/**
 *    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 <memory>

#include "mongo/util/clock_source.h"
#include "mongo/util/time_support.h"

namespace mongo {

/**
 * Mock clock source that returns a fixed time until explicitly advanced.
 *
 * Each ClockSourceMock that is constructed tracks the same shared global understanding of time.
 */
class ClockSourceMock : public ClockSource {
public:
    static constexpr auto kInitialNow = Date_t::fromMillisSinceEpoch(1);

    /**
     * Constructs a ClockSourceMock with the current time set to the Unix epoch.
     */
    ClockSourceMock() {
        _tracksSystemClock = false;
    }

    Milliseconds getPrecision() override;
    Date_t now() override;
    void setAlarm(Date_t when, unique_function<void()> action) override;

    /**
     * Advances the current time by the given value.
     */
    void advance(Milliseconds ms);

    /**
     * Resets the current time to the given value.
     */
    void reset(Date_t newNow = kInitialNow);
};

/**
 * Mock clock source where reading the clock also advances the current time by a fixed interval.
 */
class AutoAdvancingClockSourceMock : public ClockSourceMock {
public:
    AutoAdvancingClockSourceMock(Milliseconds increment) : _increment(increment) {}

    Date_t now() override {
        ClockSourceMock::advance(_increment);
        return ClockSourceMock::now();
    }

private:
    const Milliseconds _increment;
};

class SharedClockSourceAdapter final : public ClockSource {
public:
    explicit SharedClockSourceAdapter(std::shared_ptr<ClockSource> source)
        : _source(std::move(source)) {
        _tracksSystemClock = _source->tracksSystemClock();
    }

    Milliseconds getPrecision() override {
        return _source->getPrecision();
    }

    Date_t now() override {
        return _source->now();
    }

    void setAlarm(Date_t when, unique_function<void()> action) override {
        _source->setAlarm(when, std::move(action));
    }

private:
    const std::shared_ptr<ClockSource> _source;
};

}  // namespace mongo