# Copyright (c) 2022-2024, The Isaac Lab Project Developers.
# All rights reserved.
#
# SPDX-License-Identifier: BSD-3-Clause

"""
This script demonstrates the base environment concept that combines a scene with an action,
observation and event manager for a floating cube.
"""

"""Launch Isaac Sim Simulator first."""


import argparse

from omni.isaac.lab.app import AppLauncher

# add argparse arguments
parser = argparse.ArgumentParser(description="This script demonstrates how to use the concept of an Environment.")
parser.add_argument("--num_envs", type=int, default=64, help="Number of environments to spawn.")

# append AppLauncher cli args
AppLauncher.add_app_launcher_args(parser)
# parse the arguments
args_cli = parser.parse_args()

# launch omniverse app
app_launcher = AppLauncher(args_cli)
simulation_app = app_launcher.app

"""Rest everything follows."""

import torch

import omni.isaac.lab.envs.mdp as mdp
import omni.isaac.lab.sim as sim_utils
from omni.isaac.lab.assets import AssetBaseCfg, RigidObject, RigidObjectCfg
from omni.isaac.lab.envs import BaseEnv, BaseEnvCfg
from omni.isaac.lab.managers import EventTermCfg as EventTerm
from omni.isaac.lab.managers import ObservationGroupCfg as ObsGroup
from omni.isaac.lab.managers import ObservationTermCfg as ObsTerm
from omni.isaac.lab.managers import SceneEntityCfg
from omni.isaac.lab.managers.action_manager import ActionTerm, ActionTermCfg
from omni.isaac.lab.scene import InteractiveSceneCfg
from omni.isaac.lab.terrains import TerrainImporterCfg
from omni.isaac.lab.utils import configclass

##
# Scene definition
##


@configclass
class MySceneCfg(InteractiveSceneCfg):
    """Example scene configuration."""

    # add terrain
    terrain = TerrainImporterCfg(prim_path="/World/ground", terrain_type="plane", debug_vis=False)

    # add cube
    cube: RigidObjectCfg = RigidObjectCfg(
        prim_path="{ENV_REGEX_NS}/cube",
        spawn=sim_utils.CuboidCfg(
            size=(0.2, 0.2, 0.2),
            rigid_props=sim_utils.RigidBodyPropertiesCfg(max_depenetration_velocity=1.0),
            mass_props=sim_utils.MassPropertiesCfg(mass=1.0),
            physics_material=sim_utils.RigidBodyMaterialCfg(),
            visual_material=sim_utils.PreviewSurfaceCfg(diffuse_color=(0.5, 0.0, 0.0)),
        ),
        init_state=RigidObjectCfg.InitialStateCfg(pos=(0.0, 0.0, 5)),
    )

    # lights
    light = AssetBaseCfg(
        prim_path="/World/light",
        spawn=sim_utils.DistantLightCfg(color=(0.75, 0.75, 0.75), intensity=3000.0),
    )


##
# Action Term
##


class CubeActionTerm(ActionTerm):
    """Simple action term that implements a PD controller to track a target position."""

    _asset: RigidObject
    """The articulation asset on which the action term is applied."""

    def __init__(self, cfg: ActionTermCfg, env: BaseEnv):
        # call super constructor
        super().__init__(cfg, env)
        # create buffers
        self._raw_actions = torch.zeros(env.num_envs, 3, device=self.device)
        self._processed_actions = torch.zeros(env.num_envs, 3, device=self.device)
        self._vel_command = torch.zeros(self.num_envs, 6, device=self.device)
        # gains of controller
        self.p_gain = 5.0
        self.d_gain = 0.5

    """
    Properties.
    """

    @property
    def action_dim(self) -> int:
        return self._raw_actions.shape[1]

    @property
    def raw_actions(self) -> torch.Tensor:
        # desired: (x, y, z)
        return self._raw_actions

    @property
    def processed_actions(self) -> torch.Tensor:
        return self._processed_actions

