forms.py

from base64 import b64decode
from functools import wraps
from io import BytesIO, StringIO

from werkzeug.datastructures import Headers
from werkzeug.formparser import parse_form_data


def use_form(func):
    @wraps(func)
    def func_with_form_data(event, *args, **kwargs):
        body = b64decode(event["body"]) if event["isBase64Encoded"] else event["body"]

        event["headers"] = Headers(event["headers"])

        environ = {
            "wsgi.input": BytesIO(body) if isinstance(body, bytes) else StringIO(body),
            "CONTENT_LENGTH": len(body),
            "CONTENT_TYPE": event["headers"]["Content-Type"],
            "REQUEST_METHOD": "POST",
        }

        _, event["form"], event["files"] = parse_form_data(environ)

        return func(event, *args, **kwargs)

    return func_with_form_data