factor out common server implementation code

Most of the server implementation of V1 API now resides in
api.v1.server_glue. The webframeworks only supply some glue code
which is independent to changes in the API code.

nominatim/api/v1/__init__.py

@@ -8,6 +8,12 @@
 Implementation of API version v1 (aka the legacy version).
 """
 
+#pylint: disable=useless-import-alias
+
+from nominatim.api.v1.server_glue import (ASGIAdaptor as ASGIAdaptor,
+                                          EndpointFunc as EndpointFunc,
+                                          ROUTES as ROUTES)
+
 import nominatim.api.v1.format as _format
 
 list_formats = _format.dispatch.list_formats

nominatim/api/v1/server_glue.py

@@ -0,0 +1,153 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2023 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Generic part of the server implementation of the v1 API.
+Combine with the scaffolding provided for the various Python ASGI frameworks.
+"""
+from typing import Optional, Any, Type, Callable
+import abc
+
+import nominatim.api as napi
+from nominatim.api.v1.format import dispatch as formatting
+
+CONTENT_TYPE = {
+  'text': 'text/plain; charset=utf-8',
+  'xml': 'text/xml; charset=utf-8',
+  'jsonp': 'application/javascript'
+}
+
+
+class ASGIAdaptor(abc.ABC):
+    """ Adapter class for the different ASGI frameworks.
+        Wraps functionality over concrete requests and responses.
+    """
+
+    @abc.abstractmethod
+    def get(self, name: str, default: Optional[str] = None) -> Optional[str]:
+        """ Return an input parameter as a string. If the parameter was
+            not provided, return the 'default' value.
+        """
+
+    @abc.abstractmethod
+    def get_header(self, name: str, default: Optional[str] = None) -> Optional[str]:
+        """ Return a HTTP header parameter as a string. If the parameter was
+            not provided, return the 'default' value.
+        """
+
+
+    @abc.abstractmethod
+    def error(self, msg: str) -> Exception:
+        """ Construct an appropriate exception from the given error message.
+            The exception must result in a HTTP 400 error.
+        """
+
+
+    @abc.abstractmethod
+    def create_response(self, status: int, output: str, content_type: str) -> Any:
+        """ Create a response from the given parameters. The result will
+            be returned by the endpoint functions. The adaptor may also
+            return None when the response is created internally with some
+            different means.
+
+            The response must return the HTTP given status code 'status', set
+            the HTTP content-type headers to the string provided and the
+            body of the response to 'output'.
+        """
+
+
+    def build_response(self, output: str, media_type: str, status: int = 200) -> Any:
+        """ Create a response from the given output. Wraps a JSONP function
+            around the response, if necessary.
+        """
+        if media_type == 'json' and status == 200:
+            jsonp = self.get('json_callback')
+            if jsonp is not None:
+                if any(not part.isidentifier() for part in jsonp.split('.')):
+                    raise self.error('Invalid json_callback value')
+                output = f"{jsonp}({output})"
+                media_type = 'jsonp'
+
+        return self.create_response(status, output,
+                                    CONTENT_TYPE.get(media_type, 'application/json'))
+
+
+    def get_int(self, name: str, default: Optional[int] = None) -> int:
+        """ Return an input parameter as an int. Raises an exception if
+            the parameter is given but not in an integer format.
+
+            If 'default' is given, then it will be returned when the parameter
+            is missing completely. When 'default' is None, an error will be
+            raised on a missing parameter.
+        """
+        value = self.get(name)
+
+        if value is None:
+            if default is not None:
+                return default
+
+            raise self.error(f"Parameter '{name}' missing.")
+
+        try:
+            return int(value)
+        except ValueError as exc:
+            raise self.error(f"Parameter '{name}' must be a number.") from exc
+
+
+    def get_bool(self, name: str, default: Optional[bool] = None) -> bool:
+        """ Return an input parameter as bool. Only '0' is accepted as
+            an input for 'false' all other inputs will be interpreted as 'true'.
+
+            If 'default' is given, then it will be returned when the parameter
+            is missing completely. When 'default' is None, an error will be
+            raised on a missing parameter.
+        """
+        value = self.get(name)
+
+        if value is None:
+            if default is not None:
+                return default
+
+            raise self.error(f"Parameter '{name}' missing.")
+
+        return value != '0'
+
+
+def parse_format(params: ASGIAdaptor, result_type: Type[Any], default: str) -> str:
+    """ Get and check the 'format' parameter and prepare the formatter.
+        `fmtter` is a formatter and `default` the
+        format value to assume when no parameter is present.
+    """
+    fmt = params.get('format', default=default)
+    assert fmt is not None
+
+    if not formatting.supports_format(result_type, fmt):
+        raise params.error("Parameter 'format' must be one of: " +
+                           ', '.join(formatting.list_formats(result_type)))
+
+    return fmt
+
+
+async def status_endpoint(api: napi.NominatimAPIAsync, params: ASGIAdaptor) -> Any:
+    """ Server glue for /status endpoint. See API docs for details.
+    """
+    result = await api.status()
+
+    fmt = parse_format(params, napi.StatusResult, 'text')
+
+    if fmt == 'text' and result.status:
+        status_code = 500
+    else:
+        status_code = 200
+
+    return params.build_response(formatting.format_result(result, fmt), fmt,
+                                 status=status_code)
+
+EndpointFunc = Callable[[napi.NominatimAPIAsync, ASGIAdaptor], Any]
+
+ROUTES = [
+    ('status', status_endpoint)
+]

