#
# Copyright (c) 2017 Intel Corporation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

import gym
import numpy as np
import scipy.ndimage

from rl_coach.graph_managers.graph_manager import ScheduleParameters
from rl_coach.utils import lower_under_to_upper, short_dynamic_import

try:
    import roboschool
    from OpenGL import GL
except ImportError:
    from rl_coach.logger import failed_imports
    failed_imports.append("RoboSchool")

try:
    from rl_coach.gym_extensions.continuous import mujoco
except:
    from rl_coach.logger import failed_imports
    failed_imports.append("GymExtensions")

try:
    import pybullet_envs
except ImportError:
    from rl_coach.logger import failed_imports
    failed_imports.append("PyBullet")

from typing import Dict, Any, Union
from rl_coach.core_types import RunPhase, EnvironmentSteps
from rl_coach.environments.environment import Environment, EnvironmentParameters, LevelSelection
from rl_coach.spaces import DiscreteActionSpace, BoxActionSpace, ImageObservationSpace, VectorObservationSpace, \
    StateSpace, RewardSpace
from rl_coach.filters.filter import NoInputFilter, NoOutputFilter
from rl_coach.filters.reward.reward_clipping_filter import RewardClippingFilter
from rl_coach.filters.observation.observation_rescale_to_size_filter import ObservationRescaleToSizeFilter
from rl_coach.filters.observation.observation_stacking_filter import ObservationStackingFilter
from rl_coach.filters.observation.observation_rgb_to_y_filter import ObservationRGBToYFilter
from rl_coach.filters.observation.observation_to_uint8_filter import ObservationToUInt8Filter
from rl_coach.filters.filter import InputFilter
import random
from rl_coach.base_parameters import VisualizationParameters
from rl_coach.logger import screen


# Parameters
class GymEnvironmentParameters(EnvironmentParameters):
    def __init__(self, level=None):
        super().__init__(level=level)
        self.random_initialization_steps = 0
        self.max_over_num_frames = 1
        self.additional_simulator_parameters = {}

    @property
    def path(self):
        return 'rl_coach.environments.gym_environment:GymEnvironment'


# Generic parameters for vector environments such as mujoco, roboschool, bullet, etc.
class GymVectorEnvironment(GymEnvironmentParameters):
    def __init__(self, level=None):
        super().__init__(level=level)
        self.frame_skip = 1
        self.default_input_filter = NoInputFilter()
        self.default_output_filter = NoOutputFilter()


# Roboschool
gym_roboschool_envs = ['inverted_pendulum', 'inverted_pendulum_swingup', 'inverted_double_pendulum', 'reacher',
                       'hopper', 'walker2d', 'half_cheetah', 'ant', 'humanoid', 'humanoid_flagrun',
                       'humanoid_flagrun_harder', 'pong']
roboschool_v0 = {e: "{}".format(lower_under_to_upper(e) + '-v0') for e in gym_roboschool_envs}

# Mujoco
gym_mujoco_envs = ['inverted_pendulum', 'inverted_double_pendulum', 'reacher', 'hopper', 'walker2d', 'half_cheetah',
                   'ant', 'swimmer', 'humanoid', 'humanoid_standup', 'pusher', 'thrower', 'striker']

mujoco_v2 = {e: "{}".format(lower_under_to_upper(e) + '-v2') for e in gym_mujoco_envs}
mujoco_v2['walker2d'] = 'Walker2d-v2'

# Fetch
gym_fetch_envs = ['reach', 'slide', 'push', 'pick_and_place']
fetch_v1 = {e: "{}".format('Fetch' + lower_under_to_upper(e) + '-v1') for e in gym_fetch_envs}


"""
Atari Environment Components
"""

AtariInputFilter = InputFilter(is_a_reference_filter=True)
AtariInputFilter.add_reward_filter('clipping', RewardClippingFilter(-1.0, 1.0))
AtariInputFilter.add_observation_filter('observation', 'rescaling',
                                        ObservationRescaleToSizeFilter(ImageObservationSpace(np.array([84, 84, 3]),
                                                                                             high=255)))
AtariInputFilter.add_observation_filter('observation', 'to_grayscale', ObservationRGBToYFilter())
AtariInputFilter.add_observation_filter('observation', 'to_uint8', ObservationToUInt8Filter(0, 255))
AtariInputFilter.add_observation_filter('observation', 'stacking', ObservationStackingFilter(4))
AtariOutputFilter = NoOutputFilter()


