/**
 *    Copyright (C) 2024-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.
 */


#include "mongo/util/timer.h"

#include "mongo/unittest/unittest.h"
#include "mongo/util/tick_source_mock.h"

namespace mongo {
namespace {

TEST(TimerTest, Basic) {
    TickSourceMock<Milliseconds> ts;
    Timer timer(&ts);
    ASSERT_TRUE(timer.isRunning());

    ts.advance(Milliseconds(5000));
    ASSERT_EQ(timer.elapsed(), Milliseconds(5000));
    ASSERT_TRUE(timer.isRunning());
}

TEST(TimerTest, PauseUnpause) {
    TickSourceMock<Milliseconds> ts;
    Timer timer(&ts);
    ASSERT_TRUE(timer.isRunning());

    // Test that once the timer is paused, the elapsed time remains unchanged.
    ts.advance(Milliseconds(5000));
    timer.pause();
    ASSERT_FALSE(timer.isRunning());
    ts.advance(Milliseconds(5000));
    ASSERT_EQ(timer.elapsed(), Milliseconds(5000));

    // Test that once a paused timer is resumed, it resumers tracking time again.
    timer.unpause();
    ASSERT_TRUE(timer.isRunning());
    ts.advance(Milliseconds(5000));
    ASSERT_EQ(timer.elapsed(), Milliseconds(10000));

    // Pause and unpause the timer again and check that the elapsed time still correct.
    timer.pause();
    ASSERT_FALSE(timer.isRunning());
    ts.advance(Milliseconds(5000));
    ASSERT_EQ(timer.elapsed(), Milliseconds(10000));
    timer.unpause();
    ASSERT_TRUE(timer.isRunning());
    ts.advance(Milliseconds(5000));
    ASSERT_EQ(timer.elapsed(), Milliseconds(15000));
}

TEST(TimerTest, Reset) {
    TickSourceMock<Milliseconds> ts;
    Timer timer(&ts);
    ASSERT_TRUE(timer.isRunning());

    // Pause the timer.
    ts.advance(Milliseconds(5000));
    timer.pause();
    ASSERT_FALSE(timer.isRunning());
    ts.advance(Milliseconds(5000));
    ASSERT_EQ(timer.elapsed(), Milliseconds(5000));

    // Test that when a timer is reset, it clears all its internal state and restarts the timer.
    timer.reset();
    ASSERT_TRUE(timer.isRunning());
    ASSERT_EQ(timer.elapsed(), Milliseconds(0));
    ts.advance(Milliseconds(5000));
    ASSERT_EQ(timer.elapsed(), Milliseconds(5000));
}

}  // namespace
}  // namespace mongo
