Refactor/crud

.pre-commit-config.yaml

@@ -44,6 +44,6 @@ repos:
     -   id: add-trailing-comma
   # Flake8 to check style is OK
   - repo: https://gitlab.com/pycqa/flake8
-    rev: 3.8.4
+    rev: 3.9.0
     hooks:
     - id: flake8

app/database/crud/crud.py

@@ -0,0 +1,242 @@
+"""Low level CRUD functions, generalised for wider usage.
+
+Functions listed here should be accessed only from other CRUD modules,
+and not directly from the app.
+"""
+from typing import Any, List, Optional, Type, Union
+
+from pydantic import BaseModel
+from sqlalchemy.exc import (
+    IntegrityError,
+    InvalidRequestError,
+    OperationalError,
+    SQLAlchemyError,
+    StatementError,
+)
+from sqlalchemy.orm import Session
+from sqlalchemy.orm.attributes import InstrumentedAttribute
+from sqlalchemy.orm.exc import UnmappedInstanceError
+
+from app.database.models_v2 import Base
+from app.dependencies import logger
+
+
+def insert(session: Session, instance: Base) -> bool:
+    """Inserts a new row into the database.
+
+    Args:
+        session: The database connection.
+        instance: The object to save.
+
+    Returns:
+        True if successful, otherwise returns False.
+
+    Raises:
+        SQLAlchemyError: If the database tables were not created.
+
+    """
+    if issubclass(instance.__class__, Base):
+        try:
+            session.add(instance)
+            session.commit()
+            session.refresh(instance)
+            return True
+        except IntegrityError as e:
+            logger.exception(e)
+            return False
+        except OperationalError as e:
+            logger.exception(e)
+            raise SQLAlchemyError("Database tables were not created yet.")
+    return False
+
+
+def delete(session: Session, instance: Base) -> bool:
+    """Deletes a row from the database using the database model.
+
+    Args:
+        session: The database connection.
+        instance: The object to delete.
+
+    Returns:
+        True if successful, otherwise returns False.
+    """
+    return delete_multiple(session, [instance])
+
+
+def delete_multiple(session: Session, instances: List[Base]) -> bool:
+    """Deletes a multiple rows from the database using the database models.
+
+    Args:
+        session: The database connection.
+        instances: A list of objects to delete.
+
+    Returns:
+        True if successful, otherwise returns False.
+    """
+    try:
+        for instance in instances:
+            session.delete(instance)
+        session.commit()
+        return True
+    except InvalidRequestError:
+        return False
+    except UnmappedInstanceError:
+        return False
+
+
+def get_by_id(
+    session: Session,
+    entity_id: int,
+    orm_class: Type[Base],
+) -> Optional[Union[BaseModel, Base]]:
+    """Returns a schema or database model by an ID.
+
+    Args:
+        session: The database connection.
+        entity_id: The entity's ID.
+        orm_class: The database mapped model class.
+
+    Returns:
+        A BaseModel or Base model, as requested, if successful,
+        otherwise returns None.
+    """
+    keywords = {orm_class.id.key: entity_id}
+    return get_database_model_by_parameter(session, orm_class, **keywords)
+
+
+def get_database_model_by_parameter(
+    session: Session,
+    orm_class: Type[Base],
+    **kwargs: Any,
+) -> Optional[Union[BaseModel, Base]]:
+    """Returns a schema or database model by a parameter.
+
+    Args:
+        session: The database connection.
+        orm_class: The database mapped model class.
+        **kwargs: The parameter to filter by.
+            Must be in the format of: key=value.
+
+    Returns:
+        A BaseModel or Base model, as requested, if successful,
+        otherwise returns None.
+    """
+    try:
+        return session.query(orm_class).filter_by(**kwargs).first()
+    except OperationalError as e:
+        logger.exception(e)
+        return None
+
+
+def get_all_database_models(
+    session: Session,
+    orm_class: Type[Base],
+    skip: int = 0,
+    limit: int = 100,
+) -> List[Base]:
+    """Returns all models from the database.
+
+    Args:
+        session: The database connection.
+        orm_class: The database mapped model class.
+        skip: The starting index.
+            Defaults to 0.
+        limit: The amount of returned items.
+            Defaults to 100.
+
+    Returns:
+        A list database models.
+    """
+    try:
+        return session.query(orm_class).offset(skip).limit(limit).all()
+    except OperationalError as e:
+        logger.exception(e)
+        return []
+
+
+def get_property(
+    session: Session,
+    entity_id: int,
+    column: InstrumentedAttribute,
+) -> Optional[Any]:
+    """Returns the value of an entity's property.
+
+    Args:
+        session: The database connection.
+        entity_id: The entity's ID.
+        column: The database column from where to query the data.
+
+    Returns:
+        The value of the entity's database column.
+    """
+    orm_model = get_by_id(session, entity_id, column.class_)
+    if not orm_model:
+        return None
+
+    return getattr(orm_model, column.key)
+
+
+def set_property(
+    session: Session,
+    entity_id: int,
+    column: InstrumentedAttribute,
+    value: Any,
+) -> bool:
+    """Sets a new value for an entity's property.
+
+    Args:
+        session: The database connection.
+        entity_id: The entity's ID.
+        column: The database column to where the data is saved.
+        value: The new value to set.
+
+    Returns:
+        True if successful, otherwise returns False.
+    """
+    orm_model = get_by_id(session, entity_id, column.class_)
+    if not orm_model:
+        return False
+
+    setattr(orm_model, column.key, value)
+    try:
+        session.commit()
+    except IntegrityError:
+        session.rollback()
+        return False
+    except StatementError:
+        session.rollback()
+        return False
+    return True
+
+
+def update_database_by_schema_model(
+    session: Session,
+    entity_id: int,
+    schema_instance: BaseModel,
+    orm_class: Type[Base],
+) -> bool:
+    """Updates the database model by extracting data from the schema object.
+
+    ID is passed as a separate parameter for instances where an ID is named
+    something other than "id".
+
+    Args:
+        session: The database connection.
+        entity_id: The entity's ID.
+        schema_instance: The schema model whose data is used for the update.
+        orm_class: The database mapped model class.
+
+    Returns:
+        True if successful, otherwise returns False.
+    """
+    id_filter = {orm_class.id.key: entity_id}
+    try:
+        (
+            session.query(orm_class)
+            .filter_by(**id_filter)
+            .update(schema_instance.dict())
+        )
+        session.commit()
+        return True
+    except InvalidRequestError:
+        return False