# Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES, ETH Zurich, and University of Toronto
# All rights reserved.
#
# SPDX-License-Identifier: BSD-3-Clause

"""This sub-module contains the common functions that can be used to activate certain terminations.

The functions can be passed to the :class:`omni.isaac.orbit.managers.TerminationTermCfg` object to enable
the termination introduced by the function.
"""

from __future__ import annotations

import torch
from typing import TYPE_CHECKING

from omni.isaac.orbit.assets import Articulation, RigidObject
from omni.isaac.orbit.managers import SceneEntityCfg
from omni.isaac.orbit.sensors import ContactSensor

if TYPE_CHECKING:
    from omni.isaac.orbit.envs.rl_env import RLEnv

"""
MDP terminations.
"""


def time_out(env: RLEnv) -> torch.Tensor:
    """Terminate the episode when the episode length exceeds the maximum episode length."""
    return env.episode_length_buf >= env.max_episode_length


def command_resample(env: RLEnv, num_resamples: int = 1) -> torch.Tensor:
    """Terminate the episode based on the total number of times commands have been re-sampled.

    This makes the maximum episode length fluid in nature as it depends on how the commands are
    sampled. It is useful in situations where delayed rewards are used :cite:`rudin2022advanced`.
    """
    return torch.logical_and(
        (env.command_manager.time_left <= env.step_dt), (env.command_manager.command_counter == num_resamples)
    )


"""
Root terminations.
"""


def bad_orientation(
    env: RLEnv, limit_angle: float, asset_cfg: SceneEntityCfg = SceneEntityCfg("robot")
) -> torch.Tensor:
    """Terminate when the asset's orientation is too far from the desired orientation limits.

    This is computed by checking the angle between the projected gravity vector and the z-axis.
    """
    # extract the used quantities (to enable type-hinting)
    asset: RigidObject = env.scene[asset_cfg.name]
    return torch.acos(-asset.data.projected_gravity_b[:, 2]).abs() > limit_angle


def base_height(env: RLEnv, minimum_height: float, asset_cfg: SceneEntityCfg = SceneEntityCfg("robot")) -> torch.Tensor:
    """Terminate when the asset's height is below the minimum height.

    Note:
        This is currently only supported for flat terrains, i.e. the minimum height is in the world frame.
    """
    # extract the used quantities (to enable type-hinting)
    asset: RigidObject = env.scene[asset_cfg.name]
    return asset.data.root_pos_w[:, 2] < minimum_height


"""
Joint terminations.
"""


def joint_pos_limit(env: RLEnv, asset_cfg: SceneEntityCfg = SceneEntityCfg("robot")) -> torch.Tensor:
    """Terminate when the asset's joint positions are outside of the soft joint limits."""
    # extract the used quantities (to enable type-hinting)
    asset: Articulation = env.scene[asset_cfg.name]
    # compute any violations
    out_of_upper_limits = torch.any(asset.data.joint_pos > asset.data.soft_joint_pos_limits[:, 0], dim=1)
    out_of_lower_limits = torch.any(asset.data.joint_pos < asset.data.soft_joint_pos_limits[:, 1], dim=1)
    return torch.logical_or(out_of_upper_limits, out_of_lower_limits)


def joint_velocity_limit(env: RLEnv, max_velocity, asset_cfg: SceneEntityCfg = SceneEntityCfg("robot")) -> torch.Tensor:
    """Terminate when the asset's joint velocities are outside of the soft joint limits."""
    # extract the used quantities (to enable type-hinting)
    asset: Articulation = env.scene[asset_cfg.name]
    # TODO read max velocities per joint from robot
    return torch.any(torch.abs(asset.data.joint_vel) > max_velocity, dim=1)


def joint_torque_limit(env: RLEnv, asset_cfg: SceneEntityCfg = SceneEntityCfg("robot")) -> torch.Tensor:
    """Terminate when torque applied on the asset's joints are are outside of the soft joint limits."""
    # extract the used quantities (to enable type-hinting)
    asset: Articulation = env.scene[asset_cfg.name]
    return torch.any(
        torch.isclose(asset.data.computed_torques, asset.data.applied_torque),
        dim=1,
    )


"""
Contact sensor.
"""


def illegal_contact(env: RLEnv, threshold: float, sensor_cfg: SceneEntityCfg) -> torch.Tensor:
    """Terminate when the contact force on the sensor exceeds the force threshold."""
    # extract the used quantities (to enable type-hinting)
    contact_sensor: ContactSensor = env.scene.sensors[sensor_cfg.name]
    net_contact_forces = contact_sensor.data.net_forces_w_history
    # check if any contact force exceeds the threshold
    return torch.any(
        torch.max(torch.norm(net_contact_forces[:, :, sensor_cfg.body_ids], dim=-1), dim=1)[0] > threshold, dim=1
    )
