/*
    Copyright (c) 2009 Stephen Kelly <steveire@gmail.com>
    Copyright (C) 2010 Klarälvdalens Datakonsult AB,
        a KDAB Group company, info@kdab.net,
        author Stephen Kelly <stephen@kdab.com>

    This library is free software; you can redistribute it and/or modify it
    under the terms of the GNU Library General Public License as published by
    the Free Software Foundation; either version 2 of the License, or (at your
    option) any later version.

    This library 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 Library General Public
    License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to the
    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301, USA.
*/

#include "kdescendantsproxymodel.h"

#include <QtCore/QStringList>
#include <QtCore/QTimer>

#include "kdebug.h"

#define KDO(object) kDebug() << #object << object

#include "kbihash_p.h"

typedef KHash2Map<QPersistentModelIndex, int> Mapping;

class KDescendantsProxyModelPrivate
{
  KDescendantsProxyModelPrivate(KDescendantsProxyModel * qq)
    : q_ptr(qq),
      m_rowCount(0),
      m_ignoreNextLayoutAboutToBeChanged(false),
      m_ignoreNextLayoutChanged(false),
      m_relayouting(false),
      m_displayAncestorData( false ),
      m_ancestorSeparator( QLatin1String( " / " ) )
  {
  }

  Q_DECLARE_PUBLIC(KDescendantsProxyModel)
  KDescendantsProxyModel * const q_ptr;

  mutable QVector<QPersistentModelIndex> m_pendingParents;

  void scheduleProcessPendingParents() const;
  void processPendingParents();

  void synchronousMappingRefresh();

  void updateInternalIndexes(int start, int offset);

  void resetInternalData();

  void sourceRowsAboutToBeInserted(const QModelIndex &, int, int);
  void sourceRowsInserted(const QModelIndex &, int, int);
  void sourceRowsAboutToBeRemoved(const QModelIndex &, int, int);
  void sourceRowsRemoved(const QModelIndex &, int, int);
  void sourceRowsAboutToBeMoved(const QModelIndex &, int, int, const QModelIndex &, int);
  void sourceRowsMoved(const QModelIndex &, int, int, const QModelIndex &, int);
  void sourceModelAboutToBeReset();
  void sourceModelReset();
  void sourceLayoutAboutToBeChanged();
  void sourceLayoutChanged();
  void sourceDataChanged(const QModelIndex &, const QModelIndex &);
  void sourceModelDestroyed();

  Mapping m_mapping;
  int m_rowCount;
  QPair<int, int> m_removePair;
  QPair<int, int> m_insertPair;

  bool m_ignoreNextLayoutAboutToBeChanged;
  bool m_ignoreNextLayoutChanged;
  bool m_relayouting;

  bool m_displayAncestorData;
  QString m_ancestorSeparator;

  QList<QPersistentModelIndex> m_layoutChangePersistentIndexes;
  QModelIndexList m_proxyIndexes;
};

void KDescendantsProxyModelPrivate::resetInternalData()
{
  m_rowCount = 0;
  m_mapping.clear();
  m_layoutChangePersistentIndexes.clear();
  m_proxyIndexes.clear();
}

void KDescendantsProxyModelPrivate::synchronousMappingRefresh()
{
  m_rowCount = 0;
  m_mapping.clear();
  m_pendingParents.clear();

  m_pendingParents.append(QModelIndex());

  m_relayouting = true;
  while (!m_pendingParents.isEmpty())
  {
    processPendingParents();
  }
  m_relayouting = false;
}

void KDescendantsProxyModelPrivate::scheduleProcessPendingParents() const
{
  Q_Q(const KDescendantsProxyModel);
  const_cast<KDescendantsProxyModelPrivate*>(this)->processPendingParents();
}

void KDescendantsProxyModelPrivate::processPendingParents()
{
  Q_Q(KDescendantsProxyModel);
  const QVector<QPersistentModelIndex>::iterator begin = m_pendingParents.begin();
  QVector<QPersistentModelIndex>::iterator it = begin;

  // Process chunkSize elements per invokation.
  static const int chunkSize = 30;

  const QVector<QPersistentModelIndex>::iterator end =
          /* (m_pendingParents.size() > chunkSize) ? begin + chunkSize : */ m_pendingParents.end();

  QVector<QPersistentModelIndex> newPendingParents;

  while (it != end && it != m_pendingParents.end()) {
    const QModelIndex sourceParent = *it;
    if (!sourceParent.isValid() && m_rowCount > 0)
    {
      // It was removed from the source model before it was inserted.
      it = m_pendingParents.erase(it);
      continue;
    }
    const int rowCount = q->sourceModel()->rowCount(sourceParent);

