#include <gst/gst.h>
#include <glib.h>
#include <stdio.h>

static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer data);
static void on_pad_added(GstElement *element, GstPad *pad, gpointer data);

int main(int argc, char * argv[])
{
    GstElement *source, *demux, *decode, *conv, *sink, *pipeline;
    GMainLoop *loop;
    GstBus *bus;
    guint bus_watch_id;

    gst_init(NULL, NULL);
    loop = g_main_loop_new(NULL, FALSE);

    if (argc != 2)
    {
        g_printerr("Usage: %s <filename>\n", argv[0]);
        return -1;
    }

    source = gst_element_factory_make("filesrc", "op_source");
    demux = gst_element_factory_make("oggdemux", "op_demux");
    decode = gst_element_factory_make("vorbisdec", "op_decode");
    conv = gst_element_factory_make("audioconvert", "op_conv");
    sink = gst_element_factory_make("autoaudiosink", "op_sink");
    pipeline = gst_pipeline_new("op_pipeline");

    if (!source || !demux || !decode || !sink || !pipeline)
    {
        g_printerr("Error creating something!\n");
        return -1;
    }

    g_object_set(G_OBJECT(source), "location", argv[1], NULL);

    bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));
    bus_watch_id = gst_bus_add_watch(bus, bus_call, loop);
    gst_object_unref(bus);

    gst_bin_add_many(GST_BIN(pipeline),
                     source, demux, decode, conv, sink, NULL);

    gst_element_link(source, demux);
    gst_element_link_many(decode, conv, sink, NULL);
    g_signal_connect(demux, "pad-added", G_CALLBACK(on_pad_added), decode);

    g_print("Beginning play\n");
    gst_element_set_state(pipeline, GST_STATE_PLAYING);

    g_print("Starting main loop\n");
    g_main_loop_run(loop);

    g_print("Main loop ended.\n");
    gst_element_set_state(pipeline, GST_STATE_NULL);

    gst_object_unref(GST_OBJECT(pipeline));
    g_source_remove(bus_watch_id);
    g_main_loop_unref(loop);

    return 0;
}

static gboolean bus_call(GstBus *bus, GstMessage *msg, gpointer data)
{
    GMainLoop *loop = (GMainLoop *)data;

    switch (GST_MESSAGE_TYPE(msg))
    {
    case GST_MESSAGE_EOS:
        g_print("End of stream\n");
        g_main_loop_quit(loop);
        break;
    case GST_MESSAGE_ERROR:
        {
            gchar *debug;
            GError *error;

            gst_message_parse_error(msg, &error, &debug);
            g_free(debug);

            g_printerr("Error: %s\n", error->message);
            g_error_free(error);

            g_main_loop_quit(loop);
        }
        break;
    default:
        break;
    }

    return TRUE;
}

static void on_pad_added(GstElement *element, GstPad *pad, gpointer data)
{
    GstPad *sinkpad;
    GstElement *decode = (GstElement *)data;

    g_print("Dynamic pad created, linking demux -> decode\n");

    sinkpad = gst_element_get_static_pad(decode, "sink");
    gst_pad_link(pad, sinkpad);
    gst_object_unref(sinkpad);
}