/** \file errorhandler.h
 *  \brief Decide if a Xapian::Error exception should be ignored.
 */
/* Copyright (C) 2003,2006,2007 Olly Betts
 *
 * 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.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#ifndef XAPIAN_INCLUDED_ERRORHANDLER_H
#define XAPIAN_INCLUDED_ERRORHANDLER_H

#include <xapian/visibility.h>

namespace Xapian {

class Error;

/** Decide if a Xapian::Error exception should be ignored.
 *
 *  You can create your own subclass of this class and pass in an instance
 *  of it when you construct a Xapian::Enquire object.  Xapian::Error
 *  exceptions which happen during the match process are passed to this
 *  object and it can decide whether they should propagate or whether
 *  Enquire should attempt to continue.
 *
 *  The motivation is to allow searching over remote databases to handle a
 *  remote server which has died (both to allow results to be returned, and
 *  also so that such errors can be logged and dead servers temporarily removed
 *  from use).
 */
class XAPIAN_VISIBILITY_DEFAULT ErrorHandler {
    /// Don't allow assignment.
    void operator=(const ErrorHandler &);

    /// Don't allow copying.
    ErrorHandler(const Xapian::ErrorHandler &);

    /** Perform user-specified error handling.
     *
     *  This virtual method must be defined by the APU user to specify
     *  how a Xapian::Error is to be handled.
     *
     *  If you want execution to continue (where possible), then return
     *  true.  If you want the Error to be rethrown and propagate out
     *  of the library, then return false.
     *
     *  Note that it's not always possible to continue execution, so
     *  the error may be rethrown even if you return true.  The ErrorHandler
     *  is still called in this situation as you may want to log that a
     *  particular remote backend server isn't responding, and perhaps
     *  remove it from those being searched temporarily.
     *
     *  @param error	The Xapian::Error object under consideration.
     *
     *  @return  true to attempt to continue; false to rethrow the error.
     */
    virtual bool handle_error(Xapian::Error &error) = 0;

  public:
    /// Default constructor.
    ErrorHandler() {}

    /// We require a virtual destructor because we have virtual methods.
    virtual ~ErrorHandler();

    /** Handle a Xapian::Error object.
     *
     *  This method is called when a Xapian::Error object is thrown and
     *  caught inside Enquire.  If this is the first ErrorHandler that
     *  the Error has been passed to, then the handle_error() virtual
     *  method is called, which allows the API user to decide how to
     *  handle the error.
     *
     *  @param error	The Xapian::Error object under consideration.
     */
    void operator()(Xapian::Error &error);
};

}

#endif /* XAPIAN_INCLUDED_ERRORHANDLER_H */
