/***************************************************************************
 *   KShisen - A japanese game similar to mahjongg                         *
 *   Copyright 1997   Mario Weilguni <mweilguni@sime.com>                  *
 *   Copyright 2002-2004  Dave Corrie <kde@davecorrie.com>                 *
 *   Copyright 2007  Mauricio Piacentini <mauricio@tabuleiro.com>          *
 *   Copyright 2009-2012  Frederik Schwarzer <schwarzer@kde.org>           *
 *                                                                         *
 *   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, see <http://www.gnu.org/licenses/>. *
 ***************************************************************************/

#include "board.h"
#include "prefs.h"

#include <KLocalizedString>


#include "kshisen_debug.h"
#include <QMouseEvent>
#include <QPainter>
#include <QTimer>

#include <cstring>
#include <QStandardPaths>


#define EMPTY           0
#define SEASONS_START   28
#define FLOWERS_START   39

static int s_delay[5] = {1000, 750, 500, 250, 125};

bool PossibleMove::isInPath(int x, int y) const
{
    if (x == m_path.last().x && y == m_path.last().y) {
        return false;
    }
    qCDebug(KSHISEN_LOG) << "isInPath:" << x << "," << y;
    Debug();
    QList<Position>::const_iterator iter;
    // a path has at least 2 positions
    iter = m_path.constBegin();
    int pathX = iter->x;
    int pathY = iter->y;
    ++iter;
    for (; iter != m_path.constEnd(); ++iter) {
        // to fix
        if ((x == iter->x && ((y > pathY && y <= iter->y) || (y < pathY && y >= iter->y)))
                || (y == iter->y && ((x > pathX && x <= iter->x) || (x < pathX && x >= iter->x)))) {
            qCDebug(KSHISEN_LOG) << "isInPath:" << x << "," << y << "found in path" << pathX << "," << pathY << " => " << iter->x << "," << iter->y;
            return true;
        }
        pathX = iter->x;
        pathY = iter->y;
    }
    return false;
}

Board::Board(QWidget *parent)
    : QWidget(parent),
      m_markX(0), m_markY(0),
      m_field(0),
      m_xTiles(0), m_yTiles(0),
      m_delay(0), m_level(0), m_shuffle(0),
      m_gameState(Normal), m_cheat(false),
      m_gravityFlag(true), m_solvableFlag(false), m_chineseStyleFlag(false), m_tilesCanSlideFlag(false),
      m_highlightedTile(-1),
      m_paintConnection(false), m_paintPossibleMoves(false), m_paintInProgress(false),
      m_soundPick(QStandardPaths::locate(QStandardPaths::GenericDataLocation, QLatin1String("sounds/kshisen/tile-touch.ogg"))),
      m_soundFall(QStandardPaths::locate(QStandardPaths::GenericDataLocation, QLatin1String("sounds/kshisen/tile-fall-tile.ogg")))
{
    m_tileRemove1.first = -1;

    m_random.setSeed(0);
    resetTimer();

    QPalette palette;
    palette.setBrush(backgroundRole(), m_background.getBackground());
    setPalette(palette);

    loadSettings();
}

Board::~Board()
{
    delete [] m_field;
}

void Board::loadSettings()
{
    if (!loadTileset(Prefs::tileSet())) {
        qCDebug(KSHISEN_LOG) << "An error occurred when loading the tileset" << Prefs::tileSet() << "KShisen will continue with the default tileset.";
    }

    // Load background
    if (!loadBackground(Prefs::background())) {
        qCDebug(KSHISEN_LOG) << "An error occurred when loading the background" << Prefs::background() << "KShisen will continue with the default background.";
    }

    // There are tile sets, that have only one tile for e.g. the flowers group.
    // If these tile sets are played in non-chineseStyle, this one tile face
    // appears too often and not every tile matches another one with the same
    // face because they are technically different (e.g different flowers).
    // The solution is to enforce chineseStyle gameplay for tile sets that are
    // known to be reduced. Those are Egypt and Alphabet for now.
    if (Prefs::tileSet().endsWith(QLatin1String("egypt.desktop")) || Prefs::tileSet().endsWith(QLatin1String("alphabet.desktop"))) {
        setChineseStyleFlag(true);
    } else {
        setChineseStyleFlag(Prefs::chineseStyle());
    }
    setTilesCanSlideFlag(Prefs::tilesCanSlide());
    // Need to load solvable before size because setSize calls newGame which
    // uses the solvable flag. Same with shuffle.
    setSolvableFlag(Prefs::solvable());
    m_shuffle = Prefs::level() * 4 + 1;
    setSize(sizeX[Prefs::size()], sizeY[Prefs::size()]);
    setGravityFlag(Prefs::gravity());
    setDelay(s_delay[Prefs::speed()]);
    setSoundsEnabled(Prefs::sounds());

    if (m_level != Prefs::level()) {
        newGame();
    }
    m_level = Prefs::level();
}

bool Board::loadTileset(const QString &pathToTileset)
{
    if (m_tiles.loadTileset(pathToTileset)) {
        if (m_tiles.loadGraphics()) {
            Prefs::setTileSet(pathToTileset);
            Prefs::self()->save();
            resizeBoard();
        }
        return true;
    }
    //Try default
    if (m_tiles.loadDefault()) {
        if (m_tiles.loadGraphics()) {
            Prefs::setTileSet(m_tiles.path());
            Prefs::self()->save();
            resizeBoard();
        }
    }
    return false;
}

bool Board::loadBackground(const QString &pathToBackground)
{
    if (m_background.load(pathToBackground, width(), height())) {
        if (m_background.loadGraphics()) {
            Prefs::setBackground(pathToBackground);
            Prefs::self()->save();
            resizeBoard();
            return true;
        }
    }
    //Try default
    if (m_background.loadDefault()) {
        if (m_background.loadGraphics()) {
            Prefs::setBackground(m_background.path());
            Prefs::self()->save();
            resizeBoard();
        }
    }
    return false;
}

int Board::xTiles() const
{
    return m_xTiles;
}

int Board::yTiles() const
{
    return m_yTiles;
}

void Board::setField(int x, int y, int value)
{
    if (x < 0 || y < 0 || x >= xTiles() || y >= yTiles()) {
        qFatal("Attempted write to invalid field position (%u,%u)", x, y);
    }

    m_field[y * xTiles() + x] = value;
}

// TODO: Why is this called every second?
int Board::field(int x, int y) const
{
#ifdef DEBUGGING
    if (x < -1 || y < -1 || x > xTiles() || y > yTiles()) {
        qFatal("Attempted read from invalid field position (%u,%u)", x, y);
    }
#endif

    if (x < 0 || y < 0 || x >= xTiles() || y >= yTiles()) {
        return EMPTY;
    }

    return m_field[y * xTiles() + x];
}

void Board::gravity(bool update)
{
    m_gravCols.clear();
    if (!m_gravityFlag) {
        return;
    }
    bool fallingTiles = false;
    for (int i = 0; i < xTiles(); ++i) {
        if (gravity(i, update)) {
            fallingTiles = true;
            m_gravCols.append(i);
        }
    }
    if (Prefs::sounds() && fallingTiles) {
        m_soundFall.start();
    }
}

bool Board::gravity(int column, bool update)
{
    bool isAffected = false;
    if (m_gravityFlag) {
        int rptr = yTiles() - 1;
        int wptr = yTiles() - 1;
        while (rptr >= 0) {
            if (field(column, wptr) != EMPTY) {
                --rptr;
                --wptr;
            } else {
                if (field(column, rptr) != EMPTY) {
                    setField(column, wptr, field(column, rptr));
                    setField(column, rptr, EMPTY);
                    isAffected = true;
                    if (update) {
                        updateField(column, rptr);
                        updateField(column, wptr);
                    }
                    --wptr;
                    --rptr;
                } else {
                    --rptr;
                }
            }
        }
    }
    return isAffected;
}

