import gym
import numpy as np
from matplotlib import pyplot as plt
from scipy.signal import iirfilter, sosfilt, zpk2sos


class DoneOnSuccessWrapper(gym.Wrapper):
    """
    Reset on success and offsets the reward.
    Useful for GoalEnv.
    """

    def __init__(self, env: gym.Env, reward_offset: float = 0.0, n_successes: int = 1):
        super(DoneOnSuccessWrapper, self).__init__(env)
        self.reward_offset = reward_offset
        self.n_successes = n_successes
        self.current_successes = 0

    def reset(self):
        self.current_successes = 0
        return self.env.reset()

    def step(self, action):
        obs, reward, done, info = self.env.step(action)
        if info.get("is_success", False):
            self.current_successes += 1
        else:
            self.current_successes = 0
        # number of successes in a row
        done = done or self.current_successes >= self.n_successes
        reward += self.reward_offset
        return obs, reward, done, info

    def compute_reward(self, achieved_goal, desired_goal, info):
        reward = self.env.compute_reward(achieved_goal, desired_goal, info)
        return reward + self.reward_offset


class ActionNoiseWrapper(gym.Wrapper):
    """
    Add gaussian noise to the action (without telling the agent),
    to test the robustness of the control.

    :param env: (gym.Env)
    :param noise_std: (float) Standard deviation of the noise
    """

    def __init__(self, env, noise_std=0.1):
        super(ActionNoiseWrapper, self).__init__(env)
        self.noise_std = noise_std

    def step(self, action):
        noise = np.random.normal(
            np.zeros_like(action), np.ones_like(action) * self.noise_std
        )
        noisy_action = action + noise
        return self.env.step(noisy_action)


# from https://docs.obspy.org
def lowpass(data, freq, df, corners=4, zerophase=False):
    """
    Butterworth-Lowpass Filter.

    Filter data removing data over certain frequency ``freq`` using ``corners``
    corners.
    The filter uses :func:`scipy.signal.iirfilter` (for design)
    and :func:`scipy.signal.sosfilt` (for applying the filter).

    :type data: numpy.ndarray
    :param data: Data to filter.
    :param freq: Filter corner frequency.
    :param df: Sampling rate in Hz.
    :param corners: Filter corners / order.
    :param zerophase: If True, apply filter once forwards and once backwards.
        This results in twice the number of corners but zero phase shift in
        the resulting filtered trace.
    :return: Filtered data.
    """
    fe = 0.5 * df
    f = freq / fe
    # raise for some bad scenarios
    if f > 1:
        f = 1.0
        msg = (
            "Selected corner frequency is above Nyquist. "
            + "Setting Nyquist as high corner."
        )
        print(msg)
    z, p, k = iirfilter(corners, f, btype="lowpass", ftype="butter", output="zpk")
    sos = zpk2sos(z, p, k)
    if zerophase:
        firstpass = sosfilt(sos, data)
        return sosfilt(sos, firstpass[::-1])[::-1]
    else:
        return sosfilt(sos, data)


class LowPassFilterWrapper(gym.Wrapper):
    """
    Butterworth-Lowpass

    :param env: (gym.Env)
    :param freq: Filter corner frequency.
    :param df: Sampling rate in Hz.
    """

    def __init__(self, env, freq=5.0, df=25.0):
        super(LowPassFilterWrapper, self).__init__(env)
        self.freq = freq
        self.df = df
        self.signal = []

    def reset(self):
        self.signal = []
        return self.env.reset()

    def step(self, action):
        self.signal.append(action)
        filtered = np.zeros_like(action)
        for i in range(self.action_space.shape[0]):
            smoothed_action = lowpass(
                np.array(self.signal)[:, i], freq=self.freq, df=self.df
            )
            filtered[i] = smoothed_action[-1]
        return self.env.step(filtered)


class ActionSmoothingWrapper(gym.Wrapper):
    """
    Smooth the action using exponential moving average.

