feat(external): per-host enable toggles in Settings (Phase 4d)

Operator lever: disable a single file host (e.g. mega.nz when it's banning)
without touching the others. Five booleans on import_settings
(extdl_<host>_enabled, default true — works out of the box, rule #26); the
worker already reads them via getattr so no worker change. Migration 0050 +
model fields + settings GET/PATCH (uniform boolean validation) + a
'External file-host downloads' card in the subscriptions Settings tab.

Completes Phase 4. Refs FC #830.

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

alembic/versions/0050_external_link_host_toggles.py

@@ -0,0 +1,38 @@
+"""import_settings: per-host enable toggles for external file-host downloads
+
+Operator levers (#830): disable a single host (e.g. mega.nz when it's
+rate-limiting/banning) without touching the others. The worker reads these via
+getattr and defaults to enabled, so the toggles default TRUE (works out of the
+box, rule #26).
+
+Revision ID: 0050
+Revises: 0049
+Create Date: 2026-06-14
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0050"
+down_revision: Union[str, None] = "0049"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+_HOSTS = ("mega", "gdrive", "mediafire", "dropbox", "pixeldrain")
+
+
+def upgrade() -> None:
+    for host in _HOSTS:
+        op.add_column(
+            "import_settings",
+            sa.Column(
+                f"extdl_{host}_enabled", sa.Boolean(), nullable=False,
+                server_default=sa.true(),
+            ),
+        )
+
+
+def downgrade() -> None:
+    for host in _HOSTS:
+        op.drop_column("import_settings", f"extdl_{host}_enabled")

backend/app/api/settings.py

@@ -27,6 +27,20 @@ _EDITABLE_FIELDS = (
     "download_failure_warning_threshold",
     "series_suggest_enabled",
     "series_suggest_threshold",
+    "extdl_mega_enabled",
+    "extdl_gdrive_enabled",
+    "extdl_mediafire_enabled",
+    "extdl_dropbox_enabled",
+    "extdl_pixeldrain_enabled",
+)
+
+# Per-host external-download toggles — all plain booleans, validated uniformly.
+_EXTDL_TOGGLE_FIELDS = (
+    "extdl_mega_enabled",
+    "extdl_gdrive_enabled",
+    "extdl_mediafire_enabled",
+    "extdl_dropbox_enabled",
+    "extdl_pixeldrain_enabled",
 )
 
 
@@ -50,6 +64,11 @@ async def get_import_settings():
         "download_failure_warning_threshold": row.download_failure_warning_threshold,
         "series_suggest_enabled": row.series_suggest_enabled,
         "series_suggest_threshold": row.series_suggest_threshold,
+        "extdl_mega_enabled": row.extdl_mega_enabled,
+        "extdl_gdrive_enabled": row.extdl_gdrive_enabled,
+        "extdl_mediafire_enabled": row.extdl_mediafire_enabled,
+        "extdl_dropbox_enabled": row.extdl_dropbox_enabled,
+        "extdl_pixeldrain_enabled": row.extdl_pixeldrain_enabled,
     })
 
 
@@ -106,6 +125,9 @@ async def update_import_settings():
         return jsonify(
             {"error": "series_suggest_enabled must be a boolean"}
         ), 400
+    for tog in _EXTDL_TOGGLE_FIELDS:
+        if tog in body and not isinstance(body[tog], bool):
+            return jsonify({"error": f"{tog} must be a boolean"}), 400
     if "series_suggest_threshold" in body:
         v = body["series_suggest_threshold"]
         if not isinstance(v, (int, float)) or isinstance(v, bool) or v < 0 or v > 1:

backend/app/models/import_settings.py

@@ -73,6 +73,25 @@ class ImportSettings(Base):
         Float, nullable=False, default=0.5,
     )
 
