.position == rhs.position
+	}
+
+	/// Two pieces are not equal when they either do not share the same kind,
+	/// color or position
+	public static func != (lhs: Piece, rhs: Piece) -> Bool {
+		return !(lhs == rhs)
+	}
+
+	/// Checks if tho pieces are similar yet not equal.
+	/// They are considered simmilar if they share the same color and the same kind,
+	/// but differ in position.
+	public static func ~= (lhs: Piece, rhs: Piece) -> Bool {
+		return lhs.kind == rhs.kind && lhs.color == rhs.color
+			&& lhs.position != rhs.position
+	}
+
+	public func hash(into hasher: inout Hasher) {
+		hasher.combine(kind)
+		hasher.combine(color)
+		hasher.combine(position)
+	}
 }

Sources/Engine/Pieces/Queen.swift

@@ -7,12 +7,51 @@ 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 getLegalPosition() {
+		legalPositions = []
+		var last: Square.Position? = nil
+		for position in pseudoLegalPositions {
+			if !isLegal(on: position) {
+				last = position
+				continue
+			}
+
+			if !LinearDirection.isLegal(last: &last, current: position)
+				&& !DiagonalDirection.isLegal(last: &last, current: position)
+			{
+				last = nil
+			}
+
+			if last == nil {
+				legalPositions.append(position)
+				if let square = delegate?.getSquareInfo(on: position),
+					let piece = square.piece
+				{
+					if piece.color != color {
+						if let king = piece as? King {
+							delegate?.notify(.kingInCheck(self, on: king))
+							legalPositions.removeLast()
+							last = position
+							return
+						} else {
+							delegate?.notify(
+								.piecePinned(from: self, on: piece))
+							last = position
+						}
+					}
+				}
+				delegate?.addPieceToTarget(self, target: position)
+			}
+		}
 	}
 
 	override func isLegal(on pos: Square.Position) -> Bool {
-		super.isLegal(on: pos)
+		if let s = delegate?.getSquareInfo(on: pos), let p = s.piece,
+			p.color == color
+		{
+			return false
+		}
+		return true
 	}
 
 	init(with color: Color, on position: Square.Position) {

Sources/Engine/Pieces/Rook.swift

@@ -8,12 +8,48 @@ final class Rook: Piece, LinearMoves {
 		return getLinearMoves(from: position)
 	}
 
-	override var legalPositions: [Square.Position] {
-		return pseudoLegalPositions.filter { isLegal(on: $0) }
+	override func getLegalPosition() {
+		legalPositions = []
+		var last: Square.Position? = nil
+		for position in pseudoLegalPositions {
+			if !isLegal(on: position) {
+				last = position
+				continue
+			}
+
+			if !LinearDirection.isLegal(last: &last, current: position) {
+				last = nil
+			}
+			if last == nil {
+				legalPositions.append(position)
+				if let square = delegate?.getSquareInfo(on: position),
+					let piece = square.piece
+				{
+					if piece.color != color {
+						if let king = piece as? King {
+							delegate?.notify(.kingInCheck(self, on: king))
+							legalPositions.removeLast()
+							last = position
+							return
+						} else {
+							delegate?.notify(
+								.piecePinned(from: self, on: piece))
+							last = position
+						}
+					}
+				}
+				delegate?.addPieceToTarget(self, target: position)
+			}
+		}
 	}
 
 	override func isLegal(on pos: Square.Position) -> Bool {
-		super.isLegal(on: pos)
+		if let s = delegate?.getSquareInfo(on: pos), let p = s.piece,
+			p.color == color
+		{
+			return false
+		}
+		return true
 	}
 
 	init(with color: Color, on position: Square.Position) {

Sources/Engine/Square.swift

@@ -1,6 +1,6 @@
 public struct Square: Equatable {
 
-	public struct Position: Equatable {
+	public struct Position: Equatable, Hashable {
 		public let rank: Int8
 		public let file: Int8
 
@@ -16,6 +16,25 @@ public struct Square: Equatable {
 			file = f
 		}
 
+		public init?(with rep: String) throws {
+			guard rep.count < 3 else {
+				throw Board.MoveFailure.squareANIsTooLong(an: rep)
+			}
+			guard rep.count > 1 else {
+				throw Board.MoveFailure.squareANIsTooShort(an: rep)
+			}
+			guard let f1 = rep.first, let r1 = rep.last, r1.isWholeNumber else {
+				return nil
+			}
+			guard
+				let srcFile = File.init(rawValue: String(f1))?.value
+			else {
+				return nil
+			}
+			rank = Int8(String(r1))!
+			file = srcFile
+		}
+
 		public enum File: String, CustomStringConvertible {
 			case a, b, c, d, e, f, g, h
 
