# python3
# pylint: disable=g-bad-file-header
# Copyright 2019 DeepMind Technologies Limited. 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.
# ============================================================================
"""A simple agent interface."""

import abc
import dm_env

Action = int  # Only discrete-action agents for now.


class Agent(abc.ABC):
  """An agent consists of an action-selection mechanism and an update rule."""

  @abc.abstractmethod
  def select_action(self, timestep: dm_env.TimeStep) -> Action:
    """Takes in a timestep, samples from agent's policy, returns an action."""

  @abc.abstractmethod
  def update(
      self,
      timestep: dm_env.TimeStep,
      action: Action,
      new_timestep: dm_env.TimeStep,
  ) -> None:
    """Updates the agent given a transition."""
