/**
 *    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.
 */

#include "mongo/platform/basic.h"
#include "mongo/stdx/thread.h"
#include "mongo/unittest/unittest.h"
#include "mongo/util/interruptible.h"
#include "mongo/util/time_support.h"

namespace mongo {
namespace {

class DummyInterruptable final : public Interruptible {
    Date_t getDeadline() const override {
        MONGO_UNREACHABLE;
    }
    Status checkForInterruptNoAssert() noexcept override {
        MONGO_UNREACHABLE;
    }
    IgnoreInterruptsState pushIgnoreInterrupts() override {
        MONGO_UNREACHABLE;
    }
    void popIgnoreInterrupts(IgnoreInterruptsState iis) override {
        MONGO_UNREACHABLE;
    }
    DeadlineState pushArtificialDeadline(Date_t deadline, ErrorCodes::Error error) override {
        MONGO_UNREACHABLE;
    }
    void popArtificialDeadline(DeadlineState) override {
        MONGO_UNREACHABLE;
    }
    Date_t getExpirationDateForWaitForValue(Milliseconds waitFor) override {
        return Date_t::now() + waitFor;
    }
    StatusWith<stdx::cv_status> waitForConditionOrInterruptNoAssertUntil(
        stdx::condition_variable& cv, BasicLockableAdapter m, Date_t deadline) noexcept override {
        while (Date_t::now() < deadline) {
            sleepmillis(duration_cast<Milliseconds>(precision).count());
        }
        return stdx::cv_status::timeout;
    }

public:
    const Milliseconds precision = Milliseconds(5);
};

TEST(Interruptible, WaitForConditionOrInterruptTimed) {
    auto interruptible = std::make_unique<DummyInterruptable>();
    const auto sleepFor = Milliseconds(500);

    auto mutex = MONGO_MAKE_LATCH();
    stdx::condition_variable cv;
    stdx::unique_lock<Latch> lk(mutex);
    AtomicWord<Microseconds::rep> waitTimer(0);

    const auto start = Date_t::now();
    Date_t deadline = Date_t::now() + sleepFor;
    interruptible->waitForConditionOrInterruptUntil(cv,
                                                    lk,
                                                    deadline,
                                                    [&, oldWaitTimer = 0]() mutable {
                                                        /**
                                                         * Make sure it never resets the waitTimer.
                                                         * waitTimer should always monotonically
                                                         * increase.
                                                         */
                                                        ASSERT_GTE(waitTimer.load(), oldWaitTimer);
                                                        oldWaitTimer = waitTimer.load();
                                                        return false;
                                                    },
                                                    &waitTimer);
    const auto end = Date_t::now();

    const auto duration = duration_cast<Milliseconds>(end - start);
    ASSERT_GTE(duration + interruptible->precision, sleepFor);
    /**
     * The following assumes the testing environment is not heavily contended.
     * So long as the OS scheduler does not take more than 5~ms to reschedule
     * this thread, the following assertion should pass.
     */
    ASSERT_LTE(duration_cast<Microseconds>(sleepFor).count(),
               waitTimer.load() + duration_cast<Microseconds>(interruptible->precision).count());
    ASSERT_FALSE(interruptible->isWaitingForConditionOrInterrupt());
}

TEST(Interruptible, ZeroWaitTimeForImmediateReturn) {
    auto interruptible = std::make_unique<DummyInterruptable>();
    auto mutex = MONGO_MAKE_LATCH();
    stdx::condition_variable cv;
    stdx::unique_lock<Latch> lk(mutex);
    AtomicWord<Microseconds::rep> waitTimer(0);
    Date_t deadline = Date_t::now() + Milliseconds(100);

    interruptible->waitForConditionOrInterruptUntil(
        cv, lk, deadline, [&]() { return true; }, &waitTimer);
    ASSERT_EQ(waitTimer.load(), 0);
}

}  // namespace
}  // namespace mongo