/*
 * Copyright (C) Roman Arutyunyan
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


/* static table indices */
#define NGX_HTTP_V3_HEADER_AUTHORITY                 0
#define NGX_HTTP_V3_HEADER_PATH_ROOT                 1
#define NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO       4
#define NGX_HTTP_V3_HEADER_DATE                      6
#define NGX_HTTP_V3_HEADER_LAST_MODIFIED             10
#define NGX_HTTP_V3_HEADER_LOCATION                  12
#define NGX_HTTP_V3_HEADER_METHOD_GET                17
#define NGX_HTTP_V3_HEADER_SCHEME_HTTP               22
#define NGX_HTTP_V3_HEADER_SCHEME_HTTPS              23
#define NGX_HTTP_V3_HEADER_STATUS_200                25
#define NGX_HTTP_V3_HEADER_ACCEPT_ENCODING           31
#define NGX_HTTP_V3_HEADER_CONTENT_TYPE_TEXT_PLAIN   53
#define NGX_HTTP_V3_HEADER_VARY_ACCEPT_ENCODING      59
#define NGX_HTTP_V3_HEADER_ACCEPT_LANGUAGE           72
#define NGX_HTTP_V3_HEADER_SERVER                    92
#define NGX_HTTP_V3_HEADER_USER_AGENT                95


static ngx_int_t ngx_http_v3_process_pseudo_header(ngx_http_request_t *r,
    ngx_str_t *name, ngx_str_t *value);
static ngx_int_t ngx_http_v3_push_resources(ngx_http_request_t *r,
    ngx_chain_t ***out);
static ngx_int_t ngx_http_v3_push_resource(ngx_http_request_t *r,
    ngx_str_t *path, ngx_chain_t ***out);
static ngx_int_t ngx_http_v3_create_push_request(
    ngx_http_request_t *pr, ngx_str_t *path, uint64_t push_id);
static ngx_int_t ngx_http_v3_set_push_header(ngx_http_request_t *r,
    const char *name, ngx_str_t *value);
static void ngx_http_v3_push_request_handler(ngx_event_t *ev);
static ngx_chain_t *ngx_http_v3_create_push_promise(ngx_http_request_t *r,
    ngx_str_t *path, uint64_t push_id);


struct {
    ngx_str_t   name;
    ngx_uint_t  method;
} ngx_http_v3_methods[] = {

    { ngx_string("GET"),       NGX_HTTP_GET },
    { ngx_string("POST"),      NGX_HTTP_POST },
    { ngx_string("HEAD"),      NGX_HTTP_HEAD },
    { ngx_string("OPTIONS"),   NGX_HTTP_OPTIONS },
    { ngx_string("PROPFIND"),  NGX_HTTP_PROPFIND },
    { ngx_string("PUT"),       NGX_HTTP_PUT },
    { ngx_string("MKCOL"),     NGX_HTTP_MKCOL },
    { ngx_string("DELETE"),    NGX_HTTP_DELETE },
    { ngx_string("COPY"),      NGX_HTTP_COPY },
    { ngx_string("MOVE"),      NGX_HTTP_MOVE },
    { ngx_string("PROPPATCH"), NGX_HTTP_PROPPATCH },
    { ngx_string("LOCK"),      NGX_HTTP_LOCK },
    { ngx_string("UNLOCK"),    NGX_HTTP_UNLOCK },
    { ngx_string("PATCH"),     NGX_HTTP_PATCH },
    { ngx_string("TRACE"),     NGX_HTTP_TRACE }
};


ngx_int_t
ngx_http_v3_parse_request(ngx_http_request_t *r, ngx_buf_t *b)
{
    size_t                        len;
    u_char                       *p;
    ngx_int_t                     rc, n;
    ngx_str_t                    *name, *value;
    ngx_connection_t             *c;
    ngx_http_v3_parse_headers_t  *st;

    c = r->connection;
    st = r->h3_parse;

    if (st == NULL) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 parse header");

        st = ngx_pcalloc(c->pool, sizeof(ngx_http_v3_parse_headers_t));
        if (st == NULL) {
            goto failed;
        }

        r->h3_parse = st;
        r->parse_start = b->pos;
        r->state = 1;
    }

    while (b->pos < b->last) {
        rc = ngx_http_v3_parse_headers(c, st, *b->pos);

        if (rc > 0) {
            ngx_http_v3_finalize_connection(c, rc,
                                            "could not parse request headers");
            goto failed;
        }

        if (rc == NGX_ERROR) {
            goto failed;
        }

        if (rc == NGX_BUSY) {
            return NGX_BUSY;
        }

        b->pos++;

        if (rc == NGX_AGAIN) {
            continue;
        }

        name = &st->header_rep.header.name;
        value = &st->header_rep.header.value;

        n = ngx_http_v3_process_pseudo_header(r, name, value);

        if (n == NGX_ERROR) {
            goto failed;
        }

        if (n == NGX_OK && rc == NGX_OK) {
            continue;
        }

        ngx_str_set(&r->http_protocol, "HTTP/3.0");

        len = (r->method_end - r->method_start) + 1
            + (r->uri_end - r->uri_start) + 1
            + sizeof("HTTP/3") - 1;