class Atari(GymEnvironmentParameters):
    def __init__(self, level=None):
        super().__init__(level=level)
        self.frame_skip = 4
        self.max_over_num_frames = 2
        self.random_initialization_steps = 30
        self.default_input_filter = AtariInputFilter
        self.default_output_filter = AtariOutputFilter


gym_atari_envs = ['air_raid', 'alien', 'amidar', 'assault', 'asterix', 'asteroids', 'atlantis',
                  'bank_heist', 'battle_zone', 'beam_rider', 'berzerk', 'bowling', 'boxing', 'breakout', 'carnival',
                  'centipede', 'chopper_command', 'crazy_climber', 'demon_attack', 'double_dunk',
                  'elevator_action', 'enduro', 'fishing_derby', 'freeway', 'frostbite', 'gopher', 'gravitar',
                  'hero', 'ice_hockey', 'jamesbond', 'journey_escape', 'kangaroo', 'krull', 'kung_fu_master',
                  'montezuma_revenge', 'ms_pacman', 'name_this_game', 'phoenix', 'pitfall', 'pong', 'pooyan',
                  'private_eye', 'qbert', 'riverraid', 'road_runner', 'robotank', 'seaquest', 'skiing',
                  'solaris', 'space_invaders', 'star_gunner', 'tennis', 'time_pilot', 'tutankham', 'up_n_down',
                  'venture', 'video_pinball', 'wizard_of_wor', 'yars_revenge', 'zaxxon']
atari_deterministic_v4 = {e: "{}".format(lower_under_to_upper(e) + 'Deterministic-v4') for e in gym_atari_envs}
atari_no_frameskip_v4 = {e: "{}".format(lower_under_to_upper(e) + 'NoFrameskip-v4') for e in gym_atari_envs}


# default atari schedule used in the DeepMind papers
atari_schedule = ScheduleParameters()
atari_schedule.improve_steps = EnvironmentSteps(50000000)
atari_schedule.steps_between_evaluation_periods = EnvironmentSteps(250000)
atari_schedule.evaluation_steps = EnvironmentSteps(135000)
atari_schedule.heatup_steps = EnvironmentSteps(50000)


class MaxOverFramesAndFrameskipEnvWrapper(gym.Wrapper):
    def __init__(self, env, frameskip=4, max_over_num_frames=2):
        super().__init__(env)
        self.max_over_num_frames = max_over_num_frames
        self.observations_stack = []
        self.frameskip = frameskip
        self.first_frame_to_max_over = self.frameskip - self.max_over_num_frames

    def reset(self):
        return self.env.reset()

    def step(self, action):
        total_reward = 0.0
        done = None
        info = None
        self.observations_stack = []
        for i in range(self.frameskip):
            observation, reward, done, info = self.env.step(action)
            if i >= self.first_frame_to_max_over:
                self.observations_stack.append(observation)
            total_reward += reward
            if done:
                # deal with last state in episode
                if not self.observations_stack:
                    self.observations_stack.append(observation)
                break

        max_over_frames_observation = np.max(self.observations_stack, axis=0)

        return max_over_frames_observation, total_reward, done, info


# Environment
class GymEnvironment(Environment):
    def __init__(self, level: LevelSelection, frame_skip: int, visualization_parameters: VisualizationParameters,
                 target_success_rate: float=1.0, additional_simulator_parameters: Dict[str, Any] = {}, seed: Union[None, int]=None,
                 human_control: bool=False, custom_reward_threshold: Union[int, float]=None,
                 random_initialization_steps: int=1, max_over_num_frames: int=1, **kwargs):
        super().__init__(level, seed, frame_skip, human_control, custom_reward_threshold,
                         visualization_parameters, target_success_rate)

        self.random_initialization_steps = random_initialization_steps
        self.max_over_num_frames = max_over_num_frames
        self.additional_simulator_parameters = additional_simulator_parameters

        # hide warnings
        gym.logger.set_level(40)

        """
        load and initialize environment
        environment ids can be defined in 3 ways:
        1. Native gym environments like BreakoutDeterministic-v0 for example
        2. Custom gym environments written and installed as python packages.
           This environments should have a python module with a class inheriting gym.Env, implementing the
           relevant functions (_reset, _step, _render) and defining the observation and action space
           For example: my_environment_package:MyEnvironmentClass will run an environment defined in the
           MyEnvironmentClass class
        3. Custom gym environments written as an independent module which is not installed.
           This environments should have a python module with a class inheriting gym.Env, implementing the
           relevant functions (_reset, _step, _render) and defining the observation and action space.
           For example: path_to_my_environment.sub_directory.my_module:MyEnvironmentClass will run an
           environment defined in the MyEnvironmentClass class which is located in the module in the relative path
           path_to_my_environment.sub_directory.my_module
        """
        if ':' in self.env_id:
            # custom environments
            if '/' in self.env_id or '.' in self.env_id:
                # environment in a an absolute path module written as a unix path or in a relative path module
                # written as a python import path
                env_class = short_dynamic_import(self.env_id)
            else:
                # environment in a python package
                env_class = gym.envs.registration.load(self.env_id)