void Board::unmarkTile()
{
    // if nothing is marked, nothing to do
    if (m_markX == -1 || m_markY == -1) {
        return;
    }
    drawPossibleMoves(false);
    m_possibleMoves.clear();
    // We need to set m_markX and m_markY to -1 before calling
    // updateField() to ensure the tile is redrawn as unmarked.
    int oldMarkX = m_markX;
    int oldMarkY = m_markY;
    m_markX = -1;
    m_markY = -1;
    updateField(oldMarkX, oldMarkY);
}

void Board::mousePressEvent(QMouseEvent *e)
{
    // Do not process mouse events while the connection is drawn.
    // Clicking on one of the already connected tiles would have selected
    // it before removing it. This is more a workaround than a proper fix
    // but I have to understand the usage of m_paintConnection first in
    // order to consider its reusage here. (schwarzer)
    if (m_paintInProgress) {
        return;
    }
    switch (m_gameState) {
        case Normal:
            break;
        case Over:
            newGame();
            return;
        case Paused:
            setPauseEnabled(false);
            return;
        case Stuck:
            return;
    }
    // Calculate field position
    int posX = (e->pos().x() - xOffset()) / (m_tiles.qWidth() * 2);
    int posY = (e->pos().y() - yOffset()) / (m_tiles.qHeight() * 2);

    if (e->pos().x() < xOffset() || e->pos().y() < yOffset() ||
            posX >= xTiles() || posY >= yTiles()) {
        posX = -1;
        posY = -1;
    }

    // Mark tile
    if (e->button() == Qt::LeftButton) {
        clearHighlight();

        if (posX != -1) {
            marked(posX, posY);
        } else {
            // unmark when clicking outside the board
            unmarkTile();
        }
    }

    // Assist by highlighting all tiles of same type
    if (e->button() == Qt::RightButton) {
        int clickedTile = field(posX, posY);

        // Clear marked tile
        if (m_markX != -1 && field(m_markX, m_markY) != clickedTile) {
            unmarkTile();
        } else {
            m_markX = -1;
            m_markY = -1;
        }

        // Perform highlighting
        if (clickedTile != m_highlightedTile) {
            int oldHighlighted = m_highlightedTile;
            m_highlightedTile = clickedTile;
            for (int i = 0; i < xTiles(); ++i) {
                for (int j = 0; j < yTiles(); ++j) {
                    const int fieldTile = field(i, j);
                    if (fieldTile != EMPTY) {
                        if (fieldTile == oldHighlighted) {
                            updateField(i, j);
                        } else if (fieldTile == clickedTile) {
                            updateField(i, j);
                        } else if (m_chineseStyleFlag) {
                            if (clickedTile >= SEASONS_START && clickedTile <= (SEASONS_START + 3) && fieldTile >= SEASONS_START && fieldTile <= (SEASONS_START + 3)) {
                                updateField(i, j);
                            } else if (clickedTile >= FLOWERS_START && clickedTile <= (FLOWERS_START + 3) && fieldTile >= FLOWERS_START && fieldTile <= (FLOWERS_START + 3)) {
                                updateField(i, j);
                            }
                            // oldHighlighted
                            if (oldHighlighted >= SEASONS_START && oldHighlighted <= (SEASONS_START + 3) && fieldTile >= SEASONS_START && fieldTile <= (SEASONS_START + 3)) {
                                updateField(i, j);
                            } else if (oldHighlighted >= FLOWERS_START && oldHighlighted <= (FLOWERS_START + 3) && fieldTile >= FLOWERS_START && fieldTile <= (FLOWERS_START + 3)) {
                                updateField(i, j);
                            }
                        }
                    }
                }
            }
        }
    }
}

int Board::xOffset() const
{
    int tw = m_tiles.qWidth() * 2;
    return (width() - (tw * xTiles())) / 2;
}

int Board::yOffset() const
{
    int th = m_tiles.qHeight() * 2;
    return (height() - (th * yTiles())) / 2;
}

void Board::setSize(int x, int y)
{
    if (x == xTiles() && y == yTiles()) {
        return;
    }

    delete [] m_field;

    m_field = new int[ x * y ];
    m_xTiles = x;
    m_yTiles = y;
    for (int i = 0; i < x; ++i) {
        for (int j = 0; j < y; ++j) {
            setField(i, j, EMPTY);
        }
    }

    // set the minimum size of the scalable window
    const double MINIMUM_SCALE = 0.2;
    int w = qRound(m_tiles.qWidth() * 2.0 * MINIMUM_SCALE) * xTiles();
    int h = qRound(m_tiles.qHeight() * 2.0 * MINIMUM_SCALE) * yTiles();
    w += m_tiles.width();
    h += m_tiles.width();

    setMinimumSize(w, h);

    resizeBoard();
    newGame();
    emit changed();
}

void Board::resizeEvent(QResizeEvent *e)
{
    qCDebug(KSHISEN_LOG) << "[resizeEvent]";
    if (e->spontaneous()) {
        qCDebug(KSHISEN_LOG) << "[resizeEvent] spontaneous";
    }
    resizeBoard();
    emit resized();
}

void Board::resizeBoard()
{
    // calculate tile size required to fit all tiles in the window
    QSize newsize = m_tiles.preferredTileSize(QSize(width(), height()), xTiles(), yTiles());
    m_tiles.reloadTileset(newsize);
    //recalculate bg, if needed
    m_background.sizeChanged(width(), height());
    //reload our bg brush, using the cache in libkmahjongg if possible
    QPalette palette;
    palette.setBrush(backgroundRole(), m_background.getBackground());
    setPalette(palette);
}


void Board::newGame()
{
    m_gameState = Normal;
    setCheatModeEnabled(false);

    m_markX = -1;
    m_markY = -1;
    m_highlightedTile = -1; // will clear previous highlight

    resetUndo();
    resetRedo();
    m_connection.clear();
    m_possibleMoves.clear();

    // distribute all tiles on board
    int curTile = 1;
    int tileCount = 0;

    /*
     * Note by jwickers: i changed the way to distribute tiles
     *  in chinese mahjongg there are 4 tiles of each
     *  except flowers and seasons (4 flowers and 4 seasons,
     *  but one unique tile of each, that is why they are
     *  the only ones numbered)
     * That uses the chineseStyle flag
     */
    for (int y = 0; y < yTiles(); ++y) {
        for (int x = 0; x < xTiles(); ++x) {
            // do not duplicate flowers or seasons
            if (!m_chineseStyleFlag || !((curTile >= SEASONS_START && curTile <= (SEASONS_START + 3)) || (curTile >= FLOWERS_START && curTile <= (FLOWERS_START + 3)))) {
                setField(x, y, curTile);
                if (++tileCount >= 4) {
                    tileCount = 0;
                    ++curTile;
                }
            } else {
                tileCount = 0;
                setField(x, y, curTile++);
            }
            if (curTile > Board::nTiles) {
                curTile = 1;
            }
        }
    }

    if (m_shuffle == 0) {
        update();
        resetTimer();
        emit newGameStarted();
        emit changed();
        return;
    }

    // shuffle the field
    int tx = xTiles();
    int ty = yTiles();
    for (int i = 0; i < tx * ty * m_shuffle; ++i) {
        int x1 = m_random.getLong(tx);
        int y1 = m_random.getLong(ty);
        int x2 = m_random.getLong(tx);
        int y2 = m_random.getLong(ty);
        // keep and use t, because the next setField() call changes what field() will return
        // so there would a significant impact on shuffling with the field() call put into the
        // place where 't' is used
        int t  = field(x1, y1);
        setField(x1, y1, field(x2, y2));
        setField(x2, y2, t);
    }

