"""
A simple example of server sent events.
"""

import asyncio
from datetime import datetime
import json
import logging
import signal
import string
from typing import Any, cast

import pkg_resources

from bareasgi import (
    Application,
    HttpRequest,
    HttpResponse,
    text_reader,
    text_writer
)
import bareutils.header as header

logging.basicConfig(level=logging.DEBUG)

logger = logging.getLogger('server_sent_events')


async def index(_request: HttpRequest) -> HttpResponse:
    """Redirect to the index page"""
    return HttpResponse(303, [(b'Location', b'/test')], None)


async def test_page(request: HttpRequest) -> HttpResponse:
    """A request handler which provides the page to respond to server sent events"""
    host = cast(bytes, header.find(b'host', request.scope['headers'])).decode()
    fetch_url = f"{request.scope['scheme']}://{host}/events"
    html = request.info['page_template'].substitute(__FETCH_URL__=fetch_url)
    return HttpResponse(
        200,
        [(b'content-type', b'text/html')],
        text_writer(html)
    )


async def test_events(request: HttpRequest) -> HttpResponse:
    """A request handler which provides server sent events"""

    body = await text_reader(request.body)
    data = json.loads(body)

    async def send_events():
        is_cancelled = False
        while not is_cancelled:
            try:
                logger.debug('Sending event')
                message = {
                    'type': 'tick',
                    'data': {
                        'time': datetime.now().isoformat(),
                        'message': data['message']
                    }
                }
                line = json.dumps(message) + '\n'
                yield line.encode('utf-8')
                await asyncio.sleep(1)
            except asyncio.CancelledError:
                logger.debug('Cancelled')
                is_cancelled = True

    headers = [
        (b'cache-control', b'no-cache'),
        (b'content-type', b'application/json'),
        (b'connection', b'keep-alive')
    ]

    return HttpResponse(200, headers, send_events())


if __name__ == "__main__":

    page_filename = pkg_resources.resource_filename(
        __name__, "streaming_fetch.html")
    with open(page_filename, 'rt', encoding='utf-8') as file_ptr:
        page = file_ptr.read()

    app = Application(info={'page_template': string.Template(page)})

    app.http_router.add({'GET'}, '/', index)
    app.http_router.add({'GET'}, '/test', test_page)
    app.http_router.add({'POST', 'OPTION'}, '/events', test_events)

    from hypercorn.asyncio import serve
    from hypercorn.config import Config

    loop = asyncio.new_event_loop()
    asyncio.set_event_loop(loop)

    shutdown_event = asyncio.Event()

    def _signal_handler(*_: Any) -> None:
        shutdown_event.set()
    loop.add_signal_handler(signal.SIGTERM, _signal_handler)
    loop.add_signal_handler(signal.SIGINT, _signal_handler)

    config = Config()
    config.bind = ["0.0.0.0:9009"]
    config.loglevel = 'debug'
    # config.certfile = os.path.expanduser(f"~/.keys/server.crt")
    # config.keyfile = os.path.expanduser(f"~/.keys/server.key")

    loop.run_until_complete(
        serve(
            app,  # type: ignore
            config,
            shutdown_trigger=shutdown_event.wait  # type: ignore
        )
    )