"""This file implements the gym environment of minitaur.

"""

import os
import inspect
currentdir = os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe())))
parentdir = os.path.dirname(os.path.dirname(currentdir))
os.sys.path.insert(0, parentdir)

import math
import time
from pkg_resources import parse_version

import gym
from gym import spaces
from gym.utils import seeding
import numpy as np
import pybullet
import pybullet_utils.bullet_client as bc
from . import minitaur
import pybullet_data
from . import minitaur_env_randomizer

NUM_SUBSTEPS = 5
NUM_MOTORS = 8
MOTOR_ANGLE_OBSERVATION_INDEX = 0
MOTOR_VELOCITY_OBSERVATION_INDEX = MOTOR_ANGLE_OBSERVATION_INDEX + NUM_MOTORS
MOTOR_TORQUE_OBSERVATION_INDEX = MOTOR_VELOCITY_OBSERVATION_INDEX + NUM_MOTORS
BASE_ORIENTATION_OBSERVATION_INDEX = MOTOR_TORQUE_OBSERVATION_INDEX + NUM_MOTORS
ACTION_EPS = 0.01
OBSERVATION_EPS = 0.01
RENDER_HEIGHT = 720
RENDER_WIDTH = 960

duckStartPos = [0, 0, 0.25]
duckStartOrn = [0.5, 0.5, 0.5, 0.5]


class MinitaurBulletDuckEnv(gym.Env):
  """The gym environment for the minitaur.

  It simulates the locomotion of a minitaur, a quadruped robot. The state space
  include the angles, velocities and torques for all the motors and the action
  space is the desired motor angle for each motor. The reward function is based
  on how far the minitaur walks in 1000 steps and penalizes the energy
  expenditure.

  """
  metadata = {"render.modes": ["human", "rgb_array"], "video.frames_per_second": 50}

  def __init__(
      self,
      urdf_root=pybullet_data.getDataPath(),
      action_repeat=1,
      distance_weight=1.0,
      energy_weight=0.005,
      shake_weight=0.0,
      drift_weight=0.0,
      distance_limit=float("inf"),
      observation_noise_stdev=0.0,
      self_collision_enabled=True,
      motor_velocity_limit=np.inf,
      pd_control_enabled=False,  #not needed to be true if accurate motor model is enabled (has its own better PD)
      leg_model_enabled=True,
      accurate_motor_model_enabled=True,
      motor_kp=1.0,
      motor_kd=0.02,
      torque_control_enabled=False,
      motor_overheat_protection=True,
      hard_reset=True,
      on_rack=False,
      render=False,
      kd_for_pd_controllers=0.3,
      env_randomizer=minitaur_env_randomizer.MinitaurEnvRandomizer()):
    """Initialize the minitaur gym environment.