    Q_ASSERT(rowCount > 0);
    const QPersistentModelIndex sourceIndex = q->sourceModel()->index(rowCount - 1, 0, sourceParent);

    Q_ASSERT(sourceIndex.isValid());

    const QModelIndex proxyParent = q->mapFromSource(sourceParent);

    Q_ASSERT(sourceParent.isValid() == proxyParent.isValid());
    const int proxyEndRow = proxyParent.row() + rowCount;
    const int proxyStartRow = proxyEndRow - rowCount + 1;

    if (!m_relayouting)
      q->beginInsertRows(QModelIndex(), proxyStartRow, proxyEndRow);

    updateInternalIndexes(proxyStartRow, rowCount);
    m_mapping.insert(sourceIndex, proxyEndRow);
    it = m_pendingParents.erase(it);
    m_rowCount += rowCount;

    if (!m_relayouting)
      q->endInsertRows();

    for (int sourceRow = 0; sourceRow < rowCount; ++sourceRow ) {
      static const int column = 0;
      const QModelIndex child = q->sourceModel()->index(sourceRow, column, sourceParent);
      Q_ASSERT(child.isValid());

      if (q->sourceModel()->hasChildren(child))
      {
        Q_ASSERT(q->sourceModel()->rowCount(child) > 0);
        newPendingParents.append(child);
      }
    }
  }
  m_pendingParents += newPendingParents;
  if (!m_pendingParents.isEmpty())
      processPendingParents();
//   scheduleProcessPendingParents();
}

void KDescendantsProxyModelPrivate::updateInternalIndexes(int start, int offset)
{
  // TODO: Make KHash2Map support key updates and do this backwards.
  QHash<int, QPersistentModelIndex> updates;
  {
    Mapping::right_iterator it = m_mapping.rightLowerBound(start);
    const Mapping::right_iterator end = m_mapping.rightEnd();

    while (it != end)
    {
      updates.insert(it.key() + offset, *it);
      ++it;
    }
  }

  {
    QHash<int, QPersistentModelIndex>::const_iterator it = updates.constBegin();
    const QHash<int, QPersistentModelIndex>::const_iterator end = updates.constEnd();

    for ( ; it != end; ++it)
    {
      m_mapping.insert(it.value(), it.key());
    }
  }

}

KDescendantsProxyModel::KDescendantsProxyModel(QObject *parent)
  : QAbstractProxyModel(parent), d_ptr(new KDescendantsProxyModelPrivate(this))
{
}

KDescendantsProxyModel::~KDescendantsProxyModel()
{
  delete d_ptr;
}

void KDescendantsProxyModel::setRootIndex(const QModelIndex &index)
{
  Q_UNUSED(index)
}

QModelIndexList KDescendantsProxyModel::match(const QModelIndex &start, int role, const QVariant &value, int hits, Qt::MatchFlags flags) const
{
  return QAbstractProxyModel::match(start, role, value, hits, flags);
}

void KDescendantsProxyModel::setDisplayAncestorData( bool display )
{
  Q_D(KDescendantsProxyModel);
  d->m_displayAncestorData = display;
}

bool KDescendantsProxyModel::displayAncestorData() const
{
  Q_D(const KDescendantsProxyModel );
  return d->m_displayAncestorData;
}

void KDescendantsProxyModel::setAncestorSeparator( const QString &separator )
{
  Q_D(KDescendantsProxyModel);
  d->m_ancestorSeparator = separator;
}

QString KDescendantsProxyModel::ancestorSeparator() const
{
  Q_D(const KDescendantsProxyModel );
  return d->m_ancestorSeparator;
}


void KDescendantsProxyModel::setSourceModel(QAbstractItemModel *_sourceModel)
{
  beginResetModel();

