feat(routes): extract orchestration use cases

py/services/use_cases/download_model_use_case.py

@@ -0,0 +1,37 @@
+"""Use case for scheduling model downloads with consistent error handling."""
+
+from __future__ import annotations
+
+from typing import Any, Dict
+
+from ..download_coordinator import DownloadCoordinator
+
+
+class DownloadModelValidationError(ValueError):
+    """Raised when incoming payload validation fails."""
+
+
+class DownloadModelEarlyAccessError(RuntimeError):
+    """Raised when the download is gated behind Civitai early access."""
+
+
+class DownloadModelUseCase:
+    """Coordinate download scheduling through the coordinator service."""
+
+    def __init__(self, *, download_coordinator: DownloadCoordinator) -> None:
+        self._download_coordinator = download_coordinator
+
+    async def execute(self, payload: Dict[str, Any]) -> Dict[str, Any]:
+        """Schedule a download and normalize error conditions."""
+
+        try:
+            return await self._download_coordinator.schedule_download(payload)
+        except ValueError as exc:
+            raise DownloadModelValidationError(str(exc)) from exc
+        except Exception as exc:  # pragma: no cover - defensive logging path
+            message = str(exc)
+            if "401" in message:
+                raise DownloadModelEarlyAccessError(
+                    "Early Access Restriction: This model requires purchase. Please buy early access on Civitai.com."
+                ) from exc
+            raise