// cursors.h
/*
 *    Copyright (C) 2010 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.
 */


#pragma once

#include "mongo/platform/basic.h"

#include <boost/noncopyable.hpp>
#include <boost/shared_ptr.hpp>
#include <string>

#include "mongo/client/parallel.h"
#include "mongo/db/dbmessage.h"
#include "mongo/db/jsobj.h"
#include "mongo/platform/random.h"
#include "mongo/s/request.h"

namespace mongo {

class ShardedClientCursor : boost::noncopyable {
public:
    ShardedClientCursor(QueryMessage& q, ParallelSortClusteredCursor* cursor);
    virtual ~ShardedClientCursor();

    long long getId();

    /**
     * @return the cumulative number of documents seen by this cursor.
     */
    int getTotalSent() const;

    /**
     * Sends queries to the shards, gather the result for this batch and sends the response
     * to the socket.
     *
     * @return whether there is more data left
     */
    bool sendNextBatchAndReply(Request& r);

    /**
     * Sends queries to the shards and gather the result for this batch.
     *
     * @param r The request object from the client
     * @param ntoreturn Number of documents to return
     * @param buffer The buffer to use to store the results.
     * @param docCount This will contain the number of documents gathered for this batch after
     *        a successful call.
     *
     * @return true if this is not the final batch.
     */
    bool sendNextBatch(Request& r, int batchSize, BufBuilder& buffer, int& docCount);

    void accessed();
    /** @return idle time in ms */
    long long idleTime(long long now);

    std::string getNS() {
        return _cursor->getNS();
    }

    // The default initial buffer size for sending responses.
    static const int INIT_REPLY_BUFFER_SIZE;

protected:
    ParallelSortClusteredCursor* _cursor;

    int _skip;
    int _ntoreturn;

    int _totalSent;
    bool _done;

    long long _id;
    long long _lastAccessMillis;  // 0 means no timeout
};

typedef boost::shared_ptr<ShardedClientCursor> ShardedClientCursorPtr;

class CursorCache {
public:
    static long long TIMEOUT;

    typedef std::map<long long, ShardedClientCursorPtr> MapSharded;
    typedef std::map<long long, int> MapShardedInt;
    typedef std::map<long long, std::string> MapNormal;

    CursorCache();
    ~CursorCache();

    ShardedClientCursorPtr get(long long id) const;
    int getMaxTimeMS(long long id) const;
    void store(ShardedClientCursorPtr cursor, int maxTimeMS);
    void updateMaxTimeMS(long long id, int maxTimeMS);
    void remove(long long id);

    void storeRef(const std::string& server, long long id, const std::string& ns);
    void removeRef(long long id);

    /** @return the server for id or "" */
    std::string getRef(long long id) const;
    /** @return the ns for id or "" */
    std::string getRefNS(long long id) const;

    void gotKillCursors(Message& m);

    void appendInfo(BSONObjBuilder& result) const;

    long long genId();

    void doTimeouts();
    void startTimeoutThread();

private:
    mutable mongo::mutex _mutex;

    PseudoRandom _random;

    // Maps sharded cursor ID to ShardedClientCursorPtr.
    MapSharded _cursors;

    // Maps sharded cursor ID to remaining max time.  Value can be any of:
    // - the constant "kMaxTimeCursorNoTimeLimit", or
    // - the constant "kMaxTimeCursorTimeLimitExpired", or
    // - a positive integer representing milliseconds of remaining time
    MapShardedInt _cursorsMaxTimeMS;

    // Maps passthrough cursor ID to shard name.
    MapNormal _refs;

    // Maps passthrough cursor ID to namespace.
    MapNormal _refsNS;

    long long _shardedTotal;

    static const int _myLogLevel;
};

extern CursorCache cursorCache;
}