chessy/src/ChessGame.cpp

#include "ChessGame.h"
#include <sstream>
#include <stdexcept>

using namespace chessy;

MoveInfo::MoveInfo(Move move, const ChessGame& cg) :
    move{ move }, movedPiece{ cg.getBoard().getAtPosition(move.origin) },
    enPassantTarget{ 0 }
{
}


ChessGame::ChessGame(void)
{
    board.resetBoard();
}


ChessGame::ChessGame(const std::string& fenString)
{
    loadFromFen(fenString);
}


bool ChessGame::isValidMove(const Move& move) const
{
    return false;
}


std::vector<Move> ChessGame::getValidMoves(void) const
{
    std::vector<Move> ret;
    return ret;
}


void ChessGame::move(Move move)
{
    MoveInfo mi;
    mi.move = move;
    mi.movedPiece = board.getAtPosition(move.origin);
    doMove(mi);
}


void ChessGame::loadFromFen(const std::string& fenString)
{
    using namespace std;

    stringstream tokenizer (fenString);

    string board;
    string turn;
    string castling;
    string enPassant;
    string halfmoves;
    string moveCount;

    tokenizer >> board;
    tokenizer >> turn;
    tokenizer >> castling;
    tokenizer >> enPassant;
    tokenizer >> halfmoves;
    tokenizer >> moveCount;

    this->board.setBoard(board);
    this->enPassant = Index {enPassant};

    if (turn == "w"s) this->turn = WHITE_SIDE;
    else if (turn == "b"s) this->turn = BLACK_SIDE;
    else throw runtime_error("invalid turn "s + turn);

    castlingRights = 0;
    if (castling != "-")
        for (auto character : castling) {
            switch (character) {
                case 'k':
                    setCanCastleKingSide(WHITE_SIDE, true);
                    break;
                case 'q':
                    setCanCastleQueenSide(WHITE_SIDE, true);
                    break;
                case 'K':
                    setCanCastleKingSide(BLACK_SIDE, true);
                    break;
                case 'Q':
                    setCanCastleQueenSide(BLACK_SIDE, true);
                    break;
                default:
                    throw runtime_error("invalid castling right: "s + character);
            }
        }

    if (enPassant == "-"s) {
        this->enPassant = -1;
    }
    else {
        if (enPassant.size() != 2 || (enPassant[1] != '3' && enPassant[1] != '6'))
            throw runtime_error("invalid en passant string: "s + enPassant);
        this->enPassant = Index{ enPassant };
    }

    try {
        reversibleHalfMoves = stoi(halfmoves);
    }
    catch(...) {
        throw runtime_error("invalid number of halfmoves: "s + halfmoves);
    }

    try {
        this->moveCount = stoi(moveCount);
    }
    catch(...) {
        throw runtime_error("invalid number of moves: "s + halfmoves);
    }
}


std::string ChessGame::generateFen(void) const
{
    using namespace std;

    string board = this->board.getFenBoard();

    string turn = this->turn == WHITE_SIDE ? "w"s : "b"s;

    string castlingRights =
        (getCanCastleKingSide(BLACK_SIDE) ? "K"s : ""s) +
        (getCanCastleQueenSide(BLACK_SIDE)? "Q"s : ""s) +
        (getCanCastleKingSide(WHITE_SIDE) ? "k"s : ""s) +
        (getCanCastleQueenSide(WHITE_SIDE) ? "q"s : ""s);
    if (castlingRights.empty())
        castlingRights = "-"s;

    string enPassant;
    if (this->enPassant == -1) {
        enPassant = "-"s;
    }
    else {
        enPassant = this->enPassant.getName();
    }

    string halfmoves = to_string(reversibleHalfMoves);
    string mCount = to_string(moveCount);

    return board + " " + turn + " " + castlingRights + " " + enPassant + " " + halfmoves +
       " " + mCount;
}


UndoInfo ChessGame::doMove(const MoveInfo& mi)
{
    UndoInfo ui;

    ui.castlingRights = castlingRights;
    if (mi.movedPiece == KING) {
        setCanCastleKingSide(turn, false);
        setCanCastleQueenSide(turn, false);
    }

    ui.type = mi.movedPiece;
    Bitboard& b = board.getBitboards(turn)[ui.type];
    ui.before = b;

    Bitboard target = Bitboard::fromIndex(mi.move.destination);
    b &= ~Bitboard::fromIndex(mi.move.origin);
    b |= target;

    ui.captured = PieceType::EMPTY;
    for (int i = 0; i < 6; i++) {
        Bitboard& e = board.getBitboards(otherSide(turn))[i];
        if (target & e) {
            ui.captured = static_cast<PieceType>(i);
            ui.beforeCaptured = e;
            e ^= target;
            break;
        }
    }

    turn = otherSide(turn);
    moveCount++;
    ui.reversibleHalfMoves = reversibleHalfMoves;
    if(mi.movedPiece != PAWN &&
            board.getAtPosition(mi.move.destination) != EMPTY) {
        reversibleHalfMoves++;
    }
    return ui;
}


void ChessGame::undoMove(const UndoInfo& ui)
{
    turn = otherSide(turn);

    Bitboard& b = board.getBitboards(turn)[ui.type];
    b = ui.before;
    if (ui.captured != PieceType::EMPTY)
        board.getBitboards(otherSide(turn))[ui.captured] = ui.beforeCaptured;
    moveCount--;
    reversibleHalfMoves = ui.reversibleHalfMoves;
    castlingRights = ui.castlingRights;
}