            # instantiate the environment
            try:
                self.env = env_class(**self.additional_simulator_parameters)
            except:
                screen.error("Failed to instantiate Gym environment class %s with arguments %s" %
                             (env_class, self.additional_simulator_parameters), crash=False)
                raise
        else:
            self.env = gym.make(self.env_id)

        # for classic control we want to use the native renderer because otherwise we will get 2 renderer windows
        environment_to_always_use_with_native_rendering = ['classic_control', 'mujoco', 'robotics']
        self.native_rendering = self.native_rendering or \
                                any([env in str(self.env.unwrapped.__class__)
                                     for env in environment_to_always_use_with_native_rendering])
        if self.native_rendering:
            if hasattr(self, 'renderer'):
                self.renderer.close()

        # seed
        if self.seed is not None:
            self.env.seed(self.seed)
            np.random.seed(self.seed)
            random.seed(self.seed)

        # frame skip and max between consecutive frames
        self.is_robotics_env = 'robotics' in str(self.env.unwrapped.__class__)
        self.is_mujoco_env = 'mujoco' in str(self.env.unwrapped.__class__)
        self.is_atari_env = 'Atari' in str(self.env.unwrapped.__class__)
        self.timelimit_env_wrapper = self.env
        if self.is_atari_env:
            self.env.unwrapped.frameskip = 1  # this accesses the atari env that is wrapped with a timelimit wrapper env
            if self.env_id == "SpaceInvadersDeterministic-v4" and self.frame_skip == 4:
                screen.warning("Warning: The frame-skip for Space Invaders was automatically updated from 4 to 3. "
                               "This is following the DQN paper where it was noticed that a frame-skip of 3 makes the "
                               "laser rays disappear. To force frame-skip of 4, please use SpaceInvadersNoFrameskip-v4.")
                self.frame_skip = 3
            self.env = MaxOverFramesAndFrameskipEnvWrapper(self.env,
                                                           frameskip=self.frame_skip,
                                                           max_over_num_frames=self.max_over_num_frames)
        else:
            self.env.unwrapped.frameskip = self.frame_skip

        self.state_space = StateSpace({})

        # observations
        if not isinstance(self.env.observation_space, gym.spaces.dict_space.Dict):
            state_space = {'observation': self.env.observation_space}
        else:
            state_space = self.env.observation_space.spaces

        for observation_space_name, observation_space in state_space.items():
            if len(observation_space.shape) == 3:
                # we assume gym has image observations (with arbitrary number of channels) where their values are
                # within 0-255, and where the channel dimension is the last dimension
                self.state_space[observation_space_name] = ImageObservationSpace(
                    shape=np.array(observation_space.shape),
                    high=255,
                    channels_axis=-1
                )
            else:
                self.state_space[observation_space_name] = VectorObservationSpace(
                    shape=observation_space.shape[0],
                    low=observation_space.low,
                    high=observation_space.high
                )
        if 'desired_goal' in state_space.keys():
            self.goal_space = self.state_space['desired_goal']

        # actions
        if type(self.env.action_space) == gym.spaces.box.Box:
            self.action_space = BoxActionSpace(
                shape=self.env.action_space.shape,
                low=self.env.action_space.low,
                high=self.env.action_space.high
            )
        elif type(self.env.action_space) == gym.spaces.discrete.Discrete:
            actions_description = []
            if hasattr(self.env.unwrapped, 'get_action_meanings'):
                actions_description = self.env.unwrapped.get_action_meanings()
            self.action_space = DiscreteActionSpace(
                num_actions=self.env.action_space.n,
                descriptions=actions_description
            )

        if self.human_control:
            # TODO: add this to the action space
            # map keyboard keys to actions
            self.key_to_action = {}
            if hasattr(self.env.unwrapped, 'get_keys_to_action'):
                self.key_to_action = self.env.unwrapped.get_keys_to_action()
            else:
                screen.error("Error: Environment {} does not support human control.".format(self.env), crash=True)

        # initialize the state by getting a new state from the environment
        self.reset_internal_state(True)

        # render
        if self.is_rendered:
            image = self.get_rendered_image()
            scale = 1
            if self.human_control:
                scale = 2
            if not self.native_rendering:
                self.renderer.create_screen(image.shape[1]*scale, image.shape[0]*scale)

