/**
 *    Copyright (C) 2021-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    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 Server Side 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_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kSharding

#include "mongo/platform/basic.h"

#include "mongo/db/s/sharding_ddl_coordinator_service.h"

#include "mongo/base/checked_cast.h"
#include "mongo/db/dbdirectclient.h"
#include "mongo/db/pipeline/document_source_count.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/s/database_sharding_state.h"
#include "mongo/db/s/operation_sharding_state.h"
#include "mongo/db/s/sharding_ddl_coordinator.h"
#include "mongo/logv2/log.h"

#include "mongo/db/s/create_collection_coordinator.h"
#include "mongo/db/s/drop_collection_coordinator.h"
#include "mongo/db/s/drop_database_coordinator.h"
#include "mongo/db/s/rename_collection_coordinator.h"
#include "mongo/db/s/set_allow_migrations_coordinator.h"

namespace mongo {
namespace {

std::shared_ptr<ShardingDDLCoordinator> constructShardingDDLCoordinatorInstance(
    ShardingDDLCoordinatorService* service, BSONObj initialState) {
    const auto op = extractShardingDDLCoordinatorMetadata(initialState);
    LOGV2(
        5390510, "Constructing new sharding DDL coordinator", "coordinatorDoc"_attr = op.toBSON());
    switch (op.getId().getOperationType()) {
        case DDLCoordinatorTypeEnum::kDropDatabase:
            return std::make_shared<DropDatabaseCoordinator>(service, std::move(initialState));
            break;
        case DDLCoordinatorTypeEnum::kDropCollection:
            return std::make_shared<DropCollectionCoordinator>(service, std::move(initialState));
            break;
        case DDLCoordinatorTypeEnum::kRenameCollection:
            return std::make_shared<RenameCollectionCoordinator>(service, std::move(initialState));
        case DDLCoordinatorTypeEnum::kCreateCollection:
            return std::make_shared<CreateCollectionCoordinator>(service, std::move(initialState));
            break;
        case DDLCoordinatorTypeEnum::kSetAllowMigrations:
            return std::make_shared<SetAllowMigrationsCoordinator>(service,
                                                                   std::move(initialState));
        default:
            uasserted(ErrorCodes::BadValue,
                      str::stream()
                          << "Encountered unknown Sharding DDL operation type: "
                          << DDLCoordinatorType_serializer(op.getId().getOperationType()));
    }
}


}  // namespace

ShardingDDLCoordinatorService* ShardingDDLCoordinatorService::getService(OperationContext* opCtx) {
    auto registry = repl::PrimaryOnlyServiceRegistry::get(opCtx->getServiceContext());
    auto service = registry->lookupServiceByName(kServiceName);
    return checked_cast<ShardingDDLCoordinatorService*>(std::move(service));
}

std::shared_ptr<ShardingDDLCoordinatorService::Instance>
ShardingDDLCoordinatorService::constructInstance(BSONObj initialState) {
    auto coord = constructShardingDDLCoordinatorInstance(this, std::move(initialState));

    {
        stdx::lock_guard lg(_completionMutex);
        ++_numActiveCoordinators;
    }

    coord->getConstructionCompletionFuture()
        .thenRunOn(getInstanceCleanupExecutor())
        .getAsync([this](auto status) {
            stdx::lock_guard lg(_mutex);
            if (_state != State::kRecovering) {
                return;
            }
            invariant(_numCoordinatorsToWait > 0);
            if (--_numCoordinatorsToWait == 0) {
                _state = State::kRecovered;
                _recoveredCV.notify_all();
            }
        });

    coord->getCompletionFuture()
        .thenRunOn(getInstanceCleanupExecutor())
        .getAsync([this](auto status) {
            stdx::lock_guard lg(_completionMutex);
            if (--_numActiveCoordinators == 0) {
                _completedCV.notify_all();
            }
        });

    return coord;
}

void ShardingDDLCoordinatorService::waitForAllCoordinatorsToComplete(
    OperationContext* opCtx) const {
    _waitForRecoveryCompletion(opCtx);
    stdx::unique_lock lk(_completionMutex);
    opCtx->waitForConditionOrInterrupt(
        _completedCV, lk, [this]() { return _numActiveCoordinators == 0; });
}


void ShardingDDLCoordinatorService::_afterStepDown() {
    stdx::lock_guard lg(_mutex);
    _state = State::kPaused;
    _numCoordinatorsToWait = 0;
}

size_t ShardingDDLCoordinatorService::_countCoordinatorDocs(OperationContext* opCtx) {
    constexpr auto kNumCoordLabel = "numCoordinators"_sd;

    auto aggRequest = [&]() -> AggregateCommandRequest {
        auto expCtx = make_intrusive<ExpressionContext>(opCtx, nullptr, getStateDocumentsNS());
        const auto countSpec = BSON("$count" << kNumCoordLabel);
        auto stages = DocumentSourceCount::createFromBson(countSpec.firstElement(), expCtx);
        auto pipeline = Pipeline::create(std::move(stages), expCtx);
        return {getStateDocumentsNS(), pipeline->serializeToBson()};
    }();