    Args:
      urdf_root: The path to the urdf data folder.
      action_repeat: The number of simulation steps before actions are applied.
      distance_weight: The weight of the distance term in the reward.
      energy_weight: The weight of the energy term in the reward.
      shake_weight: The weight of the vertical shakiness term in the reward.
      drift_weight: The weight of the sideways drift term in the reward.
      distance_limit: The maximum distance to terminate the episode.
      observation_noise_stdev: The standard deviation of observation noise.
      self_collision_enabled: Whether to enable self collision in the sim.
      motor_velocity_limit: The velocity limit of each motor.
      pd_control_enabled: Whether to use PD controller for each motor.
      leg_model_enabled: Whether to use a leg motor to reparameterize the action
        space.
      accurate_motor_model_enabled: Whether to use the accurate DC motor model.
      motor_kp: proportional gain for the accurate motor model.
      motor_kd: derivative gain for the accurate motor model.
      torque_control_enabled: Whether to use the torque control, if set to
        False, pose control will be used.
      motor_overheat_protection: Whether to shutdown the motor that has exerted
        large torque (OVERHEAT_SHUTDOWN_TORQUE) for an extended amount of time
        (OVERHEAT_SHUTDOWN_TIME). See ApplyAction() in minitaur.py for more
        details.
      hard_reset: Whether to wipe the simulation and load everything when reset
        is called. If set to false, reset just place the minitaur back to start
        position and set its pose to initial configuration.
      on_rack: Whether to place the minitaur on rack. This is only used to debug
        the walking gait. In this mode, the minitaur's base is hanged midair so
        that its walking gait is clearer to visualize.
      render: Whether to render the simulation.
      kd_for_pd_controllers: kd value for the pd controllers of the motors
      env_randomizer: An EnvRandomizer to randomize the physical properties
        during reset().
    """
    self._time_step = 0.01
    self._action_repeat = action_repeat
    self._num_bullet_solver_iterations = 300
    self._urdf_root = urdf_root
    self._self_collision_enabled = self_collision_enabled
    self._motor_velocity_limit = motor_velocity_limit
    self._observation = []
    self._env_step_counter = 0
    self._is_render = render
    self._last_base_position = [0, 0, 0]
    self._distance_weight = distance_weight
    self._energy_weight = energy_weight
    self._drift_weight = drift_weight
    self._shake_weight = shake_weight
    self._distance_limit = distance_limit
    self._observation_noise_stdev = observation_noise_stdev
    self._action_bound = 1
    self._pd_control_enabled = pd_control_enabled
    self._leg_model_enabled = leg_model_enabled
    self._accurate_motor_model_enabled = accurate_motor_model_enabled
    self._motor_kp = motor_kp
    self._motor_kd = motor_kd
    self._torque_control_enabled = torque_control_enabled
    self._motor_overheat_protection = motor_overheat_protection
    self._on_rack = on_rack
    self._cam_dist = 1.0
    self._cam_yaw = 0
    self._duckId = -1
    self._cam_pitch = -30
    self._hard_reset = True
    self._kd_for_pd_controllers = kd_for_pd_controllers
    self._last_frame_time = 0.0
    print("urdf_root=" + self._urdf_root)
    self._env_randomizer = env_randomizer
    # PD control needs smaller time step for stability.
    if pd_control_enabled or accurate_motor_model_enabled:
      self._time_step /= NUM_SUBSTEPS
      self._num_bullet_solver_iterations /= NUM_SUBSTEPS
      self._action_repeat *= NUM_SUBSTEPS

    if self._is_render:
      self._pybullet_client = bc.BulletClient(connection_mode=pybullet.GUI)
    else:
      self._pybullet_client = bc.BulletClient()

    self.seed()
    self.reset()
    observation_high = (self.minitaur.GetObservationUpperBound() + OBSERVATION_EPS)
    observation_low = (self.minitaur.GetObservationLowerBound() - OBSERVATION_EPS)
    action_dim = 8
    action_high = np.array([self._action_bound] * action_dim)
    self.action_space = spaces.Box(-action_high, action_high, dtype=np.float32)
    self.observation_space = spaces.Box(observation_low, observation_high, dtype=np.float32)
    self.viewer = None
    self._hard_reset = hard_reset  # This assignment need to be after reset()

  def set_env_randomizer(self, env_randomizer):
    self._env_randomizer = env_randomizer

  def configure(self, args):
    self._args = args

  def reset(self):
    if self._hard_reset:
      self._pybullet_client.resetSimulation()
      self._pybullet_client.setPhysicsEngineParameter(
          numSolverIterations=int(self._num_bullet_solver_iterations))
      self._pybullet_client.setTimeStep(self._time_step)
      self._groundId = self._pybullet_client.loadURDF("%s/plane.urdf" % self._urdf_root)
      self._duckId = self._pybullet_client.loadURDF("%s/duck_vhacd.urdf" % self._urdf_root,
                                                    duckStartPos, duckStartOrn)
      self._pybullet_client.setGravity(0, 0, -10)
      acc_motor = self._accurate_motor_model_enabled
      motor_protect = self._motor_overheat_protection
      self.minitaur = (minitaur.Minitaur(pybullet_client=self._pybullet_client,
                                         urdf_root=self._urdf_root,
                                         time_step=self._time_step,
                                         self_collision_enabled=self._self_collision_enabled,
                                         motor_velocity_limit=self._motor_velocity_limit,
                                         pd_control_enabled=self._pd_control_enabled,
                                         accurate_motor_model_enabled=acc_motor,
                                         motor_kp=self._motor_kp,
                                         motor_kd=self._motor_kd,
                                         torque_control_enabled=self._torque_control_enabled,
                                         motor_overheat_protection=motor_protect,
                                         on_rack=self._on_rack,
                                         kd_for_pd_controllers=self._kd_for_pd_controllers))
    else:
      self.minitaur.Reset(reload_urdf=False)
      self._pybullet_client.resetBasePositionAndOrientation(self._duckId, duckStartPos,
                                                            duckStartOrn)
    if self._env_randomizer is not None:
      self._env_randomizer.randomize_env(self)