        # measurements
        if self.env.spec is not None:
            self.timestep_limit = self.env.spec.timestep_limit
        else:
            self.timestep_limit = None

        # the info is only updated after the first step
        self.state = self.step(self.action_space.default_action).next_state
        self.state_space['measurements'] = VectorObservationSpace(shape=len(self.info.keys()))

        if self.env.spec and custom_reward_threshold is None:
                self.reward_success_threshold = self.env.spec.reward_threshold
                self.reward_space = RewardSpace(1, reward_success_threshold=self.reward_success_threshold)

        self.target_success_rate = target_success_rate

    def _wrap_state(self, state):
        if not isinstance(self.env.observation_space, gym.spaces.Dict):
            return {'observation': state}
        return state

    def _update_state(self):
        if self.is_atari_env and hasattr(self, 'current_ale_lives') \
                and self.current_ale_lives != self.env.unwrapped.ale.lives():
            if self.phase == RunPhase.TRAIN or self.phase == RunPhase.HEATUP:
                # signal termination for life loss
                self.done = True
            elif self.phase == RunPhase.TEST and not self.done:
                # the episode is not terminated in evaluation, but we need to press fire again
                self._press_fire()
            self._update_ale_lives()
        # TODO: update the measurements
        if self.state and "desired_goal" in self.state.keys():
            self.goal = self.state['desired_goal']

    def _take_action(self, action):
        if type(self.action_space) == BoxActionSpace:
            action = self.action_space.clip_action_to_space(action)

        self.state, self.reward, self.done, self.info = self.env.step(action)
        self.state = self._wrap_state(self.state)

    def _random_noop(self):
        # simulate a random initial environment state by stepping for a random number of times between 0 and 30
        step_count = 0
        random_initialization_steps = random.randint(0, self.random_initialization_steps)
        while self.action_space is not None and (self.state is None or step_count < random_initialization_steps):
            step_count += 1
            self.step(self.action_space.default_action)

    def _press_fire(self):
        fire_action = 1
        if self.is_atari_env and self.env.unwrapped.get_action_meanings()[fire_action] == 'FIRE':
            self.current_ale_lives = self.env.unwrapped.ale.lives()
            self.step(fire_action)
            if self.done:
                self.reset_internal_state()

    def _update_ale_lives(self):
        if self.is_atari_env:
            self.current_ale_lives = self.env.unwrapped.ale.lives()

    def _restart_environment_episode(self, force_environment_reset=False):
        # prevent reset of environment if there are ale lives left
        if (self.is_atari_env and self.env.unwrapped.ale.lives() > 0) \
                and not force_environment_reset and not self.timelimit_env_wrapper._past_limit():
            self.step(self.action_space.default_action)
        else:
            self.state = self.env.reset()
            self.state = self._wrap_state(self.state)
            self._update_ale_lives()

        if self.is_atari_env:
            self._random_noop()
            self._press_fire()

        # initialize the number of lives
        self._update_ale_lives()

    def _set_mujoco_camera(self, camera_idx: int):
        """
        This function can be used to set the camera for rendering the mujoco simulator
        :param camera_idx: The index of the camera to use. Should be defined in the model
        :return: None
        """
        if self.env.unwrapped.viewer is not None and self.env.unwrapped.viewer.cam.fixedcamid != camera_idx and\
                self.env.unwrapped.viewer._ncam > camera_idx:
            from mujoco_py.generated import const
            self.env.unwrapped.viewer.cam.type = const.CAMERA_FIXED
            self.env.unwrapped.viewer.cam.fixedcamid = camera_idx

    def _get_robotics_image(self):
        self.env.render()
        image = self.env.unwrapped._get_viewer().read_pixels(1600, 900, depth=False)[::-1, :, :]
        image = scipy.misc.imresize(image, (270, 480, 3))
        return image

    def _render(self):
        self.env.render(mode='human')
        # required for setting up a fixed camera for mujoco
        if self.is_mujoco_env:
            self._set_mujoco_camera(0)

    def get_rendered_image(self):
        if self.is_robotics_env:
            # necessary for fetch since the rendered image is cropped to an irrelevant part of the simulator
            image = self._get_robotics_image()
        else:
            image = self.env.render(mode='rgb_array')
        # required for setting up a fixed camera for mujoco
        if self.is_mujoco_env:
            self._set_mujoco_camera(0)
        return image

    def get_target_success_rate(self) -> float:
        return self.target_success_rate
