chessmcu/Piece.cpp

// © 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.

#include "Piece.hpp"

Piece::~Piece() {
    return;
}

// because the Piece class is instantiated in another class using
// unique_ptr, non-pure virtual functions apparently *must*
// have definitions, or the linker freaks out
// so this is just a stub that does nothing. it doesn't matter
// because only the derived class versions should be called.

std::vector<Move> Piece::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    return moveList;
}

std::vector<Move> King::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    const int directions[8][2] = {
        {-1, 0}, // Up
        {-1, -1}, // up-left
        {-1, 1}, // up-right
        {1, 0}, // Down
        {1, -1}, // down-left
        {1, 1}, // down-right
        {0, -1}, // Left
        {0, 1} // Right
    };
    return moveList;
}

std::vector<Move> Rook::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    const int directions[4][2] = {
        {-1, 0}, // Up
        {1, 0}, // Down
        {0, -1}, // Left
        {0, 1} // Right
    };
    for (auto& dir : directions) {
        int r = from.rank + dir[0];
        int f = from.file + dir[1];

        while (r >= 0 && r < 8 && f >= 0 && f < 8) {
            const auto& target = board.boardGrid[r][f];
            auto ra = static_cast<Rank> (r);
            auto fi = static_cast<File> (f);
            Square targetSquare = {ra, fi};
            if (!target) {
                moveList.push_back({from,
                    targetSquare});
            } else if (target->getColour() != this->getColour()) {
                moveList.push_back({from,
                    targetSquare});
                break;
            } else {
                break;
            }

            r += dir[0];
            f += dir[1];
        }
    }

    return moveList;
}

std::vector<Move> Queen::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;

    return moveList;
}

std::vector<Move> Knight::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;

    return moveList;
}

std::vector<Move> Bishop::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;

    return moveList;
}

std::vector<Move> Pawn::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    const int directions[2][4][2] = {
        { // black
            {-1, 0}, // Up
            {-2, 0}, // 2up first move
            {-1, 1}, // attack to right
            {-1, -1} // attack to left
        },
        { // white
            {1, 0}, // down
            {2, 0}, // 2down first move
            {1, 1}, // attack to right
            {1, -1} // attack to left
        }
    };

    if (this->getColour() == PIECE_BLACK) {
        // go through black options
        for (auto &dir : directions[0]) {
            int r = from.rank + dir[0];
            int f = from.file + dir[1];
            if (r >= 0 && r < 8 && f >= 0 && f < 8) { // no need for a while loop as we only have finite moves in limited directions
                const auto& target = board.boardGrid[r][f];
                auto ra = static_cast<Rank> (r);
                auto fi = static_cast<File> (f);
                Square targetSquare = {ra, fi};

                if (dir[0] == -2 && !this->checkIfMoved()) {
                    // then 2 is potentially legal
                    if (!target && !(board.boardGrid[r + 1][f])) // check both squares for pieces of any colour
                        moveList.push_back({from, targetSquare});
                    else
                        break;
                } else if (abs(dir[1]) == 1) { // attempted capture (diagonal)
                    if (target && target->getColour() != this->getColour()) {
                        // legal capture
                        moveList.push_back({from, targetSquare});
                    } else {
                        break;
                    }
                } else { // normal one square forward
                    if (!target)
                        moveList.push_back({from, targetSquare});
                }
                // now check if we are on 8th rank, for promotion
            }
        }
    } else if (this->getColour() == PIECE_WHITE) {
        for (auto &dir : directions[1]) {
            // go through white options
            int r = from.rank + dir[0];
            int f = from.file + dir[1];
            if (r >= 0 && r < 8 && f >= 0 && f < 8) { // no need for a while loop as we only have finite moves in limited directions
                const auto& target = board.boardGrid[r][f];
                auto ra = static_cast<Rank> (r);
                auto fi = static_cast<File> (f);
                Square targetSquare = {ra, fi};

                if (dir[0] == 2 && !this->checkIfMoved()) {
                    // then 2 is potentially legal
                    if (!target && !(boardGrid[r - 1][f]))
                        moveList.push_back({from, targetSquare});
                    else
                        break;
                } else if (abs(dir[1]) == 1) { // attempted capture (diagonal)
                    if (target && target->getColour() != this->getColour()) { // can only move there if it's a capture
                        // legal capture
                        moveList.push_back({from, targetSquare});
                    } else {
                        break;
                    }
                } else { // normal one square forward
                    if (!target)
                        moveList.push_back({from, targetSquare});
                }
                // now check if we are on 8th rank, for promotion
            }
        }
    }

    return moveList;
}