/**
 *    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.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kCommand

#include "mongo/db/commands/mr_common.h"

#include <string>
#include <vector>

#include "mongo/db/auth/action_set.h"
#include "mongo/db/auth/action_type.h"
#include "mongo/db/auth/privilege.h"
#include "mongo/db/catalog/document_validation.h"
#include "mongo/db/commands.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/document_source_group.h"
#include "mongo/db/pipeline/document_source_limit.h"
#include "mongo/db/pipeline/document_source_match.h"
#include "mongo/db/pipeline/document_source_merge.h"
#include "mongo/db/pipeline/document_source_out.h"
#include "mongo/db/pipeline/document_source_project.h"
#include "mongo/db/pipeline/document_source_single_document_transformation.h"
#include "mongo/db/pipeline/document_source_sort.h"
#include "mongo/db/pipeline/document_source_unwind.h"
#include "mongo/db/pipeline/expression_javascript.h"
#include "mongo/db/pipeline/parsed_aggregation_projection_node.h"
#include "mongo/db/pipeline/parsed_inclusion_projection.h"
#include "mongo/db/query/util/make_data_structure.h"
#include "mongo/util/intrusive_counter.h"
#include "mongo/util/log.h"
#include "mongo/util/str.h"

namespace mongo::map_reduce_common {

namespace {
Rarely nonAtomicDeprecationSampler;  // Used to occasionally log deprecation messages.

using namespace std::string_literals;

auto translateSort(boost::intrusive_ptr<ExpressionContext> expCtx,
                   const BSONObj& sort,
                   const boost::optional<std::int64_t>& limit) {
    return DocumentSourceSort::create(expCtx, sort, limit.get_value_or(-1));
}

auto translateMap(boost::intrusive_ptr<ExpressionContext> expCtx, std::string code) {
    auto emitExpression = ExpressionInternalJsEmit::create(
        expCtx, ExpressionFieldPath::parse(expCtx, "$$ROOT", expCtx->variablesParseState), code);
    auto node = std::make_unique<parsed_aggregation_projection::InclusionNode>(
        ProjectionPolicies{ProjectionPolicies::DefaultIdPolicy::kExcludeId});
    node->addExpressionForPath(FieldPath{"emits"s}, std::move(emitExpression));
    auto inclusion = std::unique_ptr<TransformerInterface>{
        std::make_unique<parsed_aggregation_projection::ParsedInclusionProjection>(
            expCtx,
            ProjectionPolicies{ProjectionPolicies::DefaultIdPolicy::kExcludeId},
            std::move(node))};
    return make_intrusive<DocumentSourceSingleDocumentTransformation>(
        expCtx, std::move(inclusion), DocumentSourceProject::kStageName, false);
}

auto translateReduce(boost::intrusive_ptr<ExpressionContext> expCtx, std::string code) {
    auto accumulatorArguments = ExpressionObject::create(
        expCtx,
        make_vector<std::pair<std::string, boost::intrusive_ptr<Expression>>>(
            std::pair{"data"s,
                      ExpressionFieldPath::parse(expCtx, "$emits", expCtx->variablesParseState)},
            std::pair{"eval"s, ExpressionConstant::create(expCtx, Value{code})}));
    auto jsReduce = AccumulationStatement{"value", std::move(accumulatorArguments), [expCtx]() {
                                              return AccumulatorInternalJsReduce::create(expCtx);
                                          }};
    auto groupExpr = ExpressionFieldPath::parse(expCtx, "$emits.k", expCtx->variablesParseState);
    return DocumentSourceGroup::create(expCtx,
                                       std::move(groupExpr),
                                       make_vector<AccumulationStatement>(std::move(jsReduce)),
                                       boost::none);
}

auto translateFinalize(boost::intrusive_ptr<ExpressionContext> expCtx, std::string code) {
    auto jsExpression = ExpressionInternalJs::create(
        expCtx,
        ExpressionArray::create(
            expCtx,
            make_vector<boost::intrusive_ptr<Expression>>(
                ExpressionFieldPath::parse(expCtx, "$_id", expCtx->variablesParseState),
                ExpressionFieldPath::parse(expCtx, "$value", expCtx->variablesParseState))),
        code);
    auto node = std::make_unique<parsed_aggregation_projection::InclusionNode>(
        ProjectionPolicies{ProjectionPolicies::DefaultIdPolicy::kIncludeId});
    node->addProjectionForPath(FieldPath{"_id"s});
    node->addExpressionForPath(FieldPath{"value"s}, std::move(jsExpression));
    auto inclusion = std::unique_ptr<TransformerInterface>{
        std::make_unique<parsed_aggregation_projection::ParsedInclusionProjection>(
            expCtx,
            ProjectionPolicies{ProjectionPolicies::DefaultIdPolicy::kIncludeId},
            std::move(node))};
    return make_intrusive<DocumentSourceSingleDocumentTransformation>(
        expCtx, std::move(inclusion), DocumentSourceProject::kStageName, false);
}

