Split up code into functions to ease comprehension

lookup.py

@@ -15,6 +15,9 @@ app = Flask(__name__)
 app.config.from_object("config.default")
 database.init_app(app)
 
+Tags = typing.Mapping[str, str]
+Elements = sqlalchemy.orm.query.Query[model.Polygon]
+
 
 def get_random_lat_lon() -> tuple[float, float]:
     """Select random lat/lon within the UK."""
@@ -28,12 +31,10 @@ def get_random_lat_lon() -> tuple[float, float]:
     return lat, lon
 
 
-Elements = sqlalchemy.orm.query.Query
-
-
 def do_lookup(
     elements: Elements, lat: str | float, lon: str | float
 ) -> wikidata.WikidataDict:
+    """Do lookup."""
     try:
         hit = osm_lookup(elements, lat, lon)
     except wikidata.QueryError as e:
@@ -47,6 +48,7 @@ def do_lookup(
 
 
 def lat_lon_to_wikidata(lat: str | float, lon: str | float) -> dict[str, typing.Any]:
+    """Lookup lat/lon and find most appropriate Wikidata item."""
     scotland_code = scotland.get_scotland_code(lat, lon)
 
     elements: typing.Any
@@ -66,8 +68,11 @@ def lat_lon_to_wikidata(lat: str | float, lon: str | float) -> dict[str, typing.
         return {"elements": elements, "result": result}
 
     admin_level = result.get("admin_level")
+    if not admin_level:
+        return {"elements": elements, "result": result}
 
-    if not admin_level or admin_level >= 7:
+    assert isinstance(admin_level, int)
+    if admin_level >= 7:
         return {"elements": elements, "result": result}
 
     row = wikidata.geosearch(lat, lon)
@@ -79,71 +84,83 @@ def lat_lon_to_wikidata(lat: str | float, lon: str | float) -> dict[str, typing.
     return {"elements": elements, "result": result}
 
 
+def get_admin_level(tags: Tags) -> int | None:
+    """Read admin_level from tags."""
+    admin_level_tag = tags.get("admin_level")
+    return (
+        int(admin_level_tag) if admin_level_tag and admin_level_tag.isdigit() else None
+    )
+
+
+def hit_from_wikidata_tag(tags: Tags) -> wikidata.Hit | None:
+    """Check element for a wikidata tag."""
+    return (
+        {
+            "wikidata": qid,
+            "commons_cat": commons,
+        }
+        if "wikidata" in tags
+        and (commons := wikidata.qid_to_commons_category(qid := tags["wikidata"]))
+        else None
+    )
+
+
+def hit_from_ref_gss_tag(tags: Tags) -> wikidata.Hit | None:
+    """Check element for rss:gss tag."""
+    gss = tags.get("ref:gss")
+    return wikidata.get_commons_cat_from_gss(gss) if gss else None
+
+
+def hit_from_name(
+    tags: Tags, lat: str | float, lon: str | float
+) -> wikidata.Hit | None:
+    """Use name to look for hit."""
+    if not (name := tags.get("name")):
+        return None
+    if name.endswith(" CP"):  # civil parish
+        name = name[:-3]
+
+    rows = wikidata.lookup_wikidata_by_name(name, lat, lon)
+    return wikidata.commons_from_rows(rows) if len(rows) == 1 else None
+
+
 def osm_lookup(
-    elements: Elements, lat: str | float, lon: str | float  # type:ignore
+    elements: Elements, lat: str | float, lon: str | float
 ) -> wikidata.Hit | None:
     """OSM lookup."""
     ret: wikidata.Hit | None
     for e in elements:
         assert isinstance(e, model.Polygon)
         assert e.tags
-        tags: typing.Mapping[str, typing.Any] = e.tags
-        admin_level_tag = tags.get("admin_level")
-        admin_level: int | None = (
-            int(admin_level_tag)
-            if admin_level_tag and admin_level_tag.isdigit()
-            else None
-        )
+        tags: typing.Mapping[str, str] = e.tags
+        admin_level: int | None = get_admin_level(tags)
         if not admin_level and tags.get("boundary") != "political":
             continue
-        if "wikidata" in tags:
-            qid = tags["wikidata"]
-            commons = wikidata.qid_to_commons_category(qid)
-            if commons:
-                return {
-                    "wikidata": qid,
-                    "commons_cat": commons,
-                    "admin_level": admin_level,
-                    "element": e.osm_id,
-                    "geojson": typing.cast(str, e.geojson_str),
-                }
-        gss = tags.get("ref:gss")
-        if gss:
-            ret = wikidata.get_commons_cat_from_gss(gss)
-            if ret:
-                ret["admin_level"] = admin_level
-                ret["element"] = e.osm_id
-                ret["geojson"] = typing.cast(str, e.geojson_str)
-                return ret
-
-        name = tags.get("name")
-        if not name:
+        if not (
+            (hit := hit_from_wikidata_tag(tags))
+            or (hit := hit_from_ref_gss_tag(tags))
+            or (hit := hit_from_name(tags, lat, lon))
+        ):
             continue
-        if name.endswith(" CP"):
-            name = name[:-3]
-        rows = wikidata.lookup_wikidata_by_name(name, lat, lon)
+        hit["admin_level"] = admin_level
+        hit["element"] = e.osm_id
+        hit["geojson"] = typing.cast(str, e.geojson_str)
+        return hit
 
-        if len(rows) == 1:
-            ret = wikidata.commons_from_rows(rows)
-            if ret:
-                ret["admin_level"] = admin_level
-                ret["element"] = e.osm_id
-                return ret
-
-    has_wikidata_tag = [e.tags for e in elements if e.tags.get("wikidata")]
+    has_wikidata_tag = [e for e in elements if e.tags.get("wikidata")]
     if len(has_wikidata_tag) != 1:
         return None
 
-    assert has_wikidata_tag[0]
-    qid = has_wikidata_tag[0]["wikidata"]
-    return typing.cast(
-        wikidata.Hit,
-        {
-            "wikidata": qid,
-            "commons_cat": wikidata.qid_to_commons_category(qid),
-            "admin_level": admin_level,
-        },
-    )
+    e = has_wikidata_tag[0]
+    assert e.tags
+    qid = e.tags["wikidata"]
+    return {
+        "wikidata": qid,
+        "element": e.osm_id,
+        "geojson": typing.cast(str, e.geojson_str),
+        "commons_cat": wikidata.qid_to_commons_category(qid),
+        "admin_level": admin_level,
+    }
 
 
 def redirect_to_detail(q: str) -> Response:
@@ -231,7 +248,7 @@ def detail_page() -> Response | str:
         str=str,
         element_id=element,
         geojson=geojson,
-        **reply
+        **reply,
     )