/**
 *    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::kSharding

#include "mongo/platform/basic.h"

#include "mongo/db/s/config/sharding_catalog_manager.h"

#include <iomanip>
#include <set>

#include "mongo/base/status_with.h"
#include "mongo/bson/util/bson_extract.h"
#include "mongo/client/connection_string.h"
#include "mongo/client/read_preference.h"
#include "mongo/client/remote_command_targeter.h"
#include "mongo/client/replica_set_monitor.h"
#include "mongo/db/catalog/collection_options.h"
#include "mongo/db/client.h"
#include "mongo/db/commands.h"
#include "mongo/db/logical_clock.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/query/collation/collator_factory_interface.h"
#include "mongo/db/repl/repl_client_info.h"
#include "mongo/executor/network_interface.h"
#include "mongo/executor/task_executor.h"
#include "mongo/rpc/get_status_from_command_result.h"
#include "mongo/s/balancer_configuration.h"
#include "mongo/s/catalog/sharding_catalog_client.h"
#include "mongo/s/catalog/sharding_catalog_client_impl.h"
#include "mongo/s/catalog/type_collection.h"
#include "mongo/s/catalog/type_database.h"
#include "mongo/s/client/shard.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/grid.h"
#include "mongo/s/request_types/set_shard_version_request.h"
#include "mongo/s/shard_key_pattern.h"
#include "mongo/s/shard_util.h"
#include "mongo/s/write_ops/batched_command_request.h"
#include "mongo/s/write_ops/batched_command_response.h"
#include "mongo/util/log.h"
#include "mongo/util/mongoutils/str.h"
#include "mongo/util/scopeguard.h"

namespace mongo {

using CollectionUUID = UUID;
using std::string;
using std::vector;
using std::set;

namespace {

const Seconds kDefaultFindHostMaxWaitTime(20);

const ReadPreferenceSetting kConfigReadSelector(ReadPreference::Nearest, TagSet{});
const WriteConcernOptions kNoWaitWriteConcern(1, WriteConcernOptions::SyncMode::UNSET, Seconds(0));
const char kWriteConcernField[] = "writeConcern";

void checkForExistingChunks(OperationContext* opCtx, const NamespaceString& nss) {
    BSONObjBuilder countBuilder;
    countBuilder.append("count", ChunkType::ConfigNS.coll());
    countBuilder.append("query", BSON(ChunkType::ns(nss.ns())));

    // OK to use limit=1, since if any chunks exist, we will fail.
    countBuilder.append("limit", 1);

    // Use readConcern local to guarantee we see any chunks that have been written and may
    // become committed; readConcern majority will not see the chunks if they have not made it
    // to the majority snapshot.
    repl::ReadConcernArgs readConcern(repl::ReadConcernLevel::kLocalReadConcern);
    readConcern.appendInfo(&countBuilder);

    auto cmdResponse = uassertStatusOK(
        Grid::get(opCtx)->shardRegistry()->getConfigShard()->runCommandWithFixedRetryAttempts(
            opCtx,
            kConfigReadSelector,
            ChunkType::ConfigNS.db().toString(),
            countBuilder.done(),
            Shard::kDefaultConfigCommandTimeout,
            Shard::RetryPolicy::kIdempotent));
    uassertStatusOK(cmdResponse.commandStatus);

    long long numChunks;
    uassertStatusOK(bsonExtractIntegerField(cmdResponse.response, "n", &numChunks));
    uassert(ErrorCodes::ManualInterventionRequired,
            str::stream() << "A previous attempt to shard collection " << nss.ns()
                          << " failed after writing some initial chunks to config.chunks. Please "
                             "manually delete the partially written chunks for collection "
                          << nss.ns()
                          << " from config.chunks",
            numChunks == 0);
}

boost::optional<UUID> checkCollectionOptions(OperationContext* opCtx,
                                             Shard* shard,
                                             const NamespaceString& ns,
                                             const CollectionOptions options) {
    BSONObjBuilder listCollCmd;
    listCollCmd.append("listCollections", 1);
    listCollCmd.append("filter", BSON("name" << ns.coll()));

    auto response = uassertStatusOK(
        shard->runCommandWithFixedRetryAttempts(opCtx,
                                                ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                ns.db().toString(),
                                                listCollCmd.obj(),
                                                Shard::RetryPolicy::kIdempotent));