auto translateOutReplace(boost::intrusive_ptr<ExpressionContext> expCtx,
                         const StringData inputDatabase,
                         NamespaceString targetNss) {
    uassert(31278,
            "MapReduce must output to the database belonging to its input collection - Input: "s +
                inputDatabase + " Output: " + targetNss.db(),
            inputDatabase == targetNss.db());
    return DocumentSourceOut::create(std::move(targetNss), expCtx);
}

auto translateOutMerge(boost::intrusive_ptr<ExpressionContext> expCtx, NamespaceString targetNss) {
    return DocumentSourceMerge::create(targetNss,
                                       expCtx,
                                       MergeWhenMatchedModeEnum::kReplace,
                                       MergeWhenNotMatchedModeEnum::kInsert,
                                       boost::none,  // Let variables
                                       boost::none,  // pipeline
                                       std::set<FieldPath>{FieldPath("_id"s)},
                                       boost::none);  // targetCollectionVersion
}

auto translateOutReduce(boost::intrusive_ptr<ExpressionContext> expCtx,
                        NamespaceString targetNss,
                        std::string code) {
    // Because of communication for sharding, $merge must hold on to a serializable BSON object
    // at the moment so we reparse here. Note that the reduce function signature expects 2
    // arguments, the first being the key and the second being the array of values to reduce.
    auto reduceObj = BSON("args" << BSON_ARRAY("$_id" << BSON_ARRAY("$value"
                                                                    << "$$new.value"))
                                 << "eval" << code);

    auto finalProjectSpec =
        BSON(DocumentSourceProject::kStageName
             << BSON("value" << BSON(ExpressionInternalJs::kExpressionName << reduceObj)));
    auto pipelineSpec = boost::make_optional(std::vector<BSONObj>{finalProjectSpec});
    return DocumentSourceMerge::create(targetNss,
                                       expCtx,
                                       MergeWhenMatchedModeEnum::kPipeline,
                                       MergeWhenNotMatchedModeEnum::kInsert,
                                       boost::none,  // Let variables
                                       pipelineSpec,
                                       std::set<FieldPath>{FieldPath("_id"s)},
                                       boost::none);  // targetCollectionVersion
}

auto translateOut(boost::intrusive_ptr<ExpressionContext> expCtx,
                  const OutputType outputType,
                  const StringData inputDatabase,
                  NamespaceString targetNss,
                  std::string reduceCode) {
    switch (outputType) {
        case OutputType::Replace:
            return boost::make_optional(translateOutReplace(expCtx, inputDatabase, targetNss));
        case OutputType::Merge:
            return boost::make_optional(translateOutMerge(expCtx, targetNss));
        case OutputType::Reduce:
            return boost::make_optional(translateOutReduce(expCtx, targetNss, reduceCode));
        case OutputType::InMemory:;
    }
    return boost::optional<boost::intrusive_ptr<mongo::DocumentSource>>{};
}

}  // namespace

OutputOptions parseOutputOptions(const std::string& dbname, const BSONObj& cmdObj) {
    OutputOptions outputOptions;

    outputOptions.outNonAtomic = false;
    if (cmdObj["out"].type() == String) {
        outputOptions.collectionName = cmdObj["out"].String();
        outputOptions.outType = OutputType::Replace;
    } else if (cmdObj["out"].type() == Object) {
        BSONObj o = cmdObj["out"].embeddedObject();

        if (o.hasElement("normal")) {
            outputOptions.outType = OutputType::Replace;
            outputOptions.collectionName = o["normal"].String();
        } else if (o.hasElement("replace")) {
            outputOptions.outType = OutputType::Replace;
            outputOptions.collectionName = o["replace"].String();
        } else if (o.hasElement("merge")) {
            outputOptions.outType = OutputType::Merge;
            outputOptions.collectionName = o["merge"].String();
        } else if (o.hasElement("reduce")) {
            outputOptions.outType = OutputType::Reduce;
            outputOptions.collectionName = o["reduce"].String();
        } else if (o.hasElement("inline")) {
            outputOptions.outType = OutputType::InMemory;
            uassert(ErrorCodes::InvalidOptions,
                    "cannot specify 'sharded' in combination with 'inline'",
                    !o.hasElement("sharded"));
        } else {
            uasserted(13522,
                      str::stream() << "please specify one of "
                                    << "[replace|merge|reduce|inline] in 'out' object");
        }

        if (o.hasElement("db")) {
            outputOptions.outDB = o["db"].String();
            uassert(ErrorCodes::CommandNotSupported,
                    "cannot target internal database as output",
                    !(NamespaceString(outputOptions.outDB, outputOptions.collectionName)
                          .isOnInternalDb()));
        }
        if (o.hasElement("nonAtomic")) {
            outputOptions.outNonAtomic = o["nonAtomic"].Bool();
            if (outputOptions.outNonAtomic) {
                uassert(15895,
                        "nonAtomic option cannot be used with this output type",
                        (outputOptions.outType == OutputType::Reduce ||
                         outputOptions.outType == OutputType::Merge));
            } else if (nonAtomicDeprecationSampler.tick()) {
                warning() << "Setting out.nonAtomic to false in MapReduce is deprecated.";
            }
        }
    } else {
        uasserted(13606, "'out' has to be a string or an object");
    }

