/*

 * Copyright 2022-2026 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_channel.h"

#include "internal/quic_cfq.h"

#include "internal/numbers.h"

typedef struct quic_cfq_item_ex_st QUIC_CFQ_ITEM_EX;

struct quic_cfq_item_ex_st {

    QUIC_CFQ_ITEM public;

    QUIC_CFQ_ITEM_EX *prev, *next;

    unsigned char *encoded;

    cfq_free_cb *free_cb;

    void *free_cb_arg;

    uint64_t frame_type;

    size_t encoded_len;

    uint32_t priority, pn_space, flags;

    int state;

};

uint64_t ossl_quic_cfq_item_get_frame_type(const QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    return ex->frame_type;

}

const unsigned char *ossl_quic_cfq_item_get_encoded(const QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    return ex->encoded;

}

size_t ossl_quic_cfq_item_get_encoded_len(const QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    return ex->encoded_len;

}

int ossl_quic_cfq_item_get_state(const QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    return ex->state;

}

uint32_t ossl_quic_cfq_item_get_pn_space(const QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    return ex->pn_space;

}

int ossl_quic_cfq_item_is_unreliable(const QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    return (ex->flags & QUIC_CFQ_ITEM_FLAG_UNRELIABLE) != 0;

}

typedef struct quic_cfq_item_list_st {

    QUIC_CFQ_ITEM_EX *head, *tail;

} QUIC_CFQ_ITEM_LIST;

struct quic_cfq_st {

    /*

     * Invariant: A CFQ item is always in exactly one of these lists, never more

     * or less than one.

     *

     * Invariant: The list the CFQ item is determined exactly by the state field

     * of the item.

     */

    QUIC_CFQ_ITEM_LIST new_list, tx_list, free_list;

};

static int compare(const QUIC_CFQ_ITEM_EX *a, const QUIC_CFQ_ITEM_EX *b)

{

    if (a->pn_space < b->pn_space)

        return -1;

    else if (a->pn_space > b->pn_space)

        return 1;

    if (a->priority > b->priority)

        return -1;

    else if (a->priority < b->priority)

        return 1;

    return 0;

}

static void list_remove(QUIC_CFQ_ITEM_LIST *l, QUIC_CFQ_ITEM_EX *n)

{

    if (l->head == n)

        l->head = n->next;

    if (l->tail == n)

        l->tail = n->prev;

    if (n->prev != NULL)

        n->prev->next = n->next;

    if (n->next != NULL)

        n->next->prev = n->prev;

    n->prev = n->next = NULL;

}

static void list_insert_head(QUIC_CFQ_ITEM_LIST *l, QUIC_CFQ_ITEM_EX *n)

{

    n->next = l->head;

    n->prev = NULL;

    l->head = n;

    if (n->next != NULL)

        n->next->prev = n;

    if (l->tail == NULL)

        l->tail = n;

}

static void list_insert_tail(QUIC_CFQ_ITEM_LIST *l, QUIC_CFQ_ITEM_EX *n)

{

    n->prev = l->tail;

    n->next = NULL;

    l->tail = n;

    if (n->prev != NULL)

        n->prev->next = n;

    if (l->head == NULL)

        l->head = n;

}

static void list_insert_after(QUIC_CFQ_ITEM_LIST *l,

    QUIC_CFQ_ITEM_EX *ref,

    QUIC_CFQ_ITEM_EX *n)

{

    n->prev = ref;

    n->next = ref->next;

    if (ref->next != NULL)

        ref->next->prev = n;

    ref->next = n;

    if (l->tail == ref)

        l->tail = n;

}

static void list_insert_sorted(QUIC_CFQ_ITEM_LIST *l, QUIC_CFQ_ITEM_EX *n,

    int (*cmp)(const QUIC_CFQ_ITEM_EX *a,

        const QUIC_CFQ_ITEM_EX *b))

{

    QUIC_CFQ_ITEM_EX *p = l->head, *pprev = NULL;

    if (p == NULL) {

        l->head = l->tail = n;

        n->prev = n->next = NULL;

        return;

    }

    for (; p != NULL && cmp(p, n) < 0; pprev = p, p = p->next)

        ;

    if (p == NULL)

        list_insert_tail(l, n);

    else if (pprev == NULL)

        list_insert_head(l, n);

    else

        list_insert_after(l, pprev, n);

}

QUIC_CFQ *ossl_quic_cfq_new(void)

{

    QUIC_CFQ *cfq = OPENSSL_zalloc(sizeof(*cfq));

    if (cfq == NULL)

        return NULL;

    return cfq;

}

static void clear_item(QUIC_CFQ_ITEM_EX *item)

{

    if (item->free_cb != NULL) {

        item->free_cb(item->encoded, item->encoded_len, item->free_cb_arg);

        item->free_cb = NULL;

        item->encoded = NULL;

        item->encoded_len = 0;

    }

    item->state = -1;

}

static void free_list_items(QUIC_CFQ_ITEM_LIST *l)

{

    QUIC_CFQ_ITEM_EX *p, *pnext;

    for (p = l->head; p != NULL; p = pnext) {

        pnext = p->next;

        clear_item(p);

        OPENSSL_free(p);

    }

}

void ossl_quic_cfq_free(QUIC_CFQ *cfq)

