# app/tasks/dispatcher.py
"""
Task dispatcher with feature flag for gradual Celery migration.

This module provides a unified interface for dispatching background tasks.
Based on the USE_CELERY setting, tasks are either:
- Sent to Celery for persistent, reliable execution
- Run via FastAPI BackgroundTasks (fire-and-forget)

This allows for gradual rollout and instant rollback.
"""

import logging
from typing import Any

from fastapi import BackgroundTasks

from app.core.config import settings

logger = logging.getLogger(__name__)


class TaskDispatcher:
    """
    Dispatches tasks to either Celery or FastAPI BackgroundTasks.

    Usage:
        from app.tasks.dispatcher import task_dispatcher

        # In an API endpoint:
        task_id = task_dispatcher.dispatch_marketplace_import(
            background_tasks=background_tasks,
            job_id=job.id,
            url=url,
            marketplace=marketplace,
            vendor_id=vendor_id,
        )
    """

    @property
    def use_celery(self) -> bool:
        """Check if Celery is enabled."""
        return settings.use_celery

    def dispatch_marketplace_import(
        self,
        background_tasks: BackgroundTasks,
        job_id: int,
        url: str,
        marketplace: str,
        vendor_id: int,
        batch_size: int = 1000,
        language: str = "en",
    ) -> str | None:
        """
        Dispatch marketplace import task.

        Args:
            background_tasks: FastAPI BackgroundTasks instance
            job_id: ID of the MarketplaceImportJob record
            url: URL to the CSV file
            marketplace: Name of the marketplace
            vendor_id: ID of the vendor
            batch_size: Number of rows per batch
            language: Language code for translations

        Returns:
            str | None: Celery task ID if using Celery, None otherwise
        """
        if self.use_celery:
            from app.tasks.celery_tasks.marketplace import process_marketplace_import

            task = process_marketplace_import.delay(
                job_id=job_id,
                url=url,
                marketplace=marketplace,
                vendor_id=vendor_id,
                batch_size=batch_size,
                language=language,
            )
            logger.info(f"Dispatched marketplace import to Celery: task_id={task.id}")
            return task.id
        else:
            from app.tasks.background_tasks import process_marketplace_import

            background_tasks.add_task(
                process_marketplace_import,
                job_id=job_id,
                url=url,
                marketplace=marketplace,
                vendor_id=vendor_id,
                batch_size=batch_size,
                language=language,
            )
            logger.info("Dispatched marketplace import to BackgroundTasks")
            return None

    def dispatch_historical_import(
        self,
        background_tasks: BackgroundTasks,
        job_id: int,
        vendor_id: int,
    ) -> str | None:
        """
        Dispatch Letzshop historical import task.

        Args:
            background_tasks: FastAPI BackgroundTasks instance
            job_id: ID of the LetzshopHistoricalImportJob record
            vendor_id: ID of the vendor

        Returns:
            str | None: Celery task ID if using Celery, None otherwise
        """
        if self.use_celery:
            from app.tasks.celery_tasks.letzshop import process_historical_import

            task = process_historical_import.delay(job_id=job_id, vendor_id=vendor_id)
            logger.info(f"Dispatched historical import to Celery: task_id={task.id}")
            return task.id
        else:
            from app.tasks.letzshop_tasks import process_historical_import

            background_tasks.add_task(
                process_historical_import,
                job_id=job_id,
                vendor_id=vendor_id,
            )
            logger.info("Dispatched historical import to BackgroundTasks")
            return None

    def dispatch_code_quality_scan(
        self,
        background_tasks: BackgroundTasks,
        scan_id: int,
    ) -> str | None:
        """
        Dispatch code quality scan task.

        Args:
            background_tasks: FastAPI BackgroundTasks instance
            scan_id: ID of the ArchitectureScan record

        Returns:
            str | None: Celery task ID if using Celery, None otherwise
        """
        if self.use_celery:
            from app.tasks.celery_tasks.code_quality import execute_code_quality_scan

            task = execute_code_quality_scan.delay(scan_id=scan_id)
            logger.info(f"Dispatched code quality scan to Celery: task_id={task.id}")
            return task.id
        else:
            from app.tasks.code_quality_tasks import execute_code_quality_scan

            background_tasks.add_task(execute_code_quality_scan, scan_id=scan_id)
            logger.info("Dispatched code quality scan to BackgroundTasks")
            return None

    def dispatch_test_run(
        self,
        background_tasks: BackgroundTasks,
        run_id: int,
        test_path: str = "tests",
        extra_args: list[str] | None = None,
    ) -> str | None:
        """
        Dispatch test run task.

        Args:
            background_tasks: FastAPI BackgroundTasks instance
            run_id: ID of the TestRun record
            test_path: Path to tests
            extra_args: Additional pytest arguments

        Returns:
            str | None: Celery task ID if using Celery, None otherwise
        """
        if self.use_celery:
            from app.tasks.celery_tasks.test_runner import execute_test_run

            task = execute_test_run.delay(
                run_id=run_id,
                test_path=test_path,
                extra_args=extra_args,
            )
            logger.info(f"Dispatched test run to Celery: task_id={task.id}")
            return task.id
        else:
            from app.tasks.test_runner_tasks import execute_test_run

            background_tasks.add_task(
                execute_test_run,
                run_id=run_id,
                test_path=test_path,
                extra_args=extra_args,
            )
            logger.info("Dispatched test run to BackgroundTasks")
            return None

    def dispatch_product_export(
        self,
        vendor_id: int,
        triggered_by: str,
        include_inactive: bool = False,
    ) -> str | None:
        """
        Dispatch product export task (Celery only).

        This task is only available via Celery as it's designed for
        asynchronous batch exports. For synchronous exports, use
        the export service directly.

        Args:
            vendor_id: ID of the vendor to export
            triggered_by: User identifier
            include_inactive: Whether to include inactive products

        Returns:
            str | None: Celery task ID if using Celery, None otherwise
        """
        if self.use_celery:
            from app.tasks.celery_tasks.export import export_vendor_products_to_folder

            task = export_vendor_products_to_folder.delay(
                vendor_id=vendor_id,
                triggered_by=triggered_by,
                include_inactive=include_inactive,
            )
            logger.info(f"Dispatched product export to Celery: task_id={task.id}")
            return task.id
        else:
            logger.warning(
                "Product export task requires Celery. "
                "Use letzshop_export_service directly for synchronous export."
            )
            return None

    def get_task_status(self, task_id: str) -> dict[str, Any]:
        """
        Get the status of a Celery task.

        Args:
            task_id: Celery task ID

        Returns:
            dict: Task status info including state and result
        """
        if not self.use_celery:
            return {"error": "Celery not enabled"}

        from app.core.celery_config import celery_app

        result = celery_app.AsyncResult(task_id)
        return {
            "task_id": task_id,
            "state": result.state,
            "ready": result.ready(),
            "successful": result.successful() if result.ready() else None,
            "result": result.result if result.ready() else None,
        }

    def revoke_task(self, task_id: str, terminate: bool = False) -> bool:
        """
        Revoke (cancel) a Celery task.

        Args:
            task_id: Celery task ID to revoke
            terminate: If True, terminate running task; if False, just prevent execution

        Returns:
            bool: True if revocation was sent
        """
        if not self.use_celery:
            logger.warning("Cannot revoke task: Celery not enabled")
            return False

        from app.core.celery_config import celery_app

        celery_app.control.revoke(task_id, terminate=terminate)
        logger.info(f"Revoked Celery task: task_id={task_id}, terminate={terminate}")
        return True


# Singleton instance
task_dispatcher = TaskDispatcher()