    self._env_step_counter = 0
    self._last_base_position = [0, 0, 0]
    self._objectives = []
    self._pybullet_client.resetDebugVisualizerCamera(self._cam_dist, self._cam_yaw,
                                                     self._cam_pitch, [0, 0, 0])
    if not self._torque_control_enabled:
      for _ in range(100):
        if self._pd_control_enabled or self._accurate_motor_model_enabled:
          self.minitaur.ApplyAction([math.pi / 2] * 8)
        self._pybullet_client.stepSimulation()
    return self._noisy_observation()

  def seed(self, seed=None):
    self.np_random, seed = seeding.np_random(seed)
    return [seed]

  def _transform_action_to_motor_command(self, action):
    if self._leg_model_enabled:
      for i, action_component in enumerate(action):
        if not (-self._action_bound - ACTION_EPS <= action_component <=
                self._action_bound + ACTION_EPS):
          raise ValueError("{}th action {} out of bounds.".format(i, action_component))
      action = self.minitaur.ConvertFromLegModel(action)
    return action

  def step(self, action):
    """Step forward the simulation, given the action.

    Args:
      action: A list of desired motor angles for eight motors.

    Returns:
      observations: The angles, velocities and torques of all motors.
      reward: The reward for the current state-action pair.
      done: Whether the episode has ended.
      info: A dictionary that stores diagnostic information.

    Raises:
      ValueError: The action dimension is not the same as the number of motors.
      ValueError: The magnitude of actions is out of bounds.
    """
    if self._is_render:
      # Sleep, otherwise the computation takes less time than real time,
      # which will make the visualization like a fast-forward video.
      time_spent = time.time() - self._last_frame_time
      self._last_frame_time = time.time()
      time_to_sleep = self._action_repeat * self._time_step - time_spent
      if time_to_sleep > 0:
        time.sleep(time_to_sleep)
      base_pos = self.minitaur.GetBasePosition()
      self._pybullet_client.resetDebugVisualizerCamera(self._cam_dist, self._cam_yaw,
                                                       self._cam_pitch, base_pos)
    action = self._transform_action_to_motor_command(action)
    for _ in range(self._action_repeat):
      self.minitaur.ApplyAction(action)
      self._pybullet_client.stepSimulation()

    self._env_step_counter += 1
    reward = self._reward()
    done = self._termination()
    return np.array(self._noisy_observation()), reward, done, {}

  def render(self, mode="rgb_array", close=False):
    if mode != "rgb_array":
      return np.array([])
    base_pos = self.minitaur.GetBasePosition()
    view_matrix = self._pybullet_client.computeViewMatrixFromYawPitchRoll(
        cameraTargetPosition=base_pos,
        distance=self._cam_dist,
        yaw=self._cam_yaw,
        pitch=self._cam_pitch,
        roll=0,
        upAxisIndex=2)
    proj_matrix = self._pybullet_client.computeProjectionMatrixFOV(fov=60,
                                                                   aspect=float(RENDER_WIDTH) /
                                                                   RENDER_HEIGHT,
                                                                   nearVal=0.1,
                                                                   farVal=100.0)
    (_, _, px, _,
     _) = self._pybullet_client.getCameraImage(width=RENDER_WIDTH,
                                               height=RENDER_HEIGHT,
                                               viewMatrix=view_matrix,
                                               projectionMatrix=proj_matrix,
                                               renderer=pybullet.ER_BULLET_HARDWARE_OPENGL)
    rgb_array = np.array(px)
    rgb_array = rgb_array[:, :, :3]
    return rgb_array

  def get_minitaur_motor_angles(self):
    """Get the minitaur's motor angles.

