from math import atan
import numpy as np

class YawController(object):
    def __init__(self, wheel_base, steer_ratio, min_speed, max_lat_accel, max_steer_angle, kp):
        self.wheel_base = wheel_base
        self.steer_ratio = steer_ratio
        self.min_speed = min_speed
        self.max_lat_accel = max_lat_accel

        self.min_angle = -max_steer_angle
        self.max_angle = max_steer_angle

        self.kp = kp


    def get_angle(self, radius):
        angle = atan(self.wheel_base / radius) * self.steer_ratio
        return max(self.min_angle, min(self.max_angle, angle))

    def get_steering(self, linear_velocity, angular_velocity, current_velocity):
        angular_velocity = current_velocity * angular_velocity / linear_velocity if abs(linear_velocity) > 0. else 0.

        if abs(current_velocity) > 0.1:
            max_yaw_rate = abs(self.max_lat_accel / current_velocity);
            angular_velocity = max(-max_yaw_rate, min(max_yaw_rate, angular_velocity))

        return self.get_angle(max(current_velocity, self.min_speed) / angular_velocity) if abs(angular_velocity) > 0. else 0.0;

    def get_steering_P(self, pose, p1, p2):
        # this use closest pt and second closest pt to form a line and calculate
        # offset of the current position and time kp
        # https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line
        d = np.cross(p2-p1, p1-pose) / np.linalg.norm(p2-p1)
        angle = self.kp * d
        return  max(self.min_angle, min(self.max_angle, angle))
