# app/modules/task_base.py
"""
Base Celery task class for module tasks.

Provides a ModuleTask base class that handles:
- Database session lifecycle (create/close)
- Context manager pattern for session usage
- Proper cleanup on task completion or failure
- Structured logging with task context

This is the standard base class for all Celery tasks defined within modules.
It replaces the legacy app/tasks/celery_tasks/base.py for new module tasks.

Usage:
    from app.core.celery_config import celery_app
    from app.modules.task_base import ModuleTask

    @celery_app.task(bind=True, base=ModuleTask)
    def my_task(self, arg1, arg2):
        with self.get_db() as db:
            # Use db session
            result = db.query(Model).filter(...).all()
        return result
"""

import logging
from contextlib import contextmanager
from typing import Any

from celery import Task
from sqlalchemy.orm import Session

from app.core.database import SessionLocal

logger = logging.getLogger(__name__)


class ModuleTask(Task):
    """
    Base Celery task with database session management.

    Provides:
    - Database session context manager
    - Automatic session cleanup on success/failure
    - Structured logging for task lifecycle events
    - Retry tracking

    All module tasks should use this as their base class for consistent
    behavior and proper resource management.

    Example:
        @celery_app.task(bind=True, base=ModuleTask)
        def process_subscription(self, subscription_id: int):
            with self.get_db() as db:
                subscription = db.query(Subscription).get(subscription_id)
                # Process subscription...
            return {"status": "processed"}
    """

    # Mark as abstract so Celery doesn't register this as a task
    abstract = True

    @contextmanager
    def get_db(self) -> Session:
        """
        Context manager for database session.

        Yields a database session and ensures proper cleanup on both
        success and failure. Commits on success, rolls back on error.

        Yields:
            Session: SQLAlchemy database session

        Example:
            with self.get_db() as db:
                store = db.query(Store).filter(Store.id == store_id).first()
                store.status = "active"
                # Session commits automatically on exit
        """
        db = SessionLocal()
        try:
            yield db
            db.commit()
        except Exception as e:
            logger.error(
                f"Database error in task {self.name}: {e}",
                extra={
                    "task_name": self.name,
                    "task_id": getattr(self.request, "id", None),
                    "error": str(e),
                },
            )
            db.rollback()
            raise
        finally:
            db.close()

    def on_failure(
        self,
        exc: Exception,
        task_id: str,
        args: tuple,
        kwargs: dict,
        einfo: Any,
    ) -> None:
        """
        Called when task fails.

        Logs the failure with structured context for debugging and monitoring.
        """
        logger.error(
            f"Task {self.name}[{task_id}] failed: {exc}",
            extra={
                "task_name": self.name,
                "task_id": task_id,
                "args": args,
                "kwargs": kwargs,
                "exception": str(exc),
                "traceback": str(einfo),
            },
            exc_info=True,
        )

    def on_success(
        self,
        retval: Any,
        task_id: str,
        args: tuple,
        kwargs: dict,
    ) -> None:
        """
        Called when task succeeds.

        Logs successful completion with task context.
        """
        logger.info(
            f"Task {self.name}[{task_id}] completed successfully",
            extra={
                "task_name": self.name,
                "task_id": task_id,
            },
        )

    def on_retry(
        self,
        exc: Exception,
        task_id: str,
        args: tuple,
        kwargs: dict,
        einfo: Any,
    ) -> None:
        """
        Called when task is being retried.

        Logs retry attempt with reason and retry count.
        """
        retry_count = getattr(self.request, "retries", 0)
        logger.warning(
            f"Task {self.name}[{task_id}] retrying (attempt {retry_count + 1}): {exc}",
            extra={
                "task_name": self.name,
                "task_id": task_id,
                "retry_count": retry_count,
                "exception": str(exc),
            },
        )


# Alias for backward compatibility and clarity
DatabaseTask = ModuleTask

__all__ = ["ModuleTask", "DatabaseTask"]