options.py

from collections import defaultdict
from typing import Dict, FrozenSet

from sanic import Sanic, response
from sanic.router import Route

from cors import _add_cors_headers


def _compile_routes_needing_options(
    routes: Dict[str, Route]
) -> Dict[str, FrozenSet]:
    needs_options = defaultdict(list)
    # This is 21.3 and later. You will need to change this for older versions.
    for route in routes.values():
        for uri, methods in route.methods.items():
            if "OPTIONS" not in methods:
                needs_options[uri].extend(methods)
    return {
        uri: frozenset(methods) for uri, methods in dict(needs_options).items()
    }


def _options_wrapper(handler, methods):
    def wrapped_handler(request, *args, **kwargs):
        nonlocal methods
        return handler(request, methods)

    return wrapped_handler


async def options_handler(request, methods) -> response.HTTPResponse:
    resp = response.empty()
    _add_cors_headers(resp, methods)
    return resp


def setup_options(app: Sanic, _):
    app.router.reset()
    needs_options = _compile_routes_needing_options(app.router.routes_all)
    for uri, methods in needs_options.items():
        app.add_route(
            _options_wrapper(options_handler, methods),
            uri,
            methods=["OPTIONS"],
        )
    app.router.finalize()