//  UndoRedoModel.cpp
//
//  Copyright (C) 2016  Jaye Evins <evins@snaught.com>
//
//  This file is part of gLabels-qt.
//
//  gLabels-qt 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 3 of the License, or
//  (at your option) any later version.
//
//  gLabels-qt 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 gLabels-qt.  If not, see <http://www.gnu.org/licenses/>.
//


#include "UndoRedoModel.hpp"

#include "model/Model.hpp"


namespace glabels
{

        ///
        /// Constructor
        ///
        UndoRedoModel::UndoRedoModel( model::Model* model )
        {
                mModel = model;
                mNewSelection = true;

                connect( model, SIGNAL(selectionChanged()), this, SLOT(onSelectionChanged()) );
        }


        ///
        /// Checkpoint
        ///
        void UndoRedoModel::checkpoint( const QString& description )
        {
                //
                // Do not perform consecutive checkpoints that are identical.
                // E.g. moving an object by dragging, would produce a large number
                // of incremental checkpoints -- what we really want is a single
                // checkpoint so that we can undo the entire dragging effort with
                // one "undo"
                //
                if ( mNewSelection || (description != mLastDescription) )
                {

                        /* Sever old redo "thread" */
                        mRedoStack.clear();

                        /* Save state onto undo stack. */
                        auto* stateNow = new State( mModel, description );
                        mUndoStack.push( stateNow );

                        /* Track consecutive checkpoints. */
                        mNewSelection = false;
                        mLastDescription = description;

                        emit changed();
                }
        }


        ///
        /// Undo
        ///
        void UndoRedoModel::undo()
        {
                State* oldState = mUndoStack.pop();
                auto* stateNow = new State( mModel, oldState->description );

                mRedoStack.push( stateNow );

                mModel->restore( oldState->model );
                delete oldState;

                mNewSelection = true;

                emit changed();
        }


        ///
        /// Redo
        ///
        void UndoRedoModel::redo()
        {
                State* oldState = mRedoStack.pop();
                auto* stateNow = new State( mModel, oldState->description );

                mUndoStack.push( stateNow );

                mModel->restore( oldState->model );
                delete oldState;

                mNewSelection = true;

                emit changed();
        }


        ///
        /// Can we undo?
        ///
        bool UndoRedoModel::canUndo() const
        {
                return !mUndoStack.isEmpty();
        }


        ///
        /// Can we redo?
        ///
        bool UndoRedoModel::canRedo() const
        {
                return !mRedoStack.isEmpty();
        }


        ///
        /// Undo description
        ///
        QString UndoRedoModel::undoDescription() const
        {
                if ( canUndo() )
                {
                        return mUndoStack.topState()->description;
                }
                else
                {
                        return "";
                }
        }


        ///
        /// Redo description
        ///
        QString UndoRedoModel::redoDescription() const
        {
                if ( canRedo() )
                {
                        return mRedoStack.topState()->description;
                }
                else
                {
                        return "";
                }
        }


        ///
        /// Selection changed handler
        ///
        void UndoRedoModel::onSelectionChanged()
        {
                mNewSelection = true;
        }


        ///
        /// State constructor
        ///
        UndoRedoModel::State::State( model::Model* model, const QString& description )
        {
                this->model = model->save();
                this->description = description;
        }


        ///
        /// State destructor
        ///
        UndoRedoModel::State::~State()
        {
                delete model;
        }


        ///
        /// Stack constructor
        ///
        UndoRedoModel::Stack::Stack()
        {
                // empty
        }


        ///
        /// Stack destructor
        ///
        UndoRedoModel::Stack::~Stack()
        {
                clear();
        }


        ///
        /// Push state onto stack
        ///
        void UndoRedoModel::Stack::push( UndoRedoModel::State* state )
        {
                list.push_front( state );
        }


        ///
        /// Pop state from stack
        ///
        UndoRedoModel::State* UndoRedoModel::Stack::pop()
        {
                return list.takeFirst();
        }


        ///
        /// Peek at state at top of stack
        ///
        const UndoRedoModel::State* UndoRedoModel::Stack::topState() const
        {
                return list.first();
        }


        ///
        /// Is stack empty?
        ///
        bool UndoRedoModel::Stack::isEmpty() const
        {
                return list.isEmpty();
        }


        ///
        /// Clear stack
        ///
        void UndoRedoModel::Stack::clear()
        {
                while ( !isEmpty() )
                {
                        delete pop();
                }
        }

} // namespace glabels
