/**
 *    Copyright (C) 2020-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_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kSharding

#include "mongo/platform/basic.h"

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

#include <algorithm>
#include <utility>

#include "mongo/db/catalog/index_catalog.h"
#include "mongo/db/catalog_raii.h"
#include "mongo/db/client.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/dbhelpers.h"
#include "mongo/db/exec/delete.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/keypattern.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/query/internal_plans.h"
#include "mongo/db/query/plan_yield_policy.h"
#include "mongo/db/query/query_knobs_gen.h"
#include "mongo/db/query/query_planner.h"
#include "mongo/db/repl/repl_client_info.h"
#include "mongo/db/s/migration_util.h"
#include "mongo/db/s/persistent_task_store.h"
#include "mongo/db/s/range_deletion_task_gen.h"
#include "mongo/db/s/sharding_statistics.h"
#include "mongo/db/s/wait_for_majority_service.h"
#include "mongo/db/service_context.h"
#include "mongo/db/storage/remove_saver.h"
#include "mongo/db/write_concern.h"
#include "mongo/executor/task_executor.h"
#include "mongo/util/future_util.h"
#include "mongo/util/log.h"

namespace mongo {

namespace {
const WriteConcernOptions kMajorityWriteConcern(WriteConcernOptions::kMajority,
                                                WriteConcernOptions::SyncMode::UNSET,
                                                WriteConcernOptions::kWriteConcernTimeoutSharding);

MONGO_FAIL_POINT_DEFINE(hangBeforeDoingDeletion);
MONGO_FAIL_POINT_DEFINE(suspendRangeDeletion);
MONGO_FAIL_POINT_DEFINE(throwWriteConflictExceptionInDeleteRange);
MONGO_FAIL_POINT_DEFINE(throwInternalErrorInDeleteRange);

/**
 * Returns whether the currentCollection has the same UUID as the expectedCollectionUuid. Used to
 * ensure that the collection has not been dropped or dropped and recreated since the range was
 * enqueued for deletion.
 */
bool collectionUuidHasChanged(const NamespaceString& nss,
                              Collection* currentCollection,
                              UUID expectedCollectionUuid) {

    if (!currentCollection) {
        LOG(1) << "Abandoning range deletion task for " << nss.ns() << " with UUID "
               << expectedCollectionUuid << " because the collection has been dropped";
        return true;
    }

    if (currentCollection->uuid() != expectedCollectionUuid) {
        LOG(1) << "Abandoning range deletion task for " << nss.ns() << " with UUID "
               << expectedCollectionUuid << " because UUID of " << nss.ns()
               << "has changed (current is " << currentCollection->uuid() << ")";
        return true;
    }

    return false;
}

/**
 * Performs the deletion of up to numDocsToRemovePerBatch entries within the range in progress. Must
 * be called under the collection lock.
 *
 * Returns the number of documents deleted, 0 if done with the range, or bad status if deleting
 * the range failed.
 */
StatusWith<int> deleteNextBatch(OperationContext* opCtx,
                                Collection* collection,
                                BSONObj const& keyPattern,
                                ChunkRange const& range,
                                int numDocsToRemovePerBatch) {
    invariant(collection != nullptr);

    auto const& nss = collection->ns();

    // The IndexChunk has a keyPattern that may apply to more than one index - we need to
    // select the index and get the full index keyPattern here.
    auto catalog = collection->getIndexCatalog();
    const IndexDescriptor* idx = catalog->findShardKeyPrefixedIndex(opCtx, keyPattern, false);
    if (!idx) {
        std::string msg = str::stream()
            << "Unable to find shard key index for " << keyPattern.toString() << " in " << nss.ns();
        LOG(0) << msg;
        return {ErrorCodes::InternalError, msg};
    }

    // Extend bounds to match the index we found
    const KeyPattern indexKeyPattern(idx->keyPattern());
    const auto extend = [&](const auto& key) {
        return Helpers::toKeyFormat(indexKeyPattern.extendRangeBound(key, false));
    };

    const auto min = extend(range.getMin());
    const auto max = extend(range.getMax());

    LOG(1) << "begin removal of " << min << " to " << max << " in " << nss.ns();

    const auto indexName = idx->indexName();
    const IndexDescriptor* descriptor =
        collection->getIndexCatalog()->findIndexByName(opCtx, indexName);
    if (!descriptor) {
        std::string msg = str::stream()
            << "shard key index with name " << indexName << " on '" << nss.ns() << "' was dropped";
        LOG(0) << msg;
        return {ErrorCodes::InternalError, msg};
    }

    auto deleteStageParams = std::make_unique<DeleteStageParams>();
    deleteStageParams->fromMigrate = true;
    deleteStageParams->isMulti = true;
    deleteStageParams->returnDeleted = true;

    if (serverGlobalParams.moveParanoia) {
        deleteStageParams->removeSaver =
            std::make_unique<RemoveSaver>("moveChunk", nss.ns(), "cleaning");
    }

    auto exec = InternalPlanner::deleteWithIndexScan(opCtx,
                                                     collection,
                                                     std::move(deleteStageParams),
                                                     descriptor,
                                                     min,
                                                     max,
                                                     BoundInclusion::kIncludeStartKeyOnly,
                                                     PlanExecutor::YIELD_MANUAL,
                                                     InternalPlanner::FORWARD);

    if (MONGO_unlikely(hangBeforeDoingDeletion.shouldFail())) {
        LOG(0) << "Hit hangBeforeDoingDeletion failpoint";
        hangBeforeDoingDeletion.pauseWhileSet(opCtx);
    }