nominatim/server/falcon/server.py

@@ -7,70 +7,66 @@
 """
 Server implementation using the falcon webserver framework.
 """
-from typing import Type, Any, Optional, Mapping
+from typing import Optional, Mapping, cast
 from pathlib import Path
 
 import falcon
-import falcon.asgi
+from falcon.asgi import App, Request, Response
 
-from nominatim.api import NominatimAPIAsync, StatusResult
+from nominatim.api import NominatimAPIAsync
 import nominatim.api.v1 as api_impl
 
-CONTENT_TYPE = {
-  'text': falcon.MEDIA_TEXT,
-  'xml': falcon.MEDIA_XML
-}
 
-class NominatimV1:
+class ParamWrapper(api_impl.ASGIAdaptor):
-    """ Implementation of V1 version of the Nominatim API.
+    """ Adaptor class for server glue to Falcon framework.
     """
 
-    def __init__(self, project_dir: Path, environ: Optional[Mapping[str, str]]) -> None:
+    def __init__(self, req: Request, resp: Response) -> None:
-        self.api = NominatimAPIAsync(project_dir, environ)
+        self.request = req
+        self.response = resp
 
 
-    def parse_format(self, req: falcon.asgi.Request, rtype: Type[Any], default: str) -> None:
+    def get(self, name: str, default: Optional[str] = None) -> Optional[str]:
-        """ Get and check the 'format' parameter and prepare the formatter.
+        return cast(Optional[str], self.request.get_param(name, default=default))
-            `rtype` describes the expected return type and `default` the
+
-            format value to assume when no parameter is present.
+
+    def get_header(self, name: str, default: Optional[str] = None) -> Optional[str]:
+        return cast(Optional[str], self.request.get_header(name, default=default))
+
+
+    def error(self, msg: str) -> falcon.HTTPBadRequest:
+        return falcon.HTTPBadRequest(description=msg)
+
+
+    def create_response(self, status: int, output: str, content_type: str) -> None:
+        self.response.status = status
+        self.response.text = output
+        self.response.content_type = content_type
+
+
+class EndpointWrapper:
+    """ Converter for server glue endpoint functions to Falcon request handlers.
+    """
+
+    def __init__(self, func: api_impl.EndpointFunc, api: NominatimAPIAsync) -> None:
+        self.func = func
+        self.api = api
+
+
+    async def on_get(self, req: Request, resp: Response) -> None:
+        """ Implementation of the endpoint.
         """
-        req.context.format = req.get_param('format', default=default)
+        await self.func(self.api, ParamWrapper(req, resp))
-
-        if not api_impl.supports_format(rtype, req.context.format):
-            raise falcon.HTTPBadRequest(
-                description="Parameter 'format' must be one of: " +
-                            ', '.join(api_impl.list_formats(rtype)))
-
-
-    def format_response(self, req: falcon.asgi.Request, resp: falcon.asgi.Response,
-                        result: Any) -> None:
-        """ Render response into a string according to the formatter
-            set in `parse_format()`.
-        """
-        resp.text = api_impl.format_result(result, req.context.format)
-        resp.content_type = CONTENT_TYPE.get(req.context.format, falcon.MEDIA_JSON)
-
-
-    async def on_get_status(self, req: falcon.asgi.Request, resp: falcon.asgi.Response) -> None:
-        """ Implementation of status endpoint.
-        """
-        self.parse_format(req, StatusResult, 'text')
-
-        result = await self.api.status()
-
-        self.format_response(req, resp, result)
-        if result.status and req.context.format == 'text':
-            resp.status = 500
 
