Move model_cast into helpers

src/backend/helpers/model_cast.py

@@ -0,0 +1,53 @@
+from typing import Type, TypeVar
+from pydantic import BaseModel 
+import copy
+
+from models import Candidate, CandidateAI, Employer, Guest, BaseUserWithType
+
+# Ensure all user models inherit from BaseUserWithType
+assert issubclass(Candidate, BaseUserWithType), "Candidate must inherit from BaseUserWithType"
+assert issubclass(CandidateAI, BaseUserWithType), "CandidateAI must inherit from BaseUserWithType"
+assert issubclass(Employer, BaseUserWithType), "Employer must inherit from BaseUserWithType"
+assert issubclass(Guest, BaseUserWithType), "Guest must inherit from BaseUserWithType"
+
+T = TypeVar('T', bound=BaseModel)
+
+def cast_to_model(model_cls: Type[T], source: BaseModel) -> T:
+    data = {field: getattr(source, field) for field in model_cls.__fields__}
+    return model_cls(**data)
+
+def cast_to_model_safe(model_cls: Type[T], source: BaseModel) -> T:
+    data = {field: copy.deepcopy(getattr(source, field)) for field in model_cls.__fields__}
+    return model_cls(**data)
+
+def cast_to_base_user_with_type(user) -> BaseUserWithType:
+    """
+    Casts a Candidate, CandidateAI, Employer, or Guest to BaseUserWithType.
+    This is useful for FastAPI dependencies that expect a common user type.
+    """
+    if isinstance(user, BaseUserWithType):
+        return user
+    # If it's a dict, try to detect type
+    if isinstance(user, dict):
+        user_type = user.get("user_type") or user.get("type")
+        if user_type == "candidate":
+            if user.get("is_AI"):
+                return CandidateAI.model_validate(user)
+            return Candidate.model_validate(user)
+        elif user_type == "employer":
+            return Employer.model_validate(user)
+        elif user_type == "guest":
+            return Guest.model_validate(user)
+        else:
+            raise ValueError(f"Unknown user_type: {user_type}")
+    # If it's a model, check its type
+    if hasattr(user, "user_type"):
+        if getattr(user, "user_type", None) == "candidate":
+            if getattr(user, "is_AI", False):
+                return CandidateAI.model_validate(user.model_dump())
+            return Candidate.model_validate(user.model_dump())
+        elif getattr(user, "user_type", None) == "employer":
+            return Employer.model_validate(user.model_dump())
+        elif getattr(user, "user_type", None) == "guest":
+            return Guest.model_validate(user.model_dump())
+    raise TypeError(f"Cannot cast object of type {type(user)} to BaseUserWithType")