feat(downloads): native Patreon verify + uniform backend dispatch (plan #697)

The credential Verify button still ran gallery-dl --simulate for Patreon
after the cutover — testing the wrong path (and prone to the vanity
"Failed to extract campaign ID" the native resolver fixes). Wire it to the
native ingester, behind a DRY dispatch so callers never branch on platform.

- services/download_backends.py (new): the ONE place that knows which
  platforms are native vs gallery-dl. `uses_native_ingester(platform)` is
  the shared predicate; `verify_source_credential(...)` is the uniform
  probe (same (ok|None, message) contract for both backends). As a platform
  migrates, it moves into NATIVE_INGESTER_PLATFORMS here and BOTH download
  routing and verify switch together.
- PatreonClient.verify_auth(campaign_id): one authenticated /api/posts
  fetch → True (valid) / False (401/403/HTML-login) / None (drift or
  network — inconclusive, not a credential verdict).
- patreon_ingester.verify_patreon_credential(): resolve campaign id, then
  verify_auth — the verify counterpart to the download path.
- patreon_resolver.resolve_campaign_id_for_source(): extracted the
  override / id:-URL / vanity resolution into ONE helper now shared by the
  download ingester and verify (download_service no longer carries its own
  copy + regex; −`import re`).
- download_service: routes on uses_native_ingester() instead of inline
  `== "patreon"` (3 sites); uses the shared resolver.
- api/credentials: calls verify_source_credential — no platform branch.

Tests: verify_auth mapping, resolve_campaign_id_for_source (override/id:/
vanity/none), the dispatch predicate, verify_patreon_credential glue,
credentials endpoint proves Patreon uses the native path (gallery-dl verify
asserted not-called); repointed the gallery-dl verify test to subscribestar.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_api_credentials.py

@@ -155,6 +155,8 @@ async def test_verify_no_enabled_source_is_untestable(client):
 
 @pytest.mark.asyncio
 async def test_verify_runs_gallery_dl_and_stamps_on_success(client, db, monkeypatch):
+    """A gallery-dl platform routes through GalleryDLService.verify; success
+    stamps last_verified (platform-agnostic endpoint behavior)."""
     from backend.app.models import Artist, Source
     from backend.app.services import gallery_dl as gdl_mod
 
@@ -163,6 +165,45 @@ async def test_verify_runs_gallery_dl_and_stamps_on_success(client, db, monkeypa
         return (True, "Credentials valid — the feed authenticated.")
     monkeypatch.setattr(gdl_mod.GalleryDLService, "verify", _fake_verify)
 
+    await client.post("/api/credentials", json={
+        "platform": "subscribestar", "credential_type": "cookies", "data": _NETSCAPE,
+    })
+    artist = Artist(name="Maewix", slug="maewix")
+    db.add(artist)
+    await db.flush()
+    db.add(Source(
+        artist_id=artist.id, platform="subscribestar",
+        url="https://www.subscribestar.com/maewix", enabled=True, config_overrides={},
+    ))
+    await db.commit()
+
+    resp = await client.post("/api/credentials/subscribestar/verify")
+    body = await resp.get_json()
+    assert body["valid"] is True
+    assert body["last_verified"] is not None
+
+    # The stamp is persisted on the credential record.
+    rec = await (await client.get("/api/credentials/subscribestar")).get_json()
+    assert rec["last_verified"] is not None
+
+
+@pytest.mark.asyncio
+async def test_verify_patreon_uses_native_ingester_not_gallery_dl(client, db, monkeypatch):
+    """plan #697 cutover: Patreon credential verify routes through the native
+    ingester (verify_patreon_credential), NOT gallery-dl --simulate."""
+    from backend.app.models import Artist, Source
+    from backend.app.services import gallery_dl as gdl_mod
+    from backend.app.services import patreon_ingester as pi_mod
+
+    async def _native_verify(url, cookies_path, overrides):
+        return (True, "Credentials valid — the Patreon feed authenticated.")
+    monkeypatch.setattr(pi_mod, "verify_patreon_credential", _native_verify)
+
+    # gallery-dl must NOT be consulted for Patreon.
+    async def _boom(self, *args, **kwargs):
+        raise AssertionError("gallery-dl verify must not run for patreon")
+    monkeypatch.setattr(gdl_mod.GalleryDLService, "verify", _boom)
+
     await client.post("/api/credentials", json={
         "platform": "patreon", "credential_type": "cookies", "data": _NETSCAPE,
     })
@@ -180,10 +221,6 @@ async def test_verify_runs_gallery_dl_and_stamps_on_success(client, db, monkeypa
     assert body["valid"] is True
     assert body["last_verified"] is not None
 
