/*

 * Copyright 2023-2024 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <openssl/macros.h>

#include "quic_local.h"

#include "internal/time.h"

#include "internal/thread.h"

#include "internal/thread_arch.h"

#include "internal/quic_thread_assist.h"

#if !defined(OPENSSL_NO_QUIC_THREAD_ASSIST)

/* Main loop for the QUIC assist thread. */

static unsigned int assist_thread_main(void *arg)

{

    QUIC_THREAD_ASSIST *qta = arg;

    CRYPTO_MUTEX *m = ossl_quic_channel_get_mutex(qta->ch);

    QUIC_REACTOR *rtor;

    ossl_crypto_mutex_lock(m);

    rtor = ossl_quic_channel_get_reactor(qta->ch);

    for (;;) {

        OSSL_TIME deadline;

        if (qta->teardown)

            break;

        deadline = ossl_quic_reactor_get_tick_deadline(rtor);

        if (qta->now_cb != NULL

                && !ossl_time_is_zero(deadline)

                && !ossl_time_is_infinite(deadline)) {

            /*

             * ossl_crypto_condvar_wait_timeout needs to use real time for the

             * deadline

             */

            deadline = ossl_time_add(ossl_time_subtract(deadline,

                                                        qta->now_cb(qta->now_cb_arg)),

                                     ossl_time_now());

        }

        ossl_crypto_condvar_wait_timeout(qta->cv, m, deadline);

        /*

         * We have now been woken up. This can be for one of the following

         * reasons:

         *

         *   - We have been asked to teardown (qta->teardown is set);

         *   - The tick deadline has passed.

         *   - The tick deadline has changed.

         *

         * For robustness, this loop also handles spurious wakeups correctly

         * (which does not require any extra code).

         */

        if (qta->teardown)

            break;

        ossl_quic_reactor_tick(rtor, QUIC_REACTOR_TICK_FLAG_CHANNEL_ONLY);

    }

    ossl_crypto_mutex_unlock(m);

    return 1;

}

int ossl_quic_thread_assist_init_start(QUIC_THREAD_ASSIST *qta,

                                       QUIC_CHANNEL *ch,

                                       OSSL_TIME (*now_cb)(void *arg),

                                       void *now_cb_arg)

{

    CRYPTO_MUTEX *mutex = ossl_quic_channel_get_mutex(ch);

    if (mutex == NULL)

        return 0;

    qta->ch         = ch;

    qta->teardown   = 0;

    qta->joined     = 0;

    qta->now_cb     = now_cb;

    qta->now_cb_arg = now_cb_arg;

    qta->cv = ossl_crypto_condvar_new();

    if (qta->cv == NULL)

        return 0;

    qta->t = ossl_crypto_thread_native_start(assist_thread_main,

                                             qta, /*joinable=*/1);

    if (qta->t == NULL) {

        ossl_crypto_condvar_free(&qta->cv);

        return 0;

    }

    return 1;

}

int ossl_quic_thread_assist_stop_async(QUIC_THREAD_ASSIST *qta)

{

    if (!qta->teardown) {

        qta->teardown = 1;

        ossl_crypto_condvar_signal(qta->cv);

    }

    return 1;

}

int ossl_quic_thread_assist_wait_stopped(QUIC_THREAD_ASSIST *qta)

{

    CRYPTO_THREAD_RETVAL rv;

    CRYPTO_MUTEX *m = ossl_quic_channel_get_mutex(qta->ch);

    if (qta->joined)

        return 1;

    if (!ossl_quic_thread_assist_stop_async(qta))

        return 0;

    ossl_crypto_mutex_unlock(m);

    if (!ossl_crypto_thread_native_join(qta->t, &rv)) {

        ossl_crypto_mutex_lock(m);

        return 0;

    }

    qta->joined = 1;

    ossl_crypto_mutex_lock(m);

    return 1;

}

int ossl_quic_thread_assist_cleanup(QUIC_THREAD_ASSIST *qta)

{

    if (!ossl_assert(qta->joined))

        return 0;

    ossl_crypto_condvar_free(&qta->cv);

    ossl_crypto_thread_native_clean(qta->t);

    qta->ch     = NULL;

    qta->t      = NULL;

    return 1;

}

int ossl_quic_thread_assist_notify_deadline_changed(QUIC_THREAD_ASSIST *qta)

{

    if (qta->teardown)

        return 0;

    ossl_crypto_condvar_signal(qta->cv);

    return 1;

}

#endif