Add redirect to another endpoint if designation is a synthetic object

If the object has a space in it, then redirect to another API endpoint
which indicates that it is synthetic.

src/mpclookup/handlers/external.py

@@ -1,9 +1,10 @@
 """Handlers for the app's external root, ``/mpc-lookup/``."""
 
 from typing import Annotated
+from urllib.parse import urlencode
 
-from fastapi import APIRouter, Depends, Query
-from fastapi.responses import RedirectResponse
+from fastapi import APIRouter, Depends, Query, Request
+from fastapi.responses import PlainTextResponse, RedirectResponse
 from safir.dependencies.logger import logger_dependency
 from safir.metadata import get_metadata
 from structlog.stdlib import BoundLogger
@@ -60,6 +61,7 @@ async def get_index(
 async def search(
  designation: Annotated[str, Query()],
  logger: Annotated[BoundLogger, Depends(logger_dependency)],
+ request: Request,
 ) -> str:
  """
  Request a redirect to the MPCORB record for a given designation.
@@ -68,14 +70,37 @@ async def search(
  -----
  Example request:
 
- /mpc-lookup/search?designation=2011+1001+T-2
+ `/mpc-lookup/search?designation=2011+1001+T-2`
 
+ In this case, the "2011 " prefix, which is present in the DP0.3 data, will
+ be stripped out automatically so that the designation is valid.
+
+ Any designations containing spaces will be redirected to an endpoint that
+ will return a text response indicating that the object is synthetic.
  """
  logger.info("Request for designation URL", designation=designation)
  fd = designation.replace(_DESIGNATION_PREPEND, "")
- redirect_url = (
- "https://www.minorplanetcenter.net/db_search/"
- f"show_object?object_id={fd}"
- )
- logger.info("Redirecting to designation URL", redirect_url=redirect_url)
+ if " " not in fd:
+ redirect_url = (
+ "https://www.minorplanetcenter.net/db_search/"
+ f"show_object?object_id={fd}"
+ )
+ logger.info("Redirecting to MPC URL", redirect_url=redirect_url)
+ else:
+ base_url = str(request.url_for("get_synthetic_object"))
+ query_string = urlencode({"designation": designation})
+ redirect_url = base_url + "?" + query_string
+ logger.info(
+ "Redirecting synthetic object to", redirect_url=redirect_url
+ )
  return redirect_url
+
+
+@external_router.get("/synthetic_object", response_class=PlainTextResponse)
+async def get_synthetic_object(
+ designation: Annotated[str, Query()],
+) -> str:
+ return (
+ f"{designation} "
+ "appears to be a synthetic object from the DP0.3 input simulation."
+ )