+    # #830 off-platform file-host downloads — per-host enable lever (default on,
+    # rule #26). Column names are extdl_<host>_enabled so the worker reads them
+    # via getattr(settings, f"extdl_{host}_enabled", True).
+    extdl_mega_enabled: Mapped[bool] = mapped_column(
+        Boolean, nullable=False, default=True, server_default="true",
+    )
+    extdl_gdrive_enabled: Mapped[bool] = mapped_column(
+        Boolean, nullable=False, default=True, server_default="true",
+    )
+    extdl_mediafire_enabled: Mapped[bool] = mapped_column(
+        Boolean, nullable=False, default=True, server_default="true",
+    )
+    extdl_dropbox_enabled: Mapped[bool] = mapped_column(
+        Boolean, nullable=False, default=True, server_default="true",
+    )
+    extdl_pixeldrain_enabled: Mapped[bool] = mapped_column(
+        Boolean, nullable=False, default=True, server_default="true",
+    )
+
     @classmethod
     async def load(cls, session) -> ImportSettings:
         """The singleton settings row (id=1), via an async session."""

frontend/src/components/subscriptions/SettingsTab.vue

@@ -52,6 +52,52 @@
       </v-card-text>
     </v-card>
 
+    <h3 class="text-h6 mb-3 mt-6">External file-host downloads</h3>
+    <v-card variant="outlined">
+      <v-card-text v-if="importStore.settings">
+        <div class="fc-help mb-2">
+          When a creator links files on these hosts in a post, Curator downloads
+          them into the post automatically (tagged + provenance-linked like any
+          other media). Turn a host off if it starts rate-limiting or banning.
+        </div>
+        <v-row>
+          <v-col cols="12" sm="4">
+            <v-switch
+              v-model="dl.extdl_mega_enabled" label="mega.nz"
+              density="compact" hide-details color="accent" @change="saveDownloader"
+            />
+          </v-col>
+          <v-col cols="12" sm="4">
+            <v-switch
+              v-model="dl.extdl_gdrive_enabled" label="Google Drive"
+              density="compact" hide-details color="accent" @change="saveDownloader"
+            />
+          </v-col>
+          <v-col cols="12" sm="4">
+            <v-switch
+              v-model="dl.extdl_pixeldrain_enabled" label="Pixeldrain"
+              density="compact" hide-details color="accent" @change="saveDownloader"
+            />
+          </v-col>
+          <v-col cols="12" sm="4">
+            <v-switch
+              v-model="dl.extdl_mediafire_enabled" label="MediaFire"
+              density="compact" hide-details color="accent" @change="saveDownloader"
+            />
+          </v-col>
+          <v-col cols="12" sm="4">
+            <v-switch
+              v-model="dl.extdl_dropbox_enabled" label="Dropbox"
+              density="compact" hide-details color="accent" @change="saveDownloader"
+            />
+          </v-col>
+        </v-row>
+      </v-card-text>
+      <v-card-text v-else>
+        <v-skeleton-loader type="paragraph" />
+      </v-card-text>
+    </v-card>
+
     <h3 class="text-h6 mb-3 mt-6">Schedule defaults</h3>
     <v-card variant="outlined">
       <v-card-text v-if="importStore.settings">
@@ -151,6 +197,11 @@ const dl = reactive({
   download_schedule_default_seconds: 28800,
   download_event_retention_days: 90,
   download_failure_warning_threshold: 5,
+  extdl_mega_enabled: true,
+  extdl_gdrive_enabled: true,
+  extdl_mediafire_enabled: true,
+  extdl_dropbox_enabled: true,
+  extdl_pixeldrain_enabled: true,
 })
 
 watch(() => importStore.settings, (s) => { if (s) Object.assign(dl, s) }, { immediate: true })

tests/test_api_settings_downloader.py

@@ -44,3 +44,24 @@ async def test_patch_rejects_non_bool_validate(client):
         "/api/settings/import", json={"download_validate_files": "yes"}
     )
     assert resp.status_code == 400
+
+
+@pytest.mark.asyncio
+async def test_extdl_host_toggles_default_on_and_patch(client):
+    body = await (await client.get("/api/settings/import")).get_json()
+    assert body["extdl_mega_enabled"] is True
+    assert body["extdl_pixeldrain_enabled"] is True
+
+    resp = await client.patch(
+        "/api/settings/import", json={"extdl_mega_enabled": False}
+    )
+    assert resp.status_code == 200
+    assert (await resp.get_json())["extdl_mega_enabled"] is False
+
+
+@pytest.mark.asyncio
+async def test_extdl_toggle_rejects_non_bool(client):
+    resp = await client.patch(
+        "/api/settings/import", json={"extdl_gdrive_enabled": "nope"}
+    )
+    assert resp.status_code == 400