    if (outputOptions.outType != OutputType::InMemory) {
        const StringData outDb(outputOptions.outDB.empty() ? dbname : outputOptions.outDB);
        const NamespaceString nss(outDb, outputOptions.collectionName);
        uassert(ErrorCodes::InvalidNamespace,
                str::stream() << "Invalid 'out' namespace: " << nss.ns(),
                nss.isValid());
        outputOptions.finalNamespace = std::move(nss);
    }

    return outputOptions;
}

void addPrivilegesRequiredForMapReduce(const BasicCommand* commandTemplate,
                                       const std::string& dbname,
                                       const BSONObj& cmdObj,
                                       std::vector<Privilege>* out) {
    OutputOptions outputOptions = parseOutputOptions(dbname, cmdObj);

    ResourcePattern inputResource(commandTemplate->parseResourcePattern(dbname, cmdObj));
    uassert(ErrorCodes::InvalidNamespace,
            str::stream() << "Invalid input resource " << inputResource.toString(),
            inputResource.isExactNamespacePattern());
    out->push_back(Privilege(inputResource, ActionType::find));

    if (outputOptions.outType != OutputType::InMemory) {
        ActionSet outputActions;
        outputActions.addAction(ActionType::insert);
        if (outputOptions.outType == OutputType::Replace) {
            outputActions.addAction(ActionType::remove);
        } else {
            outputActions.addAction(ActionType::update);
        }

        if (shouldBypassDocumentValidationForCommand(cmdObj)) {
            outputActions.addAction(ActionType::bypassDocumentValidation);
        }

        ResourcePattern outputResource(
            ResourcePattern::forExactNamespace(NamespaceString(outputOptions.finalNamespace)));
        uassert(ErrorCodes::InvalidNamespace,
                str::stream() << "Invalid target namespace " << outputResource.ns().ns(),
                outputResource.ns().isValid());

        // TODO: check if outputNs exists and add createCollection privilege if not
        out->push_back(Privilege(outputResource, outputActions));
    }
}

bool mrSupportsWriteConcern(const BSONObj& cmd) {
    if (!cmd.hasField("out")) {
        return false;
    } else if (cmd["out"].type() == Object && cmd["out"].Obj().hasField("inline")) {
        return false;
    } else {
        return true;
    }
}

std::unique_ptr<Pipeline, PipelineDeleter> translateFromMR(
    MapReduce parsedMr, boost::intrusive_ptr<ExpressionContext> expCtx) {
    // Verify that source and output collections are different.
    // Note that $out allows for the source and the destination to match, so only reject
    // in the case that the out option is being converted to a $merge.
    auto& inNss = parsedMr.getNamespace();
    auto outNss = NamespaceString{parsedMr.getOutOptions().getDatabaseName()
                                      ? *parsedMr.getOutOptions().getDatabaseName()
                                      : parsedMr.getNamespace().db(),
                                  parsedMr.getOutOptions().getCollectionName()};

    auto outType = parsedMr.getOutOptions().getOutputType();
    if (outType == OutputType::Merge || outType == OutputType::Reduce) {
        uassert(ErrorCodes::InvalidOptions,
                "Source collection cannot be the same as destination collection in MapReduce when "
                "using merge or reduce actions",
                inNss != outNss);
    }

    // If non-inline output, verify that the target collection is *not* sharded by anything other
    // than _id.
    if (outType != OutputType::InMemory) {
        auto [shardKey, targetCollectionVersion] =
            expCtx->mongoProcessInterface->ensureFieldsUniqueOrResolveDocumentKey(
                expCtx, boost::none, boost::none, outNss);
        uassert(31313,
                "The mapReduce target collection must either be unsharded or sharded by {_id: 1} "
                "or {_id: 'hashed'}",
                shardKey == std::set<FieldPath>{FieldPath("_id"s)});
    }

    // TODO: It would be good to figure out what kind of errors this would produce in the Status.
    // It would be better not to produce something incomprehensible out of an internal translation.
    return uassertStatusOK(Pipeline::create(
        makeFlattenedList<boost::intrusive_ptr<DocumentSource>>(
            parsedMr.getQuery().map(
                [&](auto&& query) { return DocumentSourceMatch::create(query, expCtx); }),
            parsedMr.getSort().map(
                [&](auto&& sort) { return translateSort(expCtx, sort, parsedMr.getLimit()); }),
            translateMap(expCtx, parsedMr.getMap().getCode()),
            DocumentSourceUnwind::create(expCtx, "emits", false, boost::none),
            translateReduce(expCtx, parsedMr.getReduce().getCode()),
            parsedMr.getFinalize().map([&](auto&& finalize) {
                return translateFinalize(expCtx, parsedMr.getFinalize()->getCode());
            }),
            translateOut(expCtx,
                         outType,
                         parsedMr.getNamespace().db(),
                         std::move(outNss),
                         parsedMr.getReduce().getCode())),
        expCtx));
}

}  // namespace mongo::map_reduce_common