🧹 Refactor architecture: purify models layer and move validation to service layer

src/app/main.py

@@ -23,7 +23,7 @@
     RerankRequest,
     RerankResponse,
 )
-from .models import get_model as get_model, get_model_or_400
+from .models import get_model as get_model
 from .config import (
     EMBEDDING_MODELS,
     RERANK_MODELS,
@@ -37,6 +37,7 @@
     EmbeddingService,
     RerankService,
 )
+from .services.base import get_validated_model
 from .services.embedding import (
     _determine_ruri_prefix as _determine_ruri_prefix,
     _apply_prefix as _apply_prefix,
@@ -173,16 +174,18 @@ def _get_model_or_400(model_name: str, model_type: str) -> Any:
     Helper for backwards compatibility with legacy tests calling _get_model_or_400.
     """
     supported_models = EMBEDDING_MODELS if model_type == "embedding" else RERANK_MODELS
-    return get_model_or_400(model_name, supported_models, model_type)
+    return get_validated_model(
+        model_name, supported_models, model_type, loader=get_model
+    )
 
 
 # Dependency Injection Providers
 def get_embedding_service() -> BaseEmbeddingService:
-    return EmbeddingService(proxy_to_tei_func=_proxy_to_tei)
+    return EmbeddingService(proxy_to_tei_func=_proxy_to_tei, model_loader=get_model)
 
 
 def get_rerank_service() -> BaseRerankService:
-    return RerankService(proxy_to_tei_func=_proxy_to_tei)
+    return RerankService(proxy_to_tei_func=_proxy_to_tei, model_loader=get_model)
 
 
 @app.post(

src/app/models.py

@@ -120,33 +120,3 @@ def get_model(model_name: str, device: str | None = None):
         _model_cache[model_name] = model
         logging.info(f"Model '{model_name}' loaded successfully.")
         return model
-
-
-def get_model_or_400(
-    model_name: str, valid_models: Any, model_type: str = "model"
-) -> Any:
-    """
-    Validates model_name against valid_models and fetches model instance via get_model.
-    Raises HTTPException(400) if model is invalid or if get_model raises a ValueError.
-    """
-    from fastapi import HTTPException
-
-    if model_name not in valid_models:
-        suffix = "s" if not model_type.endswith("s") else ""
-        raise HTTPException(
-            status_code=400,
-            detail=f"Model '{model_name}' not found for {model_type}{suffix}.",
-        )
-
-    try:
-        # Dynamically import main to support patches on app.main.get_model in tests
-        try:
-            import app.main as main_mod
-
-            fetch_func = getattr(main_mod, "get_model", get_model)
-        except Exception:
-            fetch_func = get_model
-
-        return fetch_func(model_name)
-    except ValueError as e:
-        raise HTTPException(status_code=400, detail=str(e))

src/app/services/base.py

@@ -1,5 +1,33 @@
 from abc import ABC, abstractmethod
+from typing import Any, Callable, Collection, Optional
+from fastapi import HTTPException
 from ..schemas import EmbeddingRequest, EmbeddingResponse, RerankRequest, RerankResponse
+from ..models import get_model
+
+
+def get_validated_model(
+    model_name: str,
+    allowed_models: Collection[str],
+    service_name: str,
+    loader: Optional[Callable[[str], Any]] = None,
+) -> Any:
+    """
+    Validates model_name against allowed_models and loads the model via loader/get_model.
+    Raises HTTPException(400) if model is invalid or if loading raises a ValueError.
+    """
+    if model_name not in allowed_models:
+        suffix = "s" if not service_name.endswith("s") else ""
+        raise HTTPException(
+            status_code=400,
+            detail=f"Model '{model_name}' not found for {service_name}{suffix}.",
+        )
+
+    fetch_func = loader or get_model
+
+    try:
+        return fetch_func(model_name)
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
 
 
 class BaseEmbeddingService(ABC):

src/app/services/embedding.py

@@ -5,9 +5,8 @@
 from PIL import Image
 from fastapi import HTTPException
 
-from .base import BaseEmbeddingService
+from .base import BaseEmbeddingService, get_validated_model
 from ..image_utils import load_image_from_source
-from ..models import get_model_or_400
 from ..schemas import (
     EmbeddingRequest,
     EmbeddingResponse,
@@ -143,17 +142,18 @@ def _tokenize_and_truncate_embeddings(
     return processed_inputs, usage
 
 
-def _get_model_or_400(model_name: str) -> Any:
-    return get_model_or_400(model_name, EMBEDDING_MODELS, "embedding")
-
-
 class EmbeddingService(BaseEmbeddingService):
     """
     Default production implementation of BaseEmbeddingService.
     """
 
-    def __init__(self, proxy_to_tei_func: Optional[Any] = None):
+    def __init__(
+        self,
+        proxy_to_tei_func: Optional[Any] = None,
+        model_loader: Optional[Any] = None,
+    ):
         self.proxy_to_tei_func = proxy_to_tei_func
+        self.model_loader = model_loader
 
     async def create_embeddings(self, request: EmbeddingRequest) -> EmbeddingResponse:
         import app.main as main_mod
@@ -192,7 +192,12 @@ async def create_embeddings(self, request: EmbeddingRequest) -> EmbeddingRespons
             )
             return EmbeddingResponse(**data)
 
-        model = _get_model_or_400(request.model)
+        model = get_validated_model(
+            request.model,
+            EMBEDDING_MODELS,
+            "embedding",
+            loader=self.model_loader,
+        )
         is_multimodal = getattr(model, "supports_multimodal", False) is True
 
         if has_image and not is_multimodal:

src/app/services/rerank.py

@@ -2,8 +2,7 @@
 from typing import Any, List, Optional
 from fastapi import HTTPException
 
-from .base import BaseRerankService
-from ..models import get_model_or_400
+from .base import BaseRerankService, get_validated_model
 from ..schemas import RerankRequest, RerankResponse, RerankData, Usage
 from ..config import RERANK_MODELS
 
@@ -47,17 +46,18 @@ def _sort_and_format_rerank_results(
     return [RerankData(**result) for result in sorted_results]
 
 
-def _get_model_or_400(model_name: str) -> Any:
-    return get_model_or_400(model_name, RERANK_MODELS, "rerank")
-
-
 class RerankService(BaseRerankService):
     """
     Default production implementation of BaseRerankService.
     """
 
-    def __init__(self, proxy_to_tei_func: Optional[Any] = None):
+    def __init__(
+        self,
+        proxy_to_tei_func: Optional[Any] = None,
+        model_loader: Optional[Any] = None,
+    ):
         self.proxy_to_tei_func = proxy_to_tei_func
+        self.model_loader = model_loader
 
     async def create_rerank(self, request: RerankRequest) -> RerankResponse:
         import app.main as main_mod
@@ -95,7 +95,12 @@ async def create_rerank(self, request: RerankRequest) -> RerankResponse:
                 usage=usage,
             )
 
-        model = _get_model_or_400(request.model)
+        model = get_validated_model(
+            request.model,
+            RERANK_MODELS,
+            "rerank",
+            loader=self.model_loader,
+        )
 
         pairs = [[request.query, doc] for doc in request.documents]
         usage = _calculate_rerank_tokens(model, request.query, request.documents)