{

    if (cfq == NULL)

        return;

    free_list_items(&cfq->new_list);

    free_list_items(&cfq->tx_list);

    free_list_items(&cfq->free_list);

    OPENSSL_free(cfq);

}

static QUIC_CFQ_ITEM_EX *cfq_get_free(QUIC_CFQ *cfq)

{

    QUIC_CFQ_ITEM_EX *item = cfq->free_list.head;

    if (item != NULL)

        return item;

    item = OPENSSL_zalloc(sizeof(*item));

    if (item == NULL)

        return NULL;

    item->state = -1;

    list_insert_tail(&cfq->free_list, item);

    return item;

}

QUIC_CFQ_ITEM *ossl_quic_cfq_add_frame(QUIC_CFQ *cfq,

    uint32_t priority,

    uint32_t pn_space,

    uint64_t frame_type,

    uint32_t flags,

    const unsigned char *encoded,

    size_t encoded_len,

    cfq_free_cb *free_cb,

    void *free_cb_arg)

{

    QUIC_CFQ_ITEM_EX *item = cfq_get_free(cfq);

    if (item == NULL)

        return NULL;

    item->priority = priority;

    item->frame_type = frame_type;

    item->pn_space = pn_space;

    item->encoded = (unsigned char *)encoded;

    item->encoded_len = encoded_len;

    item->free_cb = free_cb;

    item->free_cb_arg = free_cb_arg;

    item->state = QUIC_CFQ_STATE_NEW;

    item->flags = flags;

    list_remove(&cfq->free_list, item);

    list_insert_sorted(&cfq->new_list, item, compare);

    return &item->public;

}

void ossl_quic_cfq_mark_tx(QUIC_CFQ *cfq, QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    switch (ex->state) {

    case QUIC_CFQ_STATE_NEW:

        list_remove(&cfq->new_list, ex);

        list_insert_tail(&cfq->tx_list, ex);

        ex->state = QUIC_CFQ_STATE_TX;

        break;

    case QUIC_CFQ_STATE_TX:

        break; /* nothing to do */

    default:

        assert(0); /* invalid state (e.g. in free state) */

        break;

    }

}

void ossl_quic_cfq_mark_lost(QUIC_CFQ *cfq, QUIC_CFQ_ITEM *item,

    uint32_t priority)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    if (ossl_quic_cfq_item_is_unreliable(item)) {

        ossl_quic_cfq_release(cfq, item);

        return;

    }

    switch (ex->state) {

    case QUIC_CFQ_STATE_NEW:

        if (priority != UINT32_MAX && priority != ex->priority) {

            list_remove(&cfq->new_list, ex);

            ex->priority = priority;

            list_insert_sorted(&cfq->new_list, ex, compare);

        }

        break; /* nothing to do */

    case QUIC_CFQ_STATE_TX:

        if (priority != UINT32_MAX)

            ex->priority = priority;

        list_remove(&cfq->tx_list, ex);

        list_insert_sorted(&cfq->new_list, ex, compare);

        ex->state = QUIC_CFQ_STATE_NEW;

        break;

    default:

        assert(0); /* invalid state (e.g. in free state) */

        break;

    }

}

int ossl_quic_cfq_discard_unreliable(QUIC_CFQ *cfq, QUIC_CFQ_ITEM *item)

{

    int discarded;

    if (ossl_quic_cfq_item_is_unreliable(item)) {

        ossl_quic_cfq_release(cfq, item);

        discarded = 1;

    } else {

        discarded = 0;

    }

    return discarded;

}

/*

 * Releases a CFQ item. The item may be in either state (NEW or TX) prior to the

 * call. The QUIC_CFQ_ITEM pointer must not be used following this call.

 */

void ossl_quic_cfq_release(QUIC_CFQ *cfq, QUIC_CFQ_ITEM *item)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    switch (ex->state) {

    case QUIC_CFQ_STATE_NEW:

        list_remove(&cfq->new_list, ex);

        list_insert_tail(&cfq->free_list, ex);

        clear_item(ex);

        break;

    case QUIC_CFQ_STATE_TX:

        list_remove(&cfq->tx_list, ex);

        list_insert_tail(&cfq->free_list, ex);

        clear_item(ex);

        break;

    default:

        assert(0); /* invalid state (e.g. in free state) */

        break;

    }

}

QUIC_CFQ_ITEM *ossl_quic_cfq_get_priority_head(const QUIC_CFQ *cfq,

    uint32_t pn_space)

{

    QUIC_CFQ_ITEM_EX *item = cfq->new_list.head;

    for (; item != NULL && item->pn_space != pn_space; item = item->next)

        ;

    if (item == NULL)

        return NULL;

    return &item->public;

}

QUIC_CFQ_ITEM *ossl_quic_cfq_item_get_priority_next(const QUIC_CFQ_ITEM *item,

    uint32_t pn_space)

{

    QUIC_CFQ_ITEM_EX *ex = (QUIC_CFQ_ITEM_EX *)item;

    if (ex == NULL)

        return NULL;

    ex = ex->next;

    for (; ex != NULL && ex->pn_space != pn_space; ex = ex->next)

        ;

    if (ex == NULL)

        return NULL; /* ubsan */

    return &ex->public;

}