        p = ngx_pnalloc(c->pool, len);
        if (p == NULL) {
            goto failed;
        }

        r->request_start = p;

        p = ngx_cpymem(p, r->method_start, r->method_end - r->method_start);
        *p++ = ' ';
        p = ngx_cpymem(p, r->uri_start, r->uri_end - r->uri_start);
        *p++ = ' ';
        p = ngx_cpymem(p, "HTTP/3", sizeof("HTTP/3") - 1);

        r->request_end = p;
        r->state = 0;

        return NGX_OK;
    }

    return NGX_AGAIN;

failed:

    return NGX_HTTP_PARSE_INVALID_REQUEST;
}


ngx_int_t
ngx_http_v3_parse_header(ngx_http_request_t *r, ngx_buf_t *b,
    ngx_uint_t allow_underscores)
{
    u_char                        ch;
    ngx_int_t                     rc;
    ngx_str_t                    *name, *value;
    ngx_uint_t                    hash, i, n;
    ngx_connection_t             *c;
    ngx_http_v3_parse_headers_t  *st;
    enum {
        sw_start = 0,
        sw_done,
        sw_next,
        sw_header
    };

    c = r->connection;
    st = r->h3_parse;

    switch (r->state) {

    case sw_start:
        r->parse_start = b->pos;

        if (st->state) {
            r->state = sw_next;
            goto done;
        }

        name = &st->header_rep.header.name;

        if (name->len && name->data[0] != ':') {
            r->state = sw_done;
            goto done;
        }

        /* fall through */

    case sw_done:
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 parse header done");
        return NGX_HTTP_PARSE_HEADER_DONE;

    case sw_next:
        r->parse_start = b->pos;
        r->invalid_header = 0;
        break;

    case sw_header:
        break;
    }

    while (b->pos < b->last) {
        rc = ngx_http_v3_parse_headers(c, st, *b->pos++);

        if (rc > 0) {
            ngx_http_v3_finalize_connection(c, rc,
                                            "could not parse request headers");
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (rc == NGX_ERROR) {
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (rc == NGX_DONE) {
            r->state = sw_done;
            goto done;
        }

        if (rc == NGX_OK) {
            r->state = sw_next;
            goto done;
        }
    }

    r->state = sw_header;
    return NGX_AGAIN;

done:

    name = &st->header_rep.header.name;
    value = &st->header_rep.header.value;

    r->header_name_start = name->data;
    r->header_name_end = name->data + name->len;
    r->header_start = value->data;
    r->header_end = value->data + value->len;

    hash = 0;
    i = 0;

    for (n = 0; n < name->len; n++) {
        ch = name->data[n];

        if (ch >= 'A' && ch <= 'Z') {
            /*
             * A request or response containing uppercase
             * header field names MUST be treated as malformed
             */
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (ch == '\0') {
            return NGX_HTTP_PARSE_INVALID_HEADER;
        }

        if (ch == '_' && !allow_underscores) {
            r->invalid_header = 1;
            continue;
        }

        if ((ch < 'a' || ch > 'z')
            && (ch < '0' || ch > '9')
            && ch != '-' && ch != '_')
        {
            r->invalid_header = 1;
            continue;
        }

        hash = ngx_hash(hash, ch);
        r->lowcase_header[i++] = ch;
        i &= (NGX_HTTP_LC_HEADER_LEN - 1);
    }

    r->header_hash = hash;
    r->lowcase_index = i;

    return NGX_OK;
}


static ngx_int_t
ngx_http_v3_process_pseudo_header(ngx_http_request_t *r, ngx_str_t *name,
    ngx_str_t *value)
{
    ngx_uint_t         i;
    ngx_connection_t  *c;

    if (name->len == 0 || name->data[0] != ':') {
        return NGX_DONE;
    }

    c = r->connection;

    if (name->len == 7 && ngx_strncmp(name->data, ":method", 7) == 0) {
        r->method_start = value->data;
        r->method_end = value->data + value->len;

        for (i = 0; i < sizeof(ngx_http_v3_methods)
                        / sizeof(ngx_http_v3_methods[0]); i++)
        {
            if (value->len == ngx_http_v3_methods[i].name.len
                && ngx_strncmp(value->data, ngx_http_v3_methods[i].name.data,
                               value->len) == 0)
            {
                r->method = ngx_http_v3_methods[i].method;
                break;
            }
        }

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 method \"%V\" %ui", value, r->method);
        return NGX_OK;
    }

    if (name->len == 5 && ngx_strncmp(name->data, ":path", 5) == 0) {
        r->uri_start = value->data;
        r->uri_end = value->data + value->len;

        if (ngx_http_parse_uri(r) != NGX_OK) {
            ngx_log_error(NGX_LOG_INFO, c->log, 0,
                          "client sent invalid :path header: \"%V\"", value);
            return NGX_ERROR;
        }

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 path \"%V\"", value);

        return NGX_OK;
    }

    if (name->len == 7 && ngx_strncmp(name->data, ":scheme", 7) == 0) {
        r->schema_start = value->data;
        r->schema_end = value->data + value->len;

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 schema \"%V\"", value);

        return NGX_OK;
    }

    if (name->len == 10 && ngx_strncmp(name->data, ":authority", 10) == 0) {
        r->host_start = value->data;
        r->host_end = value->data + value->len;

