Added history — though still need to be checked thoroughly

Sources/Engine/History.swift

@@ -0,0 +1,71 @@
+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 {
+			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))
+	}
+}