Implement task API with input validation; implement error handling; refactoring

tofu_api/repositories/base_repository.py

@@ -0,0 +1,94 @@
+__all__ = [
+    'BaseRepository',
+    'T_Model',
+]
+
+from abc import ABC, abstractmethod
+from typing import Generic, Optional, Type, TypeVar
+
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from tofu_api.models import BaseModel
+from .exceptions import ObjectNotFoundException
+
+T_Model = TypeVar('T_Model', bound=BaseModel)
+
+
+class BaseRepository(Generic[T_Model], ABC):
+    """
+    Base class for repositories.
+    """
+
+    # Database session
+    session: Session
+
+    @property
+    @abstractmethod
+    def model_cls(self) -> Type[T_Model]:
+        """
+        Set this to the model class.
+        """
+        raise NotImplementedError
+
+    def __init__(self, *, session: Session):
+        self.session = session
+
+    @staticmethod
+    def _or_raise(resource: Optional[T_Model], exception_msg: Optional[str] = None) -> T_Model:
+        if resource is None:
+            raise ObjectNotFoundException(exception_msg)
+        return resource
+
+    def fetch_by_id(self, resource_id: int) -> T_Model:
+        """
+        Fetches a resource by ID.
+
+        Raises an ObjectNotFoundException if no resource with the ID was found.
+        """
+        resource = self.session.get(self.model_cls, resource_id)
+        return self._or_raise(resource, f'Resource with ID {resource_id} was not found.')
+
+    def fetch_all(self) -> list[T_Model]:
+        """
+        Fetches all resources of the repository type.
+        """
+        return self.session.scalars(
+            select(self.model_cls)
+        ).all()
+
+    def commit_session(self) -> None:
+        """
+        Commits the current database session.
+        """
+        self.commit_session()
+
+    def rollback_session(self) -> None:
+        """
+        Rolls back the current database session.
+        """
+        self.rollback_session()
+
+    def save_resource(self, *resources: T_Model, commit: bool = True) -> None:
+        """
+        Saves one or multiple resources to the database by adding them to the session and committing the session.
+        Set `commit` to False to skip committing (the session will still be flushed, though).
+        """
+        for resource in resources:
+            self.session.add(resource)
+        self.session.flush()
+
+        if commit:
+            self.session.commit()
+
+    def delete_resource(self, *resources: T_Model, commit: bool = True) -> None:
+        """
+        Deletes one or multiple resources from the database.
+        Set `commit` to False to skip committing (the session will still be flushed, though).
+        """
+        for resource in resources:
+            self.session.delete(resource)
+        self.session.flush()
+
+        if commit:
+            self.session.commit()