/**
 *    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.
 */

#pragma once

#include <functional>

#include "mongo/db/session/logical_session_id.h"
#include "mongo/db/session/session_killer.h"
#include "mongo/util/periodic_runner.h"
#include "mongo/util/time_support.h"

namespace mongo {

class ServiceContext;

/**
 * A service-dependent type for the LogicalSessionCache to use to find the
 * current time, schedule periodic refresh jobs, and get a list of sessions
 * that are being used for long-running queries on the service context.
 *
 * Mongod and mongos implement their own classes to fulfill this interface.
 */
class ServiceLiaison {
public:
    virtual ~ServiceLiaison();

    /**
     * Return a list of sessions that are currently being used to run operations
     * on this service.
     */
    virtual LogicalSessionIdSet getActiveOpSessions() const = 0;

    /**
     * Return a list of sessions that are currently attached to open cursors
     */
    virtual LogicalSessionIdSet getOpenCursorSessions(OperationContext* opCtx) const = 0;

    /**
     * Schedule a job to be run at regular intervals until the server shuts down.
     *
     * The ServiceLiaison should start its background runner on construction, and
     * should continue fielding job requests through scheduleJob until join() is
     * called.
     */
    virtual void scheduleJob(PeriodicRunner::PeriodicJob job) = 0;

    /**
     * Stops the service liaison from running any more jobs scheduled
     * through scheduleJob. This method may block and wait for background threads to
     * join. Implementations should make it safe for this method to be called
     * multiple times, or concurrently by different threads.
     */
    virtual void join() = 0;

    /**
     * Return the current time.
     */
    virtual Date_t now() const = 0;

    /**
     * Deligates to a similarly named function on a cursor manager.
     */
    virtual std::pair<Status, int> killCursorsWithMatchingSessions(
        OperationContext* opCtx, const SessionKiller::Matcher& matcher) = 0;

protected:
    /**
     * Returns the service context.
     */
    virtual ServiceContext* _context() = 0;
};

}  // namespace mongo