chessmcu/inc/Piece.hpp

// © 2025 A.M. Rowsell <amr@frzn.dev>

// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as
// defined by the Mozilla Public License, v. 2.0.

#ifndef PIECE_HPP
#define PIECE_HPP

/** @file Piece.hpp
 *  @brief The header files for the Piece class.
 *
 * This file contains not only the definition of the Piece class itself, but also all
 * of the derived classes (King, Queen, Rook, etc.) I was considering having them be in
 * separate files, but each derived class does not contain that much code, so keeping them
 * all in one place seemed easier to deal with. This may change in the future!
 *
 * Also defined here are important enums that help abstract chess terms, for example the
 * PieceType, PieceColour, Rank, File, etc. These allow the code to be more readable and
 * it helps make it obvious what certain bits of code are doing.
 */

#include <cstdint>
#include <algorithm>
#include <utility>
#include <string>
#include <memory>
#include <vector>

class Board;

enum PieceType {
    PAWN, BISHOP, KNIGHT, ROOK, QUEEN, KING, EMPTY
};

enum PieceColour {
    PIECE_WHITE, PIECE_BLACK, PIECE_EMPTY
};

enum Rank {
    R1 = 0, R2 = 1, R3 = 2, R4 = 3, R5 = 4, R6 = 5, R7 = 6, R8 = 7, INVALID_RANK = 255
};

enum File {
    A = 0, B = 1, C = 2, D = 3, E = 4, F = 5, G = 6, H = 7, INVALID_FILE = 255
};

enum CastleSide {
    KINGSIDE = 1, QUEENSIDE = 2
};

/** @struct Square
 * A struct that represents a square on the chess board.
 */
struct Square {
    Rank rank; /**< enum Rank rank represents the rank of the Square */
    File file; /**< enum File file represents the file of the Square */

    /**
     * A function to test if the square is a valid square on the chessboard
     * @return True if the square is within the chessboard, False otherwise
     */
    bool isValid() const {
        return rank >= 0 && rank < 8 && file >= 0 && file < 8;
    }
};
/**
 * A struct representing the start and end squares of a Move.
 */
struct Move {
    Square from;
    Square to;
};

/**
 * @class Piece Piece.hpp "inc/Piece.hpp"
 * @brief A class abstracting chess pieces
 *
 * This is a polymorphic base class containing the basic properties all chess pieces have.
 * It is intended to be extended by a child class for each piece Type, i.e. King, Queen, etc.
 */
class Piece {
  private:
    friend class Board;
  protected:
    PieceColour colour;
    PieceType pieceType;
    std::string pieceName; /**< std::string pieceName is a string showing the full name of the piece, i.e. "PAWN" */
    std::string
    pieceSymbol; /**< std::string pieceSymbol is a single character, using the standard algebraic chess notation, ie N for Knight */
    bool hasMoved = false;

  public:

    Piece(PieceColour pColour) : colour(pColour) {
    }
    virtual ~Piece();


    PieceColour getColour() const {
        return colour;
    }

    std::string getPieceName() const {
        return pieceName;
    }

    std::string getPieceSymbol() const {
        return pieceSymbol;
    }

    PieceType getPieceType() const {
        return pieceType;
    }

    bool checkIfMoved() const {
        return hasMoved;
    }
    /**
     * A virtual const function that should get all legal moves for a piece, but it may
     * include some moves that need to be pruned, like those exposing the king to check.
     * Still working out how to handle this.
     *
     * @param from the Square the Piece is currently on
     * @param board A reference to the Board we are analyzing
     * @return std::vector of Move: a list of all potentially legal moves
     */
    virtual std::vector<Move> getLegalMoves(const Square &from, Board &board) const;

    bool finalMoveChecks(std::vector<Move> *moveList, Board &board);

};

class King : public Piece {
  private:
    friend class Board;
  public:

    King(PieceColour colour) : Piece(colour) {
        pieceName = "King";
        pieceSymbol = "K";
        pieceType = KING;
    }
    virtual std::vector<Move> getLegalMoves(const Square &from, Board &board) const override;

    bool checkForCheck(Board &board) const;

    bool checkForCastle(enum CastleSide side) const {
        if(side == KINGSIDE)
            return canCastleKS;
        else if(side == QUEENSIDE)
            return canCastleQS;
        else
            return false;
    }

    void setCastleQS(bool canCastle) {
        canCastleQS = canCastle;
    }
    void setCastleKS(bool canCastle) {
        canCastleKS = canCastle;
    }
  protected:
    bool canCastleQS = true;
    bool canCastleKS = true;
    bool inCheck = false;
};

class Rook : public Piece {
    friend class Board;
  public:

    Rook(PieceColour colour) : Piece(colour) {
        pieceName = "Rook";
        pieceSymbol = "R";
        pieceType = ROOK;
    }
    virtual std::vector<Move> getLegalMoves(const Square &from, Board &board) const override;
};

class Queen : public Piece {
    friend class Board;
  public:

    Queen(PieceColour colour) : Piece(colour) {
        pieceName = "Queen";
        pieceSymbol = "Q";
        pieceType = QUEEN;
    }
    virtual std::vector<Move> getLegalMoves(const Square &from, Board &board) const override;
};

class Knight : public Piece {
    friend class Board;
  public:

    Knight(PieceColour colour) : Piece(colour) {
        pieceName = "Knight";
        pieceSymbol = "N";
        pieceType = KNIGHT;
    }
    virtual std::vector<Move> getLegalMoves(const Square &from, Board &board) const override;
};

class Bishop : public Piece {
    friend class Board;
  public:

    Bishop(PieceColour colour) : Piece(colour) {
        pieceName = "Bishop";
        pieceSymbol = "B";
        pieceType = BISHOP;
    }
    virtual std::vector<Move> getLegalMoves(const Square &from, Board &board) const override;
};

class Pawn : public Piece {
    friend class Board;
  public:

    Pawn(PieceColour colour) : Piece(colour) {
        pieceName = "Pawn";
        pieceSymbol = "P";
        pieceType = PAWN;
    }
    virtual std::vector<Move> getLegalMoves(const Square &from, Board &board) const override;
    void promote(const Square &promotionSquare, Board &board, PieceType promoteTo);
  protected:
    bool vulnEnPassant = false;
    bool firstMove = true;
};
#endif // PIECE_HPP