  if (_sourceModel) {
    disconnect(_sourceModel, SIGNAL(rowsAboutToBeInserted(QModelIndex,int,int)),
               this, SLOT(sourceRowsAboutToBeInserted(QModelIndex,int,int)));
    disconnect(_sourceModel, SIGNAL(rowsInserted(QModelIndex,int,int)),
               this, SLOT(sourceRowsInserted(QModelIndex,int,int)));
    disconnect(_sourceModel, SIGNAL(rowsAboutToBeRemoved(QModelIndex,int,int)),
               this, SLOT(sourceRowsAboutToBeRemoved(QModelIndex,int,int)));
    disconnect(_sourceModel, SIGNAL(rowsRemoved(QModelIndex,int,int)),
               this, SLOT(sourceRowsRemoved(QModelIndex,int,int)));
//     disconnect(_sourceModel, SIGNAL(rowsAboutToBeMoved(QModelIndex,int,int,QModelIndex,int)),
//             this, SLOT(sourceRowsAboutToBeMoved(QModelIndex,int,int,QModelIndex,int)));
//     disconnect(_sourceModel, SIGNAL(rowsMoved(QModelIndex,int,int,QModelIndex,int)),
//             this, SLOT(sourceRowsMoved(QModelIndex,int,int,QModelIndex,int)));
    disconnect(_sourceModel, SIGNAL(modelAboutToBeReset()),
               this, SLOT(sourceModelAboutToBeReset()));
    disconnect(_sourceModel, SIGNAL(modelReset()),
               this, SLOT(sourceModelReset()));
    disconnect(_sourceModel, SIGNAL(dataChanged(QModelIndex,QModelIndex)),
               this, SLOT(sourceDataChanged(QModelIndex,QModelIndex)));
    disconnect(_sourceModel, SIGNAL(layoutAboutToBeChanged()),
               this, SLOT(sourceLayoutAboutToBeChanged()));
    disconnect(_sourceModel, SIGNAL(layoutChanged()),
               this, SLOT(sourceLayoutChanged()));
    disconnect(_sourceModel, SIGNAL(destroyed()),
               this, SLOT(sourceModelDestroyed()));
  }

  QAbstractProxyModel::setSourceModel(_sourceModel);

  if (_sourceModel) {
    connect(_sourceModel, SIGNAL(rowsAboutToBeInserted(QModelIndex,int,int)),
            SLOT(sourceRowsAboutToBeInserted(QModelIndex,int,int)));
    connect(_sourceModel, SIGNAL(rowsInserted(QModelIndex,int,int)),
            SLOT(sourceRowsInserted(QModelIndex,int,int)));
    connect(_sourceModel, SIGNAL(rowsAboutToBeRemoved(QModelIndex,int,int)),
            SLOT(sourceRowsAboutToBeRemoved(QModelIndex,int,int)));
    connect(_sourceModel, SIGNAL(rowsRemoved(QModelIndex,int,int)),
            SLOT(sourceRowsRemoved(QModelIndex,int,int)));
//     connect(_sourceModel, SIGNAL(rowsAboutToBeMoved(QModelIndex,int,int,QModelIndex,int)),
//             SLOT(sourceRowsAboutToBeMoved(QModelIndex,int,int,QModelIndex,int)));
//     connect(_sourceModel, SIGNAL(rowsMoved(QModelIndex,int,int,QModelIndex,int)),
//             SLOT(sourceRowsMoved(QModelIndex,int,int,QModelIndex,int)));
    connect(_sourceModel, SIGNAL(modelAboutToBeReset()),
            SLOT(sourceModelAboutToBeReset()));
    connect(_sourceModel, SIGNAL(modelReset()),
            SLOT(sourceModelReset()));
    connect(_sourceModel, SIGNAL(dataChanged(QModelIndex,QModelIndex)),
            SLOT(sourceDataChanged(QModelIndex,QModelIndex)));
    connect(_sourceModel, SIGNAL(layoutAboutToBeChanged()),
            SLOT(sourceLayoutAboutToBeChanged()));
    connect(_sourceModel, SIGNAL(layoutChanged()),
            SLOT(sourceLayoutChanged()));
    connect(_sourceModel, SIGNAL(destroyed()),
            SLOT(sourceModelDestroyed()));
  }

  endResetModel();
}

QModelIndex KDescendantsProxyModel::parent(const QModelIndex &index) const
{
  Q_UNUSED(index)
  return QModelIndex();
}

bool KDescendantsProxyModel::hasChildren(const QModelIndex &parent) const
{
  Q_D(const KDescendantsProxyModel);
  return !(d->m_mapping.isEmpty() || parent.isValid());
}

int KDescendantsProxyModel::rowCount(const QModelIndex &parent) const
{
  Q_D(const KDescendantsProxyModel);
  if (d->m_pendingParents.contains(parent) || parent.isValid() || !sourceModel())
    return 0;

  if (d->m_mapping.isEmpty() && sourceModel()->hasChildren())
  {
    Q_ASSERT(sourceModel()->rowCount() > 0);
    const_cast<KDescendantsProxyModelPrivate*>(d)->synchronousMappingRefresh();
  }
  return d->m_rowCount;
}

