/**
 *    Copyright (C) 2013 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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 Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects
 *    for all of the code used other than as permitted herein. If you modify
 *    file(s) with this exception, you may extend this exception to your
 *    version of the file(s), but you are not obligated to do so. If you do not
 *    wish to do so, delete this exception statement from your version. If you
 *    delete this exception statement from all source files in the program,
 *    then also delete it in the license file.
 */

#include <string>

#include "mongo/db/namespace_string.h"
#include "mongo/db/jsobj.h"

namespace mongo {

class OperationContext;

/**
 * Merges a chunks in the specified [minKey, maxKey) range of the specified namespace.
 * Updates the local and remote metadata by expanding the bounds of the first chunk in the
 * range, dropping the others, and incrementing the minor version of the shard to the next
 * higher version.  Returns true on success.
 *
 * Fails with errMsg if the 'epoch' was set and has changed (indicating the range is no longer
 * valid), or if the range does not exactly start and stop on chunks owned by this shard, or
 * if the chunks in this range are not contiguous.
 *
 * WARNING: On network failure, it is possible that the chunks in our local metadata may not
 * match the remote metadata, however the key ranges protected will be the same.  All metadata
 * operations are responsible for updating the metadata before performing any actions.
 *
 * Locking note:
 *     + Takes a distributed lock over the namespace
 *     + Cannot be called with any other locks held
 */
bool mergeChunks(OperationContext* txn,
                 const NamespaceString& nss,
                 const BSONObj& minKey,
                 const BSONObj& maxKey,
                 const OID& epoch,
                 std::string* errMsg);
}