    // if m_solvableFlag is false, the game does not need to be solvable; we can drop out here
    if (!m_solvableFlag) {
        update();
        resetTimer();
        emit newGameStarted();
        emit changed();
        return;
    }


    int fsize = xTiles() * yTiles() * sizeof(int);
    int *oldfield = new int[xTiles() * yTiles()];
    memcpy(oldfield, m_field, fsize);   // save field
    int *tiles = new int[xTiles() * yTiles()];
    int *pos = new int[xTiles() * yTiles()];
    //jwickers: in case the game cannot made solvable we do not want to run an infinite loop
    int maxAttempts = 200;

    while (!solvable(true) && maxAttempts > 0) {
        // generate a list of free tiles and positions
        int numberOfTiles = 0;
        for (int i = 0; i < xTiles() * yTiles(); ++i) {
            if (m_field[i] != EMPTY) {
                pos[numberOfTiles] = i;
                tiles[numberOfTiles] = m_field[i];
                ++numberOfTiles;
            }
        }

        // restore field
        memcpy(m_field, oldfield, fsize);

        // redistribute unsolved tiles
        while (numberOfTiles > 0) {
            // get a random tile
            int r1 = m_random.getLong(numberOfTiles);
            int r2 = m_random.getLong(numberOfTiles);
            int tile = tiles[r1];
            int apos = pos[r2];

            // truncate list
            tiles[r1] = tiles[numberOfTiles-1];
            pos[r2] = pos[numberOfTiles-1];
            --numberOfTiles;

            // put this tile on the new position
            m_field[apos] = tile;
        }

        // remember field
        memcpy(oldfield, m_field, fsize);
        --maxAttempts;
    }
    // debug, tell if make solvable failed
    if (maxAttempts == 0) {
        qCDebug(KSHISEN_LOG) << "NewGame make solvable failed";
    }


    // restore field
    memcpy(m_field, oldfield, fsize);
    delete [] tiles;
    delete [] pos;
    delete [] oldfield;

    update();
    resetTimer();
    emit changed();
}

bool Board::tilesMatch(int tile1, int tile2) const
{
    // identical tiles always match
    if (tile1 == tile2) {
        return true;
    }
    // when chinese style is set, there are special rules
    // for flowers and seasons
    if (m_chineseStyleFlag) {
        // if both tiles are seasons
        if (tile1 >= SEASONS_START && tile1 <= SEASONS_START + 3
                && tile2 >= SEASONS_START && tile2 <= SEASONS_START + 3) {
            return true;
        }
        // if both tiles are flowers
        if (tile1 >= FLOWERS_START && tile1 <= FLOWERS_START + 3
                && tile2 >= FLOWERS_START && tile2 <= FLOWERS_START + 3) {
            return true;
        }
    }
    return false;
}

bool Board::isTileHighlighted(int x, int y) const
{
    if (x == m_markX && y == m_markY) {
        return true;
    }

    if (tilesMatch(m_highlightedTile, field(x, y))) {
        return true;
    }

    // m_tileRemove1.first != -1 is used because the repaint of the first if
    // on undrawConnection highlighted the tiles that fell because of gravity
    if (!m_connection.isEmpty() && m_tileRemove1.first != -1) {
        if (x == m_connection.first().x && y == m_connection.first().y) {
            return true;
        }

        if (x == m_connection.last().x && y == m_connection.last().y) {
            return true;
        }
    }

    return false;
}

void Board::updateField(int x, int y)
{
    QRect r(xOffset() + x * m_tiles.qWidth() * 2,
            yOffset() + y * m_tiles.qHeight() * 2,
            m_tiles.width(),
            m_tiles.height());

    update(r);
}

void Board::showInfoRect(QPainter &p, const QString &message)
{
    int boxWidth = width() * 0.6;
    int boxHeight = height() * 0.6;
    QRect contentsRect = QRect((width() - boxWidth) / 2, (height() - boxHeight) / 2, boxWidth, boxHeight);
    QFont font;
    int fontsize = boxHeight / 13;
    font.setPointSize(fontsize);
    p.setFont(font);
    p.setBrush(QBrush(QColor(100, 100, 100, 150)));
    p.setRenderHint(QPainter::Antialiasing);
    p.drawRoundedRect(contentsRect, 10, 10);

    p.drawText(contentsRect, Qt::AlignCenter | Qt::TextWordWrap, message);
}

void Board::drawTiles(QPainter &p, QPaintEvent *e)
{
    int w = m_tiles.width();
    int h = m_tiles.height();
    int fw = m_tiles.qWidth() * 2;
    int fh = m_tiles.qHeight() * 2;
    for (int i = 0; i < xTiles(); ++i) {
        for (int j = 0; j < yTiles(); ++j) {
            int tile = field(i, j);
            if (tile == EMPTY) {
                continue;
            }

            int xpos = xOffset() + i * fw;
            int ypos = yOffset() + j * fh;
            QRect r(xpos, ypos, w, h);
            if (e->rect().intersects(r)) {
                if (isTileHighlighted(i, j)) {
                    p.drawPixmap(xpos, ypos, m_tiles.selectedTile(1));
                } else {
                    p.drawPixmap(xpos, ypos, m_tiles.unselectedTile(1));
                }

                //draw face
                p.drawPixmap(xpos, ypos, m_tiles.tileface(tile - 1));
            }
        }
    }
}

void Board::paintEvent(QPaintEvent *e)
{
    QRect ur = e->rect(); // rectangle to update
    QPainter p(this);
    p.fillRect(ur, m_background.getBackground());

    switch (m_gameState) {
        case Normal:
            drawTiles(p, e);
            break;
        case Paused:
            showInfoRect(p, i18n("Game Paused\nClick to resume game."));
            break;
        case Stuck:
            drawTiles(p, e);
            showInfoRect(p, i18n("Game Stuck\nNo more moves possible."));
            break;
        case Over:
            showInfoRect(p, i18n("Game Over\nClick to start a new game."));
            break;
    }

    if (m_paintConnection) {
        p.setPen(QPen(QColor("red"), lineWidth()));

        Path::const_iterator pt1 = m_connection.constBegin();
        Path::const_iterator pt2 = pt1 + 1;
        while (pt2 != m_connection.constEnd()) {
            p.drawLine(midCoord(pt1->x, pt1->y), midCoord(pt2->x, pt2->y));
            ++pt1;
            ++pt2;
        }
        QTimer::singleShot(delay(), this, SLOT(undrawConnection()));
        m_paintConnection = false;
    }
    if (m_paintPossibleMoves) {
        p.setPen(QPen(QColor("blue"), lineWidth()));
        // paint all possible moves
        for (QList<PossibleMove>::const_iterator iter = m_possibleMoves.constBegin(); iter != m_possibleMoves.constEnd(); ++iter) {
            Path::const_iterator pt1 = iter->m_path.constBegin();
            Path::const_iterator pt2 = pt1 + 1;
            while (pt2 != iter->m_path.constEnd()) {
                p.drawLine(midCoord(pt1->x, pt1->y), midCoord(pt2->x, pt2->y));
                ++pt1;
                ++pt2;
            }
        }
        m_paintConnection = false;
    }
    p.end();
}

