piece.go

package chess

// Color represents the color of a chess piece.
type Color int8

const (
	// NoColor represents no color
	NoColor Color = iota
	// White represents the color white
	White
	// Black represents the color black
	Black
)

// Other returns the opposie color of the receiver.
func (c Color) Other() Color {
	switch c {
	case White:
		return Black
	case Black:
		return White
	}
	return NoColor
}

// String implements the fmt.Stringer interface and returns
// the color's FEN compatible notation.
func (c Color) String() string {
	switch c {
	case White:
		return "w"
	case Black:
		return "b"
	}
	return "-"
}

// Name returns a display friendly name.
func (c Color) Name() string {
	switch c {
	case White:
		return "White"
	case Black:
		return "Black"
	}
	return "No Color"
}

// PieceType is the type of a piece.
type PieceType int8

const (
	// NoPieceType represents a lack of piece type
	NoPieceType PieceType = iota
	// King represents a king
	King
	// Queen represents a queen
	Queen
	// Rook represents a rook
	Rook
	// Bishop represents a bishop
	Bishop
	// Knight represents a knight
	Knight
	// Pawn represents a pawn
	Pawn
)

// PieceTypes returns a slice of all piece types.
func PieceTypes() [6]PieceType {
	return [6]PieceType{King, Queen, Rook, Bishop, Knight, Pawn}
}

func (p PieceType) String() string {
	switch p {
	case King:
		return "k"
	case Queen:
		return "q"
	case Rook:
		return "r"
	case Bishop:
		return "b"
	case Knight:
		return "n"
	}
	return ""
}

func (p PieceType) promotableTo() bool {
	switch p {
	case Queen, Rook, Bishop, Knight:
		return true
	}
	return false
}

// Piece is a piece type with a color.
type Piece int8

const (
	// NoPiece represents no piece
	NoPiece Piece = iota
	// WhiteKing is a white king
	WhiteKing
	// WhiteQueen is a white queen
	WhiteQueen
	// WhiteRook is a white rook
	WhiteRook
	// WhiteBishop is a white bishop
	WhiteBishop
	// WhiteKnight is a white knight
	WhiteKnight
	// WhitePawn is a white pawn
	WhitePawn
	// BlackKing is a black king
	BlackKing
	// BlackQueen is a black queen
	BlackQueen
	// BlackRook is a black rook
	BlackRook
	// BlackBishop is a black bishop
	BlackBishop
	// BlackKnight is a black knight
	BlackKnight
	// BlackPawn is a black pawn
	BlackPawn
)

var (
	allPieces = []Piece{
		WhiteKing, WhiteQueen, WhiteRook, WhiteBishop, WhiteKnight, WhitePawn,
		BlackKing, BlackQueen, BlackRook, BlackBishop, BlackKnight, BlackPawn,
	}
)

func getPiece(t PieceType, c Color) Piece {
	for _, p := range allPieces {
		if p.Color() == c && p.Type() == t {
			return p
		}
	}
	return NoPiece
}

// Type returns the type of the piece.
func (p Piece) Type() PieceType {
	switch p {
	case WhiteKing, BlackKing:
		return King
	case WhiteQueen, BlackQueen:
		return Queen
	case WhiteRook, BlackRook:
		return Rook
	case WhiteBishop, BlackBishop:
		return Bishop
	case WhiteKnight, BlackKnight:
		return Knight
	case WhitePawn, BlackPawn:
		return Pawn
	}
	return NoPieceType
}

// Color returns the color of the piece.
func (p Piece) Color() Color {
	switch p {
	case WhiteKing, WhiteQueen, WhiteRook, WhiteBishop, WhiteKnight, WhitePawn:
		return White
	case BlackKing, BlackQueen, BlackRook, BlackBishop, BlackKnight, BlackPawn:
		return Black
	}
	return NoColor
}

// String implements the fmt.Stringer interface
func (p Piece) String() string {
	return pieceUnicodes[int(p)]
}

var (
	pieceUnicodes = []string{" ", "♔", "♕", "♖", "♗", "♘", "♙", "♚", "♛", "♜", "♝", "♞", "♟"}
)

func (p Piece) getFENChar() string {
	for key, piece := range fenPieceMap {
		if piece == p {
			return key
		}
	}
	return ""
}