internal final class Knight: Piece {
	internal weak var board: Board?
	internal var kind: Kind = .Knight

	internal var unicodeRepresentation: String {
		return color == .Black ? "♞" : "♘"
	}
	internal var color: Color

	internal var position: Square.Position

	internal var pseudoLegalPositions: [Square.Position] {
		let directions: [Square.Position] = [
			.init(file: position.file + 1, rank: position.rank + 2),
			.init(file: position.file - 1, rank: position.rank + 2),
			.init(file: position.file + 1, rank: position.rank - 2),
			.init(file: position.file - 1, rank: position.rank - 2),
			.init(file: position.file + 2, rank: position.rank + 1),
			.init(file: position.file - 2, rank: position.rank + 1),
			.init(file: position.file + 2, rank: position.rank - 1),
			.init(file: position.file - 2, rank: position.rank - 1)
		]
		return directions.filter {
			let index = $0.index
			return index < 0 || index > 63
		}
	}

	internal var legalPositions: [Square.Position] {
		return pseudoLegalPositions.filter { isLegal(on: $0) }
	}

	internal func move(to dst: Square.Position) -> Bool {
		return false
	}

	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
					return false
				}
			}

		}
		return true
	}

	internal init(color: Color, on position: Square.Position) {
		self.color = color
		self.position = position
	}

}