/**
 *    Copyright (C) 2018-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/client/remote_command_targeter.h"
#include "mongo/db/auth/action_set.h"
#include "mongo/db/auth/action_type.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/commands.h"
#include "mongo/db/repl/repl_client_info.h"
#include "mongo/db/s/active_migrations_registry.h"
#include "mongo/db/s/chunk_move_write_concern_options.h"
#include "mongo/db/s/migration_source_manager.h"
#include "mongo/db/s/sharding_state.h"
#include "mongo/db/s/sharding_statistics.h"
#include "mongo/logv2/log.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/grid.h"
#include "mongo/s/request_types/move_chunk_request.h"
#include "mongo/util/concurrency/notification.h"
#include "mongo/util/concurrency/thread_pool.h"

namespace mongo {
namespace {

const WriteConcernOptions kMajorityWriteConcern(WriteConcernOptions::kMajority,
                                                // Note: Even though we're setting UNSET here,
                                                // kMajority implies JOURNAL if journaling is
                                                // supported by mongod and
                                                // writeConcernMajorityJournalDefault is set to true
                                                // in the ReplSetConfig.
                                                WriteConcernOptions::SyncMode::UNSET,
                                                WriteConcernOptions::kWriteConcernTimeoutSharding);

class MoveChunkCommand : public BasicCommand {
public:
    MoveChunkCommand() : BasicCommand("moveChunk") {}

    std::string help() const override {
        return "should not be calling this directly";
    }

    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kNever;
    }

    bool adminOnly() const override {
        return true;
    }

    bool supportsWriteConcern(const BSONObj& cmd) const override {
        return true;
    }

    Status checkAuthForCommand(Client* client,
                               const std::string& dbname,
                               const BSONObj& cmdObj) const override {
        if (!AuthorizationSession::get(client)->isAuthorizedForActionsOnResource(
                ResourcePattern::forClusterResource(), ActionType::internal)) {
            return Status(ErrorCodes::Unauthorized, "Unauthorized");
        }
        return Status::OK();
    }

    std::string parseNs(const std::string& dbname, const BSONObj& cmdObj) const override {
        return CommandHelpers::parseNsFullyQualified(cmdObj);
    }

    bool run(OperationContext* opCtx,
             const std::string& dbname,
             const BSONObj& cmdObj,
             BSONObjBuilder&) override {
        auto shardingState = ShardingState::get(opCtx);
        uassertStatusOK(shardingState->canAcceptShardedCommands());

        const MoveChunkRequest moveChunkRequest = uassertStatusOK(
            MoveChunkRequest::createFromCommand(NamespaceString(parseNs(dbname, cmdObj)), cmdObj));

        // Make sure we're as up-to-date as possible with shard information. This catches the case
        // where we might have changed a shard's host by removing/adding a shard with the same name.
        Grid::get(opCtx)->shardRegistry()->reload(opCtx);

        auto scopedMigration = uassertStatusOK(
            ActiveMigrationsRegistry::get(opCtx).registerDonateChunk(opCtx, moveChunkRequest));

        // Check if there is an existing migration running and if so, join it
        if (scopedMigration.mustExecute()) {
            auto moveChunkComplete =
                ExecutorFuture<void>(_getExecutor())
                    .then([moveChunkRequest,
                           scopedMigration = std::move(scopedMigration),
                           serviceContext = opCtx->getServiceContext()]() mutable {
                        // This local variable is created to enforce that the scopedMigration is
                        // destroyed before setting the shared state as ready.
                        // Note that captured objects of the lambda are destroyed by the executor
                        // thread after setting the shared state as ready.
                        auto scopedMigrationLocal(std::move(scopedMigration));
                        ThreadClient tc("MoveChunk", serviceContext);
                        {
                            stdx::lock_guard<Client> lk(*tc.get());
                            tc->setSystemOperationKillableByStepdown(lk);
                        }
                        auto uniqueOpCtx = Client::getCurrent()->makeOperationContext();
                        auto opCtx = uniqueOpCtx.get();

                        {
                            // Ensure that opCtx will get interrupted in the event of a stepdown.
                            // This is to ensure that the MigrationSourceManager checks that there
                            // are no pending migrationCoordinators documents (under the
                            // ActiveMigrationRegistry lock) on the same term during which the
                            // migrationCoordinators document will be persisted.
                            Lock::GlobalLock lk(opCtx, MODE_IX);
                        }