QModelIndex KDescendantsProxyModel::index(int row, int column, const QModelIndex &parent) const
{
  if (parent.isValid())
    return QModelIndex();

  if (!hasIndex(row, column, parent))
    return QModelIndex();

  return createIndex(row, column);
}

QModelIndex KDescendantsProxyModel::mapToSource(const QModelIndex &proxyIndex) const
{
  Q_D(const KDescendantsProxyModel);
  if (d->m_mapping.isEmpty() || !proxyIndex.isValid() || !sourceModel())
    return QModelIndex();

  const Mapping::right_const_iterator result = d->m_mapping.rightLowerBound(proxyIndex.row());
  Q_ASSERT(result != d->m_mapping.rightEnd());

  const int proxyLastRow = result.key();
  const QModelIndex sourceLastChild = result.value();
  Q_ASSERT(sourceLastChild.isValid());

  // proxyLastRow is greater than proxyIndex.row().
  // sourceLastChild is vertically below the result we're looking for
  // and not necessarily in the correct parent.
  // We travel up through its parent hierarchy until we are in the
  // right parent, then return the correct sibling.

  // Source:           Proxy:    Row
  // - A               - A       - 0
  // - B               - B       - 1
  // - C               - C       - 2
  // - D               - D       - 3
  // - - E             - E       - 4
  // - - F             - F       - 5
  // - - G             - G       - 6
  // - - H             - H       - 7
  // - - I             - I       - 8
  // - - - J           - J       - 9
  // - - - K           - K       - 10
  // - - - L           - L       - 11
  // - - M             - M       - 12
  // - - N             - N       - 13
  // - O               - O       - 14

  // Note that L, N and O are lastChildIndexes, and therefore have a mapping. If we
  // are trying to map G from the proxy to the source, We at this point have an iterator
  // pointing to (L -> 11). The proxy row of G is 6. (proxyIndex.row() == 6). We seek the
  // sourceIndex which is vertically above L by the distance proxyLastRow - proxyIndex.row().
  // In this case the verticalDistance is 5.

  int verticalDistance = proxyLastRow - proxyIndex.row();

  // We traverse the ancestors of L, until we can index the desired row in the source.

  QModelIndex ancestor = sourceLastChild;
  while (ancestor.isValid())
  {
    const int ancestorRow = ancestor.row();
    if (verticalDistance <= ancestorRow)
    {
      return ancestor.sibling(ancestorRow - verticalDistance, proxyIndex.column());
    }
    verticalDistance -= (ancestorRow + 1);
    ancestor = ancestor.parent();
  }
  Q_ASSERT(!"Didn't find target row.");
  return QModelIndex();
}

QModelIndex KDescendantsProxyModel::mapFromSource(const QModelIndex &sourceIndex) const
{
  Q_D(const KDescendantsProxyModel);

  if (!sourceModel())
    return QModelIndex();

  if (d->m_mapping.isEmpty())
    return QModelIndex();


  {
    // TODO: Consider a parent Mapping to speed this up.

    Mapping::right_const_iterator it = d->m_mapping.rightConstBegin();
    const Mapping::right_const_iterator end = d->m_mapping.rightConstEnd();
    const QModelIndex sourceParent = sourceIndex.parent();
    Mapping::right_const_iterator result = end;

    for ( ; it != end; ++it )
    {
      QModelIndex index = it.value();
      bool found_block = false;
      while (index.isValid())
      {
        const QModelIndex ancestor = index.parent();
        if (ancestor == sourceParent && index.row() >= sourceIndex.row())
        {
          found_block = true;
          if (result == end || it.key() < result.key())
          {
            result = it;
            break; // Leave the while loop. index is still valid.
          }
        }
        index = ancestor;
      }
      if (found_block && !index.isValid())
        // Looked through the ascendants of it.key() without finding sourceParent.
        // That means we've already got the result we need.
        break;
    }
    Q_ASSERT(result != end);
    const QModelIndex sourceLastChild = result.value();
    int proxyRow = result.key();
    QModelIndex index = sourceLastChild;
    while (index.isValid())
    {
      const QModelIndex ancestor = index.parent();
      if (ancestor == sourceParent)
      {
        return createIndex(proxyRow - (index.row() - sourceIndex.row()), sourceIndex.column());
      }
      proxyRow -= (index.row() + 1);
      index = ancestor;
    }
    Q_ASSERT(!"Didn't find valid proxy mapping.");
    return QModelIndex();
  }

