/**
 *    Copyright (C) 2022-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.
 */

#include "mongo/db/change_collection_expired_documents_remover.h"

#include "mongo/db/change_stream_change_collection_manager.h"
#include "mongo/db/change_streams_cluster_parameter_gen.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/service_context.h"
#include "mongo/logv2/log.h"
#include "mongo/platform/mutex.h"
#include "mongo/util/duration.h"
#include "mongo/util/fail_point.h"
#include "mongo/util/periodic_runner.h"
#include <algorithm>
#include <memory>

#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kQuery

namespace mongo {

// Hangs the change collection remover job before initiating the deletion process of documents.
MONGO_FAIL_POINT_DEFINE(hangBeforeRemovingExpiredChanges);

// Injects the provided ISO date to currentWallTime which is used to determine if the change
// collection document is expired or not.
MONGO_FAIL_POINT_DEFINE(injectCurrentWallTimeForRemovingExpiredDocuments);

namespace {

// TODO SERVER-61822 Provide the real implementation after 'listDatabasesForAllTenants' is
// available.
std::vector<boost::optional<TenantId>> getAllTenants() {
    return {boost::none};
}

boost::optional<int64_t> getExpireAfterSeconds(boost::optional<TenantId> tid) {
    // TODO SERVER-65950 Fetch 'expiredAfterSeconds' per tenant basis.
    return {gChangeStreamsClusterParameter.getExpireAfterSeconds()};
}

void removeExpiredDocuments(Client* client) {
    hangBeforeRemovingExpiredChanges.pauseWhileSet();

    try {
        auto opCtx = client->makeOperationContext();
        const auto clock = client->getServiceContext()->getFastClockSource();
        auto currentWallTime = clock->now();

        // If the fail point 'injectCurrentWallTimeForRemovingDocuments' is enabled then set the
        // 'currentWallTime' with the provided wall time.
        if (injectCurrentWallTimeForRemovingExpiredDocuments.shouldFail()) {
            injectCurrentWallTimeForRemovingExpiredDocuments.execute([&](const BSONObj& data) {
                currentWallTime = data.getField("currentWallTime").date();
            });
        }

        // Number of documents removed in the current pass.
        size_t removedCount = 0;

        for (const auto& tenantId : getAllTenants()) {
            auto expiredAfterSeconds = getExpireAfterSeconds(tenantId);
            invariant(expiredAfterSeconds);
            removedCount +=
                ChangeStreamChangeCollectionManager::removeExpiredChangeCollectionsDocuments(
                    opCtx.get(), tenantId, currentWallTime - Seconds(*expiredAfterSeconds));
        }

        // TODO SERVER-66636 Use server parameters to track periodic job statistics per tenant.
        if (removedCount > 0) {
            LOGV2_DEBUG(6663503,
                        3,
                        "Periodic expired change collection job finished executing",
                        "numberOfRemovals"_attr = removedCount,
                        "jobDuration"_attr = (clock->now() - currentWallTime).toString());
        }
    } catch (const DBException& exception) {
        if (exception.toStatus() != ErrorCodes::OK) {
            LOGV2_WARNING(6663504,
                          "Periodic expired change collection job was killed",
                          "errorCode"_attr = exception.toStatus());
        } else {
            LOGV2_ERROR(6663505,
                        "Periodic expired change collection job failed",
                        "reason"_attr = exception.reason());
        }
    }
}

/**
 * Defines a periodic background job to remove expired documents from change collections.
 * The job will run every 'changeCollectionRemoverJobSleepSeconds', as defined in the cluster
 * parameter.
 */
class ChangeCollectionExpiredDocumentsRemover {
public:
    ChangeCollectionExpiredDocumentsRemover(ServiceContext* serviceContext) {
        const auto period = Seconds{gChangeCollectionRemoverJobSleepSeconds.load()};
        _jobAnchor = serviceContext->getPeriodicRunner()->makeJob(
            {"ChangeCollectionExpiredDocumentsRemover", removeExpiredDocuments, period});
        _jobAnchor.start();
    }

    static void start(ServiceContext* serviceContext) {
        auto& changeCollectionExpiredDocumentsRemover = _serviceDecoration(serviceContext);
        changeCollectionExpiredDocumentsRemover =
            std::make_unique<ChangeCollectionExpiredDocumentsRemover>(serviceContext);
    }

    static void shutdown(ServiceContext* serviceContext) {
        auto& changeCollectionExpiredDocumentsRemover = _serviceDecoration(serviceContext);
        if (changeCollectionExpiredDocumentsRemover) {
            changeCollectionExpiredDocumentsRemover->_jobAnchor.stop();
            changeCollectionExpiredDocumentsRemover.reset();
        }
    }

private:
    inline static const auto _serviceDecoration = ServiceContext::declareDecoration<
        std::unique_ptr<ChangeCollectionExpiredDocumentsRemover>>();

    PeriodicJobAnchor _jobAnchor;
};
}  // namespace

void startChangeCollectionExpiredDocumentsRemover(ServiceContext* serviceContext) {
    if (!ChangeStreamChangeCollectionManager::isChangeCollectionsModeActive()) {
        return;
    }

    LOGV2(6663507, "Starting the ChangeCollectionExpiredChangeRemover");
    ChangeCollectionExpiredDocumentsRemover::start(serviceContext);
}

void shutdownChangeCollectionExpiredDocumentsRemover(ServiceContext* serviceContext) {
    if (!ChangeStreamChangeCollectionManager::isChangeCollectionsModeActive()) {
        return;
    }

    LOGV2(6663508, "Shutting down the ChangeCollectionExpiredChangeRemover");
    ChangeCollectionExpiredDocumentsRemover::shutdown(serviceContext);
}
}  // namespace mongo