# Copyright 2019 DeepMind Technologies Ltd. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Python spiel example."""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import logging
from absl import app
from absl import flags

from open_spiel.python.environments import catch
from open_spiel.python.pytorch import policy_gradient

FLAGS = flags.FLAGS

flags.DEFINE_integer("num_episodes", int(1e5), "Number of train episodes.")
flags.DEFINE_integer("eval_every", int(1e3),
                     "'How often to evaluate the policy.")
flags.DEFINE_enum("algorithm", "a2c", ["rpg", "qpg", "rm", "a2c"],
                  "Algorithms to run.")


def _eval_agent(env, agent, num_episodes):
  """Evaluates `agent` for `num_episodes`."""
  rewards = 0.0
  for _ in range(num_episodes):
    time_step = env.reset()
    episode_reward = 0
    while not time_step.last():
      agent_output = agent.step(time_step, is_evaluation=True)
      time_step = env.step([agent_output.action])
      episode_reward += time_step.rewards[0]
    rewards += episode_reward
  return rewards / num_episodes


def main_loop(unused_arg):
  """Trains a Policy Gradient agent in the catch environment."""
  env = catch.Environment()
  info_state_size = env.observation_spec()["info_state"][0]
  num_actions = env.action_spec()["num_actions"]

  train_episodes = FLAGS.num_episodes

  agent = policy_gradient.PolicyGradient(
      player_id=0,
      info_state_size=info_state_size,
      num_actions=num_actions,
      loss_str=FLAGS.algorithm,
      hidden_layers_sizes=[128, 128],
      batch_size=128,
      entropy_cost=0.01,
      critic_learning_rate=0.1,
      pi_learning_rate=0.1,
      num_critic_before_pi=3)

  # Train agent
  for ep in range(train_episodes):
    time_step = env.reset()
    while not time_step.last():
      agent_output = agent.step(time_step)
      action_list = [agent_output.action]
      time_step = env.step(action_list)
    # Episode is over, step agent with final info state.
    agent.step(time_step)

    if ep and ep % FLAGS.eval_every == 0:
      logging.info("-" * 80)
      logging.info("Episode %s", ep)
      logging.info("Loss: %s", agent.loss)
      avg_return = _eval_agent(env, agent, 100)
      logging.info("Avg return: %s", avg_return)


if __name__ == "__main__":
  app.run(main_loop)
