# Copyright 2017 Catalyst IT Limited
#
#    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 threading

from eventlet import corolocal

_th_loc_storage = threading.local()


def _get_greenlet_local_storage():
    greenlet_id = corolocal.get_ident()

    greenlet_locals = getattr(_th_loc_storage, "greenlet_locals", None)

    if not greenlet_locals:
        greenlet_locals = {}
        _th_loc_storage.greenlet_locals = greenlet_locals

    if greenlet_id in greenlet_locals:
        return greenlet_locals[greenlet_id]
    else:
        return None


def has_thread_local(var_name):
    gl_storage = _get_greenlet_local_storage()
    return gl_storage and var_name in gl_storage


def get_thread_local(var_name):
    if not has_thread_local(var_name):
        return None

    return _get_greenlet_local_storage()[var_name]


def set_thread_local(var_name, val):
    if val is None and has_thread_local(var_name):
        gl_storage = _get_greenlet_local_storage()

        # Delete variable from greenlet local storage.
        if gl_storage:
            del gl_storage[var_name]

        # Delete the entire greenlet local storage from thread local storage.
        if gl_storage and len(gl_storage) == 0:
            del _th_loc_storage.greenlet_locals[corolocal.get_ident()]

    if val is not None:
        gl_storage = _get_greenlet_local_storage()
        if not gl_storage:
            gl_storage = _th_loc_storage.greenlet_locals[
                corolocal.get_ident()] = {}

        gl_storage[var_name] = val