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#!/usr/bin/env python3
#
# Copyright 2009 Facebook
#
# 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 tornado.escape
import tornado.locks
import tornado.web
import os.path
import uuid
from tornado.options import define, options, parse_command_line
define("port", default=8888, help="run on the given port", type=int)
define("debug", default=True, help="run in debug mode")
class MessageBuffer(object):
def __init__(self):
# cond is notified whenever the message cache is updated
self.cond = tornado.locks.Condition()
self.cache = []
self.cache_size = 200
def get_messages_since(self, cursor):
"""Returns a list of messages newer than the given cursor.
``cursor`` should be the ``id`` of the last message received.
"""
results = []
for msg in reversed(self.cache):
if msg["id"] == cursor:
break
results.append(msg)
results.reverse()
return results
def add_message(self, message):
self.cache.append(message)
if len(self.cache) > self.cache_size:
self.cache = self.cache[-self.cache_size :]
self.cond.notify_all()
# Making this a non-singleton is left as an exercise for the reader.
global_message_buffer = MessageBuffer()
class MainHandler(tornado.web.RequestHandler):
def get(self):
self.render("index.html", messages=global_message_buffer.cache)
class MessageNewHandler(tornado.web.RequestHandler):
"""Post a new message to the chat room."""
def post(self):
message = {"id": str(uuid.uuid4()), "body": self.get_argument("body")}
# render_string() returns a byte string, which is not supported
# in json, so we must convert it to a character string.
message["html"] = tornado.escape.to_unicode(
self.render_string("message.html", message=message)
)
if self.get_argument("next", None):
self.redirect(self.get_argument("next"))
else:
self.write(message)
global_message_buffer.add_message(message)
class MessageUpdatesHandler(tornado.web.RequestHandler):
"""Long-polling request for new messages.
Waits until new messages are available before returning anything.
"""
async def post(self):
cursor = self.get_argument("cursor", None)
messages = global_message_buffer.get_messages_since(cursor)
while not messages:
# Save the Future returned here so we can cancel it in
# on_connection_close.
self.wait_future = global_message_buffer.cond.wait()
try:
await self.wait_future
except asyncio.CancelledError:
return
messages = global_message_buffer.get_messages_since(cursor)
if self.request.connection.stream.closed():
return
self.write(dict(messages=messages))
def on_connection_close(self):
self.wait_future.cancel()
async def main():
parse_command_line()
app = tornado.web.Application(
[
(r"/", MainHandler),
(r"/a/message/new", MessageNewHandler),
(r"/a/message/updates", MessageUpdatesHandler),
],
cookie_secret="__TODO:_GENERATE_YOUR_OWN_RANDOM_VALUE_HERE__",
template_path=os.path.join(os.path.dirname(__file__), "templates"),
static_path=os.path.join(os.path.dirname(__file__), "static"),
xsrf_cookies=True,
debug=options.debug,
)
app.listen(options.port)
await asyncio.Event().wait()
if __name__ == "__main__":
asyncio.run(main())
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