#include <ros/ros.h>
#include <tf/transform_broadcaster.h>
#include <nav_msgs/Odometry.h>
#include <geometry_msgs/Quaternion.h>
#include <geometry_msgs/TransformStamped.h>
#include <signal.h>

volatile sig_atomic_t flag = 0;

void signal_handler(int signum) {
  flag = 1;
}

int main(int argc, char** argv){
  ros::init(argc, argv, "odometry_publisher");

  // Register the signal handler
  signal(SIGINT, signal_handler);

  ros::NodeHandle n;
  ros::Publisher odom_pub = n.advertise<nav_msgs::Odometry>("odom", 50);
  tf::TransformBroadcaster odom_broadcaster;

  double x = 0.0;
  double y = 0.0;
  double th = 0.0;

  double vx = 0.1;
  double vy = -0.1;
  double vth = 0.1;

  ros::Time current_time, last_time;
  current_time = ros::Time::now();
  last_time = ros::Time::now();

  ros::Rate r(1.0);
  while(ros::ok() && !flag){
    ros::spinOnce();               // check for incoming messages
    current_time = ros::Time::now();

    // Compute odometry
    double dt = (current_time - last_time).toSec();
    double delta_x = (vx * cos(th) - vy * sin(th)) * dt;
    double delta_y = (vx * sin(th) + vy * cos(th)) * dt;
    double delta_th = vth * dt;

    x += delta_x;
    y += delta_y;
    th += delta_th;

    // Create quaternion for orientation
    geometry_msgs::Quaternion odom_quat = tf::createQuaternionMsgFromYaw(th);

    // Publish transform over tf
    geometry_msgs::TransformStamped odom_trans;
    odom_trans.header.stamp = current_time;
    odom_trans.header.frame_id = "odom";
    odom_trans.child_frame_id = "base_link";
    odom_trans.transform.translation.x = x;
    odom_trans.transform.translation.y = y;
    odom_trans.transform.translation.z = 0.0;
    odom_trans.transform.rotation = odom_quat;
    odom_broadcaster.sendTransform(odom_trans);

    // Publish odometry message
    nav_msgs::Odometry odom;
    odom.header.stamp = current_time;
    odom.header.frame_id = "odom";

    // Set position and velocity
    odom.pose.pose.position.x = x;
    odom.pose.pose.position.y = y;
    odom.pose.pose.position.z = 0.0;
    odom.pose.pose.orientation = odom_quat;

    odom.child_frame_id = "base_link";
    odom.twist.twist.linear.x = vx;
    odom.twist.twist.linear.y = vy;
    odom.twist.twist.angular.z = vth;

    odom_pub.publish(odom);

    last_time = current_time;
    r.sleep();
  }

  ROS_INFO("Odometry node shutting down.");
  ros::shutdown();
  return 0;
}