void Board::reverseSlide(int x, int y, int slideX1, int slideY1, int slideX2, int slideY2)
{
    // slide[XY]2 is the current location of the last tile to slide
    // slide[XY]1 is its destination
    // calculate the offset for the tiles to slide
    int dx = slideX1 - slideX2;
    int dy = slideY1 - slideY2;
    int current_tile;
    // move all tiles between slideX2, slideY2 and x, y to slide with that offset
    if (dx == 0) {
        if (y < slideY2) {
            for (int i = y + 1; i <= slideY2; ++i) {
                current_tile = field(x, i);
                if (current_tile == EMPTY) {
                    continue;
                }
                setField(x, i, EMPTY);
                setField(x, i + dy, current_tile);
                updateField(x, i);
                updateField(x, i + dy);
            }
        } else {
            for (int i = y - 1; i >= slideY2; --i) {
                current_tile = field(x, i);
                if (current_tile == EMPTY) {
                    continue;
                }
                setField(x, i, EMPTY);
                setField(x, i + dy, current_tile);
                updateField(x, i);
                updateField(x, i + dy);
            }
        }
    } else if (dy == 0) {
        if (x < slideX2) {
            for (int i = x + 1; i <= slideX2; ++i) {
                current_tile = field(i, y);
                if (current_tile == EMPTY) {
                    continue;
                }
                setField(i, y, EMPTY);
                setField(i + dx, y, current_tile);
                updateField(i, y);
                updateField(i + dx, y);
            }
        } else {
            for (int i = x - 1; i >= slideX2; --i) {
                current_tile = field(i, y);
                if (current_tile == EMPTY) {
                    continue;
                }
                setField(i, y, EMPTY);
                setField(i + dx, y, current_tile);
                updateField(i, y);
                updateField(i + dx, y);
            }
        }
    }
}

void Board::performSlide(int x, int y, Path &slide)
{
    // check if there is something to slide
    if (slide.isEmpty()) {
        return;
    }

    // slide.first is the current location of the last tile to slide
    // slide.last is its destination
    // calculate the offset for the tiles to slide
    int dx = slide.last().x - slide.first().x;
    int dy = slide.last().y - slide.first().y;
    int current_tile;
    // move all tiles between m_markX, m_markY and the last tile to slide with that offset
    if (dx == 0) {
        if (y < slide.first().y) {
            for (int i = slide.first().y; i > y; --i) {
                current_tile = field(x, i);
                setField(x, i, EMPTY);
                setField(x, i + dy, current_tile);
                updateField(x, i);
                updateField(x, i + dy);
            }
        } else {
            for (int i = slide.first().y; i < y; ++i) {
                current_tile = field(x, i);
                setField(x, i, EMPTY);
                setField(x, i + dy, current_tile);
                updateField(x, i);
                updateField(x, i + dy);
            }
        }
    } else if (dy == 0) {
        if (x < slide.first().x) {
            for (int i = slide.first().x; i > x; --i) {
                current_tile = field(i, y);
                setField(i, y, EMPTY);
                setField(i + dx, y, current_tile);
                updateField(i, y);
                updateField(i + dx, y);
            }
        } else {
            for (int i = slide.first().x; i < x; ++i) {
                current_tile = field(i, y);
                setField(i, y, EMPTY);
                setField(i + dx, y, current_tile);
                updateField(i, y);
                updateField(i + dx, y);
            }
        }
    }
}

void Board::performMove(PossibleMove &possibleMoves)
{
    m_connection = possibleMoves.m_path;
#ifdef DEBUGGING
    // DEBUG undo, save board state
    int fsize = xTiles() * yTiles() * sizeof(int);
    int *saved1 = new int[xTiles() * yTiles()];
    memcpy(saved1, m_field, fsize);
#endif
    // if the tiles can slide, we have to update the slided tiles too
    // and store the slide in a Move
    if (possibleMoves.m_hasSlide) {
        performSlide(m_markX, m_markY, possibleMoves.m_slide);
        madeMove(m_markX, m_markY, possibleMoves.m_path.last().x, possibleMoves.m_path.last().y, possibleMoves.m_slide);
    } else {
        madeMove(m_markX, m_markY, possibleMoves.m_path.last().x, possibleMoves.m_path.last().y);
    }
    drawPossibleMoves(false);
    drawConnection();
    m_tileRemove1 = QPair<int, int>(m_markX, m_markY);
    m_tileRemove2 = QPair<int, int>(possibleMoves.m_path.last().x, possibleMoves.m_path.last().y);
    m_markX = -1;
    m_markY = -1;
    m_possibleMoves.clear();
#ifdef DEBUGGING
    // DEBUG undo, force gravity
    undrawConnection();
    // DEBUG undo, save board2 state
    int *saved2 = new int[xTiles() * yTiles()];
    int *saved3 = new int[xTiles() * yTiles()]; // after undo
    int *saved4 = new int[xTiles() * yTiles()]; // after redo
    memcpy(saved2, m_field, fsize);
    // DEBUG undo, undo move
    bool errorFound = false;
    if (canUndo()) {
        undo();
        // DEBUG undo, compare to saved board state
        for (int i = 0; i < xTiles() * yTiles(); ++i) {
            if (saved1[i] != m_field[i]) {
                qCDebug(KSHISEN_LOG) << "[DEBUG Undo 1], tile (" << i << ") was" << saved1[i] << "before more, it is" << m_field[i] << "after undo.";
                errorFound = true;
            }
        }
        // DEBUG undo, save board state
        memcpy(saved3, m_field, fsize);
        // DEBUG undo, redo
        if (canRedo()) {
            redo();
            undrawConnection();
            // DEBUG undo, compare to saved board2 state
            for (int i = 0; i < xTiles() * yTiles(); ++i) {
                if (saved2[i] != m_field[i]) {
                    qCDebug(KSHISEN_LOG) << "[DEBUG Undo 2], tile (" << i << ") was" << saved2[i] << "after more, it is" << m_field[i] << "after redo.";
                    errorFound = true;
                }
            }
            // DEBUG undo, save board state
            memcpy(saved4, m_field, fsize);
        }
    }
    // dumpBoard on error
    if (errorFound) {
        qCDebug(KSHISEN_LOG) << "[DEBUG] Before move";
        dumpBoard(saved1);
        qCDebug(KSHISEN_LOG) << "[DEBUG] After move";
        dumpBoard(saved2);
        qCDebug(KSHISEN_LOG) << "[DEBUG] Undo";
        dumpBoard(saved3);
        qCDebug(KSHISEN_LOG) << "[DEBUG] Redo";
        dumpBoard(saved4);
    }

    // DEBUG undo, free saved boards
    delete[] saved1;
    delete[] saved2;
    delete[] saved3;
    delete[] saved4;
#endif
}

void Board::marked(int x, int y)
{
    if (field(x, y) == EMPTY) { // click on empty space on the board
        if (m_possibleMoves.count() > 1) {  // if the click is on any of the current possible moves, make that move
            for (QList<PossibleMove>::iterator iter = m_possibleMoves.begin(); iter != m_possibleMoves.end(); ++iter) {
                if (iter->isInPath(x, y)) {
                    performMove(*iter);
                    emit selectATile();
                    return;
                }
            }
        } else {
            // unmark when not clicking on a tile
            unmarkTile();
            return;
        }
    }
    // make sure that the previous connection is correctly undrawn
    undrawConnection(); // is this still needed? (schwarzer)

    if (Prefs::sounds()) {
        m_soundPick.start();
    }

    if (x == m_markX && y == m_markY) { // the piece is already marked
        // unmark the piece
        unmarkTile();
        emit selectATile();
        return;
    }

    if (m_markX == -1) { // nothing is selected so far
        m_markX = x;
        m_markY = y;
        drawPossibleMoves(false);
        m_possibleMoves.clear();
        updateField(x, y);
        emit selectAMatchingTile();
        return;
    } else if (m_possibleMoves.count() > 1) {  // if the click is on any of the current possible moves, make that move

        for (QList<PossibleMove>::iterator iter = m_possibleMoves.begin(); iter != m_possibleMoves.end(); ++iter) {
            if (iter->isInPath(x, y)) {
                performMove(*iter);
                emit selectATile();
                return;
            }
        }
    }

    int tile1 = field(m_markX, m_markY);
    int tile2 = field(x, y);

