/*
  * Session Announcement Protocol (RFC 2974) demuxer
  * Copyright (c) 2010 Martin Storsjo
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg 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 GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "avformat.h"
 #include "libavutil/avstring.h"
 #include "libavutil/intreadwrite.h"
 #include "network.h"
 #include "os_support.h"
 #include "internal.h"

 #include "avio_internal.h"

 #include "url.h"

 #if HAVE_POLL_H
 #include <poll.h>

 #endif

 #include <sys/time.h>

 
 struct SAPState {
     URLContext *ann_fd;
     AVFormatContext *sdp_ctx;

     AVIOContext sdp_pb;

     uint16_t hash;
     char *sdp;
     int eof;
 };
 
 static int sap_probe(AVProbeData *p)
 {
     if (av_strstart(p->filename, "sap:", NULL))
         return AVPROBE_SCORE_MAX;
     return 0;
 }
 
 static int sap_read_close(AVFormatContext *s)
 {
     struct SAPState *sap = s->priv_data;
     if (sap->sdp_ctx)

         av_close_input_file(sap->sdp_ctx);

     if (sap->ann_fd)

         ffurl_close(sap->ann_fd);

     av_freep(&sap->sdp);
     ff_network_close();
     return 0;
 }
 
 static int sap_read_header(AVFormatContext *s,
                            AVFormatParameters *ap)
 {
     struct SAPState *sap = s->priv_data;
     char host[1024], path[1024], url[1024];
     uint8_t recvbuf[1500];
     int port;
     int ret, i;
     AVInputFormat* infmt;
 
     if (!ff_network_init())
         return AVERROR(EIO);
 
     av_url_split(NULL, 0, NULL, 0, host, sizeof(host), &port,
                  path, sizeof(path), s->filename);
     if (port < 0)
         port = 9875;
 
     if (!host[0]) {
         /* Listen for announcements on sap.mcast.net if no host was specified */
         av_strlcpy(host, "224.2.127.254", sizeof(host));
     }
 
     ff_url_join(url, sizeof(url), "udp", NULL, host, port, "?localport=%d",
                 port);

     ret = ffurl_open(&sap->ann_fd, url, AVIO_FLAG_READ);

     if (ret)
         goto fail;
 
     while (1) {
         int addr_type, auth_len;
         int pos;
 

         ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf) - 1);

         if (ret == AVERROR(EAGAIN))
             continue;
         if (ret < 0)
             goto fail;
         recvbuf[ret] = '\0'; /* Null terminate for easier parsing */
         if (ret < 8) {
             av_log(s, AV_LOG_WARNING, "Received too short packet\n");
             continue;
         }
 
         if ((recvbuf[0] & 0xe0) != 0x20) {
             av_log(s, AV_LOG_WARNING, "Unsupported SAP version packet "
                                       "received\n");
             continue;
         }
 
         if (recvbuf[0] & 0x04) {
             av_log(s, AV_LOG_WARNING, "Received stream deletion "
                                       "announcement\n");
             continue;
         }
         addr_type = recvbuf[0] & 0x10;
         auth_len  = recvbuf[1];
         sap->hash = AV_RB16(&recvbuf[2]);
         pos = 4;
         if (addr_type)
             pos += 16; /* IPv6 */
         else
             pos += 4; /* IPv4 */
         pos += auth_len * 4;
         if (pos + 4 >= ret) {
             av_log(s, AV_LOG_WARNING, "Received too short packet\n");
             continue;
         }
 #define MIME "application/sdp"
         if (strcmp(&recvbuf[pos], MIME) == 0) {
             pos += strlen(MIME) + 1;
         } else if (strncmp(&recvbuf[pos], "v=0\r\n", 5) == 0) {
             // Direct SDP without a mime type
         } else {
             av_log(s, AV_LOG_WARNING, "Unsupported mime type %s\n",
                                       &recvbuf[pos]);
             continue;
         }
 
         sap->sdp = av_strdup(&recvbuf[pos]);
         break;
     }
 
     av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sap->sdp);

     ffio_init_context(&sap->sdp_pb, sap->sdp, strlen(sap->sdp), 0, NULL, NULL,

                   NULL, NULL);
 
     infmt = av_find_input_format("sdp");
     if (!infmt)
         goto fail;
     sap->sdp_ctx = avformat_alloc_context();
     if (!sap->sdp_ctx) {
         ret = AVERROR(ENOMEM);
         goto fail;
     }
     sap->sdp_ctx->max_delay = s->max_delay;

     sap->sdp_ctx->pb        = &sap->sdp_pb;
     ret = avformat_open_input(&sap->sdp_ctx, "temp.sdp", infmt, NULL);

     if (ret < 0)
         goto fail;
     if (sap->sdp_ctx->ctx_flags & AVFMTCTX_NOHEADER)
         s->ctx_flags |= AVFMTCTX_NOHEADER;
     for (i = 0; i < sap->sdp_ctx->nb_streams; i++) {
         AVStream *st = av_new_stream(s, i);
         if (!st) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
         avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
         st->time_base = sap->sdp_ctx->streams[i]->time_base;
     }
 
     return 0;
 
 fail:
     sap_read_close(s);
     return ret;
 }
 
 static int sap_fetch_packet(AVFormatContext *s, AVPacket *pkt)
 {
     struct SAPState *sap = s->priv_data;

     int fd = ffurl_get_file_handle(sap->ann_fd);

     int n, ret;

     struct pollfd p = {fd, POLLIN, 0};

     uint8_t recvbuf[1500];
 
     if (sap->eof)
         return AVERROR_EOF;
 
     while (1) {

         n = poll(&p, 1, 0);
         if (n <= 0 || !(p.revents & POLLIN))

             break;

         ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf));

         if (ret >= 8) {
             uint16_t hash = AV_RB16(&recvbuf[2]);
             /* Should ideally check the source IP address, too */
             if (recvbuf[0] & 0x04 && hash == sap->hash) {
                 /* Stream deletion */
                 sap->eof = 1;
                 return AVERROR_EOF;
             }
         }
     }
     ret = av_read_frame(sap->sdp_ctx, pkt);
     if (ret < 0)
         return ret;
     if (s->ctx_flags & AVFMTCTX_NOHEADER) {
         while (sap->sdp_ctx->nb_streams > s->nb_streams) {
             int i = s->nb_streams;
             AVStream *st = av_new_stream(s, i);
             if (!st) {
                 av_free_packet(pkt);
                 return AVERROR(ENOMEM);
             }
             avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
             st->time_base = sap->sdp_ctx->streams[i]->time_base;
         }
     }
     return ret;
 }
 

 AVInputFormat ff_sap_demuxer = {

     "sap",
     NULL_IF_CONFIG_SMALL("SAP input format"),
     sizeof(struct SAPState),
     sap_probe,
     sap_read_header,
     sap_fetch_packet,
     sap_read_close,
     .flags = AVFMT_NOFILE,
 };