/**
 *    Copyright (C) 2008, 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/clientcursor.h"

#include <string>
#include <time.h>
#include <vector>

#include "mongo/base/counter.h"
#include "mongo/client/dbclientinterface.h"
#include "mongo/db/audit.h"
#include "mongo/db/auth/action_set.h"
#include "mongo/db/auth/action_type.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/auth/privilege.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/client.h"
#include "mongo/db/commands.h"
#include "mongo/db/commands/server_status.h"
#include "mongo/db/commands/server_status_metric.h"
#include "mongo/db/curop.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/operation_context_impl.h"
#include "mongo/db/repl/repl_coordinator_global.h"
#include "mongo/util/exit.h"

namespace mongo {

    static Counter64 cursorStatsOpen; // gauge
    static Counter64 cursorStatsOpenPinned; // gauge
    static Counter64 cursorStatsOpenNoTimeout; // gauge
    static Counter64 cursorStatsTimedOut;

    static ServerStatusMetricField<Counter64> dCursorStatsOpen( "cursor.open.total",
                                                                        &cursorStatsOpen );
    static ServerStatusMetricField<Counter64> dCursorStatsOpenPinned( "cursor.open.pinned",
                                                                      &cursorStatsOpenPinned );
    static ServerStatusMetricField<Counter64> dCursorStatsOpenNoTimeout( "cursor.open.noTimeout",
                                                                         &cursorStatsOpenNoTimeout );
    static ServerStatusMetricField<Counter64> dCursorStatusTimedout( "cursor.timedOut",
                                                                     &cursorStatsTimedOut );

    long long ClientCursor::totalOpen() {
        return cursorStatsOpen.get();
    }

    ClientCursor::ClientCursor(CursorManager* cursorManager,
                               PlanExecutor* exec,
                               int qopts,
                               const BSONObj query,
                               bool isAggCursor)
        : _cursorManager(cursorManager),
          _countedYet(false),
          _isAggCursor(isAggCursor),
          _unownedRU(NULL) {

        _exec.reset(exec);
        _ns = exec->ns();
        _query = query;
        _queryOptions = qopts;
        if (exec->collection()) {
            invariant(cursorManager == exec->collection()->cursorManager());
        }
        init();
    }

    ClientCursor::ClientCursor(CursorManager* cursorManager)
        : _ns(cursorManager->ns()),
          _cursorManager(cursorManager),
          _countedYet(false),
          _queryOptions(QueryOption_NoCursorTimeout),
          _isAggCursor(false),
          _unownedRU(NULL) {
        init();
    }

    void ClientCursor::init() {
        invariant( _cursorManager );

        _isPinned = false;
        _isNoTimeout = false;

        _idleAgeMillis = 0;
        _leftoverMaxTimeMicros = 0;
        _pos = 0;

        if (_queryOptions & QueryOption_NoCursorTimeout) {
            // cursors normally timeout after an inactivity period to prevent excess memory use
            // setting this prevents timeout of the cursor in question.
            _isNoTimeout = true;
            cursorStatsOpenNoTimeout.increment();
        }

        _cursorid = _cursorManager->registerCursor( this );

        cursorStatsOpen.increment();
        _countedYet = true;
    }

    ClientCursor::~ClientCursor() {
        if( _pos == -2 ) {
            // defensive: destructor called twice
            wassert(false);
            return;
        }

        invariant( !_isPinned ); // Must call unsetPinned() before invoking destructor.

        if ( _countedYet ) {
            _countedYet = false;
            cursorStatsOpen.decrement();
            if ( _isNoTimeout )
                cursorStatsOpenNoTimeout.decrement();
        }

        if ( _cursorManager ) {
            // this could be null if kill() was killed
            _cursorManager->deregisterCursor( this );
        }

        // defensive:
        _cursorManager = NULL;
        _cursorid = INVALID_CURSOR_ID;
        _pos = -2;
        _isNoTimeout = false;
    }

    void ClientCursor::kill() {
        if ( _exec.get() )
            _exec->kill();

        _cursorManager = NULL;
    }

    //
    // Timing and timeouts
    //

    bool ClientCursor::shouldTimeout(int millis) {
        _idleAgeMillis += millis;
        if (_isNoTimeout || _isPinned) {
            return false;
        }
        return _idleAgeMillis > 600000;
    }

    void ClientCursor::setIdleTime( int millis ) {
        _idleAgeMillis = millis;
    }

    void ClientCursor::updateSlaveLocation(OperationContext* txn, CurOp& curop) {
        if (_slaveReadTill.isNull())
            return;

        verify(str::startsWith(_ns.c_str(), "local.oplog."));

        Client* c = curop.getClient();
        verify(c);
        OID rid = c->getRemoteID();
        if (!rid.isSet())
            return;

        repl::getGlobalReplicationCoordinator()->setLastOptimeForSlave(rid, _slaveReadTill);
    }

    //
    // Storage engine state for getMore.
    //

    void ClientCursor::setUnownedRecoveryUnit(RecoveryUnit* ru) {
        invariant(!_unownedRU);
        invariant(!_ownedRU.get());
        _unownedRU = ru;
    }

