/*
    Copyright (c) 2009 Volker Krause <vkrause@kde.org>

    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 "entitytreeviewstatesaver.h"

#include <akonadi/collection.h>
#include <akonadi/entitytreemodel.h>
#include <akonadi/item.h>

#include <KConfigGroup>
#include <KDebug>

#include <QScrollBar>
#include <QTimer>
#include <QTreeView>

namespace Akonadi {

struct State
{
  State() : selected( false ), expanded( false ), currentIndex( false ) {}
  bool selected;
  bool expanded;
  bool currentIndex;
};

class EntityTreeViewStateSaverPrivate
{
  public:
    explicit EntityTreeViewStateSaverPrivate( EntityTreeViewStateSaver *parent ) :
      q( parent ),
      view( 0 ),
      horizontalScrollBarValue( -1 ),
      verticalScrollBarValue( -1 )
    {
    }

    inline bool hasChanges() const
    {
      return !pendingCollectionChanges.isEmpty() || !pendingItemChanges.isEmpty();
    }

    static inline QString key( const QModelIndex &index )
    {
      if ( !index.isValid() )
        return QLatin1String( "x-1" );
      const Collection c = index.data( EntityTreeModel::CollectionRole ).value<Collection>();
      if ( c.isValid() )
        return QString::fromLatin1( "c%1" ).arg( c.id() );
      return QString::fromLatin1( "i%1" ).arg( index.data( EntityTreeModel::ItemIdRole ).value<Entity::Id>() );
    }

    void saveState( const QModelIndex &index, QStringList &selection, QStringList &expansion )
    {
      const QString cfgKey = key( index );
      if ( view->selectionModel()->isSelected( index ) )
        selection.append( cfgKey );
      if ( view->isExpanded( index ) )
        expansion.append( cfgKey );
      for ( int i = 0; i < view->model()->rowCount( index ); ++i ) {
        const QModelIndex child = view->model()->index( i, 0, index );
        saveState( child, selection, expansion );
      }
    }

    inline void restoreState( const QModelIndex &index, const State &state )
    {
      if ( state.selected )
        view->selectionModel()->select( index, QItemSelectionModel::Select | QItemSelectionModel::Rows );
      if ( state.expanded )
        view->setExpanded( index, true );
      if ( state.currentIndex )
        view->setCurrentIndex( index );
      QTimer::singleShot( 0, q, SLOT( restoreScrollBarState() ) );
    }

    void restoreState( const QModelIndex &index )
    {
      const Collection c = index.data( EntityTreeModel::CollectionRole ).value<Collection>();
      if ( c.isValid() ) {
        if ( pendingCollectionChanges.contains( c.id() ) ) {
          restoreState( index, pendingCollectionChanges.value( c.id() ) );
          pendingCollectionChanges.remove( c.id() );
        }
      } else {
        Entity::Id itemId = index.data( EntityTreeModel::ItemIdRole ).value<Entity::Id>();
        if ( pendingItemChanges.contains( itemId ) ) {
          restoreState( index, pendingItemChanges.value( itemId ) );
          pendingItemChanges.remove( itemId );
        }
      }
      for ( int i = 0; i < view->model()->rowCount( index ) && hasChanges(); ++i ) {
        const QModelIndex child = view->model()->index( i, 0, index );
        restoreState( child );
      }
    }

    inline void restoreScrollBarState()
    {
      if ( horizontalScrollBarValue >= 0 && horizontalScrollBarValue <= view->horizontalScrollBar()->maximum() ) {
        view->horizontalScrollBar()->setValue( horizontalScrollBarValue );
        horizontalScrollBarValue = -1;
      }
      if ( verticalScrollBarValue >= 0 && verticalScrollBarValue <= view->verticalScrollBar()->maximum() ) {
        view->verticalScrollBar()->setValue( verticalScrollBarValue );
        verticalScrollBarValue = -1;
      }
    }

    void rowsInserted( const QModelIndex &index, int start, int end )
    {
      if ( !hasChanges() ) {
        QObject::disconnect( view->model(), SIGNAL( rowsInserted( const QModelIndex&, int, int ) ),
                             q, SLOT( rowsInserted( const QModelIndex&, int, int ) ) );
        return;
      }

      for ( int i = start; i <= end && hasChanges(); ++i ) {
        const QModelIndex child = view->model()->index( i, 0, index);;
        restoreState( child );
      }
    }