}

int KDescendantsProxyModel::columnCount(const QModelIndex &parent) const
{
  if (parent.isValid() /* || rowCount(parent) == 0 */ || !sourceModel())
    return 0;

  return sourceModel()->columnCount();
}

QVariant KDescendantsProxyModel::data(const QModelIndex &index, int role) const
{
  Q_D(const KDescendantsProxyModel );

  if (!sourceModel())
    return QVariant();

  if (!index.isValid())
    return sourceModel()->data(index, role);

  QModelIndex sourceIndex = mapToSource( index );

  if ((d->m_displayAncestorData) && ( role == Qt::DisplayRole ) )
  {
    if (!sourceIndex.isValid())
    {
      return QVariant();
    }
    QString displayData = sourceIndex.data().toString();
    sourceIndex = sourceIndex.parent();
    while (sourceIndex.isValid())
    {
      displayData.prepend(d->m_ancestorSeparator);
      displayData.prepend(sourceIndex.data().toString());
      sourceIndex = sourceIndex.parent();
    }
    return displayData;
  } else {
    return sourceIndex.data(role);
  }
}

QVariant KDescendantsProxyModel::headerData(int section, Qt::Orientation orientation, int role) const
{
  if (!sourceModel() || columnCount() <= section)
    return QVariant();

  return QAbstractProxyModel::headerData(section, orientation, role);
}

Qt::ItemFlags KDescendantsProxyModel::flags(const QModelIndex &index) const
{
  if (!index.isValid() || !sourceModel())
    return QAbstractProxyModel::flags(index);

  const QModelIndex srcIndex = mapToSource(index);
  Q_ASSERT(srcIndex.isValid());
  return sourceModel()->flags(srcIndex);
}

void KDescendantsProxyModelPrivate::sourceRowsAboutToBeInserted(const QModelIndex &parent, int start, int end)
{
  Q_Q(KDescendantsProxyModel);

  if (!q->sourceModel()->hasChildren(parent))
  {
    Q_ASSERT(q->sourceModel()->rowCount(parent) == 0);
    // parent was not a parent before.
    return;
  }

  int proxyStart = -1;

  const int rowCount = q->sourceModel()->rowCount(parent);

  if (rowCount > start)
  {
    const QModelIndex belowStart = q->sourceModel()->index(start, 0, parent);
    proxyStart = q->mapFromSource(belowStart).row();
  } else if (rowCount == 0)
  {
    proxyStart = q->mapFromSource(parent).row() + 1;
  } else {
    Q_ASSERT(rowCount == start);
    static const int column = 0;
    QModelIndex idx = q->sourceModel()->index(rowCount - 1, column, parent);
    while (q->sourceModel()->hasChildren(idx))
    {
      Q_ASSERT(q->sourceModel()->rowCount(idx) > 0);
      idx = q->sourceModel()->index(q->sourceModel()->rowCount(idx) - 1, column, idx);
    }
    // The last item in the list is getting a sibling below it.
    proxyStart = q->mapFromSource(idx).row() + 1;
  }
  const int proxyEnd = proxyStart + (end - start);

  m_insertPair = qMakePair(proxyStart, proxyEnd);
  q->beginInsertRows(QModelIndex(), proxyStart, proxyEnd);
}

void KDescendantsProxyModelPrivate::sourceRowsInserted(const QModelIndex &parent, int start, int end)
{
  Q_Q(KDescendantsProxyModel);

  const QModelIndex sourceStart = q->sourceModel()->index(start, 0, parent);
  Q_ASSERT(sourceStart.isValid());

  const int rowCount = q->sourceModel()->rowCount(parent);
  Q_ASSERT(rowCount > 0);

  const int difference = end - start + 1;

  if (rowCount == difference)
  {
    // @p parent was not a parent before.
    m_pendingParents.append(parent);
    scheduleProcessPendingParents();
    return;
  }

  const int proxyStart = m_insertPair.first;

  Q_ASSERT(proxyStart >= 0);

  updateInternalIndexes(proxyStart, difference);

  if (rowCount - 1 == end)
  {
    // The previously last row (the mapped one) is no longer the last.
    // For example,

    // - A            - A           0
    // - - B          - B           1
    // - - C          - C           2
    // - - - D        - D           3
    // - - - E   ->   - E           4
    // - - F          - F           5
    // - - G     ->   - G           6
    // - H            - H           7
    // - I       ->   - I           8

    // As last children, E, F and G have mappings.
    // Consider that 'J' is appended to the children of 'C', below 'E'.