    auto cursorObj = response.response["cursor"].Obj();
    auto collections = cursorObj["firstBatch"].Obj();
    BSONObjIterator collIter(collections);
    uassert(ErrorCodes::NamespaceNotFound,
            str::stream() << "cannot find ns: " << ns.ns(),
            collIter.more());

    auto collectionDetails = collIter.next();
    CollectionOptions actualOptions;

    uassertStatusOK(actualOptions.parse(collectionDetails["options"].Obj()));
    // TODO: SERVER-33048 check idIndex field

    uassert(ErrorCodes::NamespaceExists,
            str::stream() << "ns: " << ns.ns() << " already exists with different options: "
                          << actualOptions.toBSON(),
            options.matchesStorageOptions(
                actualOptions, CollatorFactoryInterface::get(opCtx->getServiceContext())));

    if (actualOptions.isView()) {
        // Views don't have UUID.
        return boost::none;
    }

    auto collectionInfo = collectionDetails["info"].Obj();
    return uassertStatusOK(UUID::parse(collectionInfo["uuid"]));
}

}  // namespace

/**
 * Creates and writes to the config server the first chunks for a newly sharded collection. Returns
 * the version generated for the collection.
 */
ChunkVersion ShardingCatalogManager::_createFirstChunks(OperationContext* opCtx,
                                                        const NamespaceString& nss,
                                                        const ShardKeyPattern& shardKeyPattern,
                                                        const ShardId& primaryShardId,
                                                        const std::vector<BSONObj>& initPoints,
                                                        const bool distributeInitialChunks) {

    const KeyPattern keyPattern = shardKeyPattern.getKeyPattern();

    vector<BSONObj> splitPoints;
    vector<ShardId> shardIds;

    std::string primaryShardName = primaryShardId.toString();
    auto drainingCount = uassertStatusOK(_runCountCommandOnConfig(
        opCtx,
        NamespaceString(ShardType::ConfigNS),
        BSON(ShardType::name() << primaryShardName << ShardType::draining(true))));

    const bool primaryDraining = (drainingCount > 0);
    auto getPrimaryOrFirstNonDrainingShard = [&opCtx, primaryShardId, primaryDraining]() {
        if (primaryDraining) {
            vector<ShardId> allShardIds;
            Grid::get(opCtx)->shardRegistry()->getAllShardIdsNoReload(&allShardIds);

            auto dbShardId = allShardIds[0];
            if (allShardIds[0] == primaryShardId && allShardIds.size() > 1) {
                dbShardId = allShardIds[1];
            }

            return dbShardId;
        } else {
            return primaryShardId;
        }
    };

    if (initPoints.empty()) {
        // If no split points were specified use the shard's data distribution to determine them
        auto primaryShard =
            uassertStatusOK(Grid::get(opCtx)->shardRegistry()->getShard(opCtx, primaryShardId));

        auto result = uassertStatusOK(primaryShard->runCommandWithFixedRetryAttempts(
            opCtx,
            ReadPreferenceSetting{ReadPreference::PrimaryPreferred},
            nss.db().toString(),
            BSON("count" << nss.coll()),
            Shard::RetryPolicy::kIdempotent));

        long long numObjects = 0;
        uassertStatusOK(result.commandStatus);
        uassertStatusOK(bsonExtractIntegerField(result.response, "n", &numObjects));

        // Refresh the balancer settings to ensure the chunk size setting, which is sent as part of
        // the splitVector command and affects the number of chunks returned, has been loaded.
        uassertStatusOK(Grid::get(opCtx)->getBalancerConfiguration()->refreshAndCheck(opCtx));

        if (numObjects > 0) {
            splitPoints = uassertStatusOK(shardutil::selectChunkSplitPoints(
                opCtx,
                primaryShardId,
                nss,
                shardKeyPattern,
                ChunkRange(keyPattern.globalMin(), keyPattern.globalMax()),
                Grid::get(opCtx)->getBalancerConfiguration()->getMaxChunkSizeBytes(),
                0));
        }