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 authority \"%V\"", value);

        return NGX_OK;
    }

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 unknown pseudo header \"%V\" \"%V\"", name, value);

    return NGX_OK;
}


ngx_int_t
ngx_http_v3_parse_request_body(ngx_http_request_t *r, ngx_buf_t *b,
    ngx_http_chunked_t *ctx)
{
    ngx_int_t                  rc;
    ngx_connection_t          *c;
    ngx_http_v3_parse_data_t  *st;
    enum {
        sw_start = 0,
        sw_skip
    };

    c = r->connection;
    st = ctx->h3_parse;

    if (st == NULL) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 parse request body");

        st = ngx_pcalloc(c->pool, sizeof(ngx_http_v3_parse_data_t));
        if (st == NULL) {
            goto failed;
        }

        ctx->h3_parse = st;
    }

    while (b->pos < b->last && ctx->size == 0) {

        rc = ngx_http_v3_parse_data(c, st, *b->pos++);

        if (rc > 0) {
            ngx_http_v3_finalize_connection(c, rc,
                                            "could not parse request body");
            goto failed;
        }

        if (rc == NGX_ERROR) {
            goto failed;
        }

        if (rc == NGX_AGAIN) {
            ctx->state = sw_skip;
            continue;
        }

        if (rc == NGX_DONE) {
            return NGX_DONE;
        }

        /* rc == NGX_OK */

        ctx->size = st->length;
        ctx->state = sw_start;
    }

    if (ctx->state == sw_skip) {
        ctx->length = 1;
        return NGX_AGAIN;
    }

    if (b->pos == b->last) {
        ctx->length = ctx->size;
        return NGX_AGAIN;
    }

    return NGX_OK;

failed:

    return NGX_ERROR;
}


ngx_chain_t *
ngx_http_v3_create_header(ngx_http_request_t *r)
{
    u_char                    *p;
    size_t                     len, n;
    ngx_buf_t                 *b;
    ngx_str_t                  host;
    ngx_uint_t                 i, port;
    ngx_chain_t               *out, *hl, *cl, **ll;
    ngx_list_part_t           *part;
    ngx_table_elt_t           *header;
    ngx_connection_t          *c;
    ngx_http_core_loc_conf_t  *clcf;
    ngx_http_core_srv_conf_t  *cscf;
    u_char                     addr[NGX_SOCKADDR_STRLEN];

    c = r->connection;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 create header");

    out = NULL;
    ll = &out;

    if ((c->qs->id & NGX_QUIC_STREAM_UNIDIRECTIONAL) == 0
        && r->method != NGX_HTTP_HEAD)
    {
        if (ngx_http_v3_push_resources(r, &ll) != NGX_OK) {
            return NULL;
        }
    }

    len = ngx_http_v3_encode_header_block_prefix(NULL, 0, 0, 0);

    if (r->headers_out.status == NGX_HTTP_OK) {
        len += ngx_http_v3_encode_header_ri(NULL, 0,
                                            NGX_HTTP_V3_HEADER_STATUS_200);

    } else {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                             NGX_HTTP_V3_HEADER_STATUS_200,
                                             NULL, 3);
    }

    clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

    if (r->headers_out.server == NULL) {
        if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_ON) {
            n = sizeof(NGINX_VER) - 1;

        } else if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_BUILD) {
            n = sizeof(NGINX_VER_BUILD) - 1;

        } else {
            n = sizeof("nginx") - 1;
        }

        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                             NGX_HTTP_V3_HEADER_SERVER,
                                             NULL, n);
    }

    if (r->headers_out.date == NULL) {
        len += ngx_http_v3_encode_header_lri(NULL, 0, NGX_HTTP_V3_HEADER_DATE,
                                             NULL, ngx_cached_http_time.len);
    }

    if (r->headers_out.content_type.len) {
        n = r->headers_out.content_type.len;

        if (r->headers_out.content_type_len == r->headers_out.content_type.len
            && r->headers_out.charset.len)
        {
            n += sizeof("; charset=") - 1 + r->headers_out.charset.len;
        }

        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                    NGX_HTTP_V3_HEADER_CONTENT_TYPE_TEXT_PLAIN,
                                    NULL, n);
    }

    if (r->headers_out.content_length == NULL) {
        if (r->headers_out.content_length_n > 0) {
            len += ngx_http_v3_encode_header_lri(NULL, 0,
                                        NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO,
                                        NULL, NGX_OFF_T_LEN);

        } else if (r->headers_out.content_length_n == 0) {
            len += ngx_http_v3_encode_header_ri(NULL, 0,
                                       NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO);
        }
    }

    if (r->headers_out.last_modified == NULL
        && r->headers_out.last_modified_time != -1)
    {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                  NGX_HTTP_V3_HEADER_LAST_MODIFIED, NULL,
                                  sizeof("Mon, 28 Sep 1970 06:00:00 GMT") - 1);
    }

    if (r->headers_out.location
        && r->headers_out.location->value.len
        && r->headers_out.location->value.data[0] == '/'
        && clcf->absolute_redirect)
    {
        r->headers_out.location->hash = 0;

        if (clcf->server_name_in_redirect) {
            cscf = ngx_http_get_module_srv_conf(r, ngx_http_core_module);
            host = cscf->server_name;