    // both tiles do not match
    if (!tilesMatch(tile1, tile2)) {
        unmarkTile();
        emit tilesDoNotMatch();
        return;
    }

    // trace and perform the move and get the list of possible moves
    if (findPath(m_markX, m_markY, x, y, m_possibleMoves) > 0) {
        if (m_possibleMoves.count() > 1) {
            int withSlide = 0;
            for (QList<PossibleMove>::const_iterator iter = m_possibleMoves.constBegin(); iter != m_possibleMoves.constEnd(); ++iter) {
                iter->Debug();
                if (iter->m_hasSlide) {
                    ++withSlide;
                }
            }
            // if all moves have no slide, it doesn't matter
            if (withSlide > 0) {
                drawPossibleMoves(true);
                emit selectAMove();
                return;
            }
        }

        // only one move possible, perform it
        performMove(m_possibleMoves.first());
        emit selectATile();
        // game is over?
        // Must delay until after tiles fall to make this test
        // See undrawConnection GP.
    } else {
        emit invalidMove();
        m_connection.clear();
    }
}


void Board::clearHighlight()
{
    if (m_highlightedTile == -1) {
        return;
    }
    int oldHighlighted = m_highlightedTile;
    m_highlightedTile = -1;

    for (int i = 0; i < xTiles(); ++i) {
        for (int j = 0; j < yTiles(); ++j) {
            if (tilesMatch(oldHighlighted, field(i, j))) {
                updateField(i, j);
            }
        }
    }
}

bool Board::canMakePath(int x1, int y1, int x2, int y2) const
{
    if (x1 == x2) {
        for (int i = qMin(y1, y2) + 1; i < qMax(y1, y2); ++i) {
            if (field(x1, i) != EMPTY) {
                return false;
            }
        }
        return true;
    }

    if (y1 == y2) {
        for (int i = qMin(x1, x2) + 1; i < qMax(x1, x2); ++i) {
            if (field(i, y1) != EMPTY) {
                return false;
            }
        }
        return true;
    }

    return false;
}

bool Board::canSlideTiles(int x1, int y1, int x2, int y2, Path &path) const
{
    int distance = -1;
    path.clear();
    if (x1 == x2) {
        if (y1 > y2) {
            distance = y1 - y2;
            // count how much free space we have for sliding
            int start_free = -1;
            int end_free = -1;
            // find first tile empty
            for (int i = y1 - 1; i >= 0; --i) {
                if (field(x1, i) == EMPTY) {
                    start_free = i;
                    break;
                }
            }
            // if not found, cannot slide
            // if the first free tile is just next to the sliding tile, no slide (should be a normal move)
            if (start_free == -1 || start_free == (y1 - 1)) {
                return false;
            }
            // find last tile empty
            for (int i = start_free - 1; i >= 0; --i) {
                if (field(x1, i) != EMPTY) {
                    end_free = i;
                    break;
                }
            }
            // if not found, it is the border: 0

            // so we can slide of start_free - end_free, compare this to the distance
            if (distance <= (start_free - end_free)) {
                // first position of the last slided tile
                path.append(Position(x1, start_free + 1));
                // final position of the last slided tile
                path.append(Position(x1, start_free + 1 - distance));
                return true;
            } else {
                return false;
            }
        } else if (y2 > y1) {
            distance = y2 - y1;
            // count how much free space we have for sliding
            int start_free = -1;
            int end_free = yTiles();
            // find first tile empty
            for (int i = y1 + 1; i < yTiles(); ++i) {
                if (field(x1, i) == EMPTY) {
                    start_free = i;
                    break;
                }
            }
            // if not found, cannot slide
            // if the first free tile is just next to the sliding tile, no slide (should be a normal move)
            if (start_free == -1 || start_free == y1 + 1) {
                return false;
            }
            // find last tile empty
            for (int i = start_free + 1; i < yTiles(); ++i) {
                if (field(x1, i) != EMPTY) {
                    end_free = i;
                    break;
                }
            }
            // if not found, it is the border: yTiles()-1

            // so we can slide of end_free - start_free, compare this to the distance
            if (distance <= (end_free - start_free)) {
                // first position of the last slided tile
                path.append(Position(x1, start_free - 1));
                // final position of the last slided tile
                path.append(Position(x1, start_free - 1 + distance));
                return true;
            } else {
                return false;
            }
        }
        // y1 == y2 ?!
        return false;
    }

    if (y1 == y2) {
        if (x1 > x2) {
            distance = x1 - x2;
            // count how much free space we have for sliding
            int start_free = -1;
            int end_free = -1;
            // find first tile empty
            for (int i = x1 - 1; i >= 0; --i) {
                if (field(i, y1) == EMPTY) {
                    start_free = i;
                    break;
                }
            }
            // if not found, cannot slide
            // if the first free tile is just next to the sliding tile, no slide (should be a normal move)
            if (start_free == -1 || start_free == x1 - 1) {
                return false;
            }
            // find last tile empty
            for (int i = start_free - 1; i >= 0; --i) {
                if (field(i, y1) != EMPTY) {
                    end_free = i;
                    break;
                }
            }
            // if not found, it is the border: 0

            // so we can slide of start_free - end_free, compare this to the distance
            if (distance <= (start_free - end_free)) {
                // first position of the last slided tile
                path.append(Position(start_free + 1, y1));
                // final position of the last slided tile
                path.append(Position(start_free + 1 - distance, y1));
                return true;
            } else {
                return false;
            }
        } else if (x2 > x1) {
            distance = x2 - x1;
            // count how much free space we have for sliding
            int start_free = -1;
            int end_free = xTiles();
            // find first tile empty
            for (int i = x1 + 1; i < xTiles(); ++i) {
                if (field(i, y1) == EMPTY) {
                    start_free = i;
                    break;
                }
            }
            // if not found, cannot slide
            // if the first free tile is just next to the sliding tile, no slide (should be a normal move)
            if (start_free == -1 || start_free == x1 + 1) {
                return false;
            }
            // find last tile empty
            for (int i = start_free + 1; i < xTiles(); ++i) {
                if (field(i, y1) != EMPTY) {
                    end_free = i;
                    break;
                }
            }
            // if not found, it is the border: xTiles()-1

            // so we can slide of end_free - start_free, compare this to the distance
            if (distance <= (end_free - start_free)) {
                // first position of the last slided tile
                path.append(Position(start_free - 1, y1));
                // final position of the last slided tile
                path.append(Position(start_free - 1 + distance, y1));
                return true;
            } else {
                return false;
            }
        }
        // x1 == x2 ?!
        return false;
    }
    return false;
}

int Board::findPath(int x1, int y1, int x2, int y2, PossibleMoves &possibleMoves) const
{
    possibleMoves.clear();

    int numberOfPaths = 0;
    int simplePath = 0;

    // first find the simple paths
    numberOfPaths = findSimplePath(x1, y1, x2, y2, possibleMoves);

    // if the tiles can slide, 2 lines max is allowed
    if (m_tilesCanSlideFlag) {
        return numberOfPaths;
    }

    // Find paths of 3 segments
    const int dx[4] = { 1, 0, -1, 0 };
    const int dy[4] = { 0, 1, 0, -1 };

    for (int i = 0; i < 4; ++i) {
        int newX = x1 + dx[i];
        int newY = y1 + dy[i];
        while (newX >= -1 && newX <= xTiles() &&
                newY >= -1 && newY <= yTiles() &&
                field(newX, newY) == EMPTY) {
            if ((simplePath = findSimplePath(newX, newY, x2, y2, possibleMoves)) > 0) {
                possibleMoves.last().m_path.prepend(Position(x1, y1));
                numberOfPaths += simplePath;
            }
            newX += dx[i];
            newY += dy[i];
        }
    }
    return numberOfPaths;
}

int Board::findSimplePath(int x1, int y1, int x2, int y2, PossibleMoves &possibleMoves) const
{
    int numberOfPaths = 0;
    Path path;
    // Find direct line (path of 1 segment)
    if (canMakePath(x1, y1, x2, y2)) {
        path.append(Position(x1, y1));
        path.append(Position(x2, y2));
        possibleMoves.append(PossibleMove(path));
        ++numberOfPaths;
    }