        // If docs already exist for the collection, must use primary shard,
        // otherwise defer to passed-in distribution option.
        if (numObjects == 0 && distributeInitialChunks) {
            Grid::get(opCtx)->shardRegistry()->getAllShardIdsNoReload(&shardIds);
            if (primaryDraining && shardIds.size() > 1) {
                shardIds.erase(std::remove(shardIds.begin(), shardIds.end(), primaryShardId),
                               shardIds.end());
            }
        } else {
            shardIds.push_back(getPrimaryOrFirstNonDrainingShard());
        }
    } else {
        // Make sure points are unique and ordered
        auto orderedPts = SimpleBSONObjComparator::kInstance.makeBSONObjSet();

        for (const auto& initPoint : initPoints) {
            orderedPts.insert(initPoint);
        }

        for (const auto& initPoint : orderedPts) {
            splitPoints.push_back(initPoint);
        }

        if (distributeInitialChunks) {
            Grid::get(opCtx)->shardRegistry()->getAllShardIdsNoReload(&shardIds);
            if (primaryDraining) {
                shardIds.erase(std::remove(shardIds.begin(), shardIds.end(), primaryShardId),
                               shardIds.end());
            }
        } else {
            shardIds.push_back(getPrimaryOrFirstNonDrainingShard());
        }
    }

    // This is the first chunk; start the versioning from scratch
    const OID epoch = OID::gen();
    ChunkVersion version(1, 0, epoch);

    log() << "going to create " << splitPoints.size() + 1 << " chunk(s) for: " << nss
          << " using new epoch " << version.epoch();

    const auto validAfter = LogicalClock::get(opCtx)->getClusterTime().asTimestamp();

    for (unsigned i = 0; i <= splitPoints.size(); i++) {
        const BSONObj min = (i == 0) ? keyPattern.globalMin() : splitPoints[i - 1];
        const BSONObj max = (i < splitPoints.size()) ? splitPoints[i] : keyPattern.globalMax();

        // The correct version must be returned as part of this call so only increment for versions,
        // which get written
        if (i > 0) {
            version.incMinor();
        }

        ChunkType chunk;
        chunk.setNS(nss);
        chunk.setMin(min);
        chunk.setMax(max);
        chunk.setShard(shardIds[i % shardIds.size()]);
        chunk.setVersion(version);
        if (serverGlobalParams.featureCompatibility.getVersion() >=
            ServerGlobalParams::FeatureCompatibility::Version::kUpgradingTo40) {
            std::vector<ChunkHistory> initialHistory;
            initialHistory.emplace_back(ChunkHistory(validAfter, shardIds[i % shardIds.size()]));
            chunk.setHistory(std::move(initialHistory));
        }

        uassertStatusOK(Grid::get(opCtx)->catalogClient()->insertConfigDocument(
            opCtx,
            ChunkType::ConfigNS,
            chunk.toConfigBSON(),
            ShardingCatalogClient::kMajorityWriteConcern));
    }

    return version;
}

Status ShardingCatalogManager::dropCollection(OperationContext* opCtx, const NamespaceString& nss) {
    const auto catalogClient = Grid::get(opCtx)->catalogClient();
    catalogClient
        ->logChange(opCtx,
                    "dropCollection.start",
                    nss.ns(),
                    BSONObj(),
                    ShardingCatalogClientImpl::kMajorityWriteConcern)
        .ignore();

    auto shardsStatus =
        catalogClient->getAllShards(opCtx, repl::ReadConcernLevel::kLocalReadConcern);
    if (!shardsStatus.isOK()) {
        return shardsStatus.getStatus();
    }
    vector<ShardType> allShards = std::move(shardsStatus.getValue().value);

    LOG(1) << "dropCollection " << nss.ns() << " started";

    const auto dropCommandBSON = [opCtx, &nss] {
        BSONObjBuilder builder;
        builder.append("drop", nss.coll());

        if (!opCtx->getWriteConcern().usedDefault) {
            builder.append(WriteConcernOptions::kWriteConcernField,
                           opCtx->getWriteConcern().toBSON());
        }

        return builder.obj();
    }();

    std::map<std::string, BSONObj> errors;
    auto* const shardRegistry = Grid::get(opCtx)->shardRegistry();

    for (const auto& shardEntry : allShards) {
        auto swShard = shardRegistry->getShard(opCtx, shardEntry.getName());
        if (!swShard.isOK()) {
            return swShard.getStatus();
        }

        const auto& shard = swShard.getValue();

        auto swDropResult = shard->runCommandWithFixedRetryAttempts(
            opCtx,
            ReadPreferenceSetting{ReadPreference::PrimaryOnly},
            nss.db().toString(),
            dropCommandBSON,
            Shard::RetryPolicy::kIdempotent);