        } else if (r->headers_in.server.len) {
            host = r->headers_in.server;

        } else {
            host.len = NGX_SOCKADDR_STRLEN;
            host.data = addr;

            if (ngx_connection_local_sockaddr(c, &host, 0) != NGX_OK) {
                return NULL;
            }
        }

        port = ngx_inet_get_port(c->local_sockaddr);

        n = sizeof("https://") - 1 + host.len
            + r->headers_out.location->value.len;

        if (clcf->port_in_redirect) {
            port = (port == 443) ? 0 : port;

        } else {
            port = 0;
        }

        if (port) {
            n += sizeof(":65535") - 1;
        }

        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                         NGX_HTTP_V3_HEADER_LOCATION, NULL, n);

    } else {
        ngx_str_null(&host);
        port = 0;
    }

#if (NGX_HTTP_GZIP)
    if (r->gzip_vary) {
        if (clcf->gzip_vary) {
            len += ngx_http_v3_encode_header_ri(NULL, 0,
                                      NGX_HTTP_V3_HEADER_VARY_ACCEPT_ENCODING);

        } else {
            r->gzip_vary = 0;
        }
    }
#endif

    part = &r->headers_out.headers.part;
    header = part->elts;

    for (i = 0; /* void */; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }

            part = part->next;
            header = part->elts;
            i = 0;
        }

        if (header[i].hash == 0) {
            continue;
        }

        len += ngx_http_v3_encode_header_l(NULL, &header[i].key,
                                           &header[i].value);
    }

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 header len:%uz", len);

    b = ngx_create_temp_buf(r->pool, len);
    if (b == NULL) {
        return NULL;
    }

    b->last = (u_char *) ngx_http_v3_encode_header_block_prefix(b->last,
                                                                0, 0, 0);

    if (r->headers_out.status == NGX_HTTP_OK) {
        b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                                NGX_HTTP_V3_HEADER_STATUS_200);

    } else {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                 NGX_HTTP_V3_HEADER_STATUS_200,
                                                 NULL, 3);
        b->last = ngx_sprintf(b->last, "%03ui", r->headers_out.status);
    }

    if (r->headers_out.server == NULL) {
        if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_ON) {
            p = (u_char *) NGINX_VER;
            n = sizeof(NGINX_VER) - 1;

        } else if (clcf->server_tokens == NGX_HTTP_SERVER_TOKENS_BUILD) {
            p = (u_char *) NGINX_VER_BUILD;
            n = sizeof(NGINX_VER_BUILD) - 1;

        } else {
            p = (u_char *) "nginx";
            n = sizeof("nginx") - 1;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                     NGX_HTTP_V3_HEADER_SERVER,
                                                     p, n);
    }

    if (r->headers_out.date == NULL) {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                     NGX_HTTP_V3_HEADER_DATE,
                                                     ngx_cached_http_time.data,
                                                     ngx_cached_http_time.len);
    }

    if (r->headers_out.content_type.len) {
        n = r->headers_out.content_type.len;

        if (r->headers_out.content_type_len == r->headers_out.content_type.len
            && r->headers_out.charset.len)
        {
            n += sizeof("; charset=") - 1 + r->headers_out.charset.len;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                    NGX_HTTP_V3_HEADER_CONTENT_TYPE_TEXT_PLAIN,
                                    NULL, n);

        p = b->last;
        b->last = ngx_cpymem(b->last, r->headers_out.content_type.data,
                             r->headers_out.content_type.len);

        if (r->headers_out.content_type_len == r->headers_out.content_type.len
            && r->headers_out.charset.len)
        {
            b->last = ngx_cpymem(b->last, "; charset=",
                                 sizeof("; charset=") - 1);
            b->last = ngx_cpymem(b->last, r->headers_out.charset.data,
                                 r->headers_out.charset.len);

            /* update r->headers_out.content_type for possible logging */

            r->headers_out.content_type.len = b->last - p;
            r->headers_out.content_type.data = p;
        }
    }

    if (r->headers_out.content_length == NULL) {
        if (r->headers_out.content_length_n > 0) {
            p = ngx_sprintf(b->last, "%O", r->headers_out.content_length_n);
            n = p - b->last;

            b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                        NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO,
                                        NULL, n);

            b->last = ngx_sprintf(b->last, "%O",
                                  r->headers_out.content_length_n);

        } else if (r->headers_out.content_length_n == 0) {
            b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                       NGX_HTTP_V3_HEADER_CONTENT_LENGTH_ZERO);
        }
    }

    if (r->headers_out.last_modified == NULL
        && r->headers_out.last_modified_time != -1)
    {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                  NGX_HTTP_V3_HEADER_LAST_MODIFIED, NULL,
                                  sizeof("Mon, 28 Sep 1970 06:00:00 GMT") - 1);

        b->last = ngx_http_time(b->last, r->headers_out.last_modified_time);
    }

    if (host.data) {
        n = sizeof("https://") - 1 + host.len
            + r->headers_out.location->value.len;

        if (port) {
            n += ngx_sprintf(b->last, ":%ui", port) - b->last;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                   NGX_HTTP_V3_HEADER_LOCATION,
                                                   NULL, n);

        p = b->last;
        b->last = ngx_cpymem(b->last, "https://", sizeof("https://") - 1);
        b->last = ngx_cpymem(b->last, host.data, host.len);

        if (port) {
            b->last = ngx_sprintf(b->last, ":%ui", port);
        }

        b->last = ngx_cpymem(b->last, r->headers_out.location->value.data,
                             r->headers_out.location->value.len);

