// -*-eval: (highlight-doxygen-mode 1);-*-
/*
 Copyright (C) 2025 Johannes Randerath

 This file is part of FancyBirds.
 Fancybirds is free software: you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation, either version 3 of the License, or (at your option) any later
 version.

 Fancybirds 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 General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 Foobar. If not, see <https://www.gnu.org/licenses/>.
*/

/**
 * Handling the webcam and stream from the source computer.
 *
 */

#include "gst/gstbin.h"
#include "gst/gstbus.h"
#include "gst/gstclock.h"
#include "gst/gstelement.h"
#include "gst/gstelementfactory.h"
#include "gst/gstmessage.h"
#include "gst/gstobject.h"
#include "gst/gstpipeline.h"
#include "gst/gstutils.h"
#include <gst/gst.h>
#include <ini.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define CONF_KEY(sec, nam) !strcmp(section, sec) && !strcmp(name, nam)

/**
 * Holds main data to be passed around.
 * Used by Gstreamer to communicate data between the different functions and in case of a callback.
 */
typedef struct _CustomData {
  GstElement *pipeline; ///< Gstreamer pipeline holding the stream elements.
  GstElement *source;   ///< This is the video input from the physical webcam.
} CustomData;

/**
 * Holds data read from config ini file.
 * Configuration is to be written to a ini file, which is then read using inih and the results are saved in this struct and read from here whereever needed.
 */
typedef struct _ConfigData {
  GUri *url;      ///< URL of the server to stream to. Must be a valid URI.
  GUri *device;   ///< Device file. Must be an absolute path.
  GUri *ssh_key;  ///< Path to SSH Key used to authenticate with the server.
} ConfigData;

/**
 * Inih callback to save config data.
 * When inih reads the config file, it will call this function once for each value. The function writes the values to the corresponding fields in a ConfigData struct.
 * @param user A pointer to a ConfigData struct for the values to be written to.
 * @param section The name of the ini files section. Used to identify the value.
 * @param name Name of the config value. Used to identify the value.
 * @param value User-defined setting of the configuration value identified by section and name. Set to the appropriate field in ConfigData.
 * @return 0 if successful -1 if not.
 */
static int config_callback(void *user, const char *section, const char *name, const char *value) {

  ConfigData *conf = (ConfigData *)user;
  if (CONF_KEY("v4l2", "device")) {
    char *extended_value = calloc(strlen(value) + strlen("file://") + 1, sizeof(char));
    sprintf(extended_value, "file://%s", value);
    GUri *path = g_uri_parse(extended_value, G_URI_FLAGS_NONE, NULL);
    free(extended_value);
    if (path) {
      conf->device = path;
      return 0;
    }
  }
  if (CONF_KEY("remote", "url")) {
    GUri *uri = g_uri_parse(value, G_URI_FLAGS_NONE, NULL);
    if (uri) {
      conf->url = uri;
      return 0;
    }
  }
  if (CONF_KEY("remote", "ssh-key")) {
    char *extended_value = calloc(strlen(value) + strlen("file://") + 1, sizeof(char));
    sprintf(extended_value, "file://%s", value);
    GUri *path = g_uri_parse(extended_value, G_URI_FLAGS_NONE, NULL);
    free(extended_value);
    if (path) {
      conf->ssh_key = path;
      return 0;
    }
  }
  return -1;
}

int main(int argc, char *argv[]) {
  GstBus *bus;
  GstMessage *msg;
  GstElement *video_queue;
  GstElement *video_convert;
  GstElement *video_sink;
  CustomData data;
  GstStateChangeReturn ret;
  gboolean terminate = FALSE;
  ConfigData conf;

  // Read configuration data from ini file and write to conf. config_callback is called for each value.
  ini_parse("../config.ini", config_callback, &conf);

  // Initialize Gstreamer and set up the pipeline along with its elements.
  gst_init(&argc, &argv);
  data.source = gst_element_factory_make("v4l2src", "source");
  video_queue = gst_element_factory_make("queue", "video_queue");
  video_convert = gst_element_factory_make("videoconvert", "video_convert");
  video_sink = gst_element_factory_make("autovideosink", "video_sink");
  data.pipeline = gst_pipeline_new("media-pipeline");

  if (!data.source || !video_queue || !video_convert || !video_sink || !data.pipeline) {
    g_printerr("Couldn't create all elements.\n");
    return -1;
  }
  // Use the device file specified by configuration as video input source.
  g_object_set(data.source, "device", g_uri_to_string(conf.device) + strlen("file://"), NULL);

  // Add all elements to the pipeline and link them together.
  gst_bin_add_many(GST_BIN(data.pipeline), data.source, video_queue, video_convert, video_sink, NULL);
  if (!gst_element_link_many(data.source, video_queue, video_convert, video_sink, NULL)) {
    g_printerr("Couldn't link stream elements.\n");
    gst_object_unref(data.pipeline);
    return -1;
  }

  // Start streaming.
  ret = gst_element_set_state(data.pipeline, GST_STATE_PLAYING);
  if (ret == GST_STATE_CHANGE_FAILURE) {
    g_printerr("Failed to start playing.\n");
    return -1;
  }

  // Listen to any events we might want to react to.
  bus = gst_element_get_bus(data.pipeline);
  do {
    msg = gst_bus_timed_pop_filtered(bus, GST_CLOCK_TIME_NONE,
				     GST_MESSAGE_STATE_CHANGED |
				     GST_MESSAGE_ERROR |
				     GST_MESSAGE_EOS);

    switch (GST_MESSAGE_TYPE(msg)) {
      // If an error occured, print everything we know and quit.
    case GST_MESSAGE_ERROR: {
      GError *err;
      gchar *debug_info;
      gst_message_parse_error(msg, &err, &debug_info);
      g_printerr("Error received from element %s: %s\n", GST_ELEMENT_NAME(msg->src), err->message);
      g_printerr("Debug info: %s\n", debug_info ? debug_info : "none");

      g_error_free(err);
      g_free(debug_info);
      terminate = TRUE;
      break;
    }
      // Stream is done. Quit.
    case GST_MESSAGE_EOS:
      g_print("End-of-stream reached.\n");
      terminate = TRUE;
      break;
      // For every change in pipeline state, print what happened.
    case GST_MESSAGE_STATE_CHANGED:
      if (GST_MESSAGE_SRC(msg) == GST_OBJECT(data.pipeline)) {
	GstState old_state, new_state, pending_state;
	gst_message_parse_state_changed(msg, &old_state, &new_state, &pending_state);
	g_print("Changed from state %d to state %d\n", old_state, new_state);
      }
      break;
      // Unhandled event. Ignore.
    default:
      break;
    }
    
  }while (!terminate);

  g_free(conf.device);
  g_free(conf.ssh_key);
  g_free(conf.url);
  gst_object_unref(bus);
  gst_element_set_state(data.pipeline, GST_STATE_NULL);
  gst_object_unref(data.pipeline);
  
  return 0;
}