#include <ros/ros.h>
#include <tf/transform_broadcaster.h>
#include <turtlesim/Pose.h>

std::string turtle_name;

void poseCallback(const turtlesim::PoseConstPtr& msg){
    // 创建tf的广播器
    static tf::TransformBroadcaster br;

    // 初始化tf数据
    tf::Transform transform;
    transform.setOrigin(tf::Vector3(msg->x,msg->y,0.0));
    tf::Quaternion q;
    q.setRPY(0,0,msg->theta);
    transform.setRotation(q);

    // 广播world与海龟坐标系之间的tf数据
    br.sendTransform(tf::StampedTransform(transform, ros::Time::now(),"world",turtle_name));
}

int main(int argc, char** argv){
    // 初始化ros节点
    ros::init(argc,argv,"my_tf_broadcaster");

    // 输入参数作为海龟的名字
    if(argc != 2){
        ROS_ERROR("need turtle name as argument");
        return -1;
    }
    turtle_name = argv[1];

    // 订阅海龟的位置姿态话题
    ros::NodeHandle node;
    ros::Subscribe sub = node.subscribe(turtle_name+"/pose", 10, &poseCallback);

    // 循环等待回调函数
    ros::spin();

    return 0;
}

#include <ros/ros.h>
#include <tf/transform_listener.h>
#include <geometry_msgs/Twist.h>
#include <turtlesim/Spawn.h>

int main(int argc, char** argv){
    // 初始化ros节点
    ros::init(argc,argv,"my_tf_lister");

    // 创建节点句柄
    ros::NodeHandle node;

    // 请求产生turtle2
    ros::service::waitForService("/spawn");
    ros::ServiceClient add_turtle = node.serviceClient<turtlesim::Spawn>("/spawn");
    turtlesim::Spawn srv;
    add_turtle.call(srv);

    // 创建发布 turtle2 速度控制指令的发布者
    ros::Publisher turtle_vel = node.advertise<geometry_msgs::Twist>("/turtle2/cmd_val",10);

    // 创建tf的监听器
    tf::TransformListener listener;

    ros::Rate rate(10.0);
    while(node.ok()){
        // 获取turtle1与turtle2坐标系之间的tf数据
        tf::StampedTransform trandform;
        try{
            listener.waitForTransform("/turtle2", "/turtle", ros::Time(0), ros::Duration(3.0));
            listener.lookupTransform("/turtle2", "turtle1", ros::Time(0), transform);
        }
        catch(tf::TransformException &ex){
            ROS_ERROR("%s",ex.what());
            ros::Duration(1.0).sleep();
            continue;
        }

        // 根据turtle1与turtle2坐标系之间的位置关系，发布turtle2的速度控制指令
        geometry_msgs::Twist vel_msg;
        vel_msg.angular.z = 4.0 * atan2(transform.getOrigin().y(),transform.getOrigin().x())
        vel_msg.linear.x = 0.5 * sqrt(pow(transform.getOrigin().x(),2) + pow(transform.getOrigin().y(),2));
        turtle_vel.publish(vel_msg);

        rate.sleep();
    }
    return 0;
}