// get_last_error.cpp

/**
*    Copyright (C) 2013 10gen 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/db/commands/get_last_error.h"

#include "mongo/db/client.h"
#include "mongo/db/curop.h"
#include "mongo/db/commands.h"
#include "mongo/db/field_parser.h"
#include "mongo/db/lasterror.h"
#include "mongo/db/repl/rs.h"
#include "mongo/db/write_concern.h"

namespace mongo {

    /* reset any errors so that getlasterror comes back clean.

       useful before performing a long series of operations where we want to
       see if any of the operations triggered an error, but don't want to check
       after each op as that woudl be a client/server turnaround.
    */
    class CmdResetError : public Command {
    public:
        virtual bool isWriteCommandForConfigServer() const { return false; }
        virtual bool slaveOk() const {
            return true;
        }
        virtual void addRequiredPrivileges(const std::string& dbname,
                                           const BSONObj& cmdObj,
                                           std::vector<Privilege>* out) {} // No auth required
        virtual void help( stringstream& help ) const {
            help << "reset error state (used with getpreverror)";
        }
        CmdResetError() : Command("resetError", false, "reseterror") {}
        bool run(OperationContext* txn, const string& db, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
            LastError *le = lastError.get();
            verify( le );
            le->reset();
            return true;
        }
    } cmdResetError;

    /* set by replica sets if specified in the configuration.
       a pointer is used to avoid any possible locking issues with lockless reading.
       (for now, it simply orphans any old copy as config changes should be extremely rare).
       note: once non-null, never goes to null again.
    */
    BSONObj *getLastErrorDefault = 0;

    class CmdGetLastError : public Command {
    public:
        CmdGetLastError() : Command("getLastError", false, "getlasterror") { }
        virtual bool isWriteCommandForConfigServer() const      { return false; }
        virtual bool slaveOk() const      { return true;  }
        virtual void addRequiredPrivileges(const std::string& dbname,
                                           const BSONObj& cmdObj,
                                           std::vector<Privilege>* out) {} // No auth required
        virtual void help( stringstream& help ) const {
            lastError.disableForCommand(); // SERVER-11492
            help << "return error status of the last operation on this connection\n"
                 << "options:\n"
                 << "  { fsync:true } - fsync before returning, or wait for journal commit if running with --journal\n"
                 << "  { j:true } - wait for journal commit if running with --journal\n"
                 << "  { w:n } - await replication to n servers (including self) before returning\n"
                 << "  { w:'majority' } - await replication to majority of set\n"
                 << "  { wtimeout:m} - timeout for w in m milliseconds";
        }

        bool run(OperationContext* txn, const string& dbname,
                  BSONObj& cmdObj,
                  int,
                  string& errmsg,
                  BSONObjBuilder& result,
                  bool fromRepl ) {

            //
            // Correct behavior here is very finicky.
            //
            // 1.  The first step is to append the error that occurred on the previous operation.
            // This adds an "err" field to the command, which is *not* the command failing.
            //
            // 2.  Next we parse and validate write concern options.  If these options are invalid
            // the command fails no matter what, even if we actually had an error earlier.  The
            // reason for checking here is to match legacy behavior on these kind of failures -
            // we'll still get an "err" field for the write error.
            //
            // 3.  If we had an error on the previous operation, we then return immediately.
            //
            // 4.  Finally, we actually enforce the write concern.  All errors *except* timeout are
            // reported with ok : 0.0, to match legacy behavior.
            //
            // There is a special case when "wOpTime" and "wElectionId" are explicitly provided by 
            // the client (mongos) - in this case we *only* enforce the write concern if it is 
            // valid.
            //
            // We always need to either report "err" (if ok : 1) or "errmsg" (if ok : 0), even if
            // err is null.
            //

            LastError *le = lastError.disableForCommand();

            // Always append lastOp and connectionId
            Client& c = cc();
            c.appendLastOp( result );

            // for sharding; also useful in general for debugging
            result.appendNumber( "connectionId" , c.getConnectionId() );

            OpTime lastOpTime;
            BSONField<OpTime> wOpTimeField("wOpTime");
            FieldParser::FieldState extracted = FieldParser::extract(cmdObj, wOpTimeField, 
                                                                     &lastOpTime, &errmsg);
            if (!extracted) {
                result.append("badGLE", cmdObj);
                appendCommandStatus(result, false, errmsg);
                return false;
            }
            bool lastOpTimePresent = extracted != FieldParser::FIELD_NONE;
            if (!lastOpTimePresent) {
                // Use the client opTime if no wOpTime is specified
                lastOpTime = cc().getLastOp();
            }
            