    RecoveryUnit* ClientCursor::getUnownedRecoveryUnit() const {
        return _unownedRU;
    }

    void ClientCursor::setOwnedRecoveryUnit(RecoveryUnit* ru) {
        invariant(!_unownedRU);
        invariant(!_ownedRU.get());
        _ownedRU.reset(ru);
    }

    RecoveryUnit* ClientCursor::releaseOwnedRecoveryUnit() {
        return _ownedRU.release();
    }

    //
    // Pin methods
    // TODO: Simplify when we kill Cursor.  In particular, once we've pinned a CC, it won't be
    // deleted from underneath us, so we can save the pointer and ignore the ID.
    //

    ClientCursorPin::ClientCursorPin( CursorManager* cursorManager, long long cursorid )
        : _cursor( NULL ) {
        cursorStatsOpenPinned.increment();
        _cursor = cursorManager->find( cursorid, true );
    }

    ClientCursorPin::~ClientCursorPin() {
        cursorStatsOpenPinned.decrement();
        DESTRUCTOR_GUARD( release(); );
    }

    void ClientCursorPin::release() {
        if ( !_cursor )
            return;

        invariant( _cursor->isPinned() );

        if ( _cursor->cursorManager() == NULL ) {
            // The ClientCursor was killed while we had it.  Therefore, it is our responsibility to
            // kill it.
            deleteUnderlying();
        }
        else {
            // Unpin the cursor under the collection cursor manager lock.
            _cursor->cursorManager()->unpin( _cursor );
        }
    }

    void ClientCursorPin::deleteUnderlying() {
        invariant( _cursor->isPinned() );
        // Note the following subtleties of this method's implementation:
        // - We must unpin the cursor before destruction, since it is an error to destroy a pinned
        //   cursor.
        // - In addition, we must deregister the cursor before unpinning, since it is an
        //   error to unpin a registered cursor without holding the cursor manager lock (note that
        //   we can't simply unpin with the cursor manager lock here, since we need to guarantee
        //   exclusive ownership of the cursor when we are deleting it).
        if ( _cursor->cursorManager() ) {
            _cursor->cursorManager()->deregisterCursor( _cursor );
            _cursor->kill();
        }
        _cursor->unsetPinned();
        delete _cursor;
        _cursor = NULL;
    }

    ClientCursor* ClientCursorPin::c() const {
        return _cursor;
    }

    //
    // ClientCursorMonitor
    //

    /**
     * Thread for timing out old cursors
     */
    class ClientCursorMonitor : public BackgroundJob {
    public:
        std::string name() const { return "ClientCursorMonitor"; }

        void run() {
            Client::initThread("clientcursormon");
            Client& client = cc();
            Timer t;
            const int Secs = 4;
            while (!inShutdown()) {
                OperationContextImpl txn;
                cursorStatsTimedOut.increment(
                    CursorManager::timeoutCursorsGlobal(&txn, t.millisReset()));
                sleepsecs(Secs);
            }
            client.shutdown();
        }
    };

    namespace {
        // Only one instance of the ClientCursorMonitor exists
        ClientCursorMonitor clientCursorMonitor;

        void _appendCursorStats( BSONObjBuilder& b ) {
            b.append( "note" , "deprecated, use server status metrics" );
            b.appendNumber("clientCursors_size", cursorStatsOpen.get() );
            b.appendNumber("totalOpen", cursorStatsOpen.get() );
            b.appendNumber("pinned", cursorStatsOpenPinned.get() );
            b.appendNumber("totalNoTimeout", cursorStatsOpenNoTimeout.get() );
            b.appendNumber("timedOut" , cursorStatsTimedOut.get());
        }
    }

    void startClientCursorMonitor() {
        clientCursorMonitor.go();
    }

    // QUESTION: Restrict to the namespace from which this command was issued?
    // Alternatively, make this command admin-only?
    // TODO: remove this for 2.8
    class CmdCursorInfo : public Command {
    public:
        CmdCursorInfo() : Command( "cursorInfo", true ) {}
        virtual bool slaveOk() const { return true; }
        virtual void help( stringstream& help ) const {
            help << " example: { cursorInfo : 1 }, deprecated";
        }
        virtual bool isWriteCommandForConfigServer() const { return false; }
        virtual void addRequiredPrivileges(const std::string& dbname,
                                           const BSONObj& cmdObj,
                                           std::vector<Privilege>* out) {
            ActionSet actions;
            actions.addAction(ActionType::cursorInfo);
            out->push_back(Privilege(ResourcePattern::forClusterResource(), actions));
        }
        bool run(OperationContext* txn, const string& dbname, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result,
                 bool fromRepl ) {
            _appendCursorStats( result );
            return true;
        }
    } cmdCursorInfo;

    //
    // cursors stats.
    //

    class CursorServerStats : public ServerStatusSection {
    public:
        CursorServerStats() : ServerStatusSection( "cursors" ){}
        virtual bool includeByDefault() const { return true; }

        BSONObj generateSection(OperationContext* txn,
                                const BSONElement& configElement) const {
            BSONObjBuilder b;
            _appendCursorStats( b );
            return b.obj();
        }

    } cursorServerStats;

} // namespace mongo