    // If the tiles are in the same row or column, then a
    // a 'simple path' cannot be found between them
    // That is, canMakePath should have returned true above if
    // that was possible
    if (x1 == x2 || y1 == y2) {
        return numberOfPaths;
    }

    // I isolate the special code when tiles can slide even if it duplicates code for now
    // Can we make a path sliding tiles ?, the slide move is always first, then a normal path
    if (m_tilesCanSlideFlag) {
        Path slidePath;
        // Find path of 2 segments (route A)
        if (canSlideTiles(x1, y1, x2, y1, slidePath) && canMakePath(x2, y1, x2, y2)) {
            path.clear();
            path.append(Position(x1, y1));
            path.append(Position(x2, y1));
            path.append(Position(x2, y2));
            possibleMoves.append(PossibleMove(path, slidePath));
            ++numberOfPaths;
        }

        // Find path of 2 segments (route B)
        if (canSlideTiles(x1, y1, x1, y2, slidePath) && canMakePath(x1, y2, x2, y2)) {
            path.clear();
            path.append(Position(x1, y1));
            path.append(Position(x1, y2));
            path.append(Position(x2, y2));
            possibleMoves.append(PossibleMove(path, slidePath));
            ++numberOfPaths;
        }
    }

    // Even if tiles can slide, a path could still be done without sliding

    // Find path of 2 segments (route A)
    if (field(x2, y1) == EMPTY && canMakePath(x1, y1, x2, y1) &&
            canMakePath(x2, y1, x2, y2)) {
        path.clear();
        path.append(Position(x1, y1));
        path.append(Position(x2, y1));
        path.append(Position(x2, y2));
        possibleMoves.append(PossibleMove(path));
        ++numberOfPaths;
    }

    // Find path of 2 segments (route B)
    if (field(x1, y2) == EMPTY && canMakePath(x1, y1, x1, y2) &&
            canMakePath(x1, y2, x2, y2)) {
        path.clear();
        path.append(Position(x1, y1));
        path.append(Position(x1, y2));
        path.append(Position(x2, y2));
        possibleMoves.append(PossibleMove(path));
        ++numberOfPaths;
    }

    return numberOfPaths;
}

void Board::drawPossibleMoves(bool b)
{
    if (m_possibleMoves.isEmpty()) {
        return;
    }

    m_paintPossibleMoves = b;
    update();
}

void Board::drawConnection()
{
    m_paintInProgress = true;
    if (m_connection.isEmpty()) {
        return;
    }

    int x1 = m_connection.first().x;
    int y1 = m_connection.first().y;
    int x2 = m_connection.last().x;
    int y2 = m_connection.last().y;
    // lighten the fields
    updateField(x1, y1);
    updateField(x2, y2);

    m_paintConnection = true;
    update();
}

void Board::undrawConnection()
{
    if (m_tileRemove1.first != -1) {
        setField(m_tileRemove1.first, m_tileRemove1.second, EMPTY);
        setField(m_tileRemove2.first, m_tileRemove2.second, EMPTY);
        m_tileRemove1.first = -1;
        update();
    }

    gravity(true); // why is this called here? (schwarzer)

    // is already undrawn?
    if (m_connection.isEmpty()) {
        return;
    }

    // Redraw all affected fields
    Path oldConnection = m_connection;
    m_connection.clear();
    m_paintConnection = false;

    Path::const_iterator pt1 = oldConnection.constBegin();
    Path::const_iterator pt2 = pt1 + 1;
    while (pt2 != oldConnection.constEnd()) {
        if (pt1->y == pt2->y) {
            for (int i = qMin(pt1->x, pt2->x); i <= qMax(pt1->x, pt2->x); ++i) {
                updateField(i, pt1->y);
            }
        } else {
            for (int i = qMin(pt1->y, pt2->y); i <= qMax(pt1->y, pt2->y); ++i) {
                updateField(pt1->x, i);
            }
        }
        ++pt1;
        ++pt2;
    }

    PossibleMoves dummyPossibleMoves;
    // game is over?
    if (!hint_I(dummyPossibleMoves)) {
        m_gameClock.pause();
        emit endOfGame();
    }
    m_paintInProgress = false;
}

QPoint Board::midCoord(int x, int y) const
{
    QPoint p;
    int w = m_tiles.qWidth() * 2;
    int h = m_tiles.qHeight() * 2;

    if (x == -1) {
        p.setX(xOffset() - (w / 4));
    } else if (x == xTiles()) {
        p.setX(xOffset() + (w * xTiles()) + (w / 4));
    } else {
        p.setX(xOffset() + (w * x) + (w / 2));
    }

    if (y == -1) {
        p.setY(yOffset() - (w / 4));
    } else if (y == yTiles()) {
        p.setY(yOffset() + (h * yTiles()) + (w / 4));
    } else {
        p.setY(yOffset() + (h * y) + (h / 2));
    }

    return p;
}

void Board::setDelay(int newValue)
{
    if (m_delay == newValue) {
        return;
    }
    m_delay = newValue;
}

int Board::delay() const
{
    return m_delay;
}

void Board::madeMove(int x1, int y1, int x2, int y2, Path slide)
{
    Move *move;
    if (slide.empty()) {
        move = new Move(x1, y1, x2, y2, field(x1, y1), field(x2, y2));
    } else {
        move = new Move(x1, y1, x2, y2, field(x1, y1), field(x2, y2), slide.first().x, slide.first().y, slide.last().x, slide.last().y);
    }
    m_undo.append(move);
    while (m_redo.count()) {
        delete m_redo.first();
        m_redo.removeFirst();
    }
    emit changed();
}

bool Board::canUndo() const
{
    return !m_undo.isEmpty();
}

bool Board::canRedo() const
{
    return !m_redo.isEmpty();
}

void Board::undo()
{
    if (!canUndo()) {
        return;
    }

    clearHighlight();
    undrawConnection();
    Move *move = m_undo.takeLast();
    if (gravityFlag()) {
        int y;

        // When both tiles reside in the same column, the order of undo is
        // significant (we must undo the lower tile first).
        // Also in that case there cannot be a slide
        if (move->m_x1 == move->m_x2 && move->m_y1 < move->m_y2) {
            qSwap(move->m_x1, move->m_x2);
            qSwap(move->m_y1, move->m_y2);
            qSwap(move->m_tile1, move->m_tile2);
        }

        // if there is no slide, keep previous implementation: move both column up
        if (!move->m_hasSlide) {
#ifdef DEBUGGING
            qCDebug(KSHISEN_LOG) << "[undo] gravity from a no slide move";
#endif
            // move tiles from the first column up
            for (y = 0; y < move->m_y1; ++y) {
                setField(move->m_x1, y, field(move->m_x1, y + 1));
                updateField(move->m_x1, y);
            }

