eliot/game/move_selector.cpp

/*****************************************************************************
 * Eliot
 * Copyright (C) 2013 Olivier Teulière
 * Authors: Olivier Teulière <ipkiss @@ gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *****************************************************************************/

#include <boost/foreach.hpp>

#include "move_selector.h"
#include "round.h"
#include "results.h"
#include "board.h"
#include "board_layout.h"
#include "bag.h"
#include "rack.h"

#include "dic.h"
#include "debug.h"


INIT_LOGGER(game, MoveSelector);

#define PLAYED_JOKER (-1000)
#define LETTER_REPEATED_3_TIMES (-3)
#define LETTER_REPEATED_4_TIMES (-12)
#define LETTER_REPEATED_5_TIMES (-40)
#define LETTER_REPEATED_6_TIMES (-100)
#define EXTENSION_1 50
#define BENJAMIN 5


MoveSelector::MoveSelector(const Bag &iBag, const Dictionary &iDic,
                           const Board &iBoard, const Rack &iRack)
    : m_bag(iBag), m_dic(iDic), m_board(iBoard), m_rack(iRack)
{
}


Round MoveSelector::selectMaster(const BestResults &iResults) const
{
    ASSERT(!iResults.isEmpty(), "Nothing to select from");

    // Easy case
    if (iResults.size() == 1)
        return iResults.get(0);

    // Compare the rounds. The one with the highest score wins.
    // In case of equal scores, the first one wins.
    int bestIndex = 0;
    int bestScore = evalScore(iResults.get(0));
    for (unsigned num = 1; num < iResults.size(); ++num)
    {
        int score = evalScore(iResults.get(num));
        if (bestScore < score)
        {
            bestScore = score;
            bestIndex = num;
        }
    }

    return iResults.get(bestIndex);
}


int MoveSelector::evalScore(const Round &iRound) const
{
    int score = 0;
    score += evalForJokersInRack(iRound);
    score += evalForRemainingLetters(iRound);
    // Deactivated for now, as it breaks a few non-regression tests,
    // and I don't have time to fix them at the moment... :)
#if 0
    score += evalForExtensions(iRound);
    score += evalForBenjamins(iRound);
#endif
    // TODO: add more heuristics
    return score;
}


int MoveSelector::evalForJokersInRack(const Round &iRound) const
{
    return iRound.countJokersFromRack() * PLAYED_JOKER;
}


int MoveSelector::evalForRemainingLetters(const Round &iRound) const
{
    // Compute the rack remaining after playing the round
    Rack remaining = m_rack;
    for (unsigned i = 0; i < iRound.getWordLen(); ++i)
    {
        if (iRound.isPlayedFromRack(i))
        {
            remaining.remove(iRound.isJoker(i) ? Tile::Joker() : iRound.getTile(i));
        }
    }

    // If a letter is present at least 3 times in the rack, consider it bad
    // Note: the repetitions are only relevant if the rack is not rejected for
    // lack of vowels and/or consonants...
    int score = 0;
    BOOST_FOREACH(const Tile &t, m_dic.getAllTiles())
    {
        const int count = remaining.count(t);
        if (count >= 3)
        {
            if (count == 3)
                score += LETTER_REPEATED_3_TIMES;
            else if (count == 4)
                score += LETTER_REPEATED_4_TIMES;
            else if (count == 5)
                score += LETTER_REPEATED_5_TIMES;
            else if (count == 6)
                score += LETTER_REPEATED_6_TIMES;
        }
    }

    return score;
}


int MoveSelector::evalForExtensions(const Round &iRound) const
{
    // Find front and back extensions to the given round
    const wstring &roundWord = iRound.getWord();
    vector<wdstring> results;
    m_dic.searchRacc(roundWord, results);

    // Give a bonus for each extension
    // TODO: it would be better to give a bonus only for extensions
    // corresponding to letters still in the bag, and allowed by the
    // cross-checks...
    return results.size() * EXTENSION_1;
}


int MoveSelector::evalForBenjamins(const Round &iRound) const
{
    // Compute the word multiplier in case of benjamin
    // TODO: this only depends on the coordinates, so it could easily be cached
    int wordMult = 1;
    const Coord &coord = iRound.getCoord();
    const unsigned row = coord.getRow();
    const unsigned col = coord.getCol();
    if (coord.getDir() == Coord::HORIZONTAL)
    {
        // Make sure there is space for a benjamin on the board
        if (col <= 3 ||
            !m_board.isVacant(row, col - 1) ||
            !m_board.isVacant(row, col - 2) ||
            !m_board.isVacant(row, col - 3))
        {
            return 0;
        }

        // Compute the word multiplier
        wordMult *= m_board.getLayout().getWordMultiplier(row, col - 1);
        wordMult *= m_board.getLayout().getWordMultiplier(row, col - 2);
        wordMult *= m_board.getLayout().getWordMultiplier(row, col - 3);
    }
    else
    {
        // Same thing for vertical words
        if (row <= 3 ||
            !m_board.isVacant(row - 1, col) ||
            !m_board.isVacant(row - 2, col) ||
            !m_board.isVacant(row - 3, col))
        {
            return 0;
        }

        // Compute the word multiplier
        wordMult *= m_board.getLayout().getWordMultiplier(row - 1, col);
        wordMult *= m_board.getLayout().getWordMultiplier(row - 2, col);
        wordMult *= m_board.getLayout().getWordMultiplier(row - 3, col);
    }

    // Find possible benjamins
    const wstring &roundWord = iRound.getWord();
    vector<wdstring> results;
    m_dic.searchBenj(roundWord, results);

    // Give a bonus for each extension
    // TODO: it would be better to give a bonus only for benjamins
    // corresponding to letters still in the bag, and allowed by the
    // cross-checks...
    return results.size() * wordMult * BENJAMIN;
}