            OID electionId;
            BSONField<OID> wElectionIdField("wElectionId");
            extracted = FieldParser::extract(cmdObj, wElectionIdField, 
                                             &electionId, &errmsg);
            if (!extracted) {
                result.append("badGLE", cmdObj);
                appendCommandStatus(result, false, errmsg);
                return false;
            }

            bool electionIdPresent = extracted != FieldParser::FIELD_NONE;
            bool errorOccurred = false;

            // Errors aren't reported when wOpTime is used
            if ( !lastOpTimePresent ) {
                if ( le->nPrev != 1 ) {
                    errorOccurred = LastError::noError.appendSelf( result, false );
                    le->appendSelfStatus( result );
                }
                else {
                    errorOccurred = le->appendSelf( result, false );
                }
            }

            BSONObj writeConcernDoc = cmdObj;
            // Use the default options if we have no gle options aside from wOpTime/wElectionId
            const int nFields = cmdObj.nFields();
            bool useDefaultGLEOptions = (nFields == 1) || 
                (nFields == 2 && lastOpTimePresent) ||
                (nFields == 3 && lastOpTimePresent && electionIdPresent);

            if ( useDefaultGLEOptions && getLastErrorDefault ) {
                writeConcernDoc = *getLastErrorDefault;
            }

            //
            // Validate write concern no matter what, this matches 2.4 behavior
            //

            WriteConcernOptions writeConcern;
            Status status = writeConcern.parse( writeConcernDoc );

            if ( status.isOK() ) {
                // Ensure options are valid for this host
                status = validateWriteConcern( writeConcern );
            }

            if ( !status.isOK() ) {
                result.append( "badGLE", writeConcernDoc );
                return appendCommandStatus( result, status );
            }

            // Don't wait for replication if there was an error reported - this matches 2.4 behavior
            if ( errorOccurred ) {
                dassert( !lastOpTimePresent );
                return true;
            }

            // No error occurred, so we won't duplicate these fields with write concern errors
            dassert( result.asTempObj()["err"].eoo() );
            dassert( result.asTempObj()["code"].eoo() );

            // If we got an electionId, make sure it matches
            if (electionIdPresent) {
                if (!replset::theReplSet) {
                    // Ignore electionIds of 0 from mongos.
                    if (electionId != OID()) {
                        errmsg = "wElectionId passed but no replication active";
                        result.append("code", ErrorCodes::BadValue);
                        return false;
                    }
                } 
                else {
                    if (electionId != replset::theReplSet->getElectionId()) {
                        LOG(3) << "oid passed in is " << electionId
                               << ", but our id is " << replset::theReplSet->getElectionId();
                        errmsg = "election occurred after write";
                        result.append("code", ErrorCodes::WriteConcernFailed);
                        return false;
                    }
                }
            }

            cc().curop()->setMessage( "waiting for write concern" );

            WriteConcernResult wcResult;
            status = waitForWriteConcern( txn, writeConcern, lastOpTime, &wcResult );
            wcResult.appendTo( writeConcern, &result );

            // For backward compatibility with 2.4, wtimeout returns ok : 1.0
            if ( wcResult.wTimedOut ) {
                dassert( !wcResult.err.empty() ); // so we always report err
                dassert( !status.isOK() );
                result.append( "errmsg", "timed out waiting for slaves" );
                result.append( "code", status.code() );
                return true;
            }

            return appendCommandStatus( result, status );
        }

    } cmdGetLastError;

    class CmdGetPrevError : public Command {
    public:
        virtual bool isWriteCommandForConfigServer() const { return false; }
        virtual void help( stringstream& help ) const {
            help << "check for errors since last reseterror commandcal";
        }
        virtual bool slaveOk() const {
            return true;
        }
        virtual void addRequiredPrivileges(const std::string& dbname,
                                           const BSONObj& cmdObj,
                                           std::vector<Privilege>* out) {} // No auth required
        CmdGetPrevError() : Command("getPrevError", false, "getpreverror") {}
        bool run(OperationContext* txn, const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
            LastError *le = lastError.disableForCommand();
            le->appendSelf( result );
            if ( le->valid )
                result.append( "nPrev", le->nPrev );
            else
                result.append( "nPrev", -1 );
            return true;
        }
    } cmdGetPrevError;

}