        /* update r->headers_out.location->value for possible logging */

        r->headers_out.location->value.len = b->last - p;
        r->headers_out.location->value.data = p;
        ngx_str_set(&r->headers_out.location->key, "Location");
    }

#if (NGX_HTTP_GZIP)
    if (r->gzip_vary) {
        b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                      NGX_HTTP_V3_HEADER_VARY_ACCEPT_ENCODING);
    }
#endif

    part = &r->headers_out.headers.part;
    header = part->elts;

    for (i = 0; /* void */; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }

            part = part->next;
            header = part->elts;
            i = 0;
        }

        if (header[i].hash == 0) {
            continue;
        }

        b->last = (u_char *) ngx_http_v3_encode_header_l(b->last,
                                                         &header[i].key,
                                                         &header[i].value);
    }

    if (r->header_only) {
        b->last_buf = 1;
    }

    cl = ngx_alloc_chain_link(c->pool);
    if (cl == NULL) {
        return NULL;
    }

    cl->buf = b;
    cl->next = NULL;

    n = b->last - b->pos;

    len = ngx_http_v3_encode_varlen_int(NULL, NGX_HTTP_V3_FRAME_HEADERS)
          + ngx_http_v3_encode_varlen_int(NULL, n);

    b = ngx_create_temp_buf(c->pool, len);
    if (b == NULL) {
        return NULL;
    }

    b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last,
                                                    NGX_HTTP_V3_FRAME_HEADERS);
    b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last, n);

    hl = ngx_alloc_chain_link(c->pool);
    if (hl == NULL) {
        return NULL;
    }

    hl->buf = b;
    hl->next = cl;

    *ll = hl;
    ll = &cl->next;

    if (r->headers_out.content_length_n >= 0 && !r->header_only) {
        len = ngx_http_v3_encode_varlen_int(NULL, NGX_HTTP_V3_FRAME_DATA)
              + ngx_http_v3_encode_varlen_int(NULL,
                                              r->headers_out.content_length_n);

        b = ngx_create_temp_buf(c->pool, len);
        if (b == NULL) {
            return NULL;
        }

        b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last,
                                                       NGX_HTTP_V3_FRAME_DATA);
        b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last,
                                              r->headers_out.content_length_n);

        cl = ngx_alloc_chain_link(c->pool);
        if (cl == NULL) {
            return NULL;
        }

        cl->buf = b;
        cl->next = NULL;

        *ll = cl;
    }

    return out;
}


ngx_chain_t *
ngx_http_v3_create_trailers(ngx_http_request_t *r)
{
    ngx_buf_t    *b;
    ngx_chain_t  *cl;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http3 create trailers");

    /* XXX */

    b = ngx_calloc_buf(r->pool);
    if (b == NULL) {
        return NULL;
    }

    b->last_buf = 1;

    cl = ngx_alloc_chain_link(r->pool);
    if (cl == NULL) {
        return NULL;
    }

    cl->buf = b;
    cl->next = NULL;

    return cl;
}


static ngx_int_t
ngx_http_v3_push_resources(ngx_http_request_t *r, ngx_chain_t ***out)
{
    u_char                     *start, *end, *last;
    ngx_str_t                   path;
    ngx_int_t                   rc;
    ngx_uint_t                  i, push;
    ngx_table_elt_t           **h;
    ngx_http_v3_loc_conf_t     *h3lcf;
    ngx_http_complex_value_t   *pushes;

    h3lcf = ngx_http_get_module_loc_conf(r, ngx_http_v3_module);

    if (h3lcf->pushes) {
        pushes = h3lcf->pushes->elts;

        for (i = 0; i < h3lcf->pushes->nelts; i++) {

            if (ngx_http_complex_value(r, &pushes[i], &path) != NGX_OK) {
                return NGX_ERROR;
            }

            if (path.len == 0) {
                continue;
            }

            if (path.len == 3 && ngx_strncmp(path.data, "off", 3) == 0) {
                continue;
            }

            rc = ngx_http_v3_push_resource(r, &path, out);

            if (rc == NGX_ERROR) {
                return NGX_ERROR;
            }

            if (rc == NGX_ABORT) {
                return NGX_OK;
            }

            /* NGX_OK, NGX_DECLINED */
        }
    }

    if (!h3lcf->push_preload) {
        return NGX_OK;
    }

    h = r->headers_out.link.elts;

    for (i = 0; i < r->headers_out.link.nelts; i++) {

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                       "http3 parse link: \"%V\"", &h[i]->value);

        start = h[i]->value.data;
        end = h[i]->value.data + h[i]->value.len;

    next_link:

        while (start < end && *start == ' ') { start++; }

        if (start == end || *start++ != '<') {
            continue;
        }

        while (start < end && *start == ' ') { start++; }

        for (last = start; last < end && *last != '>'; last++) {
            /* void */
        }

