# Copyright 2017 The TensorFlow Agents Authors.
#
# 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.
"""Utilities for using reinforcement learning algorithms."""

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

import logging
import os
import re

import ruamel.yaml as yaml
import tensorflow as tf

from . import tools


def define_simulation_graph(batch_env, algo_cls, config):
  """Define the algortihm and environment interaction.

  Args:
    batch_env: In-graph environments object.
    algo_cls: Constructor of a batch algorithm.
    config: Configuration object for the algorithm.

  Returns:
    Object providing graph elements via attributes.
  """
  # pylint: disable=unused-variable
  step = tf.Variable(0, False, dtype=tf.int32, name='global_step')
  is_training = tf.placeholder(tf.bool, name='is_training')
  should_log = tf.placeholder(tf.bool, name='should_log')
  do_report = tf.placeholder(tf.bool, name='do_report')
  force_reset = tf.placeholder(tf.bool, name='force_reset')
  algo = algo_cls(batch_env, step, is_training, should_log, config)
  done, score, summary = tools.simulate(batch_env, algo, should_log, force_reset)
  message = 'Graph contains {} trainable variables.'
  tf.logging.info(message.format(tools.count_weights()))
  # pylint: enable=unused-variable
  return tools.AttrDict(locals())


def define_batch_env(constructor, num_agents, env_processes):
  """Create environments and apply all desired wrappers.

  Args:
    constructor: Constructor of an OpenAI gym environment.
    num_agents: Number of environments to combine in the batch.
    env_processes: Whether to step environment in external processes.

  Returns:
    In-graph environments object.
  """
  with tf.variable_scope('environments'):
    if env_processes:
      envs = [tools.wrappers.ExternalProcess(constructor) for _ in range(num_agents)]
    else:
      envs = [constructor() for _ in range(num_agents)]
    batch_env = tools.BatchEnv(envs, blocking=not env_processes)
    batch_env = tools.InGraphBatchEnv(batch_env)
  return batch_env


def define_saver(exclude=None):
  """Create a saver for the variables we want to checkpoint.

  Args:
    exclude: List of regexes to match variable names to exclude.

  Returns:
    Saver object.
  """
  variables = []
  exclude = exclude or []
  exclude = [re.compile(regex) for regex in exclude]
  for variable in tf.global_variables():
    if any(regex.match(variable.name) for regex in exclude):
      continue
    variables.append(variable)
  saver = tf.train.Saver(variables, keep_checkpoint_every_n_hours=5)
  return saver


def initialize_variables(sess, saver, logdir, checkpoint=None, resume=None):
  """Initialize or restore variables from a checkpoint if available.

  Args:
    sess: Session to initialize variables in.
    saver: Saver to restore variables.
    logdir: Directory to search for checkpoints.
    checkpoint: Specify what checkpoint name to use; defaults to most recent.
    resume: Whether to expect recovering a checkpoint or starting a new run.

  Raises:
    ValueError: If resume expected but no log directory specified.
    RuntimeError: If no resume expected but a checkpoint was found.
  """
  sess.run(tf.group(tf.local_variables_initializer(), tf.global_variables_initializer()))
  if resume and not (logdir or checkpoint):
    raise ValueError('Need to specify logdir to resume a checkpoint.')
  if logdir:
    state = tf.train.get_checkpoint_state(logdir)
    if checkpoint:
      checkpoint = os.path.join(logdir, checkpoint)
    if not checkpoint and state and state.model_checkpoint_path:
      checkpoint = state.model_checkpoint_path
    if checkpoint and resume is False:
      message = 'Found unexpected checkpoint when starting a new run.'
      raise RuntimeError(message)
    if checkpoint:
      saver.restore(sess, checkpoint)


def save_config(config, logdir=None):
  """Save a new configuration by name.

  If a logging directory is specified, is will be created and the configuration
  will be stored there. Otherwise, a log message will be printed.

  Args:
    config: Configuration object.
    logdir: Location for writing summaries and checkpoints if specified.

  Returns:
    Configuration object.
  """
  if logdir:
    with config.unlocked:
      config.logdir = logdir
    message = 'Start a new run and write summaries and checkpoints to {}.'
    tf.logging.info(message.format(config.logdir))
    tf.gfile.MakeDirs(config.logdir)
    config_path = os.path.join(config.logdir, 'config.yaml')
    with tf.gfile.GFile(config_path, 'w') as file_:
      yaml.dump(config, file_, default_flow_style=False)
  else:
    message = ('Start a new run without storing summaries and checkpoints since no '
               'logging directory was specified.')
    tf.logging.info(message)
  return config


def load_config(logdir):
  """Load a configuration from the log directory.

  Args:
    logdir: The logging directory containing the configuration file.

  Raises:
    IOError: The logging directory does not contain a configuration file.

  Returns:
    Configuration object.
  """
  config_path = logdir and os.path.join(logdir, 'config.yaml')
  if not config_path or not tf.gfile.Exists(config_path):
    message = ('Cannot resume an existing run since the logging directory does not '
               'contain a configuration file.')
    raise IOError(message)
  with tf.gfile.FastGFile(config_path, 'r') as file_:
    config = yaml.load(file_, Loader=yaml.Loader)
  message = 'Resume run and write summaries and checkpoints to {}.'
  tf.logging.info(message.format(config.logdir))
  return config


def set_up_logging():
  """Configure the TensorFlow logger."""
  tf.logging.set_verbosity(tf.logging.INFO)
  logging.getLogger('tensorflow').propagate = False
