refactor(patreon): DRY the campaigns-API request (#161)

_lookup_via_api and resolve_display_name shared ~90% of their body (same
endpoint, params, headers, error handling — differing only in which field
they pluck from data[0]). Extract _campaigns_api_first(vanity, cookies_path)
-> dict|None; callers pluck the campaign id vs the display name. Return-value
behavior preserved (the display-name path additionally gains the helper's more
granular warning logs). Covered by the existing test_patreon_resolver.py.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NsmJSQxnNxGgtM5Yz4GAqi

backend/app/services/patreon_resolver.py

@@ -91,48 +91,46 @@ def _sync_lookup(vanity: str, cookies_path: str | None) -> str | None:
     )
 
 
-def _lookup_via_api(vanity: str, cookies_path: str | None) -> str | None:
+def _campaigns_api_first(vanity: str, cookies_path: str | None) -> dict | None:
+    """The first `data` object from Patreon's campaigns API filtered by vanity
+    (`?filter[vanity]=<vanity>&fields[campaign]=name`), or None on any failure
+    (network / non-200 / non-JSON / empty). The single request shape shared by
+    _lookup_via_api (plucks the campaign id) and resolve_display_name (plucks the
+    display name)."""
     jar = _load_cookie_jar(cookies_path)
-    headers = {
-        "User-Agent": _USER_AGENT,
-        "Accept": "application/vnd.api+json",
-    }
-    params = {
-        "filter[vanity]": vanity,
-        "fields[campaign]": "name",
-    }
     try:
         resp = requests.get(
             _CAMPAIGNS_URL,
-            params=params,
+            params={"filter[vanity]": vanity, "fields[campaign]": "name"},
-            headers=headers,
+            headers={"User-Agent": _USER_AGENT, "Accept": "application/vnd.api+json"},
             cookies=jar,
             timeout=_TIMEOUT_SECONDS,
         )
     except requests.RequestException as exc:
         log.warning("Patreon campaigns API request failed for vanity=%s: %s", vanity, exc)
         return None
-
     if resp.status_code != 200:
         log.warning(
             "Patreon campaigns API returned HTTP %d for vanity=%s",
             resp.status_code, vanity,
         )
         return None
-
     try:
         payload = resp.json()
     except ValueError as exc:
         log.warning("Patreon campaigns API returned non-JSON for vanity=%s: %s", vanity, exc)
         return None
+    data = payload.get("data") if isinstance(payload, dict) else None
+    if not isinstance(data, list) or not data or not isinstance(data[0], dict):
+        return None
+    return data[0]
 
-    if not isinstance(payload, dict):
+
+def _lookup_via_api(vanity: str, cookies_path: str | None) -> str | None:
+    first = _campaigns_api_first(vanity, cookies_path)
+    if first is None:
         return None
-    data = payload.get("data")
+    campaign_id = first.get("id")
-    if not isinstance(data, list) or not data:
-        return None
-    first = data[0] if isinstance(data[0], dict) else None
-    campaign_id = first.get("id") if first else None
     if not isinstance(campaign_id, str) or not campaign_id:
         return None
     log.info("Resolved Patreon vanity=%s → campaign_id=%s", vanity, campaign_id)
@@ -144,24 +142,10 @@ def resolve_display_name(vanity: str, cookies_path: str | None) -> str | None:
     (`fields[campaign]=name`), used to name the Artist at add-time (#130). None
     on any failure — the caller falls back to the vanity handle. Sync: call from
     an executor."""
-    jar = _load_cookie_jar(cookies_path)
+    first = _campaigns_api_first(vanity, cookies_path)
-    try:
+    if first is None:
-        resp = requests.get(
-            _CAMPAIGNS_URL,
-            params={"filter[vanity]": vanity, "fields[campaign]": "name"},
-            headers={"User-Agent": _USER_AGENT, "Accept": "application/vnd.api+json"},
-            cookies=jar,
-            timeout=_TIMEOUT_SECONDS,
-        )
-        if resp.status_code != 200:
         return None
-        data = resp.json().get("data")
+    name = (first.get("attributes") or {}).get("name")
-    except (requests.RequestException, ValueError) as exc:
-        log.warning("Patreon name lookup failed for vanity=%s: %s", vanity, exc)
-        return None
-    if not isinstance(data, list) or not data or not isinstance(data[0], dict):
-        return None
-    name = (data[0].get("attributes") or {}).get("name")
     return name.strip() if isinstance(name, str) and name.strip() else None