# -*- coding: utf-8 -*-
"""Bowtie cache functions."""
import flask
from flask_socketio import emit
import eventlet
from eventlet.queue import LightQueue
import msgpack
from bowtie._component import pack
def validate(key):
"""Check that the key is a string or bytestring.
That's the only valid type of key.
"""
if not isinstance(key, (str, bytes)):
raise KeyError('Key must be of type str or bytes, found type {}'.format(type(key)))
# pylint: disable=too-few-public-methods
[docs]class _Cache:
"""Store data in the browser.
This cache uses session storage so data will stay
in the browser until the tab is closed.
All data must be serializable, which means if the
serialization transforms the data it won't be the same
when it is fetched.
Examples
--------
>>> from bowtie import cache
>>> cache['a'] = True # doctest: +SKIP
>>> cache['a'] # doctest: +SKIP
True
>>> cache['b'] = np.arange(5) # doctest: +SKIP
>>> cache['b'] # doctest: +SKIP
[1, 2, 3, 4, 5]
"""
def __getitem__(self, key):
"""Load the value stored with the key.
Parameters
----------
key : str
The key to lookup the value stored.
Returns
-------
object
The value if the key exists in the cache, otherwise None.
"""
validate(key)
signal = 'cache_load'
event = LightQueue(1)
if flask.has_request_context():
emit(signal, {'data': pack(key)}, callback=event.put)
else:
sio = flask.current_app.extensions['socketio']
sio.emit(signal, {'data': pack(key)}, callback=event.put)
return msgpack.unpackb(bytes(event.get(timeout=10)), encoding='utf8')
def __setitem__(self, key, value):
"""Store the key value pair.
Parameters
----------
key : str
The key to determine where it's stored, you'll need this to load the value later.
value : object
The value to store in the cache.
Returns
-------
None
"""
validate(key)
signal = 'cache_save'
if flask.has_request_context():
emit(signal, {'key': pack(key), 'data': pack(value)})
else:
sio = flask.current_app.extensions['socketio']
sio.emit(signal, {'key': pack(key), 'data': pack(value)})
eventlet.sleep()
# pylint: disable=invalid-name
cache = _Cache()