Can now move pieces

Sources/Engine/Board.swift

@@ -4,7 +4,7 @@ enum Event {
 }
 protocol EventDelegate {
 	func notify(_ event: Event)
-	func movePiece(_ piece: Piece, to dst: Square.Position)
+	func movePiece(_ piece: Piece, to dst: Square.Position) throws
 }
 public class Board: CustomStringConvertible, EventDelegate {
 	public typealias Grid = [[Square]]
@@ -24,8 +24,87 @@ public class Board: CustomStringConvertible, EventDelegate {
 
 	}
 
-	func movePiece(_ piece: Piece, to dst: Square.Position) {
+	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)
+	}
 
+	public enum MoveFailure: Error, CustomStringConvertible {
+		case sourceSquareUnreachable(pos: Square.Position)
+		case destinationSquareUnreachable(pos: Square.Position)
+		case squareHasNoPiece(pos: Square.Position)
+		case destinationIsIllegal(pos: Square.Position)
+		case squareANIsTooLong(an: String)
+		case squareANIsTooShort(an: String)
+
+		public var description: String {
+			return switch self {
+			case .sourceSquareUnreachable(let pos):
+				"The source square given \(pos.rank) \(pos.file) is unreachable."
+			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."
+			case .destinationIsIllegal(let pos):
+				"The destination square given \(pos.rank) \(pos.file) is illegal to be moved to."
+			case .squareANIsTooLong(let an):
+				"The algebraic notation \(an) is too long. (Needs to be 2 characters)"
+			case .squareANIsTooShort(let an):
+				"The algebraic notation \(an) is too short. (Needs to be 2 characters)"
+			}
+		}
+	}
+
+	public func move(src: String, dst: String) throws {
+		guard src.count < 3 else {
+			throw MoveFailure.squareANIsTooLong(an: src)
+		}
+		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 {
+		guard let srcSquare = self[src] else {
+			throw MoveFailure.sourceSquareUnreachable(pos: src)
+		}
+		guard self[dst] != nil else {
+			throw MoveFailure.destinationSquareUnreachable(pos: src)
+		}
+		guard let piece = srcSquare.piece else {
+			throw MoveFailure.squareHasNoPiece(pos: src)
+		}
+
+		try piece.move(to: dst)
 	}
 
 	public func getSquareInfo(on pos: Square.Position) -> Square? {