from types import MappingProxyType
from urllib.parse import urlparse

from aiohttp import web
from aiohttp_session import get_session, session_middleware
from aiohttp_session.redis_storage import RedisStorage
from aioredis import create_pool


def create_app(**options):
    """Create aiohttp app with custom middleware."""
    app = web.Application(middlewares=[
        session_middleware_factory,
    ])
    app.router.add_route('GET', '/', view)
    app.settings = MappingProxyType(dict(
        REDIS_URL='redis://127.0.0.1:6379/0',
        **options
    ))

    return app


async def session_middleware_factory(app, handler):
    """Wrapper to Session Middleware factory.

    Create Redis pool and setup session storage inside of coroutine.
    """
    # Parse Redis URL
    parsed = urlparse(app.settings['REDIS_URL'])

    # Create Redis connection pool
    pool = await create_pool(
        (parsed.hostname, parsed.port),
        db=int(parsed.path.lstrip('/')),
    )

    # Do the trick, by passing app & handler back to original session
    # middleware factory. Do not forget to await on results here as original
    # session middleware factory is also awaitable.
    return await session_middleware(RedisStorage(pool))(app, handler)


async def view(request):
    """View function to work with session."""
    session = await get_session(request)
    session['counter'] = (session.get('counter') or 0) + 1

    return web.json_response({
        'counter': session['counter'],
    })


#: Global application to serve with Gunicorn
app = create_app()