/**
 *    Copyright (C) 2021-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/platform/basic.h"

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

#include "mongo/db/pipeline/change_stream_helpers_legacy.h"
#include "mongo/db/pipeline/change_stream_topology_change_info.h"

namespace mongo {

REGISTER_INTERNAL_DOCUMENT_SOURCE(_internalChangeStreamCheckTopologyChange,
                                  LiteParsedDocumentSourceChangeStreamInternal::parse,
                                  DocumentSourceChangeStreamCheckTopologyChange::createFromBson,
                                  true);

StageConstraints DocumentSourceChangeStreamCheckTopologyChange::constraints(
    Pipeline::SplitState pipeState) const {
    return {StreamType::kStreaming,
            PositionRequirement::kNone,
            HostTypeRequirement::kAnyShard,
            DiskUseRequirement::kNoDiskUse,
            FacetRequirement::kNotAllowed,
            TransactionRequirement::kNotAllowed,
            LookupRequirement::kNotAllowed,
            UnionRequirement::kNotAllowed,
            ChangeStreamRequirement::kChangeStreamStage};
}


boost::intrusive_ptr<DocumentSourceChangeStreamCheckTopologyChange>
DocumentSourceChangeStreamCheckTopologyChange::createFromBson(
    const BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx) {
    uassert(5669601,
            str::stream() << "the '" << kStageName << "' spec must be an object",
            elem.type() == Object && elem.Obj().isEmpty());
    return new DocumentSourceChangeStreamCheckTopologyChange(expCtx);
}

DocumentSource::GetNextResult DocumentSourceChangeStreamCheckTopologyChange::doGetNext() {
    auto nextInput = pSource->getNext();

    if (!nextInput.isAdvanced()) {
        return nextInput;
    }

    auto eventDoc = nextInput.getDocument();

    const StringData eventOpType =
        eventDoc[DocumentSourceChangeStream::kOperationTypeField].getStringData();

    // Throw the 'ChangeStreamTopologyChangeInfo' exception, wrapping the topology change event
    // along with its metadata. This will bypass the remainder of the pipeline and will be passed
    // directly up to mongoS.
    if (eventOpType == change_stream_legacy::getNewShardDetectedOpName(pExpCtx)) {
        uasserted(ChangeStreamTopologyChangeInfo(eventDoc.toBsonWithMetaData()),
                  "Collection migrated to new shard");
    }

    return nextInput;
}

Value DocumentSourceChangeStreamCheckTopologyChange::serialize(
    boost::optional<ExplainOptions::Verbosity> explain) const {
    if (explain) {
        return Value(DOC(DocumentSourceChangeStream::kStageName
                         << DOC("stage"
                                << "internalCheckTopologyChange"_sd)));
    }

    return Value(Document{{kStageName, Document()}});
}

}  // namespace mongo