    """
    Operations
    """

    def process_actions(self, actions: torch.Tensor):
        # store the raw actions
        self._raw_actions[:] = actions
        # no-processing of actions
        self._processed_actions[:] = self._raw_actions[:]

    def apply_actions(self):
        # implement a PD controller to track the target position
        pos_error = self._processed_actions - (self._asset.data.root_pos_w - self._env.scene.env_origins)
        vel_error = -self._asset.data.root_lin_vel_w
        # set velocity targets
        self._vel_command[:, :3] = self.p_gain * pos_error + self.d_gain * vel_error
        self._asset.write_root_velocity_to_sim(self._vel_command)


@configclass
class CubeActionTermCfg(ActionTermCfg):
    """Configuration for the cube action term."""

    class_type: type = CubeActionTerm


##
# Observation Term
##


def base_position(env: BaseEnv, asset_cfg: SceneEntityCfg) -> torch.Tensor:
    """Root linear velocity in the asset's root frame."""
    # extract the used quantities (to enable type-hinting)
    asset: RigidObject = env.scene[asset_cfg.name]
    return asset.data.root_pos_w - env.scene.env_origins


##
# Environment settings
##


@configclass
class ActionsCfg:
    """Action specifications for the MDP."""

    joint_pos = CubeActionTermCfg(asset_name="cube")


@configclass
class ObservationsCfg:
    """Observation specifications for the MDP."""

    @configclass
    class PolicyCfg(ObsGroup):
        """Observations for policy group."""

        # cube velocity
        position = ObsTerm(func=base_position, params={"asset_cfg": SceneEntityCfg("cube")})

        def __post_init__(self):
            self.enable_corruption = True
            self.concatenate_terms = True

    # observation groups
    policy: PolicyCfg = PolicyCfg()


@configclass
class EventCfg:
    """Configuration for events."""

    reset_base = EventTerm(
        func=mdp.reset_root_state_uniform,
        mode="reset",
        params={
            "pose_range": {"x": (-0.5, 0.5), "y": (-0.5, 0.5), "yaw": (-3.14, 3.14)},
            "velocity_range": {
                "x": (-0.5, 0.5),
                "y": (-0.5, 0.5),
                "z": (-0.5, 0.5),
            },
            "asset_cfg": SceneEntityCfg("cube"),
        },
    )


##
# Environment configuration
##


@configclass
class CubeEnvCfg(BaseEnvCfg):
    """Configuration for the locomotion velocity-tracking environment."""

    # Scene settings
    scene: MySceneCfg = MySceneCfg(num_envs=args_cli.num_envs, env_spacing=2.5, replicate_physics=True)
    # Basic settings
    observations: ObservationsCfg = ObservationsCfg()
    actions: ActionsCfg = ActionsCfg()
    events: EventCfg = EventCfg()

    def __post_init__(self):
        """Post initialization."""
        # general settings
        self.decimation = 2
        # simulation settings
        self.sim.dt = 0.01
        self.sim.physics_material = self.scene.terrain.physics_material


def main():
    """Main function."""

    # setup base environment
    env = BaseEnv(cfg=CubeEnvCfg())

    # setup target position commands
    target_position = torch.rand(env.num_envs, 3, device=env.device) * 2
    target_position[:, 2] += 2.0
    # offset all targets so that they move to the world origin
    target_position -= env.scene.env_origins

    # simulate physics
    count = 0
    while simulation_app.is_running():
        with torch.inference_mode():
            # reset
            if count % 300 == 0:
                env.reset()
                count = 0

            # step env
            obs, _ = env.step(target_position)
            # print mean squared position error between target and current position
            error = torch.norm(obs["policy"] - target_position).mean().item()
            print(f"[Step: {count:04d}]: Mean position error: {error:.4f}")
            # update counter
            count += 1


if __name__ == "__main__":
    # run the main function
    main()
    # close sim app
    simulation_app.close()
