/**
 *    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 <map>
#include <vector>

#include "mongo/bson/util/bson_extract.h"
#include "mongo/client/read_preference.h"
#include "mongo/client/remote_command_targeter.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/commands.h"
#include "mongo/db/commands/list_databases_gen.h"
#include "mongo/s/client/shard.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/cluster_commands_helpers.h"
#include "mongo/s/commands/strategy.h"
#include "mongo/s/grid.h"

namespace mongo {
namespace {

class ListDatabasesCmd : public BasicCommand {
public:
    ListDatabasesCmd() : BasicCommand("listDatabases", "listdatabases") {}

    const std::set<std::string>& apiVersions() const {
        return kApiVersions1;
    }

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

    bool maintenanceOk() const override {
        return false;
    }

    bool adminOnly() const override {
        return true;
    }


    bool supportsWriteConcern(const BSONObj& cmd) const override {
        return false;
    }

    std::string help() const override {
        return "list databases in a cluster";
    }

    /* listDatabases is always authorized,
     * however the results returned will be redacted
     * based on read privileges if auth is enabled
     * and the current user does not have listDatabases permisison.
     */
    Status checkAuthForCommand(Client* client,
                               const std::string& dbname,
                               const BSONObj& cmdObj) const override {
        return Status::OK();
    }


    bool run(OperationContext* opCtx,
             const std::string& dbname_unused,
             const BSONObj& cmdObj,
             BSONObjBuilder& result) override {
        CommandHelpers::handleMarkKillOnClientDisconnect(opCtx);

        IDLParserErrorContext ctx("listDatabases");
        auto cmd = ListDatabasesCommand::parse(ctx, cmdObj);
        auto* as = AuthorizationSession::get(opCtx->getClient());

        // { nameOnly: bool } - Default false.
        const bool nameOnly = cmd.getNameOnly();

        // { authorizedDatabases: bool } - Dynamic default based on perms.
        const bool authorizedDatabases = ([as](const boost::optional<bool>& authDB) {
            const bool mayListAllDatabases = as->isAuthorizedForActionsOnResource(
                ResourcePattern::forClusterResource(), ActionType::listDatabases);
            if (authDB) {
                uassert(ErrorCodes::Unauthorized,
                        "Insufficient permissions to list all databases",
                        authDB.get() || mayListAllDatabases);
                return authDB.get();
            }

            // By default, list all databases if we can, otherwise
            // only those we're allowed to find on.
            return !mayListAllDatabases;
        })(cmd.getAuthorizedDatabases());

        auto const shardRegistry = Grid::get(opCtx)->shardRegistry();

        std::map<std::string, long long> sizes;
        std::map<std::string, std::unique_ptr<BSONObjBuilder>> dbShardInfo;

        std::vector<ShardId> shardIds;
        shardRegistry->getAllShardIdsNoReload(&shardIds);
        shardIds.emplace_back(ShardRegistry::kConfigServerShardId);

        // { filter: matchExpression }.
        auto filteredCmd = applyReadWriteConcern(
            opCtx, this, CommandHelpers::filterCommandRequestForPassthrough(cmdObj));

        for (const ShardId& shardId : shardIds) {
            const auto shardStatus = shardRegistry->getShard(opCtx, shardId);
            if (!shardStatus.isOK()) {
                continue;
            }
            const auto s = shardStatus.getValue();

            auto response = uassertStatusOK(
                s->runCommandWithFixedRetryAttempts(opCtx,
                                                    ReadPreferenceSetting::get(opCtx),
                                                    "admin",
                                                    filteredCmd,
                                                    Shard::RetryPolicy::kIdempotent));
            uassertStatusOK(response.commandStatus);
            BSONObj x = std::move(response.response);

            BSONObjIterator j(x["databases"].Obj());
            while (j.more()) {
                BSONObj dbObj = j.next().Obj();

                const auto name = dbObj["name"].String();

                // If this is the admin db, only collect its stats from the config servers.
                if (name == "admin" && !s->isConfig()) {
                    continue;
                }

                // We don't collect config server info for dbs other than "admin" and "config".
                if (s->isConfig() && name != "config" && name != "admin") {
                    continue;
                }

                const long long size = dbObj["sizeOnDisk"].numberLong();

                long long& sizeSumForDbAcrossShards = sizes[name];
                if (size == 1) {
                    if (sizeSumForDbAcrossShards <= 1) {
                        sizeSumForDbAcrossShards = 1;
                    }
                } else {
                    sizeSumForDbAcrossShards += size;
                }

                auto& bb = dbShardInfo[name];
                if (!bb) {
                    bb.reset(new BSONObjBuilder());
                }

                bb->appendNumber(s->getId().toString(), size);
            }
        }

        // Now that we have aggregated results for all the shards, convert to a response,
        // and compute total sizes.
        long long totalSize = 0;

        {
            BSONArrayBuilder dbListBuilder(result.subarrayStart("databases"));
            for (const auto& sizeEntry : sizes) {
                const auto& name = sizeEntry.first;
                const long long size = sizeEntry.second;

                // Skip the local database, since all shards have their own independent local
                if (name == NamespaceString::kLocalDb)
                    continue;

                if (authorizedDatabases && !as->isAuthorizedForAnyActionOnAnyResourceInDB(name)) {
                    // We don't have listDatabases on the cluser or find on this database.
                    continue;
                }

                BSONObjBuilder temp;
                temp.append("name", name);
                if (!nameOnly) {
                    temp.appendNumber("sizeOnDisk", size);
                    temp.appendBool("empty", size == 1);
                    temp.append("shards", dbShardInfo[name]->obj());

                    uassert(ErrorCodes::BadValue,
                            str::stream() << "Found negative 'sizeOnDisk' in: " << name,
                            size >= 0);

                    totalSize += size;
                }

                dbListBuilder.append(temp.obj());
            }
        }

        if (!nameOnly) {
            result.appendNumber("totalSize", totalSize);
            result.appendNumber("totalSizeMb", totalSize / (1024 * 1024));
        }

        return true;
    }

} listDatabasesCmd;

}  // namespace
}  // namespace mongo