                        // Note: This internal authorization is tied to the lifetime of the client.
                        AuthorizationSession::get(opCtx->getClient())
                            ->grantInternalAuthorization(opCtx->getClient());

                        Status status = {ErrorCodes::InternalError, "Uninitialized value"};

                        try {
                            _runImpl(opCtx, moveChunkRequest);
                            status = Status::OK();
                        } catch (const DBException& e) {
                            status = e.toStatus();
                            LOGV2_WARNING(23777,
                                          "Chunk move failed with {error}",
                                          "Error while doing moveChunk",
                                          "error"_attr = redact(status));

                            if (status.code() == ErrorCodes::LockTimeout) {
                                ShardingStatistics::get(opCtx)
                                    .countDonorMoveChunkLockTimeout.addAndFetch(1);
                            }
                        }

                        scopedMigrationLocal.signalComplete(status);
                        uassertStatusOK(status);
                    });
            moveChunkComplete.get(opCtx);
        } else {
            uassertStatusOK(scopedMigration.waitForCompletion(opCtx));
        }

        if (moveChunkRequest.getWaitForDelete()) {
            // Ensure we capture the latest opTime in the system, since range deletion happens
            // asynchronously with a different OperationContext. This must be done after the above
            // join, because each caller must set the opTime to wait for writeConcern for on its own
            // OperationContext.
            auto& replClient = repl::ReplClientInfo::forClient(opCtx->getClient());
            replClient.setLastOpToSystemLastOpTime(opCtx);

            WriteConcernResult writeConcernResult;
            writeConcernResult.wTimedOut = false;
            Status majorityStatus = waitForWriteConcern(
                opCtx, replClient.getLastOp(), kMajorityWriteConcern, &writeConcernResult);

            if (!majorityStatus.isOK()) {
                if (!writeConcernResult.wTimedOut) {
                    uassertStatusOK(majorityStatus);
                }
                return false;
            }
        }

        return true;
    }

private:
    static void _runImpl(OperationContext* opCtx, const MoveChunkRequest& moveChunkRequest) {
        if (moveChunkRequest.getFromShardId() == moveChunkRequest.getToShardId()) {
            // TODO: SERVER-46669 handle wait for delete.
            return;
        }

        // Resolve the donor and recipient shards and their connection string
        auto const shardRegistry = Grid::get(opCtx)->shardRegistry();

        const auto donorConnStr =
            uassertStatusOK(shardRegistry->getShard(opCtx, moveChunkRequest.getFromShardId()))
                ->getConnString();
        const auto recipientHost = uassertStatusOK([&] {
            auto recipientShard =
                uassertStatusOK(shardRegistry->getShard(opCtx, moveChunkRequest.getToShardId()));

            return recipientShard->getTargeter()->findHost(
                opCtx, ReadPreferenceSetting{ReadPreference::PrimaryOnly});
        }());

        MigrationSourceManager migrationSourceManager(
            opCtx, moveChunkRequest, donorConnStr, recipientHost);

        migrationSourceManager.startClone();
        migrationSourceManager.awaitToCatchUp();
        migrationSourceManager.enterCriticalSection();
        migrationSourceManager.commitChunkOnRecipient();
        migrationSourceManager.commitChunkMetadataOnConfig();
    }

private:
    // Returns a single-threaded executor to be used to run moveChunk commands. The executor is
    // initialized on the first call to this function. Uses a shared_ptr because a shared_ptr is
    // required to work with ExecutorFutures.
    static std::shared_ptr<ThreadPool> _getExecutor() {
        static Mutex mutex = MONGO_MAKE_LATCH("MoveChunkExecutor::_mutex");
        static std::shared_ptr<ThreadPool> executor;

        stdx::lock_guard<Latch> lg(mutex);
        if (!executor) {
            ThreadPool::Options options;
            options.poolName = "MoveChunk";
            options.minThreads = 0;
            // We limit the size of the thread pool to a single thread because currently there can
            // only be one moveChunk operation on a shard at a time.
            options.maxThreads = 1;
            executor = std::make_shared<ThreadPool>(std::move(options));
            executor->startup();
        }

        return executor;
    }
} moveChunkCmd;

}  // namespace
}  // namespace mongo