    PlanYieldPolicy planYieldPolicy(exec.get(), PlanExecutor::YIELD_MANUAL);

    int numDeleted = 0;
    do {
        BSONObj deletedObj;

        if (throwWriteConflictExceptionInDeleteRange.shouldFail()) {
            throw WriteConflictException();
        }

        if (throwInternalErrorInDeleteRange.shouldFail()) {
            uasserted(ErrorCodes::InternalError, "Failing for test");
        }

        PlanExecutor::ExecState state = exec->getNext(&deletedObj, nullptr);

        if (state == PlanExecutor::IS_EOF) {
            break;
        }

        if (state == PlanExecutor::FAILURE) {
            warning() << PlanExecutor::statestr(state) << " - cursor error while trying to delete "
                      << redact(min) << " to " << redact(max) << " in " << nss
                      << ": FAILURE, stats: " << Explain::getWinningPlanStats(exec.get());
            break;
        }

        invariant(PlanExecutor::ADVANCED == state);
        ShardingStatistics::get(opCtx).countDocsDeletedOnDonor.addAndFetch(1);

    } while (++numDeleted < numDocsToRemovePerBatch);

    return numDeleted;
}


template <typename Callable>
auto withTemporaryOperationContext(Callable&& callable) {
    ThreadClient tc(migrationutil::kRangeDeletionThreadName, getGlobalServiceContext());
    {
        stdx::lock_guard<Client> lk(*tc.get());
        tc->setSystemOperationKillable(lk);
    }
    auto uniqueOpCtx = Client::getCurrent()->makeOperationContext();
    auto opCtx = uniqueOpCtx.get();
    return callable(opCtx);
}

ExecutorFuture<int> deleteBatchAndWaitForReplication(
    const std::shared_ptr<executor::TaskExecutor>& executor,
    const NamespaceString& nss,
    const UUID& collectionUuid,
    const BSONObj& keyPattern,
    const ChunkRange& range,
    int numDocsToRemovePerBatch) {
    // Delete a batch and wait for majority write concern.
    return withTemporaryOperationContext([=](OperationContext* opCtx) {
        AutoGetCollection autoColl(opCtx, nss, MODE_IX);
        auto* const collection = autoColl.getCollection();

        // Ensure the collection exists and has not been dropped or dropped and recreated.
        uassert(ErrorCodes::RangeDeletionAbandonedBecauseCollectionWithUUIDDoesNotExist,
                "Collection has been dropped since enqueuing this range "
                "deletion task. No need to delete documents.",
                !collectionUuidHasChanged(nss, collection, collectionUuid));

        auto numDeleted = uassertStatusOK(
            deleteNextBatch(opCtx, collection, keyPattern, range, numDocsToRemovePerBatch));

        LOG(0) << "Deleted " << numDeleted << " documents in pass in namespace " << nss.ns()
               << " with UUID " << collectionUuid << " for range " << range.toString();

        repl::ReplClientInfo::forClient(opCtx->getClient()).setLastOpToSystemLastOpTime(opCtx);
        auto clientOpTime = repl::ReplClientInfo::forClient(opCtx->getClient()).getLastOp();

        LOG(0) << "Waiting for majority replication of local deletions in namespace " << nss.ns()
               << " with UUID " << collectionUuid << " for range " << redact(range.toString());

        // Asynchronously wait for majority write concern.
        return WaitForMajorityService::get(opCtx->getServiceContext())
            .waitUntilMajority(clientOpTime)
            .thenRunOn(executor)
            .then([=] { return numDeleted; });
    });
}

