/**
 *    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.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kControl

#include "mongo/platform/basic.h"

#include "mongo/db/sessions_collection_config_server.h"

#include "mongo/client/query.h"
#include "mongo/db/commands.h"
#include "mongo/db/dbdirectclient.h"
#include "mongo/db/logical_session_id.h"
#include "mongo/db/operation_context.h"
#include "mongo/rpc/get_status_from_command_result.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/commands/cluster_commands_helpers.h"
#include "mongo/s/grid.h"
#include "mongo/s/request_types/shard_collection_gen.h"
#include "mongo/util/log.h"

namespace mongo {

// Returns an error if the collection didn't exist and we couldn't
// shard it into existence, either.
Status SessionsCollectionConfigServer::_shardCollectionIfNeeded(OperationContext* opCtx) {
    // First, check if the collection is already sharded.
    auto res = _checkCacheForSessionsCollection(opCtx);
    if (res.isOK()) {
        return res;
    }

    // If we don't have any shards, we can't set up this collection yet.
    if (Grid::get(opCtx)->shardRegistry()->getNumShards() == 0) {
        return {ErrorCodes::ShardNotFound,
                "Cannot create config.system.sessions until there are shards"};
    }

    // First, shard the sessions collection to create it.
    ConfigsvrShardCollectionRequest shardCollection;
    shardCollection.set_configsvrShardCollection(
        NamespaceString(SessionsCollection::kSessionsFullNS.toString()));
    shardCollection.setKey(BSON("_id" << 1));

    DBDirectClient client(opCtx);
    BSONObj info;
    if (!client.runCommand(
            "admin", CommandHelpers::appendMajorityWriteConcern(shardCollection.toBSON()), info)) {
        return getStatusFromCommandResult(info);
    }

    return Status::OK();
}

Status SessionsCollectionConfigServer::_generateIndexesIfNeeded(OperationContext* opCtx) {
    try {
        scatterGatherOnlyVersionIfUnsharded(opCtx,
                                            SessionsCollection::kSessionsDb.toString(),
                                            NamespaceString(SessionsCollection::kSessionsFullNS),
                                            SessionsCollection::generateCreateIndexesCmd(),
                                            ReadPreferenceSetting::get(opCtx),
                                            Shard::RetryPolicy::kNoRetry);
        return Status::OK();
    } catch (const DBException& ex) {
        return ex.toStatus();
    }
}

Status SessionsCollectionConfigServer::setupSessionsCollection(OperationContext* opCtx) {
    stdx::lock_guard<stdx::mutex> lk(_mutex);
    {
        // Only try to set up this collection until we have done so successfully once.
        // Note: if there is a config server election, it's possible that two different
        // primaries could both run the createIndexes scatter-gather query; this is ok.
        if (_collectionSetUp) {
            return Status::OK();
        }

        auto res = _shardCollectionIfNeeded(opCtx);
        if (!res.isOK()) {
            log() << "Failed to create config.system.sessions: " << res.reason()
                  << ", will try again at the next refresh interval";
            return res;
        }

        res = _generateIndexesIfNeeded(opCtx);
        if (!res.isOK()) {
            log() << "Failed to generate TTL index for config.system.sessions on all shards, "
                  << "will try again on the next refresh interval";
        }

        _collectionSetUp = true;
        return res;
    }
}

}  // namespace mongo