            // move tiles from the second column up
            for (y = 0; y < move->m_y2; ++y) {
                setField(move->m_x2, y, field(move->m_x2, y + 1));
                updateField(move->m_x2, y);
            }
        } else { // else check all tiles from the slide that may have fallen down
#ifdef DEBUGGING
            qCDebug(KSHISEN_LOG) << "[undo] gravity from slide s1(" << move->m_slideX1 << "," << move->m_slideY1 << ")=>s2(" << move->m_slideX2 << "," << move->m_slideY2 << ") matching (" << move->m_x1 << "," << move->m_y1 << ")=>(" << move->m_x2 << "," << move->m_y2 << ")";
#endif
            // horizontal slide
            // because tiles that slides horizontaly may fall down
            // in columns different than the taken tiles columns
            // we need to take them back up then undo the slide
            if (move->m_slideY1 == move->m_slideY2) {
#ifdef DEBUGGING
                qCDebug(KSHISEN_LOG) << "[undo] gravity from horizontal slide";
#endif
                // last slide tile went from slide_x1 -> slide_x2
                // the number of slided tiles is n = abs(x1 - slide_x1)
                int n = move->m_x1 - move->m_slideX1;
                if (n < 0) {
                    n = -n;
                }
                // distance slided is
                int dx = move->m_slideX2 - move->m_slideX1;
                if (dx < 0) {
                    dx = -dx;
                }
#ifdef DEBUGGING
                qCDebug(KSHISEN_LOG) << "[undo] n =" << n;
#endif
                // slided tiles may fall down after the slide
                // so any tiles on top of the columns between
                // slide_x2 -> slide_x2 +/- n (excluded) should go up to slide_y1
                if (move->m_slideX2 > move->m_slideX1) {  // slide to the right
#ifdef DEBUGGING
                    qCDebug(KSHISEN_LOG) << "[undo] slide right";
#endif
                    for (int i = move->m_slideX2; i > move->m_slideX2 - n; --i) {
                        // find top tile
                        int j;
                        for (j = 0; j < yTiles(); ++j) {
                            if (field(i, j) != EMPTY) {
                                break;
                            }
                        }

                        // ignore if the tile did not fall
                        if (j <= move->m_slideY1) {
                            continue;
                        }
#ifdef DEBUGGING
                        qCDebug(KSHISEN_LOG) << "[undo] moving (" << i << "," << j << ") up to (" << i << "," << move->m_slideY1 << ")";
#endif
                        // put it back up
                        setField(i, move->m_slideY1, field(i, j));
                        setField(i, j, EMPTY);
                        updateField(i, j);
                        updateField(i, move->m_slideY1);
                    }
                } else { // slide to the left
#ifdef DEBUGGING
                    qCDebug(KSHISEN_LOG) << "[undo] slide left";
#endif
                    for (int i = move->m_slideX2; i < move->m_slideX2 + n; ++i) {
                        // find top tile
                        int j;
                        for (j = 0; j < yTiles(); ++j) {
                            if (field(i, j) != EMPTY) {
                                break;
                            }
                        }

                        // ignore if the tile did not fall
                        if (j <= move->m_slideY1) {
                            continue;
                        }
#ifdef DEBUGGING
                        qCDebug(KSHISEN_LOG) << "[undo] moving (" << i << "," << j << ") up to (" << i << "," << move->m_slideY1 << ")";
#endif
                        // put it back up
                        setField(i, move->m_slideY1, field(i, j));
                        setField(i, j, EMPTY);
                        updateField(i, j);
                        updateField(i, move->m_slideY1);
                    }
                }
                // move tiles from the second column up
#ifdef DEBUGGING
                qCDebug(KSHISEN_LOG) << "[undo] moving up column x2" << move->m_x2;
#endif
                for (y = 0; y <= move->m_y2; ++y) {
#ifdef DEBUGGING
                    qCDebug(KSHISEN_LOG) << "[undo] moving up tile" << y + 1;
#endif
                    setField(move->m_x2, y, field(move->m_x2, y + 1));
                    updateField(move->m_x2, y);
                }
                // and all columns that fell after the tiles slided between
                // only if they were not replaced by a sliding tile !!
                // x1 -> x1+dx should go up one
                // if their height > slide_y1
                // because they have fallen after the slide
                if (move->m_slideX2 > move->m_slideX1) {  // slide to the right
                    if (move->m_slideY1 > 0) {
                        for (int i = move->m_x1 + dx; i >= move->m_x1; --i) {
#ifdef DEBUGGING
                            qCDebug(KSHISEN_LOG) << "[undo] moving up column" << i << "until" << move->m_slideY1;
#endif
                            for (int j = 0; j < move->m_slideY1; ++j) {
#ifdef DEBUGGING
                                qCDebug(KSHISEN_LOG) << "[undo] moving up tile" << j + 1;
#endif
                                setField(i, j, field(i, j + 1));
                                updateField(i, j);
                            }
#ifdef DEBUGGING
                            qCDebug(KSHISEN_LOG) << "[undo] clearing last tile" << move->m_slideY1;
#endif
                            setField(i, move->m_slideY1, EMPTY);
                            updateField(i, move->m_slideY1);
                        }
                    }
                } else { // slide to the left
                    if (move->m_slideY1 > 0) {
                        for (int i = move->m_x1 - dx; i <= move->m_x1; ++i) {
#ifdef DEBUGGING
                            qCDebug(KSHISEN_LOG) << "[undo] moving up column" << i << "until" << move->m_slideY1;
#endif
                            for (int j = 0; j < move->m_slideY1; ++j) {
#ifdef DEBUGGING
                                qCDebug(KSHISEN_LOG) << "[undo] moving up tile" << j + 1;
#endif
                                setField(i, j, field(i, j + 1));
                                updateField(i, j);
                            }
#ifdef DEBUGGING
                            qCDebug(KSHISEN_LOG) << "[undo] clearing last tile" << move->m_slideY1;
#endif
                            setField(i, move->m_slideY1, EMPTY);
                            updateField(i, move->m_slideY1);
                        }
                    }
                }

                // then undo the slide to put the tiles back to their original location
#ifdef DEBUGGING
                qCDebug(KSHISEN_LOG) << "[undo] reversing slide";
#endif
                reverseSlide(move->m_x1, move->m_y1, move->m_slideX1, move->m_slideY1, move->m_slideX2, move->m_slideY2);

            } else {
                // vertical slide, in fact nothing special is necessary
                // the default implementation works because it only affects
                // the two columns were tiles were taken
#ifdef DEBUGGING
                qCDebug(KSHISEN_LOG) << "[undo] gravity from vertical slide";
#endif

                // move tiles from the first column up
                for (y = 0; y < move->m_y1; ++y) {
                    setField(move->m_x1, y, field(move->m_x1, y + 1));
                    updateField(move->m_x1, y);
                }

                // move tiles from the second column up
                for (y = 0; y < move->m_y2; ++y) {
                    setField(move->m_x2, y, field(move->m_x2, y + 1));
                    updateField(move->m_x2, y);
                }
            }
        }
    } else { // no gravity
        // undo slide if any
        if (move->m_hasSlide) {
            // perform the slide in reverse
            reverseSlide(move->m_x1, move->m_y1, move->m_slideX1, move->m_slideY1, move->m_slideX2, move->m_slideY2);
        }
    }

    // replace taken tiles
    setField(move->m_x1, move->m_y1, move->m_tile1);
    setField(move->m_x2, move->m_y2, move->m_tile2);
    updateField(move->m_x1, move->m_y1);
    updateField(move->m_x2, move->m_y2);

    m_redo.prepend(move);
    emit changed();
}

void Board::redo()
{
    if (canRedo()) {
        clearHighlight();
        undrawConnection();
        Move *move = m_redo.takeFirst();
        // redo the slide if any
        if (move->m_hasSlide) {
            Path s;
            s.append(Position(move->m_slideX1, move->m_slideY1));
            s.append(Position(move->m_slideX2, move->m_slideY2));
            performSlide(move->m_x1, move->m_y1, s);
        }
        setField(move->m_x1, move->m_y1, EMPTY);
        setField(move->m_x2, move->m_y2, EMPTY);
        updateField(move->m_x1, move->m_y1);
        updateField(move->m_x2, move->m_y2);
        gravity(true);
        m_undo.append(move);
        emit changed();
    }
}

void Board::showHint()
{
    undrawConnection();

    if (hint_I(m_possibleMoves)) {
        m_connection = m_possibleMoves.first().m_path;
        drawConnection();
    }
}


