/**
 *    Copyright (C) 2023-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 <queue>

#include "mongo/db/pipeline/document_source.h"

namespace mongo {

class DocumentSourceChangeStreamSplitLargeEvent : public DocumentSource {
public:
    static constexpr StringData kStageName = "$changeStreamSplitLargeEvent"_sd;
    static constexpr size_t kBSONObjMaxChangeEventSize = BSONObjMaxInternalSize - (8 * 1024);

    static boost::intrusive_ptr<DocumentSourceChangeStreamSplitLargeEvent> create(
        const boost::intrusive_ptr<ExpressionContext>& expCtx,
        const DocumentSourceChangeStreamSpec& spec);

    static boost::intrusive_ptr<DocumentSourceChangeStreamSplitLargeEvent> createFromBson(
        BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);

    DocumentSource::GetModPathsReturn getModifiedPaths() const final;

    // This stage does not reference any user or system variables.
    void addVariableRefs(std::set<Variables::Id>* refs) const final {}

    Value serialize(SerializationOptions opts = SerializationOptions()) const final override;

    StageConstraints constraints(Pipeline::SplitState pipeState) const final;

    void validatePipelinePosition(bool alreadyOptimized,
                                  Pipeline::SourceContainer::const_iterator pos,
                                  const Pipeline::SourceContainer& container) const final;

    boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
        return boost::none;
    }

    const char* getSourceName() const final {
        return kStageName.rawData();
    }

protected:
    Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr,
                                                     Pipeline::SourceContainer* container) final;

    DocumentSource::GetNextResult doGetNext() final;

private:
    // This constructor is private, callers should use the 'create()' method above.
    DocumentSourceChangeStreamSplitLargeEvent(const boost::intrusive_ptr<ExpressionContext>& expCtx,
                                              boost::optional<ResumeTokenData> resumeAfterSplit);

    Document _popFromQueue();

    /**
     * In case of resume after split, check whether 'eventDoc' is the split event. If so, extract
     * and return the resume token's fragment number. Otherwise, return zero.
     */
    size_t _handleResumeAfterSplit(const Document& eventDoc, size_t eventBsonSize);

    boost::optional<ResumeTokenData> _resumeAfterSplit;
    std::queue<Document> _splitEventQueue;
};

}  // namespace mongo