-    # The stamp is persisted on the credential record.
-    rec = await (await client.get("/api/credentials/patreon")).get_json()
-    assert rec["last_verified"] is not None
-
 
 @pytest.mark.asyncio
 async def test_verify_reports_auth_failure(client, db, monkeypatch):

tests/test_download_backends.py

@@ -0,0 +1,23 @@
+"""download_backends — the single predicate that routes a platform to the
+native ingester vs. gallery-dl. Pure, no DB."""
+
+from backend.app.services.download_backends import (
+    NATIVE_INGESTER_PLATFORMS,
+    uses_native_ingester,
+)
+
+
+def test_patreon_is_native():
+    assert uses_native_ingester("patreon") is True
+    assert "patreon" in NATIVE_INGESTER_PLATFORMS
+
+
+def test_gallery_dl_platforms_are_not_native():
+    # The five platforms still served by gallery-dl must NOT route to the
+    # native ingester — guards an accidental over-broad migration.
+    for platform in ("subscribestar", "hentaifoundry", "discord", "pixiv", "deviantart"):
+        assert uses_native_ingester(platform) is False
+
+
+def test_unknown_platform_is_not_native():
+    assert uses_native_ingester("nonsense") is False

tests/test_download_service.py

@@ -288,7 +288,8 @@ async def test_run_patreon_ingester_resolves_vanity_and_runs(
     _artist, source = seed_artist_and_source
 
     monkeypatch.setattr(
-        dl_mod, "resolve_campaign_id", AsyncMock(return_value="4242"),
+        dl_mod, "resolve_campaign_id_for_source",
+        AsyncMock(return_value=("4242", "4242")),
     )
     run_kwargs = {}
 
@@ -335,7 +336,8 @@ async def test_run_patreon_ingester_unresolvable_fails_loud(
     _artist, source = seed_artist_and_source
 
     monkeypatch.setattr(
-        dl_mod, "resolve_campaign_id", AsyncMock(return_value=None),
+        dl_mod, "resolve_campaign_id_for_source",
+        AsyncMock(return_value=(None, None)),
     )
     svc = DownloadService(
         async_session=db, sync_session=db_sync,

tests/test_patreon_client.py

@@ -238,3 +238,40 @@ def test_fetch_other_status_raises_api_error_with_code(monkeypatch, status):
 def test_fetch_ok_returns_payload(monkeypatch):
     client = _client_returning(monkeypatch, _FakeResp(200, json_data={"data": []}))
     assert client._fetch("5555", None) == {"data": []}
+
+
+# -- verify_auth (credential probe; (True/False/None, message) contract) ---
+
+
+def test_verify_auth_ok_when_page_authenticates(monkeypatch):
+    client = _client_returning(monkeypatch, _FakeResp(200, json_data={"data": []}))
+    ok, msg = client.verify_auth("5555")
+    assert ok is True
+    assert "valid" in msg.lower()
+
+
+@pytest.mark.parametrize("status", [401, 403])
+def test_verify_auth_false_when_rejected(monkeypatch, status):
+    client = _client_returning(monkeypatch, _FakeResp(status))
+    ok, _msg = client.verify_auth("5555")
+    assert ok is False
+
+
+def test_verify_auth_inconclusive_on_drift(monkeypatch):
+    # 200 + JSON but missing top-level 'data' → drift → inconclusive, NOT a
+    # credential verdict (our parser is stale, the cookie may be fine).
+    client = _client_returning(monkeypatch, _FakeResp(200, json_data={"included": []}))
+    ok, msg = client.verify_auth("5555")
+    assert ok is None
+    assert "api shape changed" in msg.lower()
+
+
+def test_verify_auth_inconclusive_on_network(monkeypatch):
+    import requests
+    client = PatreonClient(cookies_path=None)
+
+    def _raise(*a, **k):
+        raise requests.ConnectionError("boom")
+    monkeypatch.setattr(client._session, "get", _raise)
+    ok, _msg = client.verify_auth("5555")
+    assert ok is None

