Return gateway resource for /gateways/{id}

This is instead of redirecting to /gateways/{id}/structures as this is
now moving more towards *not* reproducing an actual OPTIMADE
implementation.

optimade_gateway/routers/gateways.py

@@ -7,7 +7,6 @@
 where, `id` may be left out.
 """
 from fastapi import APIRouter, Depends, Request
-from fastapi.responses import RedirectResponse
 from optimade.models import ToplevelLinks
 from optimade.server.query_params import EntryListingQueryParams
 from optimade.server.schemas import ERROR_RESPONSES
@@ -121,15 +120,20 @@ async def post_gateways(
 async def get_gateway(request: Request, gateway_id: str) -> GatewaysResponseSingle:
     """`GET /gateways/{gateway ID}`
 
-    Represent an OPTIMADE server.
-
-    !!! note
-        For now, redirect to the gateway's `/structures` entry listing endpoint.
-
+    Return a single [`GatewayResource`][optimade_gateway.models.gateways.GatewayResource].
     """
-    from optimade_gateway.routers.utils import validate_resource
+    from optimade.server.routers.utils import meta_values
+    from optimade_gateway.routers.utils import get_valid_resource
+
+    result = await get_valid_resource(GATEWAYS_COLLECTION, gateway_id)
 
-    await validate_resource(GATEWAYS_COLLECTION, gateway_id)
-    return RedirectResponse(
-        request.url.replace(path=f"{request.url.path.rstrip('/')}/structures")
+    return GatewaysResponseSingle(
+        links=ToplevelLinks(next=None),
+        data=result,
+        meta=meta_values(
+            url=request.url,
+            data_returned=1,
+            data_available=await GATEWAYS_COLLECTION.count(),
+            more_data_available=False,
+        ),
     )

tests/conftest.py

@@ -132,6 +132,19 @@ async def _get_gateway(id: str) -> dict:
     return _get_gateway
 
 
+@pytest.fixture
+async def random_gateway() -> dict:
+    """Get a random gateway currently in the MongoDB"""
+    from optimade_gateway.mongo.database import MONGO_DB
+
+    gateway_ids = set()
+    async for gateway in MONGO_DB["gateways"].find(
+        filter={}, projection={"id": True, "_id": False}
+    ):
+        gateway_ids.add(gateway["id"])
+    return gateway_ids.pop()
+
+
 @pytest.fixture
 async def reset_db_after(top_dir: Path) -> None:
     """Reset MongoDB with original test data after the test has run"""

tests/routers/test_gateways.py

@@ -190,6 +190,7 @@ async def test_post_gateways_database_ids(
         assert db["id"] in data["database_ids"]
 
 
+@pytest.mark.usefixtures("reset_db_after")
 async def test_post_gateways_create_with_db_ids(
     client: Callable[
         [str, FastAPI, str, Literal["get", "post", "put", "delete", "patch"]],
@@ -252,3 +253,30 @@ async def test_post_gateways_create_with_db_ids(
     db_datum = await MONGO_DB["gateways"].find_one(mongo_filter)
     for db in db_datum["databases"]:
         assert db["id"] in [data["databases"][0]["id"], data["database_ids"][0]]
+
+
+async def test_get_single_gateway(
+    client: Callable[
+        [str, FastAPI, str, Literal["get", "post", "put", "delete", "patch"]],
+        Awaitable[httpx.Response],
+    ],
+    random_gateway: str,
+    top_dir: Path,
+):
+    """Test GET /gateways/{gateway_id}"""
+    import json
+
+    from optimade_gateway.models.responses import GatewaysResponseSingle
+
+    response = await client(f"/gateways/{random_gateway}")
+
+    assert response.status_code == 200, f"Request failed: {response.json()}"
+    response = GatewaysResponseSingle(**response.json())
+    assert response
+
+    with open(top_dir / "tests/static/test_gateways.json") as handle:
+        test_data = json.load(handle)
+
+    assert response.meta.data_returned == 1
+    assert response.meta.data_available == len(test_data)
+    assert not response.meta.more_data_available