    // - A            - A           0
    // - - B          - B           1
    // - - C          - C           2
    // - - - D        - D           3
    // - - - E   ->   - E           4
    // - - - J        - ???         5
    // - - F          - F           6
    // - - G     ->   - G           7
    // - H            - H           8
    // - I       ->   - I           9

    // The updateInternalIndexes call above will have updated the F and G mappings correctly because proxyStart is 5.
    // That means that E -> 4 was not affected by the updateInternalIndexes call.
    // Now the mapping for E -> 4 needs to be updated so that it's a mapping for J -> 5.

    Q_ASSERT(!m_mapping.isEmpty());
    static const int column = 0;
    const QModelIndex oldIndex = q->sourceModel()->index(rowCount - 1 - difference, column, parent);
    Q_ASSERT(m_mapping.leftContains(oldIndex));

    const QModelIndex newIndex = q->sourceModel()->index(rowCount - 1, column, parent);

    QModelIndex indexAbove = oldIndex;

    if (start > 0) {
      // If we have something like this:
      //
      // - A
      // - - B
      // - - C
      //
      // and we then insert D as a sibling of A below it, we need to remove the mapping for A,
      // and the row number used for D must take into account the descendants of A.

      while (q->sourceModel()->hasChildren(indexAbove)) {
      Q_ASSERT(q->sourceModel()->rowCount(indexAbove) > 0);
        indexAbove = q->sourceModel()->index(q->sourceModel()->rowCount(indexAbove) - 1,  column, indexAbove);
      }
      Q_ASSERT(q->sourceModel()->rowCount(indexAbove) == 0);
    }

    Q_ASSERT(m_mapping.leftContains(indexAbove));

    const int newProxyRow = m_mapping.leftToRight(indexAbove) + difference;

    // oldIndex is E in the source. proxyRow is 4.
    m_mapping.removeLeft(oldIndex);

    // newIndex is J. (proxyRow + difference) is 5.
    m_mapping.insert(newIndex, newProxyRow);
  }

  for (int row = start; row <= end; ++row)
  {
    static const int column = 0;
    const QModelIndex idx = q->sourceModel()->index(row, column, parent);
    Q_ASSERT(idx.isValid());
    if (q->sourceModel()->hasChildren(idx))
    {
      Q_ASSERT(q->sourceModel()->rowCount(idx) > 0);
      m_pendingParents.append(idx);
    }
  }

  m_rowCount += difference;

  q->endInsertRows();
  scheduleProcessPendingParents();
}

void KDescendantsProxyModelPrivate::sourceRowsAboutToBeRemoved(const QModelIndex &parent, int start, int end)
{
  Q_Q(KDescendantsProxyModel);

  const int proxyStart = q->mapFromSource(q->sourceModel()->index(start, 0, parent)).row();

  static const int column = 0;
  QModelIndex idx = q->sourceModel()->index(end, column, parent);
  while (q->sourceModel()->hasChildren(idx))
  {
    Q_ASSERT(q->sourceModel()->rowCount(idx) > 0);
    idx = q->sourceModel()->index(q->sourceModel()->rowCount(idx) - 1, column, idx);
  }
  const int proxyEnd = q->mapFromSource(idx).row();

  m_removePair = qMakePair(proxyStart, proxyEnd);

  q->beginRemoveRows(QModelIndex(), proxyStart, proxyEnd);
}

static QModelIndex getFirstDeepest(QAbstractItemModel *model, const QModelIndex &parent, int *count) {
  static const int column = 0;
  Q_ASSERT(model->hasChildren(parent));
  Q_ASSERT(model->rowCount(parent) > 0);
  for (int row = 0; row < model->rowCount(parent); ++row) {
    (*count)++;
    const QModelIndex child = model->index(row, column, parent);
    Q_ASSERT(child.isValid());
    if (model->hasChildren(child))
      return getFirstDeepest(model, child, count);
  }
  return model->index(model->rowCount(parent) - 1, column, parent);
}

void KDescendantsProxyModelPrivate::sourceRowsRemoved(const QModelIndex &parent, int start, int end)
{
  Q_Q(KDescendantsProxyModel);
  Q_UNUSED(end)

  const int rowCount = q->sourceModel()->rowCount(parent);


  const int proxyStart = m_removePair.first;
  const int proxyEnd = m_removePair.second;

  const int difference = proxyEnd - proxyStart + 1;
  {
    Mapping::right_iterator it = m_mapping.rightLowerBound(proxyStart);
    const Mapping::right_iterator endIt = m_mapping.rightUpperBound(proxyEnd);

    if (endIt != m_mapping.rightEnd())
      while (it != endIt)
        it = m_mapping.eraseRight(it);
    else
      while (it != m_mapping.rightUpperBound(proxyEnd))
        it = m_mapping.eraseRight(it);
  }

