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/**
 *    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.
 */

#pragma once

#include "mongo/db/index/duplicate_key_tracker.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/index/multikey_paths.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/storage/temporary_record_store.h"
#include "mongo/platform/atomic_word.h"

namespace mongo {

class BSONObj;
class IndexAccessMethod;
class OperationContext;

class IndexBuildInterceptor {
public:
    enum class Op { kInsert, kDelete };

    /**
     * The OperationContext is used to construct a temporary table in the storage engine to
     * intercept side writes. This interceptor must not exist longer than the operation context used
     * to construct it, as the underlying TemporaryRecordStore needs it to destroy itself.
     */
    IndexBuildInterceptor(OperationContext* opCtx, IndexCatalogEntry* entry);

    /**
     * Client writes that are concurrent with an index build will have their index updates written
     * to a temporary table. After the index table scan is complete, these updates will be applied
     * to the underlying index table.
     *
     * On success, `numKeysOut` if non-null will contain the number of keys added or removed.
     */
    Status sideWrite(OperationContext* opCtx,
                     IndexAccessMethod* indexAccessMethod,
                     const BSONObj* obj,
                     RecordId loc,
                     Op op,
                     int64_t* const numKeysOut);

    /**
     * Given a set of duplicate keys, record the keys for later verification by a call to
     * checkConstraints();
     */
    Status recordDuplicateKeys(OperationContext* opCtx, const std::vector<BSONObj>& keys);

    /**
     * Returns Status::OK if all previously recorded duplicate key constraint violations have been
     * resolved for the index. Returns a DuplicateKey error if there are still duplicate key
     * constraint violations on the index.
     */
    Status checkDuplicateKeyConstraints(OperationContext* opCtx) const;

    /**
     * Performs a resumable scan on the side writes table, and either inserts or removes each key
     * from the underlying IndexAccessMethod. This will only insert as many records as are visible
     * in the current snapshot.
     *
     * This is resumable, so subsequent calls will start the scan at the record immediately
     * following the last inserted record from a previous call to drainWritesIntoIndex.
     */
    Status drainWritesIntoIndex(OperationContext* opCtx, const InsertDeleteOptions& options);


    /**
     * Returns 'true' if there are no visible records remaining to be applied from the side writes
     * table. Ensure that this returns 'true' when an index build is completed.
     */
    bool areAllWritesApplied(OperationContext* opCtx) const;

    /**
     * Returns true if all recorded duplicate key constraint violations have been checked.
     */
    bool areAllConstraintsChecked(OperationContext* opCtx) const;

    /**
      * When an index builder wants to commit, use this to retrieve any recorded multikey paths
      * that were tracked during the build.
      */
    boost::optional<MultikeyPaths> getMultikeyPaths() const;

private:
    using SideWriteRecord = std::pair<RecordId, BSONObj>;

    Status _applyWrite(OperationContext* opCtx,
                       const BSONObj& doc,
                       const InsertDeleteOptions& options,
                       int64_t* const keysInserted,
                       int64_t* const keysDeleted);

    // The entry for the index that is being built.
    IndexCatalogEntry* _indexCatalogEntry;

    // This temporary record store is owned by the interceptor and dropped along with it.
    std::unique_ptr<TemporaryRecordStore> _sideWritesTable;

    std::unique_ptr<DuplicateKeyTracker> _duplicateKeyTracker;

    int64_t _numApplied{0};

    AtomicWord<long long> _sideWritesCounter{0};

    mutable stdx::mutex _multikeyPathMutex;
    boost::optional<MultikeyPaths> _multikeyPaths;
};

}  // namespace mongo