import numpy as np
from argparse import Namespace
from xuance.common import Union, Optional, BaseCallback
from xuance.environment import DummyVecEnv, SubprocVecEnv
from xuance.tensorflow import Module
from xuance.tensorflow.utils import NormalizeFunctions, ActivationFunctions, InitializeFunctions
from xuance.tensorflow.policies import REGISTRY_Policy
from xuance.tensorflow.agents import OnPolicyAgent


class PG_Agent(OnPolicyAgent):
    """The implementation of PG agent.

    Args:
        config: the Namespace variable that provides hyperparameters and other settings.
        envs: the vectorized environments.
        callback: A user-defined callback function object to inject custom logic during training.
    """

    def __init__(self,
                 config: Namespace,
                 envs: Union[DummyVecEnv, SubprocVecEnv],
                 callback: Optional[BaseCallback] = None):
        super(PG_Agent, self).__init__(config, envs, callback)
        self.memory = self._build_memory()  # build memory
        self.policy = self._build_policy()  # build policy
        self.learner = self._build_learner(self.config, self.policy, self.callback)  # build learner

    def _build_policy(self) -> Module:
        normalize_fn = NormalizeFunctions[self.config.normalize] if hasattr(self.config, "normalize") else None
        initializer = InitializeFunctions[self.config.initialize] if hasattr(self.config, "initialize") else None
        activation = ActivationFunctions[self.config.activation]

        # build representation.
        representation = self._build_representation(self.config.representation, self.observation_space, self.config)

        # build policy.
        if self.config.policy == "Categorical_Actor":
            policy = REGISTRY_Policy["Categorical_Actor"](
                action_space=self.action_space, representation=representation,
                actor_hidden_size=self.config.actor_hidden_size,
                normalize=normalize_fn, initialize=initializer, activation=activation,
                use_distributed_training=self.distributed_training)
        elif self.config.policy == "Gaussian_Actor":
            policy = REGISTRY_Policy["Gaussian_Actor"](
                action_space=self.action_space, representation=representation,
                actor_hidden_size=self.config.actor_hidden_size,
                normalize=normalize_fn, initialize=initializer, activation=activation,
                activation_action=ActivationFunctions[self.config.activation_action],
                use_distributed_training=self.distributed_training)
        else:
            raise AttributeError(f"PG currently does not support the policy named {self.config.policy}.")

        return policy

    def get_terminated_values(self, observations_next: np.ndarray, rewards: np.ndarray = None):
        """Returns values for terminated states.

        Parameters:
            observations_next (np.ndarray): The terminal observations.
            rewards (np.ndarray): The rewards for terminated states.

        Returns:
            values_next: The values for terminal states.
        """
        values_next = self._process_reward(rewards)
        return values_next
