import argparse
import datetime
import json
import os

from tornado import escape
from tornado import gen
from tornado import ioloop
from tornado import web

from jupyterhub.services.auth import HubAuthenticated


class AnnouncementRequestHandler(HubAuthenticated, web.RequestHandler):
    """Dynamically manage page announcements"""

    hub_users = []
    allow_admin = True

    def initialize(self, storage):
        """Create storage for announcement text"""
        self.storage = storage

    @web.authenticated
    def post(self):
        """Update announcement"""
        user = self.get_current_user()
        doc = escape.json_decode(self.request.body)
        self.storage["announcement"] = doc["announcement"]
        self.storage["timestamp"] = datetime.datetime.now().isoformat()
        self.storage["user"] = user["name"]
        self.write_to_json(self.storage)

    def get(self):
        """Retrieve announcement"""
        self.write_to_json(self.storage)

    @web.authenticated
    def delete(self):
        """Clear announcement"""
        self.storage["announcement"] = ""
        self.write_to_json(self.storage)

    def write_to_json(self, doc):
        """Write dictionary document as JSON"""
        self.set_header("Content-Type", "application/json; charset=UTF-8")
        self.write(escape.utf8(json.dumps(doc)))


def main():
    args = parse_arguments()
    application = create_application(**vars(args))
    application.listen(args.port)
    ioloop.IOLoop.current().start()


def parse_arguments():
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--api-prefix",
        "-a",
        default=os.environ.get("JUPYTERHUB_SERVICE_PREFIX", "/"),
        help="application API prefix",
    )
    parser.add_argument(
        "--port", "-p", default=8888, help="port for API to listen on", type=int
    )
    return parser.parse_args()


def create_application(api_prefix="/", handler=AnnouncementRequestHandler, **kwargs):
    storage = dict(announcement="", timestamp="", user="")
    return web.Application([(api_prefix, handler, dict(storage=storage))])


if __name__ == "__main__":
    main()