        if (!swDropResult.isOK()) {
            return swDropResult.getStatus().withContext(
                str::stream() << "Error dropping collection on shard " << shardEntry.getName());
        }

        auto& dropResult = swDropResult.getValue();

        auto dropStatus = std::move(dropResult.commandStatus);
        auto wcStatus = std::move(dropResult.writeConcernStatus);
        if (!dropStatus.isOK() || !wcStatus.isOK()) {
            if (dropStatus.code() == ErrorCodes::NamespaceNotFound && wcStatus.isOK()) {
                // Generally getting NamespaceNotFound is okay to ignore as it simply means that
                // the collection has already been dropped or doesn't exist on this shard.
                // If, however, we get NamespaceNotFound but also have a write concern error then we
                // can't confirm whether the fact that the namespace doesn't exist is actually
                // committed.  Thus we must still fail on NamespaceNotFound if there is also a write
                // concern error. This can happen if we call drop, it succeeds but with a write
                // concern error, then we retry the drop.
                continue;
            }

            errors.emplace(shardEntry.getHost(), std::move(dropResult.response));
        }
    }

    if (!errors.empty()) {
        StringBuilder sb;
        sb << "Dropping collection failed on the following hosts: ";

        for (auto it = errors.cbegin(); it != errors.cend(); ++it) {
            if (it != errors.cbegin()) {
                sb << ", ";
            }

            sb << it->first << ": " << it->second;
        }

        return {ErrorCodes::OperationFailed, sb.str()};
    }

    LOG(1) << "dropCollection " << nss.ns() << " shard data deleted";

    // Remove chunk data
    Status result =
        catalogClient->removeConfigDocuments(opCtx,
                                             ChunkType::ConfigNS,
                                             BSON(ChunkType::ns(nss.ns())),
                                             ShardingCatalogClient::kMajorityWriteConcern);
    if (!result.isOK()) {
        return result;
    }

    LOG(1) << "dropCollection " << nss.ns() << " chunk data deleted";

    // Mark the collection as dropped
    CollectionType coll;
    coll.setNs(nss);
    coll.setDropped(true);
    coll.setEpoch(ChunkVersion::DROPPED().epoch());
    coll.setUpdatedAt(Grid::get(opCtx)->getNetwork()->now());

    const bool upsert = false;
    result = ShardingCatalogClientImpl::updateShardingCatalogEntryForCollection(
        opCtx, nss, coll, upsert);
    if (!result.isOK()) {
        return result;
    }

    LOG(1) << "dropCollection " << nss.ns() << " collection marked as dropped";

    for (const auto& shardEntry : allShards) {
        auto swShard = shardRegistry->getShard(opCtx, shardEntry.getName());
        if (!swShard.isOK()) {
            return swShard.getStatus();
        }

        const auto& shard = swShard.getValue();

        SetShardVersionRequest ssv = SetShardVersionRequest::makeForVersioningNoPersist(
            shardRegistry->getConfigServerConnectionString(),
            shardEntry.getName(),
            fassert(28781, ConnectionString::parse(shardEntry.getHost())),
            nss,
            ChunkVersion::DROPPED(),
            true);

        auto ssvResult = shard->runCommandWithFixedRetryAttempts(
            opCtx,
            ReadPreferenceSetting{ReadPreference::PrimaryOnly},
            "admin",
            ssv.toBSON(),
            Shard::RetryPolicy::kIdempotent);

        if (!ssvResult.isOK()) {
            return ssvResult.getStatus();
        }

        auto ssvStatus = std::move(ssvResult.getValue().commandStatus);
        if (!ssvStatus.isOK()) {
            return ssvStatus;
        }

        auto unsetShardingStatus = shard->runCommandWithFixedRetryAttempts(
            opCtx,
            ReadPreferenceSetting{ReadPreference::PrimaryOnly},
            "admin",
            BSON("unsetSharding" << 1),
            Shard::RetryPolicy::kIdempotent);

        if (!unsetShardingStatus.isOK()) {
            return unsetShardingStatus.getStatus();
        }

        auto unsetShardingResult = std::move(unsetShardingStatus.getValue().commandStatus);
        if (!unsetShardingResult.isOK()) {
            return unsetShardingResult;
        }
    }