        if (last == start || last == end) {
            continue;
        }

        path.len = last - start;
        path.data = start;

        start = last + 1;

        while (start < end && *start == ' ') { start++; }

        if (start == end) {
            continue;
        }

        if (*start == ',') {
            start++;
            goto next_link;
        }

        if (*start++ != ';') {
            continue;
        }

        last = ngx_strlchr(start, end, ',');

        if (last == NULL) {
            last = end;
        }

        push = 0;

        for ( ;; ) {

            while (start < last && *start == ' ') { start++; }

            if (last - start >= 6
                && ngx_strncasecmp(start, (u_char *) "nopush", 6) == 0)
            {
                start += 6;

                if (start == last || *start == ' ' || *start == ';') {
                    push = 0;
                    break;
                }

                goto next_param;
            }

            if (last - start >= 11
                && ngx_strncasecmp(start, (u_char *) "rel=preload", 11) == 0)
            {
                start += 11;

                if (start == last || *start == ' ' || *start == ';') {
                    push = 1;
                }

                goto next_param;
            }

            if (last - start >= 4
                && ngx_strncasecmp(start, (u_char *) "rel=", 4) == 0)
            {
                start += 4;

                while (start < last && *start == ' ') { start++; }

                if (start == last || *start++ != '"') {
                    goto next_param;
                }

                for ( ;; ) {

                    while (start < last && *start == ' ') { start++; }

                    if (last - start >= 7
                        && ngx_strncasecmp(start, (u_char *) "preload", 7) == 0)
                    {
                        start += 7;

                        if (start < last && (*start == ' ' || *start == '"')) {
                            push = 1;
                            break;
                        }
                    }

                    while (start < last && *start != ' ' && *start != '"') {
                        start++;
                    }

                    if (start == last) {
                        break;
                    }

                    if (*start == '"') {
                        break;
                    }

                    start++;
                }
            }

        next_param:

            start = ngx_strlchr(start, last, ';');

            if (start == NULL) {
                break;
            }

            start++;
        }

        if (push) {
            while (path.len && path.data[path.len - 1] == ' ') {
                path.len--;
            }
        }

        if (push && path.len
            && !(path.len > 1 && path.data[0] == '/' && path.data[1] == '/'))
        {
            rc = ngx_http_v3_push_resource(r, &path, out);

            if (rc == NGX_ERROR) {
                return NGX_ERROR;
            }

            if (rc == NGX_ABORT) {
                return NGX_OK;
            }

            /* NGX_OK, NGX_DECLINED */
        }

        if (last < end) {
            start = last + 1;
            goto next_link;
        }
    }

    return NGX_OK;
}


static ngx_int_t
ngx_http_v3_push_resource(ngx_http_request_t *r, ngx_str_t *path,
    ngx_chain_t ***ll)
{
    uint64_t                   push_id;
    ngx_int_t                  rc;
    ngx_chain_t               *cl;
    ngx_connection_t          *c;
    ngx_http_v3_srv_conf_t    *h3scf;
    ngx_http_v3_connection_t  *h3c;

    c = r->connection;
    h3c = c->qs->parent->data;
    h3scf = ngx_http_get_module_srv_conf(r, ngx_http_v3_module);

    ngx_log_debug5(NGX_LOG_DEBUG_HTTP, c->log, 0,
                   "http3 push \"%V\" pushing:%ui/%ui id:%uL/%uL",
                   path, h3c->npushing, h3scf->max_concurrent_pushes,
                   h3c->next_push_id, h3c->max_push_id);

    if (!ngx_path_separator(path->data[0])) {
        ngx_log_error(NGX_LOG_WARN, c->log, 0,
                      "non-absolute path \"%V\" not pushed", path);
        return NGX_DECLINED;
    }

    if (h3c->next_push_id > h3c->max_push_id) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 abort pushes due to max_push_id");
        return NGX_ABORT;
    }

    if (h3c->npushing >= h3scf->max_concurrent_pushes) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0,
                       "http3 abort pushes due to max_concurrent_pushes");
        return NGX_ABORT;
    }

    push_id = h3c->next_push_id++;

    rc = ngx_http_v3_create_push_request(r, path, push_id);
    if (rc != NGX_OK) {
        return rc;
    }

    cl = ngx_http_v3_create_push_promise(r, path, push_id);
    if (cl == NULL) {
        return NGX_ERROR;
    }

    for (**ll = cl; **ll; *ll = &(**ll)->next);

    return NGX_OK;
}


static ngx_int_t
ngx_http_v3_create_push_request(ngx_http_request_t *pr, ngx_str_t *path,
    uint64_t push_id)
{
    ngx_pool_t                *pool;
    ngx_connection_t          *c, *pc;
    ngx_http_request_t        *r;
    ngx_http_log_ctx_t        *ctx;
    ngx_http_connection_t     *hc;
    ngx_http_core_srv_conf_t  *cscf;
    ngx_http_v3_connection_t  *h3c;

    pc = pr->connection;

    r = NULL;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                   "http3 create push request id:%uL", push_id);

    c = ngx_http_v3_create_push_stream(pc, push_id);
    if (c == NULL) {
        return NGX_ABORT;
    }

