# Copyright 2022 Alibaba Group Holding 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.
# ==============================================================================

import asyncio
import logging
from threading import Thread, BoundedSemaphore

import torch


def wrap_torch_future(f: torch.futures.Future) -> asyncio.futures.Future:
  r""" Convert a torch future to a standard asyncio future.
  """
  loop = asyncio.get_event_loop()
  aio_future = loop.create_future()
  def on_done(*_):
    try:
      result = f.wait()
    except Exception as e:
      loop.call_soon_threadsafe(aio_future.set_exception, e)
    else:
      loop.call_soon_threadsafe(aio_future.set_result, result)
  f.add_done_callback(on_done)
  return aio_future


class ConcurrentEventLoop(object):
  r""" Concurrent event loop context.

  Args:
    concurrency: max processing concurrency.
  """
  def __init__(self, concurrency):
    self._concurrency = concurrency
    self._sem = BoundedSemaphore(concurrency)
    self._loop = asyncio.new_event_loop()
    self._runner_t = Thread(target=self._run_loop)
    self._runner_t.daemon = True

  def start_loop(self):
    if not self._runner_t.is_alive():
      self._runner_t.start()

  def shutdown_loop(self):
    self.wait_all()
    if self._runner_t.is_alive():
      self._loop.stop()
      self._runner_t.join(timeout=1)

  def wait_all(self):
    r""" Wait all pending tasks to be finished.
    """
    for _ in range(self._concurrency):
      self._sem.acquire()
    for _ in range(self._concurrency):
      self._sem.release()

  def add_task(self, coro, callback=None):
    r""" Add an asynchronized coroutine task to run.

    Args:
      coro: the async coroutine func.
      callback: the callback func applied on the returned results
        after the coroutine task is finished.

    Note that any results returned by `callback` func will be ignored,
    so it is preferable to handle all in your `callback` func and do
    not return any results.
    """
    def on_done(f: asyncio.futures.Future):
      try:
        res = f.result()
        if callback is not None:
          callback(res)
      except Exception as e:
        logging.error("coroutine task failed: %s", e)
      self._sem.release()
    self._sem.acquire()
    fut = asyncio.run_coroutine_threadsafe(coro, self._loop)
    fut.add_done_callback(on_done)

  def run_task(self, coro):
    r""" Run a coroutine task synchronously.
    """
    with self._sem:
      fut = asyncio.run_coroutine_threadsafe(coro, self._loop)
      return fut.result()

  def _run_loop(self):
    self._loop.run_forever()