// dbhelpers.cpp

/**
*    Copyright (C) 2008 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/>.
*/

#include "stdafx.h"
#include "db.h"
#include "dbhelpers.h"
#include "query.h"

namespace mongo {

    /* Get the first object from a collection.  Generally only useful if the collection
       only ever has a single object -- which is a "singleton collection.

       Returns: true if object exists.
    */
    bool getSingleton(const char *ns, BSONObj& result) {
        DBContext context(ns);

        auto_ptr<Cursor> c = DataFileMgr::findAll(ns);
        if ( !c->ok() )
            return false;

        result = c->current();
        return true;
    }

    void putSingleton(const char *ns, BSONObj obj) {
        DBContext context(ns);
        stringstream ss;
        updateObjects(ns, obj, /*pattern=*/emptyObj, /*upsert=*/true, ss);
    }

    void emptyCollection(const char *ns) {
        DBContext context(ns);
        deleteObjects(ns, emptyObj, false);
    }

} // namespace mongo