"""Example of hierarchical training using the multi-agent API.

The example env is that of a "windy maze". The agent observes the current wind
direction and can either choose to stand still, or move in that direction.

You can try out the env directly with:

    $ python hierarchical_training.py --flat

A simple hierarchical formulation involves a high-level agent that issues goals
(i.e., go north / south / east / west), and a low-level agent that executes
these goals over a number of time-steps. This can be implemented as a
multi-agent environment with a top-level agent and low-level agents spawned
for each higher-level action. The lower level agent is rewarded for moving
in the right direction.

You can try this formulation with:

    $ python hierarchical_training.py  # gets ~100 rew after ~100k timesteps

Note that the hierarchical formulation actually converges slightly slower than
using --flat in this example.
"""

import argparse
from gym.spaces import Discrete, Tuple
import logging
import os

import ray
from ray import tune
from ray.tune import function
from ray.rllib.examples.env.windy_maze_env import WindyMazeEnv, \
    HierarchicalWindyMazeEnv
from ray.rllib.utils.test_utils import check_learning_achieved

parser = argparse.ArgumentParser()
parser.add_argument("--flat", action="store_true")
parser.add_argument(
    "--framework",
    choices=["tf", "tf2", "tfe", "torch"],
    default="tf",
    help="The DL framework specifier.")
parser.add_argument(
    "--as-test",
    action="store_true",
    help="Whether this script should be run as a test: --stop-reward must "
    "be achieved within --stop-timesteps AND --stop-iters.")
parser.add_argument(
    "--stop-iters",
    type=int,
    default=200,
    help="Number of iterations to train.")
parser.add_argument(
    "--stop-timesteps",
    type=int,
    default=100000,
    help="Number of timesteps to train.")
parser.add_argument(
    "--stop-reward",
    type=float,
    default=0.0,
    help="Reward at which we stop training.")

logger = logging.getLogger(__name__)

if __name__ == "__main__":
    args = parser.parse_args()
    ray.init()

    stop = {
        "training_iteration": args.stop_iters,
        "timesteps_total": args.stop_timesteps,
        "episode_reward_mean": args.stop_reward,
    }

    if args.flat:
        results = tune.run(
            "PPO",
            stop=stop,
            config={
                "env": WindyMazeEnv,
                "num_workers": 0,
                "framework": args.framework,
            },
        )
    else:
        maze = WindyMazeEnv(None)

        def policy_mapping_fn(agent_id, episode, worker, **kwargs):
            if agent_id.startswith("low_level_"):
                return "low_level_policy"
            else:
                return "high_level_policy"

        config = {
            "env": HierarchicalWindyMazeEnv,
            "num_workers": 0,
            "entropy_coeff": 0.01,
            "multiagent": {
                "policies": {
                    "high_level_policy": (None, maze.observation_space,
                                          Discrete(4), {
                                              "gamma": 0.9
                                          }),
                    "low_level_policy": (None,
                                         Tuple([
                                             maze.observation_space,
                                             Discrete(4)
                                         ]), maze.action_space, {
                                             "gamma": 0.0
                                         }),
                },
                "policy_mapping_fn": function(policy_mapping_fn),
            },
            "framework": args.framework,
            # Use GPUs iff `RLLIB_NUM_GPUS` env var set to > 0.
            "num_gpus": int(os.environ.get("RLLIB_NUM_GPUS", "0")),
        }

        results = tune.run("PPO", stop=stop, config=config, verbose=1)

    if args.as_test:
        check_learning_achieved(results, args.stop_reward)

    ray.shutdown()
