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

"""Script to play a checkpoint if an RL agent from RL-Games."""

from __future__ import annotations

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


import argparse

from omni.isaac.orbit.app import AppLauncher

# add argparse arguments
parser = argparse.ArgumentParser(description="Play a checkpoint of an RL agent from RL-Games.")
parser.add_argument("--headless", action="store_true", default=False, help="Force display off at all times.")
parser.add_argument("--cpu", action="store_true", default=False, help="Use CPU pipeline.")
parser.add_argument("--num_envs", type=int, default=None, help="Number of environments to simulate.")
parser.add_argument("--task", type=str, default=None, help="Name of the task.")
parser.add_argument("--checkpoint", type=str, default=None, help="Path to model checkpoint.")
parser.add_argument(
    "--use_last_checkpoint",
    action="store_true",
    help="When no checkpoint provided, use the last saved model. Otherwise use the best saved model.",
)
args_cli = parser.parse_args()

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

"""Rest everything follows."""


import gym
import math
import os

from rl_games.common import env_configurations, vecenv
from rl_games.common.player import BasePlayer
from rl_games.torch_runner import Runner

import omni.isaac.contrib_envs  # noqa: F401
import omni.isaac.orbit_envs  # noqa: F401
from omni.isaac.orbit_envs.utils import get_checkpoint_path, parse_env_cfg
from omni.isaac.orbit_envs.utils.wrappers.rl_games import RlGamesGpuEnv, RlGamesVecEnvWrapper

from config import parse_rlg_cfg


def main():
    """Play with RL-Games agent."""
    # parse env configuration
    env_cfg = parse_env_cfg(args_cli.task, use_gpu=not args_cli.cpu, num_envs=args_cli.num_envs)
    agent_cfg = parse_rlg_cfg(args_cli.task)

    # wrap around environment for rl-games
    rl_device = agent_cfg["params"]["config"]["device"]
    clip_obs = agent_cfg["params"]["env"].get("clip_observations", math.inf)
    clip_actions = agent_cfg["params"]["env"].get("clip_actions", math.inf)

    # create isaac environment
    env = gym.make(args_cli.task, cfg=env_cfg)
    # wrap around environment for rl-games
    env = RlGamesVecEnvWrapper(env, rl_device, clip_obs, clip_actions)

    # register the environment to rl-games registry
    # note: in agents configuration: environment name must be "rlgpu"
    vecenv.register(
        "IsaacRlgWrapper", lambda config_name, num_actors, **kwargs: RlGamesGpuEnv(config_name, num_actors, **kwargs)
    )
    env_configurations.register("rlgpu", {"vecenv_type": "IsaacRlgWrapper", "env_creator": lambda **kwargs: env})

    # specify directory for logging experiments
    log_root_path = os.path.join("logs", "rl_games", agent_cfg["params"]["config"]["name"])
    log_root_path = os.path.abspath(log_root_path)
    print(f"[INFO] Loading experiment from directory: {log_root_path}")
    # find checkpoint
    if args_cli.checkpoint is None:
        # specify directory for logging runs
        if "full_experiment_name" not in agent_cfg["params"]["config"]:
            run_dir = os.path.join("*", "nn")
        else:
            run_dir = os.path.join(agent_cfg["params"]["config"]["full_experiment_name"], "nn")
        # specify name of checkpoint
        if args_cli.use_last_checkpoint:
            checkpoint_file = None
        else:
            checkpoint_file = f"{agent_cfg['params']['config']['name']}.pth"
        # get path to previous checkpoint
        resume_path = get_checkpoint_path(log_root_path, run_dir, checkpoint_file)
    else:
        resume_path = os.path.abspath(args_cli.checkpoint)
    # load previously trained model
    agent_cfg["params"]["load_checkpoint"] = True
    agent_cfg["params"]["load_path"] = resume_path
    print(f"[INFO]: Loading model checkpoint from: {agent_cfg['params']['load_path']}")

    # set number of actors into agent config
    agent_cfg["params"]["config"]["num_actors"] = env.unwrapped.num_envs
    # create runner from rl-games
    runner = Runner()
    runner.load(agent_cfg)
    # obtain the agent from the runner
    agent: BasePlayer = runner.create_player()
    agent.restore(resume_path)
    agent.reset()
    # flag for inference
    is_deterministic = True

    # reset environment
    obs = env.reset()
    # required: enables the flag for batched observations
    _ = agent.get_batch_size(obs, 1)
    # simulate environment
    # note: We simplified the logic in rl-games player.py (:func:`BasePlayer.run()`) function in an
    #   attempt to have complete control over environment stepping. However, this removes other
    #   operations such as masking that is used for multi-agent learning by RL-Games.
    while simulation_app.is_running():
        # convert obs to agent format
        obs = agent.obs_to_torch(obs)
        # agent stepping
        actions = agent.get_action(obs, is_deterministic)
        # env stepping
        obs, _, dones, _ = env.step(actions)
        # check if simulator is stopped
        if env.unwrapped.sim.is_stopped():
            break
        # perform operations for terminated episodes
        if len(dones) > 0:
            # reset rnn state for terminated episodes
            if agent.is_rnn and agent.states is not None:
                for s in agent.states:
                    s[:, dones, :] = 0.0

    # close the simulator
    env.close()
    simulation_app.close()


if __name__ == "__main__":
    main()