    EntityTreeViewStateSaver *q;
    QTreeView *view;
    QHash<Entity::Id, State> pendingCollectionChanges, pendingItemChanges;
    int horizontalScrollBarValue, verticalScrollBarValue;
};

EntityTreeViewStateSaver::EntityTreeViewStateSaver( QTreeView * view ) :
  QObject( view ),
  d( new EntityTreeViewStateSaverPrivate( this ) )
{
  d->view = view;
}

EntityTreeViewStateSaver::~EntityTreeViewStateSaver()
{
  delete d;
}

void EntityTreeViewStateSaver::saveState( KConfigGroup &configGroup ) const
{
  if ( !d->view->model() )
    return;

  configGroup.deleteGroup();
  QStringList selection, expansion;
  const int rowCount = d->view->model()->rowCount();
  for ( int i = 0; i < rowCount; ++i ) {
    const QModelIndex index = d->view->model()->index( i, 0 );
    d->saveState( index, selection, expansion );
  }

  const QString currentIndex = d->key( d->view->selectionModel()->currentIndex() );

  configGroup.writeEntry( "Selection", selection );
  configGroup.writeEntry( "Expansion", expansion );
  configGroup.writeEntry( "CurrentIndex", currentIndex );
  configGroup.writeEntry( "ScrollBarHorizontal", d->view->horizontalScrollBar()->value() );
  configGroup.writeEntry( "ScrollBarVertical", d->view->verticalScrollBar()->value() );
}

void EntityTreeViewStateSaver::restoreState (const KConfigGroup & configGroup) const
{
  if ( !d->view->model() )
    return;

  const QStringList selection = configGroup.readEntry( "Selection", QStringList() );
  foreach ( const QString &key, selection ) {
    Entity::Id id = key.mid( 1 ).toLongLong();
    if ( id < 0 )
      continue;
    if ( key.startsWith( QLatin1Char( 'c' ) ) )
      d->pendingCollectionChanges[id].selected = true;
    else if ( key.startsWith( QLatin1Char( 'i' ) ) )
      d->pendingItemChanges[id].selected = true;
  }

  const QStringList expansion = configGroup.readEntry( "Expansion", QStringList() );
  foreach ( const QString &key, expansion ) {
    Entity::Id id = key.mid( 1 ).toLongLong();
    if ( id < 0 )
      continue;
    if ( key.startsWith( QLatin1Char( 'c' ) ) )
      d->pendingCollectionChanges[id].expanded = true;
    else if ( key.startsWith( QLatin1Char( 'i' ) ) )
      d->pendingItemChanges[id].expanded = true;
  }

  const QString key = configGroup.readEntry( "CurrentIndex", QString() );
  const Entity::Id id = key.mid( 1 ).toLongLong();
  if ( id >= 0 ) {
    if ( key.startsWith( QLatin1Char( 'c' ) ) )
      d->pendingCollectionChanges[id].currentIndex = true;
    else if ( key.startsWith( QLatin1Char( 'i' ) ) )
      d->pendingItemChanges[id].currentIndex = true;
  }

  d->horizontalScrollBarValue = configGroup.readEntry( "ScrollBarHorizontal", -1 );
  d->verticalScrollBarValue = configGroup.readEntry( "ScrollBarVertical", -1 );

  // initial restore run, for everything already loaded
  for ( int i = 0; i < d->view->model()->rowCount() && d->hasChanges(); ++i ) {
    const QModelIndex index = d->view->model()->index( i, 0 );
    d->restoreState( index );
  }
  d->restoreScrollBarState();

  // watch the model for stuff coming in delayed
  if ( d->hasChanges() )
    connect( d->view->model(), SIGNAL( rowsInserted( const QModelIndex&, int, int ) ),
             SLOT( rowsInserted( const QModelIndex&, int, int ) ) );
}

} // namespace Akonadi

#include "entitytreeviewstatesaver.moc"
