/**
 * Copyright (c) 2011-2014 MongoDB Inc.
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * 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
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * 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 GNU Affero General 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/auth/authorization_session.h"
#include "mongo/db/commands.h"
#include "mongo/db/commands/run_aggregate.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/pipeline/pipeline.h"

namespace mongo {
namespace {

bool isMergePipeline(const std::vector<BSONObj>& pipeline) {
    if (pipeline.empty()) {
        return false;
    }
    return pipeline[0].hasField("$mergeCursors");
}

class PipelineCommand : public BasicCommand {
public:
    PipelineCommand() : BasicCommand("aggregate") {}

    std::string help() const override {
        return "Runs the aggregation command. See http://dochub.mongodb.org/core/aggregation for "
               "more details.";
    }

    bool supportsWriteConcern(const BSONObj& cmd) const override {
        return Pipeline::aggSupportsWriteConcern(cmd);
    }

    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kOptIn;
    }

    bool supportsReadConcern(const std::string& dbName,
                             const BSONObj& cmdObj,
                             repl::ReadConcernLevel level) const override {
        // Aggregations that are run directly against a collection allow any read concern.
        // Otherwise, if the aggregate is collectionless then the read concern must be 'local' (e.g.
        // $currentOp). The exception to this is a $changeStream on a whole database, which is
        // considered collectionless but must be read concern 'majority'. Further read concern
        // validation is done one the pipeline is parsed.
        return level == repl::ReadConcernLevel::kLocalReadConcern ||
            level == repl::ReadConcernLevel::kMajorityReadConcern ||
            !AggregationRequest::parseNs(dbName, cmdObj).isCollectionlessAggregateNS();
    }

    ReadWriteType getReadWriteType() const {
        return ReadWriteType::kRead;
    }

    Status checkAuthForCommand(Client* client,
                               const std::string& dbname,
                               const BSONObj& cmdObj) const override {
        const NamespaceString nss(AggregationRequest::parseNs(dbname, cmdObj));
        return AuthorizationSession::get(client)->checkAuthForAggregate(nss, cmdObj, false);
    }

    bool run(OperationContext* opCtx,
             const std::string& dbname,
             const BSONObj& cmdObj,
             BSONObjBuilder& result) override {
        const auto aggregationRequest =
            uassertStatusOK(AggregationRequest::parseFromBSON(dbname, cmdObj, boost::none));

        return CommandHelpers::appendCommandStatus(
            result,
            runAggregate(opCtx,
                         aggregationRequest.getNamespaceString(),
                         aggregationRequest,
                         cmdObj,
                         result));
    }

    Status explain(OperationContext* opCtx,
                   const OpMsgRequest& request,
                   ExplainOptions::Verbosity verbosity,
                   BSONObjBuilder* out) const override {
        std::string dbname = request.getDatabase().toString();
        const BSONObj& cmdObj = request.body;
        const auto aggregationRequest =
            uassertStatusOK(AggregationRequest::parseFromBSON(dbname, cmdObj, verbosity));

        return runAggregate(
            opCtx, aggregationRequest.getNamespaceString(), aggregationRequest, cmdObj, *out);
    }

} pipelineCmd;

}  // namespace
}  // namespace mongo