tests/test_patreon_ingester.py

@@ -370,3 +370,32 @@ def test_ledger_key_video_has_no_filehash():
         kind="postfile", filehash=None, post_id="p9",
     )
     assert _ledger_key(video) == "p9:clip.mp4"
+
+
+# --- verify_patreon_credential (the verify counterpart, plan #697) ---------
+
+
+@pytest.mark.asyncio
+async def test_verify_patreon_credential_unresolvable_is_inconclusive():
+    from backend.app.services.patreon_ingester import verify_patreon_credential
+
+    # No campaign id resolvable from a non-Patreon URL → can't test → None.
+    ok, msg = await verify_patreon_credential("not-a-patreon-url", None, {})
+    assert ok is None
+    assert "campaign id" in msg.lower()
+
+
+@pytest.mark.asyncio
+async def test_verify_patreon_credential_delegates_to_client(monkeypatch):
+    import backend.app.services.patreon_ingester as mod
+
+    async def _fake_resolve(url, cookies_path, overrides):
+        return "123", None
+    monkeypatch.setattr(mod, "resolve_campaign_id_for_source", _fake_resolve)
+    monkeypatch.setattr(
+        mod.PatreonClient, "verify_auth",
+        lambda self, campaign_id: (True, f"ok:{campaign_id}"),
+    )
+    ok, msg = await mod.verify_patreon_credential("https://patreon.com/x", None, {})
+    assert ok is True
+    assert msg == "ok:123"

tests/test_patreon_resolver.py

@@ -2,7 +2,10 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
-from backend.app.services.patreon_resolver import resolve_campaign_id
+from backend.app.services.patreon_resolver import (
+    resolve_campaign_id,
+    resolve_campaign_id_for_source,
+)
 
 
 @pytest.mark.asyncio
@@ -86,3 +89,48 @@ async def test_loads_cookies_file_when_present(tmp_path):
     assert result == "9"
     _, kwargs = mock_get.call_args
     assert kwargs.get("cookies") is not None
+
+
+# -- resolve_campaign_id_for_source (shared by download + verify) ----------
+
+
+@pytest.mark.asyncio
+async def test_for_source_uses_cached_override_without_lookup():
+    with patch("backend.app.services.patreon_resolver.requests.get") as mock_get:
+        cid, resolved = await resolve_campaign_id_for_source(
+            "https://patreon.com/alice", None, {"patreon_campaign_id": "999"},
+        )
+    assert cid == "999"
+    assert resolved is None  # cached → no newly-resolved id to cache
+    mock_get.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_for_source_extracts_id_url_without_lookup():
+    with patch("backend.app.services.patreon_resolver.requests.get") as mock_get:
+        cid, resolved = await resolve_campaign_id_for_source(
+            "https://www.patreon.com/id:4242", None, {},
+        )
+    assert cid == "4242"
+    assert resolved is None
+    mock_get.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_for_source_resolves_vanity_and_reports_it():
+    fake = MagicMock()
+    fake.status_code = 200
+    fake.json.return_value = {"data": [{"id": "777", "type": "campaign"}]}
+    with patch("backend.app.services.patreon_resolver.requests.get", return_value=fake):
+        cid, resolved = await resolve_campaign_id_for_source(
+            "https://patreon.com/alice", None, {},
+        )
+    assert cid == "777"
+    assert resolved == "777"  # newly resolved → caller caches it
+
+
+@pytest.mark.asyncio
+async def test_for_source_unresolvable_returns_none():
+    cid, resolved = await resolve_campaign_id_for_source("not-a-patreon-url", None, {})
+    assert cid is None
+    assert resolved is None