/**
 *    Copyright (C) 2017 MongoDB 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 "mongo/db/storage/kv/kv_prefix.h"

namespace mongo {
int64_t KVPrefix::_nextValue = 0;
stdx::mutex KVPrefix::_nextValueMutex;
const KVPrefix KVPrefix::kNotPrefixed = KVPrefix(-1);

std::string KVPrefix::toString() const {
    StackStringBuilder ss;
    ss << "KVPrefix(" << _value << ")";
    return ss.str();
}


/* static */ KVPrefix KVPrefix::fromBSONElement(const BSONElement value) {
    if (value.eoo()) {
        return kNotPrefixed;
    }

    return KVPrefix(static_cast<int64_t>(value.Long()));
}

/* static */ void KVPrefix::setLargestPrefix(KVPrefix largestPrefix) {
    if (!storageGlobalParams.groupCollections) {
        return;
    }

    stdx::lock_guard<stdx::mutex> lk(_nextValueMutex);
    _nextValue = largestPrefix._value + 1;
}

/* static */ KVPrefix KVPrefix::getNextPrefix(const NamespaceString& ns) {
    if (!storageGlobalParams.groupCollections || ns.isOplog()) {
        return kNotPrefixed;
    }

    return generateNextPrefix();
}

/* static */ KVPrefix KVPrefix::generateNextPrefix() {
    stdx::lock_guard<stdx::mutex> lk(_nextValueMutex);
    return KVPrefix(_nextValue++);
}
}