    hc = ngx_palloc(c->pool, sizeof(ngx_http_connection_t));
    if (hc == NULL) {
        goto failed;
    }

    h3c = c->qs->parent->data;
    ngx_memcpy(hc, h3c, sizeof(ngx_http_connection_t));
    c->data = hc;

    ctx = ngx_palloc(c->pool, sizeof(ngx_http_log_ctx_t));
    if (ctx == NULL) {
        goto failed;
    }

    ctx->connection = c;
    ctx->request = NULL;
    ctx->current_request = NULL;

    c->log->handler = ngx_http_log_error;
    c->log->data = ctx;
    c->log->action = "processing pushed request headers";

    c->log_error = NGX_ERROR_INFO;

    r = ngx_http_create_request(c);
    if (r == NULL) {
        goto failed;
    }

    c->data = r;

    ngx_str_set(&r->http_protocol, "HTTP/3.0");

    r->method_name = ngx_http_core_get_method;
    r->method = NGX_HTTP_GET;

    cscf = ngx_http_get_module_srv_conf(r, ngx_http_core_module);

    r->header_in = ngx_create_temp_buf(r->pool,
                                       cscf->client_header_buffer_size);
    if (r->header_in == NULL) {
        goto failed;
    }

    if (ngx_list_init(&r->headers_in.headers, r->pool, 4,
                      sizeof(ngx_table_elt_t))
        != NGX_OK)
    {
        goto failed;
    }

    r->headers_in.connection_type = NGX_HTTP_CONNECTION_CLOSE;

    r->schema.data = ngx_pstrdup(r->pool, &pr->schema);
    if (r->schema.data == NULL) {
        goto failed;
    }

    r->schema.len = pr->schema.len;

    r->uri_start = ngx_pstrdup(r->pool, path);
    if (r->uri_start == NULL) {
        goto failed;
    }

    r->uri_end = r->uri_start + path->len;

    if (ngx_http_parse_uri(r) != NGX_OK) {
        goto failed;
    }

    if (ngx_http_process_request_uri(r) != NGX_OK) {
        goto failed;
    }

    if (ngx_http_v3_set_push_header(r, "host", &pr->headers_in.server)
        != NGX_OK)
    {
        goto failed;
    }

    if (pr->headers_in.accept_encoding) {
        if (ngx_http_v3_set_push_header(r, "accept-encoding",
                                        &pr->headers_in.accept_encoding->value)
            != NGX_OK)
        {
            goto failed;
        }
    }

    if (pr->headers_in.accept_language) {
        if (ngx_http_v3_set_push_header(r, "accept-language",
                                        &pr->headers_in.accept_language->value)
            != NGX_OK)
        {
            goto failed;
        }
    }

    if (pr->headers_in.user_agent) {
        if (ngx_http_v3_set_push_header(r, "user-agent",
                                        &pr->headers_in.user_agent->value)
            != NGX_OK)
        {
            goto failed;
        }
    }

    c->read->handler = ngx_http_v3_push_request_handler;
    c->read->handler = ngx_http_v3_push_request_handler;

    ngx_post_event(c->read, &ngx_posted_events);

    return NGX_OK;

failed:

    if (r) {
        ngx_http_free_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
    }

    c->destroyed = 1;

    pool = c->pool;

    ngx_close_connection(c);

    ngx_destroy_pool(pool);

    return NGX_ERROR;
}


static ngx_int_t
ngx_http_v3_set_push_header(ngx_http_request_t *r, const char *name,
    ngx_str_t *value)
{
    u_char                     *p;
    ngx_table_elt_t            *h;
    ngx_http_header_t          *hh;
    ngx_http_core_main_conf_t  *cmcf;

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http3 push header \"%s\": \"%V\"", name, value);

    cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);

    p = ngx_pnalloc(r->pool, value->len + 1);
    if (p == NULL) {
        return NGX_ERROR;
    }

    ngx_memcpy(p, value->data, value->len);
    p[value->len] = '\0';

    h = ngx_list_push(&r->headers_in.headers);
    if (h == NULL) {
        return NGX_ERROR;
    }

    h->key.data = (u_char *) name;
    h->key.len = ngx_strlen(name);
    h->hash = ngx_hash_key(h->key.data, h->key.len);
    h->lowcase_key = (u_char *) name;
    h->value.data = p;
    h->value.len = value->len;

    hh = ngx_hash_find(&cmcf->headers_in_hash, h->hash,
                       h->lowcase_key, h->key.len);

    if (hh && hh->handler(r, h, hh->offset) != NGX_OK) {
        return NGX_ERROR;
    }

    return NGX_OK;
}


static void
ngx_http_v3_push_request_handler(ngx_event_t *ev)
{
    ngx_connection_t    *c;
    ngx_http_request_t  *r;

    c = ev->data;
    r = c->data;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http3 push request handler");

    ngx_http_process_request(r);
}


static ngx_chain_t *
ngx_http_v3_create_push_promise(ngx_http_request_t *r, ngx_str_t *path,
    uint64_t push_id)
{
    size_t        n, len;
    ngx_buf_t    *b;
    ngx_chain_t  *hl, *cl;

