Implement BaseModel class, TimestampMixin, TzDateTime type; cleanup Task model

tofu_api/common/database/__init__.py

@@ -1 +1,3 @@
+from .metadata import MetaData
 from .sqlalchemy import SQLAlchemy
+from .typing import Col, Rel

tofu_api/common/database/metadata.py

@@ -0,0 +1,25 @@
+from sqlalchemy import MetaData as _MetaData
+
+__all__ = [
+    'MetaData',
+]
+
+
+class MetaData(_MetaData):
+    """
+    App specific subclass of the SQLAlchemy MetaData class.
+    """
+
+    # Define naming convention for constraints
+    _naming_convention = {
+        "ix": 'ix_%(column_0_label)s',
+        "uq": "uq_%(table_name)s_%(column_0_name)s",
+        "ck": "ck_%(table_name)s_%(constraint_name)s",
+        "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
+        "pk": "pk_%(table_name)s"
+    }
+
+    def __init__(self, *args, naming_convention=None, **kwargs):
+        if not naming_convention:
+            naming_convention = self._naming_convention
+        super().__init__(*args, naming_convention=naming_convention, **kwargs)

tofu_api/common/database/mixins.py

@@ -0,0 +1,23 @@
+from datetime import datetime
+
+from sqlalchemy import Column, func
+from sqlalchemy.orm import declarative_mixin
+
+from tofu_api.common.database import Col
+from tofu_api.common.database.types import TzDateTime
+
+__all__ = [
+    'TimestampMixin'
+]
+
+
+@declarative_mixin
+class TimestampMixin:
+    """
+    Mixin for database models that provides the "created_at" and "modified_at" columns.
+    """
+    # Created timestamp (automatically set to NOW() once on object creation)
+    created_at: Col[datetime] = Column(TzDateTime, nullable=False, server_default=func.now())
+
+    # Modified timestamp (automatically set to NOW() on each update)
+    modified_at: Col[datetime] = Column(TzDateTime, nullable=False, server_default=func.now(), onupdate=func.now())

tofu_api/common/database/types/__init__.py

@@ -0,0 +1 @@
+from .tz_date_time import TzDateTime

tofu_api/common/database/types/tz_date_time.py

@@ -0,0 +1,39 @@
+from datetime import datetime, timezone
+
+from sqlalchemy import DateTime, TypeDecorator
+
+__all__ = [
+    'TzDateTime',
+]
+
+
+class TzDateTime(TypeDecorator):
+    """
+    Custom SQLAlchemy data type for timezone aware datetimes.
+    """
+    impl = DateTime
+    cache_ok = True
+
+    @property
+    def python_type(self):
+        return datetime
+
+    def process_bind_param(self, value: datetime, dialect):
+        """
+        Convert a datetime object that is bound to a query parameter.
+        """
+        if value is not None and value.tzinfo:
+            value = value.astimezone(timezone.utc).replace(tzinfo=None)
+        return value
+
+    def process_result_value(self, value: datetime, dialect):
+        """
+        Convert a datetime object from a query result.
+        """
+        return value.replace(tzinfo=timezone.utc) if value is not None else None
+
+    def process_literal_param(self, value: datetime, dialect):
+        """
+        Convert a literal parameter value to be rendered inline within a statement.
+        """
+        return self.process_bind_param(value, dialect)

tofu_api/common/database/typing.py

@@ -0,0 +1,14 @@
+from typing import TypeVar, Union
+
+from sqlalchemy import Column
+from sqlalchemy.orm import RelationshipProperty
+
+__all__ = [
+    'Col',
+    'Rel',
+]
+
+# Define type aliases for SQLAlchemy columns and relationships in declarative models
+_T = TypeVar('_T')
+Col = Union[Column, _T]
+Rel = Union[RelationshipProperty, _T]

tofu_api/common/json/__init__.py

@@ -0,0 +1 @@
+from .json_encoder import JSONEncoder

tofu_api/common/json/json_encoder.py

@@ -0,0 +1,29 @@
+from datetime import datetime
+from typing import Any
+
+from flask.json import JSONEncoder as _FlaskJSONEncoder
+
+__all__ = [
+    'JSONEncoder',
+]
+
+
+class JSONEncoder(_FlaskJSONEncoder):
+    """
+    Custom JSON encoder built on top of the Flask JSONEncoder class.
+    """
+
+    def default(self, obj: Any) -> Any:
+        """
+        Convert any object to a JSON serializable type.
+        """
+        # Convert datetimes to ISO format without microseconds (e.g. '2022-01-02T10:20:30+00:00')
+        if isinstance(obj, datetime):
+            return obj.isoformat(timespec='seconds')
+
+        # Use to_dict() method on objects that have it
+        if hasattr(obj, 'to_dict'):
+            return obj.to_dict()
+
+        # Fallback to the Flask JSONEncoder
+        return super().default(obj)