#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"

extern "C" {
    #include <gst/gst.h>
    #include <gst/app/gstappsink.h>
}

#include <iostream>

int main(int argc, char *argv[])
{
    GstElement* playbin = nullptr;
    GstElement* sink = nullptr;
    gchar *uri;

    gst_init (&argc, &argv);

    if (argc < 2) {
        g_print ("usage: %s <media file or uri>\n", argv[0]);
        return 1;
    }

    if (gst_uri_is_valid (argv[1]))
        uri = g_strdup (argv[1]);
    else
        uri = gst_filename_to_uri (argv[1], NULL);

    playbin = gst_element_factory_make ("playbin", NULL);

    if (!playbin) {
        g_print ("'playbin' gstreamer plugin missing\n");
        return 1;
    }

    sink = gst_element_factory_make ("appsink", "appsink");
    GstCaps* sinkcaps = nullptr;
    sinkcaps = gst_caps_new_simple ("video/x-raw",
          "format", G_TYPE_STRING, "GRAY8",
          "width", G_TYPE_INT, 640,
          "height", G_TYPE_INT, 480,
          "framerate", GST_TYPE_FRACTION, 24, 1,
          NULL);
    g_object_set (sink,"caps",sinkcaps,NULL);
    gst_caps_unref (sinkcaps);

    if ( sink == nullptr ){
        g_print("appsink not initialised\n");
        return 1;
    }

    g_object_set (playbin, "uri", uri, NULL);
    g_object_set (playbin, "mute", TRUE, NULL);
    g_object_set (playbin, "video-sink", sink, NULL);
    g_free (uri);

    // loop = g_main_loop_new (NULL, FALSE);
    gst_element_set_state (playbin, GST_STATE_PLAYING);

    GstSample* sample = nullptr;
    cv::VideoWriter writer;
    writer.open("output.avi",CV_FOURCC('X','V','I','D'),24,cv::Size(640,480),true);
    if (!writer.isOpened())
    {
        std::cout << "Error in opening file for video writing" << std::endl;
        return 0;
    }

    do {
        g_signal_emit_by_name (sink, "pull-sample", &sample);
        if ( !sample )
            break;
        // g_print("got sample: %p", sample);
        // GstBuffer *buffer;
        // GstCaps *caps;
        GstStructure *s;
        gint width, height, fps;
        gboolean res;
        /* get the snapshot buffer format now. We set the caps on the appsink so
        * that it can only be an rgb buffer. The only thing we have not specified
        * on the caps is the height, which is dependant on the pixel-aspect-ratio
        * of the source material */
        GstCaps* caps = gst_sample_get_caps (sample);
        if (!caps)
        {
            g_print ("could not get snapshot format\n");
            std::exit (-5);
        }
        s = gst_caps_get_structure (caps, 0);

        // /* we need to get the final caps on the buffer to get the size */
        res = gst_structure_get_int (s, "width", &width);
        res |= gst_structure_get_int (s, "height", &height);
        res |= gst_structure_get_int(s, "framerate", &fps);
        g_print("w: %d, H: %d, F: %d\n",width,height,fps);

        if (!res)
        {
            g_print ("could not get snapshot dimension\n");
            std::exit (-6);
        }
        // g_print("width %d height %d\n",width,height);
        GstBuffer* buffer = gst_sample_get_buffer (sample);
        GstMapInfo map;
        gst_buffer_map (buffer, &map, GST_MAP_READ);
        cv::Mat image(cv::Size(640, 480), CV_8UC3, (char*)map.data, cv::Mat::AUTO_STEP);
        // g_print("Size %lu\n",map.size);
        writer.write(image);
        // cv::imshow("Gstreamer",image);
        // if (cv::waitKey(1000.0/24.0) == 27)
            // break;

        gst_buffer_unmap (buffer, &map);
        gst_sample_unref (sample);

  }
  while (sample != nullptr);

  gst_element_set_state(playbin, GST_STATE_NULL);
  g_object_unref(playbin);
//   g_source_remove(bus_watch_id)


}