#ifdef DEBUGGING
void Board::makeHintMove()
{
    PossibleMoves possibleMoves;

    if (hint_I(possibleMoves)) {
        m_markX = -1;
        m_markY = -1;
        marked(possibleMoves.first().m_path.first().x, possibleMoves.first().m_path.first().y);
        marked(possibleMoves.first().m_path.last().x, possibleMoves.first().m_path.last().y);
    }
}


void Board::dumpBoard() const
{
    qCDebug(KSHISEN_LOG) << "Board contents:";
    for (int y = 0; y < yTiles(); ++y) {
        QString row;
        for (int x = 0; x < xTiles(); ++x) {
            int tile = field(x, y);
            if (tile == EMPTY) {
                row += " --";
            } else {
                row += QString("%1").arg(tile, 3);
            }
        }
        qCDebug(KSHISEN_LOG) << row;
    }
}

void Board::dumpBoard(const int *board) const
{
    qCDebug(KSHISEN_LOG) << "Board contents:";
    for (int y = 0; y < yTiles(); ++y) {
        QString row;
        for (int x = 0; x < xTiles(); ++x) {
            int tile = board[y * xTiles() + x];
            if (tile == EMPTY) {
                row += " --";
            } else {
                row += QString("%1").arg(tile, 3);
            }
        }
        qCDebug(KSHISEN_LOG) << row;
    }
}
#endif

int Board::lineWidth() const
{
    int width = qRound(m_tiles.height() / 10.0);
    if (width < 3) {
        width = 3;
    }

    return width;
}

bool Board::hint_I(PossibleMoves &possibleMoves) const
{
    short done[Board::nTiles];
    for (short i = 0; i < Board::nTiles; ++i) {
        done[i] = 0;
    }

    for (int x = 0; x < xTiles(); ++x) {
        for (int y = 0; y < yTiles(); ++y) {
            int tile = field(x, y);
            if (tile != EMPTY && done[tile - 1] != 4) {
                // for all these types of tile search paths
                for (int xx = 0; xx < xTiles(); ++xx) {
                    for (int yy = 0; yy < yTiles(); ++yy) {
                        if (xx != x || yy != y) {
                            if (tilesMatch(field(xx, yy), tile)) {
                                if (findPath(x, y, xx, yy, possibleMoves) > 0) {
                                    return true;
                                }
                            }
                        }
                    }
                }
                done[tile - 1]++;
            }
        }
    }
    return false;
}

int Board::tilesLeft() const
{
    int left = 0;

    for (int i = 0; i < xTiles(); ++i) {
        for (int j = 0; j < yTiles(); ++j) {
            if (field(i, j) != EMPTY) {
                ++left;
            }
        }
    }

    return left;
}

int Board::currentTime() const
{
    return m_gameClock.seconds();
}

bool Board::solvable(bool noRestore)
{
    int *oldField = 0;

    if (!noRestore) {
        oldField = new int [xTiles() * yTiles()];
        memcpy(oldField, m_field, xTiles() * yTiles() * sizeof(int));
    }

    PossibleMoves p;
    while (hint_I(p)) {
        if (!tilesMatch(field(p.first().m_path.first().x, p.first().m_path.first().y), field(p.first().m_path.last().x, p.first().m_path.last().y))) {
            qFatal("Removing unmatched tiles: (%u,%u) => %u (%u,%u) => %u",
                   p.first().m_path.first().x,
                   p.first().m_path.first().y,
                   field(p.first().m_path.first().x, p.first().m_path.first().y),
                   p.first().m_path.last().x,
                   p.first().m_path.last().y,
                   field(p.first().m_path.last().x, p.first().m_path.last().y));
        }
        setField(p.first().m_path.first().x, p.first().m_path.first().y, EMPTY);
        setField(p.first().m_path.last().x, p.first().m_path.last().y, EMPTY);
    }

    int left = tilesLeft();

    if (!noRestore) {
        memcpy(m_field, oldField, xTiles() * yTiles() * sizeof(int));
        delete [] oldField;
    }

    return left == 0;
}

bool Board::solvableFlag() const
{
    return m_solvableFlag;
}

void Board::setSolvableFlag(bool enabled)
{
    if (m_solvableFlag == enabled) {
        return;
    }
    m_solvableFlag = enabled;
    // if the solvable flag was set and the current game is not solvable, start a new game
    if (m_solvableFlag && !solvable()) {
        newGame();
    }
}

bool Board::gravityFlag() const
{
    return m_gravityFlag;
}

void Board::setGravityFlag(bool enabled)
{
    if (m_gravityFlag == enabled) {
        return;
    }
    m_gravityFlag = enabled;
    // start a new game if the player is in the middle of a game
    if (canUndo() || canRedo()) {
        newGame();
    }
}

void Board::setChineseStyleFlag(bool enabled)
{
    if (m_chineseStyleFlag == enabled) {
        return;
    }
    m_chineseStyleFlag = enabled;
    // we need to force a newGame() because board generation is different
    newGame();
}

void Board::setTilesCanSlideFlag(bool enabled)
{
    if (m_tilesCanSlideFlag == enabled) {
        return;
    }
    m_tilesCanSlideFlag = enabled;
    // start a new game if the player is in the middle of a game
    if (canUndo() || canRedo()) {
        newGame();
    }
}

void Board::setPauseEnabled(bool enabled)
{
    if ((m_gameState == Paused && enabled) || m_gameState == Stuck) {
        return;
    }
    if (enabled) {
        m_gameState = Paused;
        m_gameClock.pause();
    } else {
        m_gameState = Normal;
        m_gameClock.resume();
    }
    emit changed();
    update();
}

QSize Board::sizeHint() const
{
    int dpi = logicalDpiX();
    if (dpi < 75) {
        dpi = 75;
    }
    return QSize(9 * dpi, 7 * dpi);
}

void Board::resetTimer()
{
    m_gameClock.restart();
}

void Board::resetUndo()
{
    if (!canUndo()) {
        return;
    }
    qDeleteAll(m_undo);
    m_undo.clear();
}

void Board::resetRedo()
{
    if (!canRedo()) {
        return;
    }
    qDeleteAll(m_redo);
    m_redo.clear();
}

void Board::setGameStuckEnabled(bool enabled)
{
    if (m_gameState == Stuck && enabled) {
        return;
    }
    if (enabled) {
        m_gameState = Stuck;
        m_gameClock.pause();
    } else {
        m_gameState = Normal;
        m_gameClock.resume();
    }
    emit changed();
    update();
}

void Board::setGameOverEnabled(bool enabled)
{
    if (m_gameState == Over && enabled) {
        return;
    }
    m_gameState = Over;
    emit changed();
    update();
}

void Board::setCheatModeEnabled(bool enabled)
{
    if (m_cheat == enabled) {
        return;
    }
    m_cheat = enabled;
    emit cheatStatusChanged();
}

bool Board::isOver() const
{
    return m_gameState == Over;
}

bool Board::isPaused() const
{
    return m_gameState == Paused;
}

bool Board::isStuck() const
{
    return m_gameState == Stuck;
}

bool Board::hasCheated() const
{
    return m_cheat;
}

void Board::setSoundsEnabled(bool enabled)
{
    Prefs::setSounds(enabled);
    Prefs::self()->save();
}


// vim: expandtab:tabstop=4:shiftwidth=4
// kate: space-indent on; indent-width 4
