#include <gst/gst.h>
#include <opencv2/opencv.hpp>
#ifdef HAVE_GTK
#include <gtk/gtk.h>
#include <gdk-pixbuf/gdk-pixbuf.h>
#endif

#include <stdlib.h>

#define CAPS "video/x-raw,format=RGB,width=320,pixel-aspect-ratio=1/1"

int main (int argc, char *argv[])
{
	GstElement *pipeline, *sink;
	gint width, height;
	GstSample *sample;
	gchar *descr;
	GError *error = NULL;
	gint64 duration, position;
	GstStateChangeReturn ret;
	gboolean res;
	GstMapInfo map;

	gst_init (&argc, &argv);

	if (argc != 2)
	{
		g_print ("usage: %s <uri>\n Writes snapshot.png in the current directory\n", argv[0]);
		exit (-1);
	}

	/* create a new pipeline */
	descr = g_strdup_printf ("uridecodebin uri=%s ! videoconvert ! videoscale ! appsink name=sink caps=\"" CAPS "\"", argv[1]);
	pipeline = gst_parse_launch (descr, &error);

	if (error != NULL)
	{
		g_print ("could not construct pipeline: %s\n", error->message);
		g_error_free (error);
		exit (-2);
	}

	/* get sink */
	sink = gst_bin_get_by_name (GST_BIN (pipeline), "sink");

	/* set to PAUSED to make the first frame arrive in the sink */
	ret = gst_element_set_state (pipeline, GST_STATE_PAUSED);
	switch (ret)
	{
		case GST_STATE_CHANGE_FAILURE:
			g_print ("failed to play the file\n");
			exit (-1);
		case GST_STATE_CHANGE_NO_PREROLL:
			/* for live sources, we need to set the pipeline to PLAYING before we can
			* receive a buffer. We don't do that yet */
			g_print ("live sources not supported yet\n");
			exit (-3);
		default:
			break;
	}
	/* This can block for up to 5 seconds. If your machine is really overloaded,
	* it might time out before the pipeline prerolled and we generate an error. A
	* better way is to run a mainloop and catch errors there. */
	ret = gst_element_get_state (pipeline, NULL, NULL, 5 * GST_SECOND);
	if (ret == GST_STATE_CHANGE_FAILURE)
	{
		g_print ("failed to play the file\n");
		exit (-4);
	}

	/* get the duration */
	gst_element_query_duration (pipeline, GST_FORMAT_TIME, &duration);

	if (duration != -1)
	/* we have a duration, seek to 5% */
	position = duration * 5 / 100;
	else
	/* no duration, seek to 1 second, this could EOS */
	position = 1 * GST_SECOND;

	/* seek to the a position in the file. Most files have a black first frame so
	* by seeking to somewhere else we have a bigger chance of getting something
	* more interesting. An optimisation would be to detect black images and then
	* seek a little more */
	gst_element_seek_simple (pipeline, GST_FORMAT_TIME, GST_SEEK_FLAG_KEY_UNIT | GST_SEEK_FLAG_FLUSH, position);

	/* get the preroll buffer from appsink, this block untils appsink really
	* prerolls */
	g_signal_emit_by_name (sink, "pull-preroll", &sample, NULL);

	/* if we have a buffer now, convert it to a pixbuf. It's possible that we
	* don't have a buffer because we went EOS right away or had an error. */
	if (sample)
	{
		GstBuffer *buffer;
		GstCaps *caps;
		GstStructure *s;

		/* 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 */
		caps = gst_sample_get_caps (sample);
		if (!caps)
		{
			g_print ("could not get snapshot format\n");
			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);
		if (!res)
		{
			g_print ("could not get snapshot dimension\n");
			exit (-6);
		}

		/* create pixmap from buffer and save, gstreamer video buffers have a stride
		 * that is rounded up to the nearest multiple of 4 */
		buffer = gst_sample_get_buffer (sample);
		gst_buffer_map (buffer, &map, GST_MAP_READ);
		#ifdef HAVE_GTK
			GdkPixbuf *pixbuf = gdk_pixbuf_new_from_data (map.data,
			GDK_COLORSPACE_RGB, FALSE, 8, width, height,
			GST_ROUND_UP_4 (width * 3), NULL, NULL);

			/* save the pixbuf */
			gdk_pixbuf_save (pixbuf, "snapshot.png", "png", &error, NULL);
		#endif
		#ifdef HAVE_OPENCV
			cv::Mat image(cv::Size(width, height), CV_8UC3, (char*)map.data, cv::Mat::AUTO_STEP);
			cv::Mat edges;
			cv::cvtColor(image, edges, CV_RGB2GRAY);
			cv::GaussianBlur(edges, edges, cv::Size(7,7), 1.5, 1.5);
			cv::Canny(edges, edges, 0, 30, 3);
			cv::imwrite("snapshot_edges.png",edges);
		#endif

		gst_buffer_unmap (buffer, &map);
		gst_sample_unref (sample);
	}
	else
	{
		g_print ("could not make snapshot\n");
	}

	/* cleanup and exit */
	gst_element_set_state (pipeline, GST_STATE_NULL);
	gst_object_unref (pipeline);

	exit (0);
}