# Copyright (c) 2022-2023, The ORBIT Project Developers.
# All rights reserved.
#
# SPDX-License-Identifier: BSD-3-Clause

"""Action manager for processing actions sent to the environment."""

from __future__ import annotations

import torch
from abc import ABC, abstractmethod
from prettytable import PrettyTable
from typing import TYPE_CHECKING, Sequence

from omni.isaac.orbit.assets import AssetBase

from .manager_base import ManagerBase
from .manager_cfg import ActionTermCfg

if TYPE_CHECKING:
    from omni.isaac.orbit.envs import BaseEnv


class ActionTerm(ABC):
    """Base class for action terms.

    The action term is responsible for processing the raw actions sent to the environment
    and applying them to the asset managed by the term. The action term is comprised of two
    operations:

    * Processing of actions: This operation is performed once per **environment step** and
      is responsible for pre-processing the raw actions sent to the environment.
    * Applying actions: This operation is performed once per **simulation step** and is
      responsible for applying the processed actions to the asset managed by the term.
    """

    def __init__(self, cfg: ActionTermCfg, env: BaseEnv):
        """Initialize the action term.

        Args:
            cfg: The configuration object.
            env: The environment instance.
        """
        # store the inputs
        self.cfg = cfg
        self._env = env
        # parse config to obtain asset to which the term is applied
        self._asset: AssetBase = self._env.scene[self.cfg.asset_name]

    """
    Properties.
    """

    @property
    def num_envs(self) -> int:
        """Number of environments."""
        return self._env.num_envs

    @property
    def device(self) -> str:
        """Device on which to perform computations."""
        return self._asset.device

    @property
    @abstractmethod
    def action_dim(self) -> int:
        """Dimension of the action term."""
        raise NotImplementedError

    @property
    @abstractmethod
    def raw_actions(self) -> torch.Tensor:
        """The input/raw actions sent to the term."""
        raise NotImplementedError

    @property
    @abstractmethod
    def processed_actions(self) -> torch.Tensor:
        """The actions computed by the term after applying any processing."""
        raise NotImplementedError

    """
    Operations.
    """

    @abstractmethod
    def process_actions(self, actions: torch.Tensor):
        """Processes the actions sent to the environment.

        Note:
            This function is called once per environment step by the manager.

        Args:
            actions: The actions to process.
        """
        raise NotImplementedError

    @abstractmethod
    def apply_actions(self):
        """Applies the actions to the asset managed by the term.

        Note:
            This is called at every simulation step by the manager.
        """
        raise NotImplementedError


class ActionManager(ManagerBase):
    """Manager for processing and applying actions for a given world.

    The action manager handles the interpretation and application of user-defined
    actions on a given world. It is comprised of different action terms that decide
    the dimension of the expected actions.

    The action manager performs operations at two stages:

    * processing of actions: It splits the input actions to each term and performs any
      pre-processing needed. This should be called once at every environment step.
    * apply actions: This operation typically sets the processed actions into the assets in the
      scene (such as robots). It should be called before every simulation step.
    """

    def __init__(self, cfg: object, env: BaseEnv):
        """Initialize the action manager.

        Args:
            cfg: The configuration object or dictionary (``dict[str, ActionTermCfg]``).
            env: The environment instance.
        """
        super().__init__(cfg, env)
        # create buffers to store actions
        self._action = torch.zeros((self.num_envs, self.total_action_dim), device=self.device)
        self._prev_action = torch.zeros_like(self._action)

    def __str__(self) -> str:
        """Returns: A string representation for action manager."""
        msg = f"<ActionManager> contains {len(self._term_names)} active terms.\n"

        # create table for term information
        table = PrettyTable()
        table.title = f"Active Action Terms (shape: {self.total_action_dim})"
        table.field_names = ["Index", "Name", "Dimension"]
        # set alignment of table columns
        table.align["Name"] = "l"
        table.align["Dimension"] = "r"
        # add info on each term
        for index, (name, term) in enumerate(zip(self._term_names, self._terms)):
            table.add_row([index, name, term.action_dim])
        # convert table to string
        msg += table.get_string()

        return msg

    """
    Properties.
    """

    @property
    def total_action_dim(self) -> int:
        """Total dimension of actions."""
        return sum(self.action_term_dim)

    @property
    def active_terms(self) -> list[str]:
        """Name of active action terms."""
        return self._term_names

    @property
    def action_term_dim(self) -> list[int]:
        """Shape of each action term."""
        return [term.action_dim for term in self._terms]

    @property
    def action(self) -> torch.Tensor:
        """The actions sent to the environment. Shape is ``(num_envs, total_action_dim)``."""
        return self._action

    @property
    def prev_action(self) -> torch.Tensor:
        """The previous actions sent to the environment. Shape is ``(num_envs, total_action_dim)``."""
        return self._prev_action

    """
    Operations.
    """

    def reset(self, env_ids: Sequence[int] | None = None) -> dict[str, torch.Tensor]:
        """Resets the action history.

        Args:
            env_ids: The environment ids. Defaults to None, in which case
                all environments are considered.

        Returns:
            An empty dictionary.
        """
        # resolve environment ids
        if env_ids is None:
            env_ids = slice(None)
        # reset the action history
        self._prev_action[env_ids] = 0.0
        self._action[env_ids] = 0.0
        # reset the terms
        return {}

    def process_action(self, action: torch.Tensor):
        """Processes the actions sent to the environment.

        Note:
            This function should be called once per environment step.

        Args:
            action: The actions to process.
        """
        # check if action dimension is valid
        if self.total_action_dim != action.shape[1]:
            raise ValueError(f"Invalid action shape, expected: {self.total_action_dim}, received: {action.shape[1]}.")
        # store the input actions
        self._prev_action[:] = self._action
        self._action[:] = action.to(self.device)

        # split the actions and apply to each tensor
        idx = 0
        for term in self._terms:
            term_actions = action[:, idx : idx + term.action_dim]
            term.process_actions(term_actions)

    def apply_action(self) -> None:
        """Applies the actions to the environment/simulation.

        Note:
            This should be called at every simulation step.
        """
        for term in self._terms:
            term.apply_actions()

    """
    Helper functions.
    """

    def _prepare_terms(self):
        """Prepares a list of action terms."""
        # parse action terms from the config
        self._term_names: list[str] = list()
        self._terms: list[ActionTerm] = list()

        # check if config is dict already
        if isinstance(self.cfg, dict):
            cfg_items = self.cfg.items()
        else:
            cfg_items = self.cfg.__dict__.items()
        for term_name, term_cfg in cfg_items:
            # check valid type
            if not isinstance(term_cfg, ActionTermCfg):
                raise TypeError(
                    f"Configuration for the term '{term_name}' is not of type ActionTermCfg."
                    f" Received: '{type(term_cfg)}'."
                )
            # create the action term
            term = term_cfg.class_type(term_cfg, self._env)
            # sanity check if term is valid type
            if not isinstance(term, ActionTerm):
                raise TypeError(f"Returned object for the term '{term_name}' is not of type ActionType.")
            # add term name and parameters
            self._term_names.append(term_name)
            self._terms.append(term)
