/***************************************************************************
    qgsrelationmanager.h
     --------------------------------------
    Date                 : 1.3.2013
    Copyright            : (C) 2013 Matthias Kuhn
    Email                : matthias dot kuhn at gmx dot ch
 ***************************************************************************
 *                                                                         *
 *   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.                                   *
 *                                                                         *
 ***************************************************************************/

#ifndef QGSRELATIONMANAGER_H
#define QGSRELATIONMANAGER_H

#include <QObject>
#include <QPair>
#include <QDomNode>
#include <QDomDocument>

#include "qgsrelation.h"

class QgsProject;
class QgsVectorLayer;

/**
 * This class manages a set of relations between layers.
 */
class CORE_EXPORT QgsRelationManager : public QObject
{
    Q_OBJECT

  public:
    explicit QgsRelationManager( QgsProject *project );

    /**
     * Will set the specified relations and remove any relation currently set.
     *
     * @param relations A list of relations to set.
     */
    void setRelations( const QList<QgsRelation>& relations );

    /**
     * Get access to the relations managed by this class.
     *
     * @return A QMap where the key is the relation id, the value the relation object.
     */
    const QMap<QString, QgsRelation>& relations() const;

    /**
     * Add a relation.
     *
     * @param relation The relation to add.
     */
    void addRelation( const QgsRelation& relation );

    /**
     * Remove a relation.
     *
     * @param id The id of the relation to remove.
     */
    void removeRelation( const QString& id );

    /**
     * Remove a relation.
     *
     * @param relation The relation to remove.
     */
    void removeRelation( const QgsRelation& relation );

    /**
     * Get access to a relation by its id.
     *
     * @param id The id to search for
     *
     * @return A relation. Invalid if not found.
     */
    QgsRelation relation( const QString& id ) const;

    /**
     * Remove any relation managed by this class.
     */
    void clear();

    /**
     * Get all relations where the specified layer (and field) is the referencing part (i.e. the child table with the foreign key).
     *
     * @param layer     The layer which should be searched for.
     * @param fieldIdx  The field which should be part of the foreign key. If not set will return all relations.
     *
     * @return A list of relations matching the given layer and fieldIdx.
     */
    QList<QgsRelation> referencingRelations( QgsVectorLayer *layer = 0, int fieldIdx = -2 ) const;

    /**
     * Get all relations where this layer is the referenced part (i.e. the parent table with the primary key being referenced from another layer).
     *
     * @param layer   The layer which should be searched for.
     *
     * @return A list of relations where the specified layer is the referenced part.
     */
    QList<QgsRelation> referencedRelations( QgsVectorLayer *layer = 0 ) const;

  signals:
    /** this signal is emitted when the relations were loaded after reading a project */
    void relationsLoaded();

    /**
     * Emitted when relations are added or removed to the manager.
     * @note added in QGIS 2.5
     */
    void changed();

  private slots:
    void readProject( const QDomDocument &doc );
    void writeProject( QDomDocument &doc );
    void layersRemoved( const QStringList& layers );

  private:
    /** The references */
    QMap<QString, QgsRelation> mRelations;

    QgsProject* mProject;
};

#endif // QGSRELATIONMANAGER_H