@@ -70,11 +89,29 @@ public struct Square: Equatable {
 		public static func += (lhs: inout Position, rhs: (Int8, Int8)) {
 			lhs = lhs + rhs
 		}
+
+		public static func - (lhs: Position, rhs: Position) -> Position {
+			.init(rank: lhs.rank - rhs.rank, file: lhs.file - rhs.file)
+		}
+
+		public static func - (lhs: Position, rhs: (Int8, Int8)) -> Position {
+			.init(rank: lhs.rank - rhs.0, file: lhs.file - rhs.1)
+		}
+
+		public static func -= (lhs: inout Position, rhs: Position) {
+			lhs = lhs - rhs
+		}
+
+		public static func -= (lhs: inout Position, rhs: (Int8, Int8)) {
+			lhs = lhs - rhs
+		}
 	}
 
 	public let position: Position
 	public internal(set) var piece: Piece? = nil
 	public let color: Color
+	public typealias Targets = [Piece]
+	public internal(set) var targetted: Targets = []
 
 	public static func == (lhs: Square, rhs: Square) -> Bool {
 		return lhs.position == rhs.position

Sources/Engine/utils.swift

@@ -1,4 +1,15 @@
-public enum Color: UInt8 {
+public enum Color: UInt8, CustomStringConvertible {
 	case Black = 0
 	case White = 1
+
+	public var description: String {
+		return switch self {
+		case .Black: "b"
+		case .White: "w"
+		}
+	}
+
+	public static prefix func ! (rhs: Self) -> Self {
+		return rhs == .White ? .Black : .White
+	}
 }

Sources/exe/main.swift

@@ -1,28 +1,109 @@
 import Engine
 
-let board = Board(
-	fen: .init(
-		fen: "rnbqkb1r/pppppppp/2n5/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"))
-// let board: Board = .init()
+enum Command: Equatable {
+	case quit
+	case noop
+	case print
+	case move(from: String, to: String)
+	case history(command: String? = nil)
+	case highlightThreatened(color: Color)
+	case highlightPositions(of: Square.Position)
+
+	init?(rawValue: String) {
+		let args = rawValue.lowercased().split(separator: " ")
+		guard !args.isEmpty else {
+			return nil
+		}
+
+		switch args[0] {
+		case "quit", "q":
+			self = .quit
+		case "noop", "n":
+			self = .noop
+		case "print", "p":
+			self = .print
+		case "move" where args.count == 3, "m" where args.count == 3:
+			self = .move(from: String(args[1]), to: String(args[2]))
+		case "history" where args.count == 2, "h" where args.count == 2:
+			self = .history(command: String(args[1]))
+		case "history", "h":
+			self = .history()
+		case "highlight" where args.count == 2, "hi" where args.count == 2:
+			let color: Color? =
+				switch args[1] {
+				case "w", "white":
+					.White
+				case "b", "black":
+					.Black
+				default:
+					nil
+				}
+			if let c = color {
+				self = .highlightThreatened(color: c)
+				return
+			}
+
+			if let position = try? Square.Position(with: String(args[1])) {
+				self = .highlightPositions(of: position)
+				return
+			}
+			return nil
+		default:
+			return nil
+		}
+	}
+}
+let board: Board = .init()
 print(board)
 
+var command: Command = .noop
+
+while command != .quit {
+	if let line = readLine(), let c = Command(rawValue: line.lowercased()) {
+		command = c
+		switch command {
+		case .print: print(board)
+		case .noop, .quit: continue
+		case .move(let from, let to):
+			do {
+				try board.move(src: from, dst: to)
+			} catch {
+				print(error)
+				continue
+			}
+		case .history(let command):
+			if let c = command {
+				if let fmc = Int(c),
+					fmc > -1 && fmc < board.history.values.count
+				{
+					print(board.history.values[fmc])
+				} else if c == "count" {
+					print(board.history.values.count)
+				} else {
+					print(board.history.values)
+				}
+			} else {
+				print(board.history.values)
+			}
+		case .highlightThreatened(let color):
+			if let ts = board.threatenedSquares[color] {
+				let color = Board.TerminalColors(fg: .def, bg: .red)
+				print(ts.count)
+				print(board.text(with: [color: Array(ts)]))
+			}
+		case .highlightPositions(let pos):
+			if let square = board.getSquareInfo(on: pos),
+				let piece =
+					square.piece
+			{
+				let color = Board.TerminalColors(fg: .def, bg: .green)
+				print(board.text(with: [color: piece.legalPositions]))
+			}
+		}
+	}
+}
+
 // Execute every time the timer changes
 // board.on(.timer) { time in
 
 // }
-
-do {
-	try board.move(src: "e4", dst: "f6")
-} catch {
-	print(error)
-}
-do {
-	try board.move(src: .init(rank: 2, file: 5), dst: .init(rank: 4, file: 5))
-} catch {
-	print(error)
-}
-
-print(board)
-print(board.fen)
-
-// let square = board.getSquareInfo(on: .init(rank: 2, file: 7))

Tests/EngineTests/EngineTests.swift

@@ -109,8 +109,11 @@ final class EngineTests: XCTestCase {
 		let board: Board = .init()
 		let fen = board.fen.value
 		board.fen.set(
-			from: board.board, castling: board.fen.castlingAvailibility,
-			enPassant: board.fen.enPassant)
+			from: board.board, activeColor: board.fen.activeColor,
+			castling: board.fen.castlingAvailibility,
+			enPassant: board.fen.enPassant,
+			halfMoveClock:
+				board.fen.halfMoveClock, fullMoveClock: board.fen.fullMoveClock)
 		XCTAssertEqual(
 			fen, board.fen.value, "Expected \(fen) got \(board.fen.value)")
 	}