    DBDirectClient client(opCtx);
    auto cursor = uassertStatusOKWithContext(
        DBClientCursor::fromAggregationRequest(
            &client, std::move(aggRequest), false /* secondaryOk */, true /* useExhaust */),
        "Failed to establish a cursor for aggregation");

    if (!cursor->more()) {
        return 0;
    }

    auto res = cursor->nextSafe();
    auto numCoordField = res.getField(kNumCoordLabel);
    invariant(numCoordField);
    return numCoordField.numberLong();
}

void ShardingDDLCoordinatorService::_waitForRecoveryCompletion(OperationContext* opCtx) const {
    stdx::unique_lock lk(_mutex);
    opCtx->waitForConditionOrInterrupt(
        _recoveredCV, lk, [this]() { return _state == State::kRecovered; });
}

ExecutorFuture<void> ShardingDDLCoordinatorService::_rebuildService(
    std::shared_ptr<executor::ScopedTaskExecutor> executor, const CancellationToken& token) {
    return ExecutorFuture<void>(**executor)
        .then([this] {
            AllowOpCtxWhenServiceRebuildingBlock allowOpCtxBlock(Client::getCurrent());
            auto opCtx = cc().makeOperationContext();
            const auto numCoordinators = _countCoordinatorDocs(opCtx.get());
            if (numCoordinators > 0) {
                LOGV2(5622500,
                      "Found Sharding DDL Coordinators to rebuild",
                      "numCoordinators"_attr = numCoordinators);
            }
            stdx::lock_guard lg(_mutex);
            if (numCoordinators > 0) {
                _state = State::kRecovering;
                _numCoordinatorsToWait = numCoordinators;
            } else {
                _state = State::kRecovered;
                _recoveredCV.notify_all();
            }
        })
        .onError([this](const Status& status) {
            LOGV2_ERROR(5469630,
                        "Failed to rebuild Sharding DDL coordinator service",
                        "error"_attr = status);
            return status;
        });
}

std::shared_ptr<ShardingDDLCoordinatorService::Instance>
ShardingDDLCoordinatorService::getOrCreateInstance(OperationContext* opCtx, BSONObj coorDoc) {

    // Wait for all coordinators to be recovered before to allow the creation of new ones.
    _waitForRecoveryCompletion(opCtx);

    auto coorMetadata = extractShardingDDLCoordinatorMetadata(coorDoc);
    const auto& nss = coorMetadata.getId().getNss();

    if (!nss.isConfigDB()) {
        // Check that the operation context has a database version for this namespace
        const auto clientDbVersion = OperationShardingState::get(opCtx).getDbVersion(nss.db());
        uassert(ErrorCodes::IllegalOperation,
                "Request sent without attaching database version",
                clientDbVersion);
        DatabaseShardingState::checkIsPrimaryShardForDb(opCtx, nss.db());
        coorMetadata.setDatabaseVersion(clientDbVersion);
    }

    coorMetadata.setForwardableOpMetadata(boost::optional<ForwardableOperationMetadata>(opCtx));
    const auto patchedCoorDoc = coorDoc.addFields(coorMetadata.toBSON());

    auto [coordinator, created] = [&] {
        try {
            auto [coordinator, created] =
                PrimaryOnlyService::getOrCreateInstance(opCtx, patchedCoorDoc);
            return std::make_pair(
                checked_pointer_cast<ShardingDDLCoordinator>(std::move(coordinator)),
                std::move(created));
        } catch (const DBException& ex) {
            LOGV2_ERROR(5390512,
                        "Failed to create instance of sharding DDL coordinator",
                        "coordinatorId"_attr = coorMetadata.getId(),
                        "reason"_attr = redact(ex));
            throw;
        }
    }();

    // If the existing instance doesn't have conflicting options just return that one
    if (!created) {
        coordinator->checkIfOptionsConflict(coorDoc);
    }

    return coordinator;
}


std::shared_ptr<executor::TaskExecutor> ShardingDDLCoordinatorService::getInstanceCleanupExecutor()
    const {
    return PrimaryOnlyService::getInstanceCleanupExecutor();
}

}  // namespace mongo
