class QgsFeatureRequest
{
%TypeHeaderCode
#include <qgsfeaturerequest.h>
%End

  public:
    enum Flag
    {
      NoFlags,
      NoGeometry,          //!< Geometry is not required. It may still be returned if e.g. required for a filter condition.
      SubsetOfAttributes,  //!< Fetch only a subset of attributes (setSubsetOfAttributes sets this flag)
      ExactIntersect       //!< Use exact geometry intersection (slower) instead of bounding boxes
    };
    typedef QFlags<QgsFeatureRequest::Flag> Flags;

    enum FilterType
    {
      FilterNone,       //!< No filter is applied
      FilterRect,       //!< Filter using a rectangle, no need to set NoGeometry
      FilterFid,        //!< Filter using feature ID
      FilterExpression, //!< Filter using expression
      FilterFids        //!< Filter using feature IDs
    };

    static const QString AllAttributes;

    //! construct a default request: for all features get attributes and geometries
    QgsFeatureRequest();
    //! construct a request with feature ID filter
    explicit QgsFeatureRequest( QgsFeatureId fid );
    //! construct a request with rectangle filter
    explicit QgsFeatureRequest( const QgsRectangle& rect );
    //! construct a request with a filter expression
    explicit QgsFeatureRequest( const QgsExpression& expr, const QgsExpressionContext& context = QgsExpressionContext() );

    FilterType filterType() const;

    //! Set rectangle from which features will be taken. Empty rectangle removes the filter.
    //!
    QgsFeatureRequest& setFilterRect( const QgsRectangle& rect );
    const QgsRectangle& filterRect() const;

    //! Set feature ID that should be fetched.
    QgsFeatureRequest& setFilterFid( qint64 fid );
    qint64 filterFid() const;

    //! Set feature ID that should be fetched.
    QgsFeatureRequest& setFilterFids( const QgsFeatureIds& fids );
    const QgsFeatureIds& filterFids() const;

    /** Set the filter expression. {@see QgsExpression}
     * @param expression expression string
     * @see filterExpression
     * @see setExpressionContext
     */
    QgsFeatureRequest& setFilterExpression( const QString& expression );

    /** Returns the filter expression if set.
     * @see setFilterExpression
     * @see expressionContext
     */
    QgsExpression* filterExpression() const;

    /** Modifies the existing filter expression to add an additional expression filter. The
     * filter expressions are combined using AND, so only features matching both
     * the existing expression and the additional expression will be returned.
     * @note added in QGIS 2.14
     */
    QgsFeatureRequest& combineFilterExpression( const QString& expression );

    /** Returns the expression context used to evaluate filter expressions.
     * @note added in QGIS 2.12
     * @see setExpressionContext
     */
    QgsExpressionContext* expressionContext();

    /** Sets the expression context used to evaluate filter expressions.
     * @note added in QGIS 2.12
     * @see expressionContext
     */
    QgsFeatureRequest& setExpressionContext( const QgsExpressionContext& context );

    /**
     * Disables filter conditions.
     * The spatial filter (filterRect) will be kept in place.
     *
     * @return The object the method is called on for chaining
     *
     * @note Added in 2.12
     */
    QgsFeatureRequest& disableFilter();

    /** Set the maximum number of features to request.
     * @param limit maximum number of features, or -1 to request all features.
     * @see limit()
     * @note added in QGIS 2.14
     */
    QgsFeatureRequest& setLimit( long limit );

    /** Returns the maximum number of features to request, or -1 if no limit set.
     * @see setLimit
     * @note added in QGIS 2.14
     */
    long limit() const;

    //! Set flags that affect how features will be fetched
    QgsFeatureRequest& setFlags( const Flags& flags );
    const Flags& flags() const;

    //! Set a subset of attributes that will be fetched. Empty list means that all attributes are used.
    //! To disable fetching attributes, reset the FetchAttributes flag (which is set by default)
    QgsFeatureRequest& setSubsetOfAttributes( const QgsAttributeList& attrs );
    const QgsAttributeList& subsetOfAttributes() const;

    //! Set a subset of attributes by names that will be fetched
    QgsFeatureRequest& setSubsetOfAttributes( const QStringList& attrNames, const QgsFields& fields );

    //! Set a simplification method for geometries that will be fetched
    //! @note added in 2.2
    QgsFeatureRequest& setSimplifyMethod( const QgsSimplifyMethod& simplifyMethod );
    //! Get simplification method for geometries that will be fetched
    //! @note added in 2.2
    const QgsSimplifyMethod& simplifyMethod() const;

    /**
     * Check if a feature is accepted by this requests filter
     *
     * @param feature  The feature which will be tested
     *
     * @return true, if the filter accepts the feature
     *
     * @note added in 2.1
     */
    bool acceptFeature( const QgsFeature& feature );

};


/** Base class that can be used for any class that is capable of returning features
 * @note added in 2.4
 */
class QgsAbstractFeatureSource
{
%TypeHeaderCode
#include <qgsfeaturerequest.h>
%End
  public:
    virtual ~QgsAbstractFeatureSource();

    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest& request ) = 0;

  protected:
    void iteratorOpened( QgsAbstractFeatureIterator* it );
    void iteratorClosed( QgsAbstractFeatureIterator* it );
};