/**
 *    Copyright (C) 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/base/init.h"
#include "mongo/base/error_codes.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/client_basic.h"
#include "mongo/db/commands.h"
#include "mongo/s/config.h"
#include "mongo/s/grid.h"
#include "mongo/s/stale_exception.h"
#include "mongo/s/strategy.h"

namespace mongo {

using std::string;
using std::stringstream;
using std::vector;

/**
 * Base class for mongos plan cache commands.
 * Cluster plan cache commands don't do much more than
 * forwarding the commands to all shards and combining the results.
 */
class ClusterPlanCacheCmd : public Command {
    MONGO_DISALLOW_COPYING(ClusterPlanCacheCmd);

public:
    virtual ~ClusterPlanCacheCmd() {}

    bool slaveOk() const {
        return false;
    }

    bool slaveOverrideOk() const {
        return true;
    }

    virtual bool isWriteCommandForConfigServer() const {
        return false;
    }

    void help(stringstream& ss) const {
        ss << _helpText;
    }

    Status checkAuthForCommand(ClientBasic* client,
                               const std::string& dbname,
                               const BSONObj& cmdObj) {
        AuthorizationSession* authzSession = AuthorizationSession::get(client);
        ResourcePattern pattern = parseResourcePattern(dbname, cmdObj);

        if (authzSession->isAuthorizedForActionsOnResource(pattern, _actionType)) {
            return Status::OK();
        }

        return Status(ErrorCodes::Unauthorized, "unauthorized");
    }

    // Cluster plan cache command entry point.
    bool run(OperationContext* txn,
             const std::string& dbname,
             BSONObj& cmdObj,
             int options,
             std::string& errmsg,
             BSONObjBuilder& result);

public:
    /**
     * Instantiates a command that can be invoked by "name", which will be described by
     * "helpText", and will require privilege "actionType" to run.
     */
    ClusterPlanCacheCmd(const std::string& name, const std::string& helpText, ActionType actionType)
        : Command(name), _helpText(helpText), _actionType(actionType) {}

private:
    std::string _helpText;
    ActionType _actionType;
};

//
// Cluster plan cache command implementation(s) below
//

bool ClusterPlanCacheCmd::run(OperationContext* txn,
                              const std::string& dbName,
                              BSONObj& cmdObj,
                              int options,
                              std::string& errMsg,
                              BSONObjBuilder& result) {
    const std::string fullns = parseNs(dbName, cmdObj);
    NamespaceString nss(fullns);

    // Dispatch command to all the shards.
    // Targeted shard commands are generally data-dependent but plan cache
    // commands are tied to query shape (data has no effect on query shape).
    vector<Strategy::CommandResult> results;
    Strategy::commandOp(dbName, cmdObj, options, nss.ns(), BSONObj(), &results);

    // Set value of first shard result's "ok" field.
    bool clusterCmdResult = true;

    for (vector<Strategy::CommandResult>::const_iterator i = results.begin(); i != results.end();
         ++i) {
        const Strategy::CommandResult& cmdResult = *i;

        // XXX: In absence of sensible aggregation strategy,
        //      promote first shard's result to top level.
        if (i == results.begin()) {
            result.appendElements(cmdResult.result);
            clusterCmdResult = cmdResult.result["ok"].trueValue();
        }

        // Append shard result as a sub object.
        // Name the field after the shard.
        string shardName = cmdResult.shardTargetId;
        result.append(shardName, cmdResult.result);
    }

    return clusterCmdResult;
}

//
// Register plan cache commands at startup
//

namespace {

MONGO_INITIALIZER(RegisterPlanCacheCommands)(InitializerContext* context) {
    // Leaked intentionally: a Command registers itself when constructed.

    new ClusterPlanCacheCmd("planCacheListQueryShapes",
                            "Displays all query shapes in a collection.",
                            ActionType::planCacheRead);

    new ClusterPlanCacheCmd("planCacheClear",
                            "Drops one or all cached queries in a collection.",
                            ActionType::planCacheWrite);

    new ClusterPlanCacheCmd("planCacheListPlans",
                            "Displays the cached plans for a query shape.",
                            ActionType::planCacheRead);

    return Status::OK();
}

}  // namespace

}  // namespace mongo