WSGI adaptor to serve RPC services

[kanghyojun]

Python runtime of Nirum has to provide a WSGI adaptor which takes an RPC service and serves it. See also nirum-lang/nirum#25.

The generated service code will look like the following:

from nirum.rpc import WsgiApp, Service


class CustomerService(Service):
    # GET /tokens/:token/key                -> get_key_by_token
    # GET /api/group_tokens/?arg=token      -> group_tokens
    # POST /jsonrpc
    # {"method": "group_tokens", "param": {"abc", "def"}}
    # GET /api/get_key_by_token/?arg=token  -> get_key_by_token
    __nirum_service_methods__ = {'get_key_by_token', 'group_tokens'}
    __nirum_http_routing__ = {
        'get_key_by_token': ('get', '/tokens/:token/key/'),
    }

    def get_key_by_token(token: 'Token') -> 'Key':
        raise NotImplementedError('get_key_by_token')

    def group_tokens(
        token: typing.AbstractSet['Token']
    ) -> typing.AbstractSet[typing.AbstractSet['Token']]:
        raise NotImplementedError('group_tokens')


class CustomerServiceImpl(CustomerService):

    pass


app = WsgiApp(CustomerService()) # wsgi app

where the Nirum IDL looks like the following:

boxed token (uuid);
union key = phone       (text phone_number)
         | qr-code     (text url)
         | credit-card (blob hash)
         ;

service customer (
   [http-get: "/tokens/:token/key/"]
   key get-key-by-token (token token),

   {{token}} group-tokens ({token} tokens),
);