"""
Background worker for backtest execution.
"""
from datetime import datetime
from concurrent.futures import ThreadPoolExecutor
import logging

from sqlalchemy.orm import Session

from app.core.database import SessionLocal
from app.models.backtest import Backtest, BacktestStatus
from app.services.backtest.engine import BacktestEngine

logger = logging.getLogger(__name__)

# Thread pool for background execution
executor = ThreadPoolExecutor(max_workers=2)


def submit_backtest(backtest_id: int) -> None:
    """
    Submit a backtest job for background execution.
    Returns immediately, backtest runs in background thread.
    """
    executor.submit(_run_backtest_job, backtest_id)
    logger.info(f"Backtest {backtest_id} submitted for background execution")


def _run_backtest_job(backtest_id: int) -> None:
    """
    Execute backtest in background thread.
    Creates its own database session.
    """
    db: Session = SessionLocal()

    try:
        # Update status to running
        backtest = db.query(Backtest).get(backtest_id)
        if not backtest:
            logger.error(f"Backtest {backtest_id} not found")
            return

        backtest.status = BacktestStatus.RUNNING
        db.commit()
        logger.info(f"Backtest {backtest_id} started")

        # Run backtest
        engine = BacktestEngine(db)
        engine.run(backtest_id)

        # Update status to completed
        backtest.status = BacktestStatus.COMPLETED
        backtest.completed_at = datetime.utcnow()
        db.commit()
        logger.info(f"Backtest {backtest_id} completed successfully")

    except Exception as e:
        logger.exception(f"Backtest {backtest_id} failed: {e}")

        # Update status to failed
        try:
            backtest = db.query(Backtest).get(backtest_id)
            if backtest:
                backtest.status = BacktestStatus.FAILED
                backtest.error_message = str(e)[:1000]  # Limit error message length
                backtest.completed_at = datetime.utcnow()
                db.commit()
        except Exception as commit_error:
            logger.exception(f"Failed to update backtest status: {commit_error}")

    finally:
        db.close()


def get_executor_status() -> dict:
    """Get current executor status for monitoring."""
    return {
        "max_workers": executor._max_workers,
        "pending_tasks": executor._work_queue.qsize() if hasattr(executor, '_work_queue') else 0,
    }