/*
 * Copyright 2024-2025 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 "internal/quic_reactor_wait_ctx.h"
#include "internal/common.h"
#include "internal/thread_arch.h"
#include <assert.h>

struct quic_reactor_wait_slot_st {
    OSSL_LIST_MEMBER(quic_reactor_wait_slot, QUIC_REACTOR_WAIT_SLOT);
    QUIC_REACTOR            *rtor;              /* primary key */
    size_t                  blocking_count;     /* datum */
};

DEFINE_LIST_OF_IMPL(quic_reactor_wait_slot, QUIC_REACTOR_WAIT_SLOT);

void ossl_quic_reactor_wait_ctx_init(QUIC_REACTOR_WAIT_CTX *ctx)
{
    ossl_list_quic_reactor_wait_slot_init(&ctx->slots);
}

static void slot_activate(QUIC_REACTOR_WAIT_SLOT *slot)
{
    if (++slot->blocking_count == 1)
        ossl_quic_reactor_enter_blocking_section(slot->rtor);
}

static void slot_deactivate(QUIC_REACTOR_WAIT_SLOT *slot)
{
    assert(slot->blocking_count > 0);

    if (--slot->blocking_count > 0)
        return;

    ossl_quic_reactor_leave_blocking_section(slot->rtor);
}

int ossl_quic_reactor_wait_ctx_enter(QUIC_REACTOR_WAIT_CTX *ctx,
                                     QUIC_REACTOR *rtor)
{
    QUIC_REACTOR_WAIT_SLOT *slot;

    OSSL_LIST_FOREACH(slot, quic_reactor_wait_slot, &ctx->slots)
        if (slot->rtor == rtor)
            break;

    if (slot == NULL) {
        if ((slot = OPENSSL_zalloc(sizeof(QUIC_REACTOR_WAIT_SLOT))) == NULL)
            return 0;

        slot->rtor = rtor;
        ossl_list_quic_reactor_wait_slot_insert_tail(&ctx->slots, slot);
    }

    slot_activate(slot);
    return 1;
}

void ossl_quic_reactor_wait_ctx_leave(QUIC_REACTOR_WAIT_CTX *ctx,
                                      QUIC_REACTOR *rtor)
{
    QUIC_REACTOR_WAIT_SLOT *slot;

    OSSL_LIST_FOREACH(slot, quic_reactor_wait_slot, &ctx->slots)
        if (slot->rtor == rtor)
            break;

    assert(slot != NULL);
    slot_deactivate(slot);
}

void ossl_quic_reactor_wait_ctx_cleanup(QUIC_REACTOR_WAIT_CTX *ctx)
{
    QUIC_REACTOR_WAIT_SLOT *slot, *nslot;

    OSSL_LIST_FOREACH_DELSAFE(slot, nslot, quic_reactor_wait_slot, &ctx->slots) {
        assert(slot->blocking_count == 0);
        OPENSSL_free(slot);
    }
}