    LOG(1) << "dropCollection " << nss.ns() << " completed";

    catalogClient
        ->logChange(opCtx,
                    "dropCollection",
                    nss.ns(),
                    BSONObj(),
                    ShardingCatalogClientImpl::kMajorityWriteConcern)
        .ignore();

    return Status::OK();
}

void ShardingCatalogManager::shardCollection(OperationContext* opCtx,
                                             const NamespaceString& nss,
                                             const boost::optional<UUID> uuid,
                                             const ShardKeyPattern& fieldsAndOrder,
                                             const BSONObj& defaultCollation,
                                             bool unique,
                                             const vector<BSONObj>& initPoints,
                                             const bool distributeInitialChunks,
                                             const ShardId& dbPrimaryShardId) {
    const auto catalogClient = Grid::get(opCtx)->catalogClient();
    const auto shardRegistry = Grid::get(opCtx)->shardRegistry();

    const auto primaryShard = uassertStatusOK(shardRegistry->getShard(opCtx, dbPrimaryShardId));

    // Fail if there are partially written chunks from a previous failed shardCollection.
    checkForExistingChunks(opCtx, nss);

    // Record start in changelog
    {
        BSONObjBuilder collectionDetail;
        collectionDetail.append("shardKey", fieldsAndOrder.toBSON());
        collectionDetail.append("collection", nss.ns());
        if (uuid) {
            uuid->appendToBuilder(&collectionDetail, "uuid");
        }
        collectionDetail.append("primary", primaryShard->toString());
        collectionDetail.append("numChunks", static_cast<int>(initPoints.size() + 1));
        catalogClient
            ->logChange(opCtx,
                        "shardCollection.start",
                        nss.ns(),
                        collectionDetail.obj(),
                        ShardingCatalogClient::kMajorityWriteConcern)
            .transitional_ignore();
    }

    // const NamespaceString nss(ns);

    // Construct the collection default collator.
    std::unique_ptr<CollatorInterface> defaultCollator;
    if (!defaultCollation.isEmpty()) {
        defaultCollator = uassertStatusOK(CollatorFactoryInterface::get(opCtx->getServiceContext())
                                              ->makeFromBSON(defaultCollation));
    }

    const auto& collVersion = _createFirstChunks(
        opCtx, nss, fieldsAndOrder, dbPrimaryShardId, initPoints, distributeInitialChunks);

    {
        CollectionType coll;
        coll.setNs(nss);
        if (uuid) {
            coll.setUUID(*uuid);
        }
        coll.setEpoch(collVersion.epoch());

        // TODO(schwerin): The following isn't really a date, but is stored as one in-memory and in
        // config.collections, as a historical oddity.
        coll.setUpdatedAt(Date_t::fromMillisSinceEpoch(collVersion.toLong()));
        coll.setKeyPattern(fieldsAndOrder.toBSON());
        coll.setDefaultCollation(defaultCollator ? defaultCollator->getSpec().toBSON() : BSONObj());
        coll.setUnique(unique);

        uassertStatusOK(ShardingCatalogClientImpl::updateShardingCatalogEntryForCollection(
            opCtx, nss, coll, true /*upsert*/));
    }

    auto shard = uassertStatusOK(shardRegistry->getShard(opCtx, dbPrimaryShardId));
    invariant(!shard->isConfig());

    // Tell the primary mongod to refresh its data
    // TODO:  Think the real fix here is for mongos to just
    //        assume that all collections are sharded, when we get there
    SetShardVersionRequest ssv = SetShardVersionRequest::makeForVersioningNoPersist(
        shardRegistry->getConfigServerConnectionString(),
        dbPrimaryShardId,
        primaryShard->getConnString(),
        nss,
        collVersion,
        true);

    auto ssvResponse =
        shard->runCommandWithFixedRetryAttempts(opCtx,
                                                ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                                                "admin",
                                                ssv.toBSON(),
                                                Shard::RetryPolicy::kIdempotent);
    auto status = ssvResponse.isOK() ? std::move(ssvResponse.getValue().commandStatus)
                                     : std::move(ssvResponse.getStatus());
    if (!status.isOK()) {
        warning() << "could not update initial version of " << nss.ns() << " on shard primary "
                  << dbPrimaryShardId << causedBy(redact(status));
    }

