36 lines
1.2 KiB
Python
36 lines
1.2 KiB
Python
from typing import Awaitable, Callable, Iterable
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from aiohttp.web_middlewares import middleware
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from aiohttp.web_request import Request
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from aiohttp.web_response import StreamResponse
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Handler = Callable[[Request], Awaitable[StreamResponse]]
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Middleware = Callable[[Request, Handler], Awaitable[StreamResponse]]
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def cors(allow_headers: Iterable[str]) -> Middleware:
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@middleware # type: ignore[misc]
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async def impl(request: Request, handler: Handler) -> StreamResponse:
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is_options = request.method == "OPTIONS"
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is_preflight = is_options and "Access-Control-Request-Method" in request.headers
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if is_preflight:
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resp = StreamResponse()
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else:
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resp = await handler(request)
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origin = request.headers.get("Origin")
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if not origin:
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return resp
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resp.headers["Access-Control-Allow-Origin"] = "*"
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resp.headers["Access-Control-Expose-Headers"] = "*"
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if is_options:
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resp.headers["Access-Control-Allow-Headers"] = ", ".join(allow_headers)
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resp.headers["Access-Control-Allow-Methods"] = ", ".join(
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("OPTIONS", "POST")
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)
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return resp
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return impl # type: ignore[no-any-return]
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