"""APScheduler integration for maintenance flow auto-session creation."""
import logging
import uuid
from datetime import datetime, timezone

from apscheduler.schedulers.asyncio import AsyncIOScheduler
from apscheduler.schedulers.base import SchedulerNotRunningError
from apscheduler.jobstores.base import JobLookupError
from apscheduler.triggers.cron import CronTrigger
import pytz
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

logger = logging.getLogger(__name__)

scheduler = AsyncIOScheduler()


async def _fire_maintenance_schedule(schedule_id: str) -> None:
    """Create batch sessions for a scheduled maintenance run."""
    # Import all models first to ensure SQLAlchemy mapper relationships resolve
    import app.models  # noqa: F401
    from app.core.database import async_session_maker
    from app.models.maintenance_schedule import MaintenanceSchedule
    from app.models.session import Session
    from app.models.target_list import TargetList
    from app.models.tree import Tree

    async with async_session_maker() as db:
        try:
            result = await db.execute(
                select(MaintenanceSchedule).where(
                    MaintenanceSchedule.id == uuid.UUID(schedule_id),
                    MaintenanceSchedule.is_active == True,
                )
            )
            schedule = result.scalar_one_or_none()
            if not schedule:
                logger.warning(f"Schedule {schedule_id} not found or inactive")
                return

            tree_result = await db.execute(
                select(Tree).where(Tree.id == schedule.tree_id)
            )
            tree = tree_result.scalar_one_or_none()
            if not tree:
                logger.error(f"Tree {schedule.tree_id} not found for schedule {schedule_id}")
                return

            if tree.tree_type != "maintenance":
                logger.warning(f"Skipping schedule {schedule_id}: tree {tree.id} is not a maintenance flow")
                return

            if not tree.is_active or tree.status == "draft":
                logger.warning(
                    f"Skipping schedule {schedule_id}: tree {tree.id} is inactive or draft"
                )
                return

            # Resolve targets
            targets: list[dict] = []
            if schedule.target_list_id:
                list_result = await db.execute(
                    select(TargetList).where(TargetList.id == schedule.target_list_id)
                )
                target_list = list_result.scalar_one_or_none()
                if target_list:
                    targets = list(target_list.targets)

            if not targets:
                targets = [{"label": "Unassigned"}]

            batch_id = uuid.uuid4()
            tree_snapshot = {
                **tree.tree_structure,
                "name": tree.name,
                "description": tree.description,
                "tree_type": tree.tree_type,
            }

            sessions_to_add = []
            for target in targets:
                session = Session(
                    tree_id=tree.id,
                    user_id=schedule.created_by,
                    tree_snapshot=tree_snapshot,
                    path_taken=[],
                    decisions=[],
                    custom_steps=[],
                    session_variables={},
                    batch_id=batch_id,
                    target_label=target.get("label", ""),
                )
                sessions_to_add.append(session)

            for s in sessions_to_add:
                db.add(s)

            # Update schedule tracking
            schedule.last_run_at = datetime.now(timezone.utc)
            from croniter import croniter
            tz = pytz.timezone(schedule.timezone)
            now = datetime.now(tz)
            cron = croniter(schedule.cron_expression, now)
            schedule.next_run_at = cron.get_next(datetime).astimezone(timezone.utc)

            await db.commit()
            logger.info(
                f"Schedule {schedule_id} fired: created {len(sessions_to_add)} sessions "
                f"(batch {batch_id}) for tree '{tree.name}'"
            )
        except Exception:
            logger.exception(f"Error firing maintenance schedule {schedule_id}")
            await db.rollback()


async def load_all_schedules(db: AsyncSession) -> None:
    """Load all active schedules into APScheduler on startup."""
    # Import all models to ensure SQLAlchemy mapper relationships resolve
    # before any ORM queries are executed.
    import app.models  # noqa: F401
    from app.models.maintenance_schedule import MaintenanceSchedule
    result = await db.execute(
        select(MaintenanceSchedule).where(MaintenanceSchedule.is_active == True)
    )
    schedules = result.scalars().all()
    for schedule in schedules:
        register_schedule(schedule)
    logger.info(f"Loaded {len(schedules)} active maintenance schedule(s)")


def register_schedule(schedule) -> None:
    """Register or update a schedule in APScheduler."""
    job_id = f"maintenance_{schedule.id}"
    try:
        tz = pytz.timezone(schedule.timezone)
        trigger = CronTrigger.from_crontab(schedule.cron_expression, timezone=tz)
        scheduler.add_job(
            _fire_maintenance_schedule,
            trigger=trigger,
            id=job_id,
            args=[str(schedule.id)],
            replace_existing=True,
            misfire_grace_time=3600,
        )
        logger.info(f"Registered schedule {schedule.id} ({schedule.cron_expression})")
    except Exception:
        logger.exception(f"Failed to register schedule {schedule.id}")


def unregister_schedule(schedule_id: str) -> None:
    """Remove a schedule from APScheduler."""
    job_id = f"maintenance_{schedule_id}"
    if scheduler.get_job(job_id):
        try:
            scheduler.remove_job(job_id)
            logger.info(f"Unregistered schedule {schedule_id}")
        except (SchedulerNotRunningError, JobLookupError):
            logger.warning(f"Could not remove job {job_id}: scheduler not running or job already removed")