/**
 *    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.
 */

#include "mongo/platform/basic.h"

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

#include <boost/smart_ptr/intrusive_ptr.hpp>

#include "mongo/db/exec/document_value/value.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/pipeline/document_source_replace_root_gen.h"
#include "mongo/db/pipeline/lite_parsed_document_source.h"

namespace mongo {

using boost::intrusive_ptr;

Document ReplaceRootTransformation::applyTransformation(const Document& input) {
    // Extract subdocument in the form of a Value.
    Value newRoot = _newRoot->evaluate(input, &_expCtx->variables);

    // To ensure an accurate user-facing message, any user-facing syntax that uses this stage
    // internally must provide an message opener that complies with its documentation.
    StringData msgOpener = [&]() {
        switch (_specifiedName) {
            case UserSpecifiedName::kReplaceRoot:
                return "'newRoot' expression "_sd;
            case UserSpecifiedName::kReplaceWith:
                return "'replacement document' "_sd;
            default:
                MONGO_UNREACHABLE;
        }
    }();

    // The newRoot expression, if it exists, must evaluate to an object.
    uassert(40228,
            str::stream() << msgOpener.toString()
                          << "must evaluate to an object, but resulting value was: "
                          << newRoot.toString() << ". Type of resulting value: '"
                          << typeName(newRoot.getType())
                          << "'. Input document: " << input.toString(),
            newRoot.getType() == BSONType::Object);

    // Turn the value into a document.
    MutableDocument newDoc(newRoot.getDocument());
    newDoc.copyMetaDataFrom(input);
    return newDoc.freeze();
}

REGISTER_DOCUMENT_SOURCE(replaceRoot,
                         LiteParsedDocumentSourceDefault::parse,
                         DocumentSourceReplaceRoot::createFromBson);
REGISTER_DOCUMENT_SOURCE(replaceWith,
                         LiteParsedDocumentSourceDefault::parse,
                         DocumentSourceReplaceRoot::createFromBson);

intrusive_ptr<DocumentSource> DocumentSourceReplaceRoot::createFromBson(
    BSONElement elem, const intrusive_ptr<ExpressionContext>& expCtx) {
    const auto stageName = elem.fieldNameStringData();
    auto newRootExpression = [&]() {
        if (stageName == kAliasNameReplaceWith) {
            return Expression::parseOperand(expCtx, elem, expCtx->variablesParseState);
        }

        invariant(
            stageName == kStageName,
            str::stream() << "Unexpected stage registered with DocumentSourceReplaceRoot parser: "
                          << stageName);
        uassert(40229,
                str::stream() << "expected an object as specification for " << kStageName
                              << " stage, got " << typeName(elem.type()),
                elem.type() == Object);

        auto spec =
            ReplaceRootSpec::parse(IDLParserErrorContext(kStageName), elem.embeddedObject());

        // The IDL doesn't give us back the type we need to feed into the expression parser, and
        // the expression parser needs the extra state in 'vps' and 'expCtx', so for now we have
        // to adapt the two.
        BSONObj parsingBson = BSON("newRoot" << spec.getNewRoot());
        return Expression::parseOperand(
            expCtx, parsingBson.firstElement(), expCtx->variablesParseState);
    }();

    // Whether this was specified as $replaceWith or $replaceRoot, always use the name $replaceRoot
    // to simplify the serialization process.
    const bool isIndependentOfAnyCollection = false;
    return new DocumentSourceSingleDocumentTransformation(
        expCtx,
        std::make_unique<ReplaceRootTransformation>(
            expCtx,
            newRootExpression,
            (stageName == kStageName) ? ReplaceRootTransformation::UserSpecifiedName::kReplaceRoot
                                      : ReplaceRootTransformation::UserSpecifiedName::kReplaceWith),
        kStageName.rawData(),
        isIndependentOfAnyCollection);
}

}  // namespace mongo