 
 def get_application(project_dir: Path,
-                    environ: Optional[Mapping[str, str]] = None) -> falcon.asgi.App:
+                    environ: Optional[Mapping[str, str]] = None) -> App:
-    """ Create a Nominatim falcon ASGI application.
+    """ Create a Nominatim Falcon ASGI application.
     """
-    app = falcon.asgi.App()
+    api = NominatimAPIAsync(project_dir, environ)
 
-    api = NominatimV1(project_dir, environ)
+    app = App()
-
+    for name, func in api_impl.ROUTES:
-    app.add_route('/status', api, suffix='status')
+        app.add_route('/' + name, EndpointWrapper(func, api))
 
     return app

nominatim/server/sanic/server.py

@@ -7,75 +7,58 @@
 """
 Server implementation using the sanic webserver framework.
 """
-from typing import Any, Optional, Mapping
+from typing import Any, Optional, Mapping, Callable, cast, Coroutine
 from pathlib import Path
 
-import sanic
+from sanic import Request, HTTPResponse, Sanic
+from sanic.exceptions import SanicException
+from sanic.response import text as TextResponse
 
-from nominatim.api import NominatimAPIAsync, StatusResult
+from nominatim.api import NominatimAPIAsync
 import nominatim.api.v1 as api_impl
 
-api = sanic.Blueprint('NominatimAPI')
+class ParamWrapper(api_impl.ASGIAdaptor):
-
+    """ Adaptor class for server glue to Sanic framework.
-CONTENT_TYPE = {
-  'text': 'text/plain; charset=utf-8',
-  'xml': 'text/xml; charset=utf-8'
-}
-
-def usage_error(msg: str) -> sanic.HTTPResponse:
-    """ Format the response for an error with the query parameters.
     """
-    return sanic.response.text(msg, status=400)
+
+    def __init__(self, request: Request) -> None:
+        self.request = request
 
 
-def api_response(request: sanic.Request, result: Any) -> sanic.HTTPResponse:
+    def get(self, name: str, default: Optional[str] = None) -> Optional[str]:
-    """ Render a response from the query results using the configured
+        return cast(Optional[str], self.request.args.get(name, default))
-        formatter.
-    """
-    body = api_impl.format_result(result, request.ctx.format)
-    return sanic.response.text(body,
-                               content_type=CONTENT_TYPE.get(request.ctx.format,
-                                                             'application/json'))
 
 
-@api.on_request # type: ignore[misc]
+    def get_header(self, name: str, default: Optional[str] = None) -> Optional[str]:
-async def extract_format(request: sanic.Request) -> Optional[sanic.HTTPResponse]:
+        return cast(Optional[str], self.request.headers.get(name, default))
-    """ Get and check the 'format' parameter and prepare the formatter.
-        `ctx.result_type` describes the expected return type and
-        `ctx.default_format` the format value to assume when no parameter
-        is present.
-    """
-    assert request.route is not None
-
-    request.ctx.format = request.args.get('format', request.route.ctx.default_format)
-    if not api_impl.supports_format(request.route.ctx.result_type, request.ctx.format):
-        return usage_error("Parameter 'format' must be one of: " +
-                           ', '.join(api_impl.list_formats(request.route.ctx.result_type)))
-
-    return None
 
 
-@api.get('/status', ctx_result_type=StatusResult, ctx_default_format='text')
+    def error(self, msg: str) -> SanicException:
-async def status(request: sanic.Request) -> sanic.HTTPResponse:
+        return SanicException(msg, status_code=400)
-    """ Implementation of status endpoint.
-    """
-    result = await request.app.ctx.api.status()
-    response = api_response(request, result)
 
-    if request.ctx.format == 'text' and result.status:
-        response.status = 500
 
