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  /* Author: Omid Heidari */
  
  #include <moveit/planning_interface/planning_interface.h>
  #include <moveit/planning_scene/planning_scene.h>
  #include <moveit/robot_state/conversions.h>
  
  #include <moveit_msgs/MotionPlanRequest.h>
  
  #include <ros/ros.h>
  
  #include <limits>
  #include <vector>
  #include <Eigen/Geometry>
  #include <unordered_map>
  
  #include "lerp_interface/lerp_interface.h"
  
  namespace lerp_interface
  {
  LERPInterface::LERPInterface(const ros::NodeHandle& nh) : nh_(nh), name_("LERPInterface")
  {
  }
  
  bool LERPInterface::solve(const planning_scene::PlanningSceneConstPtr& planning_scene,
                            const planning_interface::MotionPlanRequest& req,
                            moveit_msgs::MotionPlanDetailedResponse& res)
  {
    // Load the planner-specific parameters
    nh_.getParam("num_steps", num_steps_);
  
    ros::WallTime start_time = ros::WallTime::now();
    moveit::core::RobotModelConstPtr robot_model = planning_scene->getRobotModel();
    moveit::core::RobotStatePtr start_state(new moveit::core::RobotState(robot_model));
    *start_state = planning_scene->getCurrentState();
    const moveit::core::JointModelGroup* joint_model_group = start_state->getJointModelGroup(req.group_name);
    std::vector<std::string> joint_names = joint_model_group->getVariableNames();
    dof_ = joint_names.size();
    std::vector<double> start_joint_values;
    start_state->copyJointGroupPositions(joint_model_group, start_joint_values);
  
    // This planner only supports one goal constriant in the request
    std::vector<moveit_msgs::Constraints> goal_constraints = req.goal_constraints;
    std::vector<moveit_msgs::JointConstraint> goal_joint_constraint = goal_constraints[0].joint_constraints;
  
    std::vector<double> goal_joint_values;
    goal_joint_values.reserve(goal_joint_constraint.size());
  
    for (const auto& constraint : goal_joint_constraint)
    {
      goal_joint_values.push_back(constraint.position);
    }
  
    // ==================== Interpolation
    trajectory_msgs::JointTrajectory joint_trajectory;
    interpolate(joint_names, start_state, joint_model_group, start_joint_values, goal_joint_values, joint_trajectory);
  
    // ==================== feed the response
    res.trajectory.resize(1);
    res.trajectory[0].joint_trajectory.joint_names = joint_names;
    res.trajectory[0].joint_trajectory.header = req.start_state.joint_state.header;
    res.trajectory[0].joint_trajectory = joint_trajectory;
  
    res.error_code.val = moveit_msgs::MoveItErrorCodes::SUCCESS;
    res.processing_time.push_back((ros::WallTime::now() - start_time).toSec());
  
    res.group_name = req.group_name;
    res.trajectory_start.joint_state.name = joint_names;
    res.trajectory_start.joint_state.position = start_joint_values;
  
    return true;
  }
  
  void LERPInterface::interpolate(const std::vector<std::string>& joint_names, moveit::core::RobotStatePtr& rob_state,
                                  const moveit::core::JointModelGroup* joint_model_group,
                                  const std::vector<double>& start_joint_vals, const std::vector<double>& goal_joint_vals,
                                  trajectory_msgs::JointTrajectory& joint_trajectory)
  {
    joint_trajectory.points.resize(num_steps_ + 1);
  
    std::vector<double> dt_vector;
    for (int joint_index = 0; joint_index < dof_; ++joint_index)
    {
      double dt = (goal_joint_vals[joint_index] - start_joint_vals[joint_index]) / num_steps_;
      dt_vector.push_back(dt);
    }
  
    for (int step = 0; step <= num_steps_; ++step)
    {
      std::vector<double> joint_values;
      for (int k = 0; k < dof_; ++k)
      {
        double joint_value = start_joint_vals[k] + step * dt_vector[k];
        joint_values.push_back(joint_value);
      }
      rob_state->setJointGroupPositions(joint_model_group, joint_values);
      rob_state->update();
  
      joint_trajectory.joint_names = joint_names;
      joint_trajectory.points[step].positions = joint_values;
    }
  }
  
  }  // namespace lerp_interface
  