/* example-begin helloworld.c */      
#include <gst/gst.h>
 
 
 GstElement *pipeline = NULL;
 
 static void
 blocked_cb (GstPad *pad, gboolean blocked,
     gpointer user_data)
 {
   gchar *name = gst_pad_get_name (pad);
   if (blocked)
   {
     g_debug ("Pad %s blocked successfully", name);
   }
   else
   {
     g_debug ("Pad %s unblocked successfully", name);
   }
   gst_object_unref (GST_OBJECT (pad));
   g_free (name);
 
 }
 
 /* this function will be called when a block has succeeded, it will unlink the
  * previous sink element and link the new sink element. 
  * It will remove previous sink from pipeline (bin) and add new_sink_ele pipeline
  * 
   .----------.      .-------------.
   | decoder |      | old_sink_ele |
  ...        src -> sink           |
   '----------'\     '-------------'
                \     .--------------.
                 \    | new_sink_ele |
                  -> sink            |
                      '--------------'
 */
 static void
 unlink_and_replace (GstPad *decoder_src_pad, gboolean blocked,
     gpointer user_data_new_sink_ele)
 {
   g_debug ("%s: Blocked pad successfully, unlinking and replacing downstream", G_STRFUNC);
   GstPad *old_sink_ele_sink_pad = NULL;
   old_sink_ele_sink_pad = gst_pad_get_peer (decoder_src_pad);
 
   if (old_sink_ele_sink_pad == NULL)
   {
     return;
   }
 
   GstElement *new_sink_ele = (GstElement *)user_data_new_sink_ele;
   GstElement *old_sink_ele = gst_pad_get_parent_element (old_sink_ele_sink_pad);
 
   if (old_sink_ele == NULL)
   {
     gst_object_unref (GST_OBJECT (old_sink_ele_sink_pad));
     return;
   }
 
   gst_pad_unlink (decoder_src_pad, old_sink_ele_sink_pad);
 
   if (new_sink_ele)
   {
     GstElement *decoder = NULL;
 
     gst_bin_add (GST_BIN (pipeline), new_sink_ele);
 
     decoder = gst_pad_get_parent_element (decoder_src_pad);
     gst_element_link (decoder, new_sink_ele);
 
     gst_element_sync_state_with_parent (new_sink_ele);
 
     gst_object_unref (GST_OBJECT (decoder));
     gst_pad_set_blocked_async (decoder_src_pad, FALSE, blocked_cb, NULL);
     gst_object_unref (GST_OBJECT (new_sink_ele)); // do we need this ?
   }
 
   gst_bin_remove (GST_BIN (pipeline), old_sink_ele);
   gst_object_unref (GST_OBJECT (old_sink_ele_sink_pad));
   gst_object_unref (GST_OBJECT (old_sink_ele));
 }
 
 int 
 main (int argc, char *argv[]) 
 {
   GstElement *filesrc, *decoder, *alsaaudiosink = NULL, *pulseaudiosink = NULL;
   GstPad *decoder_src = NULL;
 
   gst_init(&argc, &argv);
 
   if (argc != 2) {
     g_print ("usage: %s <mp3 filename>\n", argv[0]);
     exit (-1);
   }
 
   /* create a new pipeline to hold the elements */
   pipeline = gst_pipeline_new ("pipeline");
 
   /* create a disk reader */
   filesrc = gst_element_factory_make ("filesrc", "disk_source");
   g_object_set (G_OBJECT (filesrc), "location", argv[1], NULL);
 
   /* now it's time to get the decoder */
   decoder = gst_element_factory_make ("mad", "decoder");
   
 
   /* and an audio sink */
   alsaaudiosink = gst_element_factory_make ("alsasink", "alsa_play_audio");
 
   /* add objects to the main pipeline */
   gst_bin_add_many (GST_BIN (pipeline), filesrc, decoder, alsaaudiosink, NULL);
 
   /* link src to sink */
   gst_element_link(filesrc, decoder);
   gst_element_link(decoder,alsaaudiosink);
 
   /* start playing */
   gst_element_set_state (pipeline, GST_STATE_PLAYING);
 
   static int is_playing = 1;
   static int is_quiting = 0;
   static int is_alsasink = 1;
 
     while (1) {
       if(!(gst_bin_iterate_elements (GST_BIN (pipeline)))) break;
 
     printf("    q:Quit, p:Pause/Play, t:Test: ");
     char ch =0 ;
     ch=getchar();
 
     switch (ch) {
     case 'p':
       if(is_playing)  {
         /* pause */
         gst_element_set_state (pipeline, GST_STATE_PAUSED);
 
       }
       else {
         /* start playing */
         gst_element_set_state (pipeline, GST_STATE_PLAYING);
 
       }
       is_playing = !is_playing;
     break;
     case 't':
       printf("================================================================\n");
       if(is_alsasink) {
 
         decoder_src = gst_element_get_pad (decoder, "src");
         g_debug ("%s (%d): block decoder src pad\n", __FUNCTION__, __LINE__);
         pulseaudiosink = gst_element_factory_make ("pulsesink", "pulse_play_audio");
         gst_pad_set_blocked_async (decoder_src, TRUE, unlink_and_replace, pulseaudiosink);
         
         }
       else {
 
         decoder_src = gst_element_get_pad (decoder, "src");
         g_debug ("%s (%d): block decoder src pad\n", __FUNCTION__, __LINE__);
         alsaaudiosink = gst_element_factory_make ("alsasink", "alsa_play_audio");
         gst_pad_set_blocked_async (decoder_src, TRUE, unlink_and_replace, alsaaudiosink);
 
       }
 
       is_alsasink = !is_alsasink;
     
     break;
     case 'q':
       is_quiting = 1;
     break;
     default:
     break;
     }
 
     if(is_quiting) break;
     
     
       GstFormat fmt = GST_FORMAT_TIME;
       gint64 pos, len;
       
       if (gst_element_query_position (pipeline, &fmt, &pos)
         && gst_element_query_duration (pipeline, &fmt, &len)) {
         g_print ("Time: %" GST_TIME_FORMAT " / %" GST_TIME_FORMAT "\n",
            GST_TIME_ARGS (pos), GST_TIME_ARGS (len));
       }
 
     sleep(2);
   }
   
 
   /* stop the pipeline */
   gst_element_set_state (pipeline, GST_STATE_NULL);
 
   /* we don't need a reference to these objects anymore */
   gst_object_unref (GST_OBJECT (pipeline));
   /* unreffing the pipeline unrefs the contained elements as well */
 
   exit (0);
 }