    :param env: (gym.Env)
    :param smoothing_coef: (float) Smoothing coefficient (0 no smoothing, 1 very smooth)
    """

    def __init__(self, env, smoothing_coef: float = 0.0):
        super(ActionSmoothingWrapper, self).__init__(env)
        self.smoothing_coef = smoothing_coef
        self.smoothed_action = None
        # from https://github.com/rail-berkeley/softlearning/issues/3
        # for smoothing latent space
        # self.alpha = self.smoothing_coef
        # self.beta = np.sqrt(1 - self.alpha ** 2) / (1 - self.alpha)

    def reset(self):
        self.smoothed_action = None
        return self.env.reset()

    def step(self, action):
        if self.smoothed_action is None:
            self.smoothed_action = np.zeros_like(action)
        self.smoothed_action = (
            self.smoothing_coef * self.smoothed_action
            + (1 - self.smoothing_coef) * action
        )
        return self.env.step(self.smoothed_action)


class DelayedRewardWrapper(gym.Wrapper):
    """
    Delay the reward by `delay` steps, it makes the task harder but more realistic.
    The reward is accumulated during those steps.

    :param env: (gym.Env)
    :param delay: (int) Number of steps the reward should be delayed.
    """

    def __init__(self, env, delay=10):
        super(DelayedRewardWrapper, self).__init__(env)
        self.delay = delay
        self.current_step = 0
        self.accumulated_reward = 0.0

    def reset(self):
        self.current_step = 0
        self.accumulated_reward = 0.0
        return self.env.reset()

    def step(self, action):
        obs, reward, done, info = self.env.step(action)

        self.accumulated_reward += reward
        self.current_step += 1

        if self.current_step % self.delay == 0 or done:
            reward = self.accumulated_reward
            self.accumulated_reward = 0.0
        else:
            reward = 0.0
        return obs, reward, done, info


class HistoryWrapper(gym.Wrapper):
    """
    Stack past observations and actions to give an history to the agent.

    :param env: (gym.Env)
    :param horizon: (int) Number of steps to keep in the history.
    """

    def __init__(self, env: gym.Env, horizon: int = 5):
        assert isinstance(env.observation_space, gym.spaces.Box)

        wrapped_obs_space = env.observation_space
        wrapped_action_space = env.action_space

        # TODO (external): double check, it seems wrong when we have different low and highs
        low_obs = np.repeat(wrapped_obs_space.low, horizon, axis=-1)
        high_obs = np.repeat(wrapped_obs_space.high, horizon, axis=-1)

        low_action = np.repeat(wrapped_action_space.low, horizon, axis=-1)
        high_action = np.repeat(wrapped_action_space.high, horizon, axis=-1)

        low = np.concatenate((low_obs, low_action))
        high = np.concatenate((high_obs, high_action))

        # Overwrite the observation space
        env.observation_space = gym.spaces.Box(
            low=low, high=high, dtype=wrapped_obs_space.dtype
        )

        super(HistoryWrapper, self).__init__(env)

        self.horizon = horizon
        self.low_action, self.high_action = low_action, high_action
        self.low_obs, self.high_obs = low_obs, high_obs
        self.low, self.high = low, high
        self.obs_history = np.zeros(low_obs.shape, low_obs.dtype)
        self.action_history = np.zeros(low_action.shape, low_action.dtype)

    def _create_obs_from_history(self):
        return np.concatenate((self.obs_history, self.action_history))

    def reset(self):
        # Flush the history
        self.obs_history[...] = 0
        self.action_history[...] = 0
        obs = self.env.reset()
        self.obs_history[..., -obs.shape[-1] :] = obs
        return self._create_obs_from_history()

    def step(self, action):
        obs, reward, done, info = self.env.step(action)
        last_ax_size = obs.shape[-1]

        self.obs_history = np.roll(self.obs_history, shift=-last_ax_size, axis=-1)
        self.obs_history[..., -obs.shape[-1] :] = obs

        self.action_history = np.roll(
            self.action_history, shift=-action.shape[-1], axis=-1
        )
        self.action_history[..., -action.shape[-1] :] = action
        return self._create_obs_from_history(), reward, done, info


class HistoryWrapperObsDict(gym.Wrapper):
    """
    History Wrapper for dict observation.