  m_removePair = qMakePair(-1, -1);
  m_rowCount -= difference;
  Q_ASSERT(m_rowCount >= 0);

  updateInternalIndexes(proxyStart, -1 * difference);

  if (rowCount != start || rowCount == 0) {
    q->endRemoveRows();
    return;
  }

  static const int column = 0;
  const QModelIndex newEnd = q->sourceModel()->index(rowCount - 1, column, parent);
  Q_ASSERT(newEnd.isValid());

  if (m_mapping.isEmpty()) {
    m_mapping.insert(newEnd, newEnd.row());
    q->endRemoveRows();
    return;
  }
  if (q->sourceModel()->hasChildren(newEnd)) {
    int count = 0;
    const QModelIndex firstDeepest = getFirstDeepest(q->sourceModel(), newEnd, &count);
    Q_ASSERT(firstDeepest.isValid());
    const int firstDeepestProxy = m_mapping.leftToRight(firstDeepest);

    m_mapping.insert(newEnd, firstDeepestProxy - count);
    q->endRemoveRows();
    return;
  }
  Mapping::right_iterator lowerBound = m_mapping.rightLowerBound(proxyStart);
  if (lowerBound == m_mapping.rightEnd()) {
    int proxyRow = (lowerBound - 1).key();

    for (int row = newEnd.row(); row >= 0; --row ) {
      const QModelIndex newEndSibling = q->sourceModel()->index(row, column, parent);
      if (!q->sourceModel()->hasChildren(newEndSibling)) {
        ++proxyRow;
      } else {
        break;
      }
    }
    m_mapping.insert(newEnd, proxyRow);
    q->endRemoveRows();
    return;
  } else if (lowerBound == m_mapping.rightBegin()) {
    int proxyRow = rowCount - 1;
    QModelIndex trackedParent = parent;
    while (trackedParent.isValid()) {
      proxyRow += (trackedParent.row() + 1);
      trackedParent = trackedParent.parent();
    }
    m_mapping.insert(newEnd, proxyRow);
    q->endRemoveRows();
    return;
  }
  const Mapping::right_iterator boundAbove = lowerBound - 1;

  QVector<QModelIndex> targetParents;
  targetParents.push_back(parent);
  {
    QModelIndex target = parent;
    int count = 0;
    while (target.isValid()) {
      if (target == boundAbove.value()) {
        m_mapping.insert(newEnd, count + boundAbove.key() + newEnd.row() + 1);
        q->endRemoveRows();
        return;
      }
      count += (target.row() + 1);
      target = target.parent();
      if (target.isValid())
        targetParents.push_back(target);
    }
  }

  QModelIndex boundParent = boundAbove.value().parent();
  QModelIndex prevParent = boundParent;
  Q_ASSERT(boundParent.isValid());
  while (boundParent.isValid()) {
    prevParent = boundParent;
    boundParent = boundParent.parent();

    if (targetParents.contains(prevParent))
      break;

    if (!m_mapping.leftContains(prevParent))
      break;

    if (m_mapping.leftToRight(prevParent) > boundAbove.key())
      break;
  }

  QModelIndex trackedParent = parent;

  int proxyRow = boundAbove.key();

  Q_ASSERT(prevParent.isValid());
  proxyRow -= prevParent.row();
  while (trackedParent != boundParent) {
    proxyRow += (trackedParent.row() + 1);
    trackedParent = trackedParent.parent();
  }
  m_mapping.insert(newEnd, proxyRow + newEnd.row());
  q->endRemoveRows();
}

void KDescendantsProxyModelPrivate::sourceRowsAboutToBeMoved(const QModelIndex &srcParent, int srcStart, int srcEnd, const QModelIndex &destParent, int destStart)
{
  Q_UNUSED(srcParent)
  Q_UNUSED(srcStart)
  Q_UNUSED(srcEnd)
  Q_UNUSED(destParent)
  Q_UNUSED(destStart)
  Q_Q(KDescendantsProxyModel);
  q->beginResetModel();
}

void KDescendantsProxyModelPrivate::sourceRowsMoved(const QModelIndex &srcParent, int srcStart, int srcEnd, const QModelIndex &destParent, int destStart)
{
  Q_UNUSED(srcParent)
  Q_UNUSED(srcStart)
  Q_UNUSED(srcEnd)
  Q_UNUSED(destParent)
  Q_UNUSED(destStart)
  Q_Q(KDescendantsProxyModel);
  resetInternalData();
  q->endResetModel();
}