-    return response
+    def create_response(self, status: int, output: str,
+                        content_type: str) -> HTTPResponse:
+        return TextResponse(output, status=status, content_type=content_type)
+
+
+def _wrap_endpoint(func: api_impl.EndpointFunc)\
+       -> Callable[[Request], Coroutine[Any, Any, HTTPResponse]]:
+    async def _callback(request: Request) -> HTTPResponse:
+        return cast(HTTPResponse, await func(request.app.ctx.api, ParamWrapper(request)))
+
+    return _callback
 
 
 def get_application(project_dir: Path,
-                    environ: Optional[Mapping[str, str]] = None) -> sanic.Sanic:
+                    environ: Optional[Mapping[str, str]] = None) -> Sanic:
     """ Create a Nominatim sanic ASGI application.
     """
-    app = sanic.Sanic("NominatimInstance")
+    app = Sanic("NominatimInstance")
 
     app.ctx.api = NominatimAPIAsync(project_dir, environ)
 
-    app.blueprint(api)
+    for name, func in api_impl.ROUTES:
+        app.add_route(_wrap_endpoint(func), f"/{name}", name=f"v1_{name}_simple")
 
     return app

nominatim/server/starlette/server.py

@@ -7,7 +7,7 @@
 """
 Server implementation using the starlette webserver framework.
 """
-from typing import Any, Type, Optional, Mapping
+from typing import Any, Optional, Mapping, Callable, cast, Coroutine
 from pathlib import Path
 
 from starlette.applications import Starlette
@@ -16,58 +16,50 @@ from starlette.exceptions import HTTPException
 from starlette.responses import Response
 from starlette.requests import Request
 
-from nominatim.api import NominatimAPIAsync, StatusResult
+from nominatim.api import NominatimAPIAsync
 import nominatim.api.v1 as api_impl
 
-CONTENT_TYPE = {
+class ParamWrapper(api_impl.ASGIAdaptor):
-  'text': 'text/plain; charset=utf-8',
+    """ Adaptor class for server glue to Starlette framework.
-  'xml': 'text/xml; charset=utf-8'
-}
-
-def parse_format(request: Request, rtype: Type[Any], default: str) -> None:
-    """ Get and check the 'format' parameter and prepare the formatter.
-        `rtype` describes the expected return type and `default` the
-        format value to assume when no parameter is present.
     """
-    fmt = request.query_params.get('format', default=default)
 
-    if not api_impl.supports_format(rtype, fmt):
+    def __init__(self, request: Request) -> None:
-        raise HTTPException(400, detail="Parameter 'format' must be one of: " +
+        self.request = request
-                                        ', '.join(api_impl.list_formats(rtype)))
-
-    request.state.format = fmt
 
 
-def format_response(request: Request, result: Any) -> Response:
+    def get(self, name: str, default: Optional[str] = None) -> Optional[str]:
-    """ Render response into a string according.
+        return self.request.query_params.get(name, default=default)
-    """
-    fmt = request.state.format
-    return Response(api_impl.format_result(result, fmt),
-                    media_type=CONTENT_TYPE.get(fmt, 'application/json'))
 
 
-async def on_status(request: Request) -> Response:
+    def get_header(self, name: str, default: Optional[str] = None) -> Optional[str]:
-    """ Implementation of status endpoint.
+        return self.request.headers.get(name, default)
-    """
-    parse_format(request, StatusResult, 'text')
-    result = await request.app.state.API.status()
-    response = format_response(request, result)
-
-    if request.state.format == 'text' and result.status:
-        response.status_code = 500
-
-    return response
 
 
-V1_ROUTES = [
+    def error(self, msg: str) -> HTTPException:
-    Route('/status', endpoint=on_status)
+        return HTTPException(400, detail=msg)
-]
+
+
+    def create_response(self, status: int, output: str, content_type: str) -> Response:
+        return Response(output, status_code=status, media_type=content_type)
+
+
+def _wrap_endpoint(func: api_impl.EndpointFunc)\
+        -> Callable[[Request], Coroutine[Any, Any, Response]]:
+    async def _callback(request: Request) -> Response:
+        return cast(Response, await func(request.app.state.API, ParamWrapper(request)))
+
+    return _callback
+
 
 def get_application(project_dir: Path,
                     environ: Optional[Mapping[str, str]] = None) -> Starlette:
     """ Create a Nominatim falcon ASGI application.
     """
-    app = Starlette(debug=True, routes=V1_ROUTES)
+    routes = []
+    for name, func in api_impl.ROUTES:
+        routes.append(Route(f"/{name}", endpoint=_wrap_endpoint(func)))
+
+    app = Starlette(debug=True, routes=routes)
 
     app.state.API = NominatimAPIAsync(project_dir, environ)