/**
 * Delete the range in a sequence of batches until there are no more documents to
 * delete or deletion returns an error.
 */
ExecutorFuture<void> deleteRangeInBatches(const std::shared_ptr<executor::TaskExecutor>& executor,
                                          const NamespaceString& nss,
                                          const UUID& collectionUuid,
                                          const BSONObj& keyPattern,
                                          const ChunkRange& range,
                                          int numDocsToRemovePerBatch,
                                          Milliseconds delayBetweenBatches) {
    return AsyncTry([=] {
               // Returns number of documents deleted.
               return deleteBatchAndWaitForReplication(
                   executor, nss, collectionUuid, keyPattern, range, numDocsToRemovePerBatch);
           })
        .until([](StatusWith<int> swNumDeleted) {
            // Continue iterating until there are no more documents to delete, retrying on
            // any error that doesn't indicate that this node is stepping down.
            return (swNumDeleted.isOK() && swNumDeleted.getValue() == 0) ||
                swNumDeleted.getStatus() ==
                ErrorCodes::RangeDeletionAbandonedBecauseCollectionWithUUIDDoesNotExist ||
                ErrorCodes::isShutdownError(swNumDeleted.getStatus()) ||
                ErrorCodes::isNotMasterError(swNumDeleted.getStatus());
        })
        .withDelayBetweenIterations(delayBetweenBatches)
        .on(executor)
        .ignoreValue();
}

/**
 * Notify the secondaries that this range is being deleted. Secondaries will watch for this update,
 * and kill any queries that may depend on documents in the range -- excepting any queries with a
 * read-concern option 'ignoreChunkMigration'.
 */
void notifySecondariesThatDeletionIsOccurring(const NamespaceString& nss,
                                              const UUID& collectionUuid,
                                              const ChunkRange& range) {
    withTemporaryOperationContext([&](OperationContext* opCtx) {
        AutoGetCollection autoAdmin(opCtx, NamespaceString::kServerConfigurationNamespace, MODE_IX);
        Helpers::upsert(opCtx,
                        NamespaceString::kServerConfigurationNamespace.ns(),
                        BSON("_id"
                             << "startRangeDeletion"
                             << "ns" << nss.ns() << "uuid" << collectionUuid << "min"
                             << range.getMin() << "max" << range.getMax()));
    });
}

void removePersistentRangeDeletionTask(const NamespaceString& nss,
                                       const UUID& collectionUuid,
                                       const ChunkRange& range) {
    withTemporaryOperationContext([&](OperationContext* opCtx) {
        try {
            PersistentTaskStore<RangeDeletionTask> store(opCtx,
                                                         NamespaceString::kRangeDeletionNamespace);
            store.remove(opCtx,
                         QUERY(RangeDeletionTask::kCollectionUuidFieldName
                               << collectionUuid << RangeDeletionTask::kRangeFieldName
                               << range.toBSON()));
        } catch (const DBException& e) {
            LOG(0) << "Failed to delete range deletion task for range " << range
                   << " in collection " << nss << causedBy(e.what());
        }
    });
}

}  // namespace

SharedSemiFuture<void> removeDocumentsInRange(
    const std::shared_ptr<executor::TaskExecutor>& executor,
    SemiFuture<void> waitForActiveQueriesToComplete,
    const NamespaceString& nss,
    const UUID& collectionUuid,
    const BSONObj& keyPattern,
    const ChunkRange& range,
    int numDocsToRemovePerBatch,
    Seconds delayForActiveQueriesOnSecondariesToComplete,
    Milliseconds delayBetweenBatches) {
    return std::move(waitForActiveQueriesToComplete)
        .thenRunOn(executor)
        .onError([&](Status s) {
            // The code does not expect the input future to have an error set on it, so we
            // invariant here to prevent future misuse (no pun intended).
            invariant(s.isOK());
        })
        .then([=]() mutable {
            suspendRangeDeletion.pauseWhileSet();
            // Wait for possibly ongoing queries on secondaries to complete.
            return sleepUntil(executor,
                              executor->now() + delayForActiveQueriesOnSecondariesToComplete);
        })
        .then([=]() mutable {
            LOG(0) << "Beginning deletion of any documents in " << nss.ns() << " range "
                   << redact(range.toString()) << "with numDocsToRemovePerBatch "
                   << numDocsToRemovePerBatch;

            notifySecondariesThatDeletionIsOccurring(nss, collectionUuid, range);

            return deleteRangeInBatches(executor,
                                        nss,
                                        collectionUuid,
                                        keyPattern,
                                        range,
                                        numDocsToRemovePerBatch,
                                        delayBetweenBatches);
        })
        .onCompletion([=](Status s) {
            if (s.isOK()) {
                LOG(0) << "Completed deletion of documents in " << nss.ns() << " range "
                       << redact(range.toString());
            } else {
                LOG(0) << "Failed to delete of documents in " << nss.ns() << " range "
                       << redact(range.toString()) << causedBy(redact(s));
            }

            if (s.isOK() ||
                s.code() ==
                    ErrorCodes::RangeDeletionAbandonedBecauseCollectionWithUUIDDoesNotExist) {
                removePersistentRangeDeletionTask(nss, collectionUuid, range);

                LOG(1) << "Completed removal of persistent range deletion task for " << nss.ns()
                       << " range " << redact(range.toString());
            }

            // Propagate any errors to callers waiting on the result.
            return s;
        })
        .semi()
        .share();
}  // namespace mongo

}  // namespace mongo