    :param env: (gym.Env)
    :param horizon: (int) Number of steps to keep in the history.
    """

    def __init__(self, env, horizon=5):
        assert isinstance(env.observation_space.spaces["observation"], gym.spaces.Box)

        wrapped_obs_space = env.observation_space.spaces["observation"]
        wrapped_action_space = env.action_space

        # TODO (external): double check, it seems wrong when we have different low and highs
        low_obs = np.repeat(wrapped_obs_space.low, horizon, axis=-1)
        high_obs = np.repeat(wrapped_obs_space.high, horizon, axis=-1)

        low_action = np.repeat(wrapped_action_space.low, horizon, axis=-1)
        high_action = np.repeat(wrapped_action_space.high, horizon, axis=-1)

        low = np.concatenate((low_obs, low_action))
        high = np.concatenate((high_obs, high_action))

        # Overwrite the observation space
        env.observation_space.spaces["observation"] = gym.spaces.Box(
            low=low, high=high, dtype=wrapped_obs_space.dtype
        )

        super(HistoryWrapperObsDict, self).__init__(env)

        self.horizon = horizon
        self.low_action, self.high_action = low_action, high_action
        self.low_obs, self.high_obs = low_obs, high_obs
        self.low, self.high = low, high
        self.obs_history = np.zeros(low_obs.shape, low_obs.dtype)
        self.action_history = np.zeros(low_action.shape, low_action.dtype)

    def _create_obs_from_history(self):
        return np.concatenate((self.obs_history, self.action_history))

    def reset(self):
        # Flush the history
        self.obs_history[...] = 0
        self.action_history[...] = 0
        obs_dict = self.env.reset()
        obs = obs_dict["observation"]
        self.obs_history[..., -obs.shape[-1] :] = obs

        obs_dict["observation"] = self._create_obs_from_history()

        return obs_dict

    def step(self, action):
        obs_dict, reward, done, info = self.env.step(action)
        obs = obs_dict["observation"]
        last_ax_size = obs.shape[-1]

        self.obs_history = np.roll(self.obs_history, shift=-last_ax_size, axis=-1)
        self.obs_history[..., -obs.shape[-1] :] = obs

        self.action_history = np.roll(
            self.action_history, shift=-action.shape[-1], axis=-1
        )
        self.action_history[..., -action.shape[-1] :] = action

        obs_dict["observation"] = self._create_obs_from_history()

        return obs_dict, reward, done, info


class PlotActionWrapper(gym.Wrapper):
    """
    Wrapper for plotting the taken actions.
    Only works with 1D actions for now.
    Optionally, it can be used to plot the observations too.

    :param env: (gym.Env)
    :param plot_freq: (int) Plot every `plot_freq` episodes
    """

    def __init__(self, env, plot_freq=5):
        super(PlotActionWrapper, self).__init__(env)
        self.plot_freq = plot_freq
        self.current_episode = 0
        # Observation buffer (Optional)
        # self.observations = []
        # Action buffer
        self.actions = []

    def reset(self):
        self.current_episode += 1
        if self.current_episode % self.plot_freq == 0:
            self.plot()
            # Reset
            self.actions = []
        obs = self.env.reset()
        self.actions.append([])
        # self.observations.append(obs)
        return obs

    def step(self, action):
        obs, reward, done, info = self.env.step(action)

        self.actions[-1].append(action)
        # self.observations.append(obs)

        return obs, reward, done, info

    def plot(self):
        actions = self.actions
        x = np.arange(sum([len(episode) for episode in actions]))
        plt.figure("Actions")
        plt.title("Actions during exploration", fontsize=14)
        plt.xlabel("Timesteps", fontsize=14)
        plt.ylabel("Action", fontsize=14)

        start = 0
        for i in range(len(self.actions)):
            end = start + len(self.actions[i])
            plt.plot(x[start:end], self.actions[i])
            # Clipped actions: real behavior, note that it is between [-2, 2] for the Pendulum
            # plt.scatter(x[start:end], np.clip(self.actions[i], -1, 1), s=1)
            # plt.scatter(x[start:end], self.actions[i], s=1)
            start = end

        plt.show()


class FeatureExtractorFreezeParammetersWrapper(gym.Wrapper):
    """
    Freezes parameters of the feature extractor.
    """

    def __init__(self, env: gym.Env):

        super(FeatureExtractorFreezeParammetersWrapper, self).__init__(env)
        for param in self.feature_extractor.parameters():
            param.requires_grad = False