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http3 create push promise id:%uL", push_id);

    len = ngx_http_v3_encode_varlen_int(NULL, push_id);

    len += ngx_http_v3_encode_header_block_prefix(NULL, 0, 0, 0);

    len += ngx_http_v3_encode_header_ri(NULL, 0,
                                        NGX_HTTP_V3_HEADER_METHOD_GET);

    len += ngx_http_v3_encode_header_lri(NULL, 0,
                                         NGX_HTTP_V3_HEADER_AUTHORITY,
                                         NULL, r->headers_in.server.len);

    if (path->len == 1 && path->data[0] == '/') {
        len += ngx_http_v3_encode_header_ri(NULL, 0,
                                            NGX_HTTP_V3_HEADER_PATH_ROOT);

    } else {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                             NGX_HTTP_V3_HEADER_PATH_ROOT,
                                             NULL, path->len);
    }

    if (r->schema.len == 5 && ngx_strncmp(r->schema.data, "https", 5) == 0) {
        len += ngx_http_v3_encode_header_ri(NULL, 0,
                                            NGX_HTTP_V3_HEADER_SCHEME_HTTPS);

    } else if (r->schema.len == 4
               && ngx_strncmp(r->schema.data, "http", 4) == 0)
    {
        len += ngx_http_v3_encode_header_ri(NULL, 0,
                                            NGX_HTTP_V3_HEADER_SCHEME_HTTP);

    } else {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                             NGX_HTTP_V3_HEADER_SCHEME_HTTP,
                                             NULL, r->schema.len);
    }

    if (r->headers_in.accept_encoding) {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                     NGX_HTTP_V3_HEADER_ACCEPT_ENCODING, NULL,
                                     r->headers_in.accept_encoding->value.len);
    }

    if (r->headers_in.accept_language) {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                     NGX_HTTP_V3_HEADER_ACCEPT_LANGUAGE, NULL,
                                     r->headers_in.accept_language->value.len);
    }

    if (r->headers_in.user_agent) {
        len += ngx_http_v3_encode_header_lri(NULL, 0,
                                          NGX_HTTP_V3_HEADER_USER_AGENT, NULL,
                                          r->headers_in.user_agent->value.len);
    }

    b = ngx_create_temp_buf(r->pool, len);
    if (b == NULL) {
        return NULL;
    }

    b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last, push_id);

    b->last = (u_char *) ngx_http_v3_encode_header_block_prefix(b->last,
                                                                0, 0, 0);

    b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                                NGX_HTTP_V3_HEADER_METHOD_GET);

    b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                  NGX_HTTP_V3_HEADER_AUTHORITY,
                                                  r->headers_in.server.data,
                                                  r->headers_in.server.len);

    if (path->len == 1 && path->data[0] == '/') {
        b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                                 NGX_HTTP_V3_HEADER_PATH_ROOT);

    } else {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                  NGX_HTTP_V3_HEADER_PATH_ROOT,
                                                  path->data, path->len);
    }

    if (r->schema.len == 5 && ngx_strncmp(r->schema.data, "https", 5) == 0) {
        b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                              NGX_HTTP_V3_HEADER_SCHEME_HTTPS);

    } else if (r->schema.len == 4
               && ngx_strncmp(r->schema.data, "http", 4) == 0)
    {
        b->last = (u_char *) ngx_http_v3_encode_header_ri(b->last, 0,
                                               NGX_HTTP_V3_HEADER_SCHEME_HTTP);

    } else {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                                NGX_HTTP_V3_HEADER_SCHEME_HTTP,
                                                r->schema.data, r->schema.len);
    }

    if (r->headers_in.accept_encoding) {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                     NGX_HTTP_V3_HEADER_ACCEPT_ENCODING,
                                     r->headers_in.accept_encoding->value.data,
                                     r->headers_in.accept_encoding->value.len);
    }

    if (r->headers_in.accept_language) {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                     NGX_HTTP_V3_HEADER_ACCEPT_LANGUAGE,
                                     r->headers_in.accept_language->value.data,
                                     r->headers_in.accept_language->value.len);
    }

    if (r->headers_in.user_agent) {
        b->last = (u_char *) ngx_http_v3_encode_header_lri(b->last, 0,
                                          NGX_HTTP_V3_HEADER_USER_AGENT,
                                          r->headers_in.user_agent->value.data,
                                          r->headers_in.user_agent->value.len);
    }

    cl = ngx_alloc_chain_link(r->pool);
    if (cl == NULL) {
        return NULL;
    }

    cl->buf = b;
    cl->next = NULL;

    n = b->last - b->pos;

    len = ngx_http_v3_encode_varlen_int(NULL, NGX_HTTP_V3_FRAME_PUSH_PROMISE)
          + ngx_http_v3_encode_varlen_int(NULL, n);

    b = ngx_create_temp_buf(r->pool, len);
    if (b == NULL) {
        return NULL;
    }

    b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last,
                                               NGX_HTTP_V3_FRAME_PUSH_PROMISE);
    b->last = (u_char *) ngx_http_v3_encode_varlen_int(b->last, n);

    hl = ngx_alloc_chain_link(r->pool);
    if (hl == NULL) {
        return NULL;
    }

    hl->buf = b;
    hl->next = cl;

    return hl;
}