    Returns:
      A numpy array of motor angles.
    """
    return np.array(self._observation[MOTOR_ANGLE_OBSERVATION_INDEX:MOTOR_ANGLE_OBSERVATION_INDEX +
                                      NUM_MOTORS])

  def get_minitaur_motor_velocities(self):
    """Get the minitaur's motor velocities.

    Returns:
      A numpy array of motor velocities.
    """
    return np.array(
        self._observation[MOTOR_VELOCITY_OBSERVATION_INDEX:MOTOR_VELOCITY_OBSERVATION_INDEX +
                          NUM_MOTORS])

  def get_minitaur_motor_torques(self):
    """Get the minitaur's motor torques.

    Returns:
      A numpy array of motor torques.
    """
    return np.array(
        self._observation[MOTOR_TORQUE_OBSERVATION_INDEX:MOTOR_TORQUE_OBSERVATION_INDEX +
                          NUM_MOTORS])

  def get_minitaur_base_orientation(self):
    """Get the minitaur's base orientation, represented by a quaternion.

    Returns:
      A numpy array of minitaur's orientation.
    """
    return np.array(self._observation[BASE_ORIENTATION_OBSERVATION_INDEX:])

  def lost_duck(self):
    points = self._pybullet_client.getContactPoints(self._duckId, self._groundId)
    return len(points) > 0

  def is_fallen(self):
    """Decide whether the minitaur has fallen.

    If the up directions between the base and the world is larger (the dot
    product is smaller than 0.85) or the base is very low on the ground
    (the height is smaller than 0.13 meter), the minitaur is considered fallen.

    Returns:
      Boolean value that indicates whether the minitaur has fallen.
    """
    orientation = self.minitaur.GetBaseOrientation()
    rot_mat = self._pybullet_client.getMatrixFromQuaternion(orientation)
    local_up = rot_mat[6:]
    pos = self.minitaur.GetBasePosition()
    return (np.dot(np.asarray([0, 0, 1]), np.asarray(local_up)) < 0.85 or pos[2] < 0.13)

  def _termination(self):
    position = self.minitaur.GetBasePosition()
    distance = math.sqrt(position[0]**2 + position[1]**2)
    return self.lost_duck() or self.is_fallen() or distance > self._distance_limit

  def _reward(self):
    current_base_position = self.minitaur.GetBasePosition()
    forward_reward = current_base_position[0] - self._last_base_position[0]
    drift_reward = -abs(current_base_position[1] - self._last_base_position[1])
    shake_reward = -abs(current_base_position[2] - self._last_base_position[2])
    self._last_base_position = current_base_position
    energy_reward = np.abs(
        np.dot(self.minitaur.GetMotorTorques(),
               self.minitaur.GetMotorVelocities())) * self._time_step
    reward = (self._distance_weight * forward_reward - self._energy_weight * energy_reward +
              self._drift_weight * drift_reward + self._shake_weight * shake_reward)
    self._objectives.append([forward_reward, energy_reward, drift_reward, shake_reward])
    return reward

  def get_objectives(self):
    return self._objectives

  def _get_observation(self):
    self._observation = self.minitaur.GetObservation()
    return self._observation

  def _noisy_observation(self):
    self._get_observation()
    observation = np.array(self._observation)
    if self._observation_noise_stdev > 0:
      observation += (
          np.random.normal(scale=self._observation_noise_stdev, size=observation.shape) *
          self.minitaur.GetObservationUpperBound())
    return observation

  if parse_version(gym.__version__) < parse_version('0.9.6'):
    _render = render
    _reset = reset
    _seed = seed
    _step = step