    catalogClient
        ->logChange(opCtx,
                    "shardCollection.end",
                    nss.ns(),
                    BSON("version" << collVersion.toString()),
                    ShardingCatalogClient::kMajorityWriteConcern)
        .transitional_ignore();
}

void ShardingCatalogManager::generateUUIDsForExistingShardedCollections(OperationContext* opCtx) {
    // Retrieve all collections in config.collections that do not have a UUID. Some collections
    // may already have a UUID if an earlier upgrade attempt failed after making some progress.
    auto shardedColls =
        uassertStatusOK(
            Grid::get(opCtx)->shardRegistry()->getConfigShard()->exhaustiveFindOnConfig(
                opCtx,
                ReadPreferenceSetting{ReadPreference::PrimaryOnly},
                repl::ReadConcernLevel::kLocalReadConcern,
                CollectionType::ConfigNS,
                BSON(CollectionType::uuid.name() << BSON("$exists" << false) << "dropped" << false),
                BSONObj(),   // sort
                boost::none  // limit
                ))
            .docs;

    if (shardedColls.empty()) {
        LOG(0) << "all sharded collections already have UUIDs";

        // We did a local read of the collections collection above and found that all sharded
        // collections already have UUIDs. However, the data may not be majority committed (a
        // previous setFCV attempt may have failed with a write concern error). Since the current
        // Client doesn't know the opTime of the last write to the collections collection, make it
        // wait for the last opTime in the system when we wait for writeConcern.
        repl::ReplClientInfo::forClient(opCtx->getClient()).setLastOpToSystemLastOpTime(opCtx);
        return;
    }

    // Generate and persist a new UUID for each collection that did not have a UUID.
    LOG(0) << "generating UUIDs for " << shardedColls.size()
           << " sharded collections that do not yet have a UUID";
    for (auto& coll : shardedColls) {
        auto collType = uassertStatusOK(CollectionType::fromBSON(coll));
        invariant(!collType.getUUID());

        auto uuid = CollectionUUID::gen();
        collType.setUUID(uuid);

        uassertStatusOK(ShardingCatalogClientImpl::updateShardingCatalogEntryForCollection(
            opCtx, collType.getNs(), collType, false /* upsert */));
        LOG(2) << "updated entry in config.collections for sharded collection " << collType.getNs()
               << " with generated UUID " << uuid;
    }
}

void ShardingCatalogManager::createCollection(OperationContext* opCtx,
                                              const NamespaceString& ns,
                                              const CollectionOptions& collOptions) {
    const auto catalogClient = Grid::get(opCtx)->catalogClient();
    auto shardRegistry = Grid::get(opCtx)->shardRegistry();

    auto dbEntry =
        uassertStatusOK(catalogClient->getDatabase(
                            opCtx, ns.db().toString(), repl::ReadConcernLevel::kLocalReadConcern))
            .value;
    const auto& primaryShardId = dbEntry.getPrimary();
    auto primaryShard = uassertStatusOK(shardRegistry->getShard(opCtx, primaryShardId));

    BSONObjBuilder createCmdBuilder;
    createCmdBuilder.append("create", ns.coll());
    collOptions.appendBSON(&createCmdBuilder);
    createCmdBuilder.append(kWriteConcernField, opCtx->getWriteConcern().toBSON());
    auto swResponse = primaryShard->runCommandWithFixedRetryAttempts(
        opCtx,
        ReadPreferenceSetting{ReadPreference::PrimaryOnly},
        ns.db().toString(),
        createCmdBuilder.obj(),
        Shard::RetryPolicy::kIdempotent);

    auto createStatus = Shard::CommandResponse::getEffectiveStatus(swResponse);
    if (!createStatus.isOK() && createStatus != ErrorCodes::NamespaceExists) {
        uassertStatusOK(createStatus);
    }

    checkCollectionOptions(opCtx, primaryShard.get(), ns, collOptions);

    // TODO: SERVER-33094 use UUID returned to write config.collections entries.

    // Make sure to advance the opTime if writes didn't occur during the execution of this
    // command. This is to ensure that this request will wait for the opTime that at least
    // reflects the current state (that this command observed) while waiting for replication
    // to satisfy the write concern.
    repl::ReplClientInfo::forClient(opCtx->getClient()).setLastOpToSystemLastOpTime(opCtx);
}

}  // namespace mongo