void KDescendantsProxyModelPrivate::sourceModelAboutToBeReset()
{
  Q_Q(KDescendantsProxyModel);
  q->beginResetModel();
}

void KDescendantsProxyModelPrivate::sourceModelReset()
{
  Q_Q(KDescendantsProxyModel);
  resetInternalData();
  if (q->sourceModel()->hasChildren())
  {
    Q_ASSERT(q->sourceModel()->rowCount() > 0);
    m_pendingParents.append(QModelIndex());
    scheduleProcessPendingParents();
  }
  q->endResetModel();
}

void KDescendantsProxyModelPrivate::sourceLayoutAboutToBeChanged()
{
  Q_Q(KDescendantsProxyModel);

  if (m_ignoreNextLayoutChanged) {
      m_ignoreNextLayoutChanged = false;
      return;
  }

  if (m_mapping.isEmpty())
    return;

  QPersistentModelIndex srcPersistentIndex;
  foreach(const QPersistentModelIndex &proxyPersistentIndex, q->persistentIndexList()) {
      m_proxyIndexes << proxyPersistentIndex;
      Q_ASSERT(proxyPersistentIndex.isValid());
      srcPersistentIndex = q->mapToSource(proxyPersistentIndex);
      Q_ASSERT(srcPersistentIndex.isValid());
      m_layoutChangePersistentIndexes << srcPersistentIndex;
  }

  q->layoutAboutToBeChanged();
}

void KDescendantsProxyModelPrivate::sourceLayoutChanged()
{
  Q_Q(KDescendantsProxyModel);

  if (m_ignoreNextLayoutAboutToBeChanged) {
      m_ignoreNextLayoutAboutToBeChanged = false;
      return;
  }

  if (m_mapping.isEmpty())
    return;

  m_rowCount = 0;

  synchronousMappingRefresh();

  for (int i = 0; i < m_proxyIndexes.size(); ++i) {
      q->changePersistentIndex(m_proxyIndexes.at(i), q->mapFromSource(m_layoutChangePersistentIndexes.at(i)));
  }

  m_layoutChangePersistentIndexes.clear();
  m_proxyIndexes.clear();

  q->layoutChanged();
}

void KDescendantsProxyModelPrivate::sourceDataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight)
{
  Q_Q(KDescendantsProxyModel);
  Q_ASSERT(topLeft.model() == q->sourceModel());
  Q_ASSERT(bottomRight.model() == q->sourceModel());

  const int topRow = topLeft.row();
  const int bottomRow = bottomRight.row();

  for(int i = topRow; i <= bottomRow; ++i)
  {
    const QModelIndex sourceTopLeft = q->sourceModel()->index(i, topLeft.column(), topLeft.parent());
    Q_ASSERT(sourceTopLeft.isValid());
    const QModelIndex proxyTopLeft = q->mapFromSource(sourceTopLeft);
    // TODO. If an index does not have any descendants, then we can emit in blocks of rows.
    // As it is we emit once for each row.
    const QModelIndex sourceBottomRight = q->sourceModel()->index(i, bottomRight.column(), bottomRight.parent());
    const QModelIndex proxyBottomRight = q->mapFromSource(sourceBottomRight);
    Q_ASSERT(proxyTopLeft.isValid());
    Q_ASSERT(proxyBottomRight.isValid());
    emit q->dataChanged(proxyTopLeft, proxyBottomRight);
  }
}

void KDescendantsProxyModelPrivate::sourceModelDestroyed()
{
  Q_Q(KDescendantsProxyModel);
  resetInternalData();
//   q->endResetModel();
}

QMimeData* KDescendantsProxyModel::mimeData( const QModelIndexList & indexes ) const
{
  if (!sourceModel())
    return QAbstractProxyModel::mimeData(indexes);
  Q_ASSERT(sourceModel());
  QModelIndexList sourceIndexes;
  foreach(const QModelIndex& index, indexes)
    sourceIndexes << mapToSource(index);
  return sourceModel()->mimeData(sourceIndexes);
}

QStringList KDescendantsProxyModel::mimeTypes() const
{
  if (!sourceModel())
    return QAbstractProxyModel::mimeTypes();
  Q_ASSERT(sourceModel());
  return sourceModel()->mimeTypes();
}

Qt::DropActions KDescendantsProxyModel::supportedDropActions() const
{
  if (!sourceModel())
    return QAbstractProxyModel::supportedDropActions();
  return sourceModel()->supportedDropActions();
}

#include "moc_kdescendantsproxymodel.cpp"
