public enum Kind: String, CaseIterable {
	case Pawn, Knight, Bishop, Rook, Queen, King

	var value: Int8 {
		switch self {
		case .Pawn: 1
		case .Bishop: 3
		case .Knight: 3
		case .Rook: 5
		case .Queen: 9
		case .King: -1
		}
	}

	func fenRepresentation(with color: Color) -> String {
		let str =
			switch self {
			case .Pawn: "P"
			case .Bishop: "B"
			case .Knight: "N"
			case .Rook: "R"
			case .Queen: "Q"
			case .King: "K"
			}

		return color == .White ? str : str.lowercased()
	}

	static subscript(_ c: Character) -> (Self, Color)? {
		let v = c.uppercased()

		guard
			v == "N"
				|| (Self.allCases.contains { String($0.rawValue.first!) == v })
		else {
			return nil
		}

		let kind: Self =
			switch v {
			case "P": .Pawn
			case "N": .Knight
			case "B": .Bishop
			case "R": .Rook
			case "Q": .Queen
			case "K": .King
			default: .Pawn
			}

		let color: Color = c.isUppercase ? .White : .Black

		return (kind, color)
	}
}

public class Piece {
	#warning("TODO: TO be removed, handle everything through the delegate")
	internal weak var board: Board?
	public internal(set) var color: Color
	public var unicodeRepresentation: String {
		return ""
	}
	public internal(set) var kind: Kind
	public internal(set) var position: Square.Position
	internal var pseudoLegalPositions: [Square.Position] {
		return []
	}
	internal var legalPositions: [Square.Position] {
		return []
	}
	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)
	}
	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))
					return false
				}
			}

		}
		return true
	}

	internal init(kind: Kind, on pos: Square.Position, with col: Color) {
		self.kind = kind
		self.position = pos
		self.color = col
	}
}