"""External blocklist import background task.

Registers an APScheduler job that downloads all enabled blocklist sources,
validates their entries, and applies bans via fail2ban on a configurable
schedule.  The default schedule is daily at 03:00 UTC; it is stored in the
application :class:`~app.models.blocklist.ScheduleConfig` settings and can
be updated at runtime through the blocklist router.

The scheduler job ID is ``"blocklist_import"`` — using a stable id means
re-registering the job (e.g. after a schedule update) safely replaces the
existing entry without creating duplicates.
"""

from __future__ import annotations

from typing import TYPE_CHECKING, Any

import structlog

from app.db import open_db
from app.models.blocklist import ScheduleFrequency
from app.services import blocklist_service
from app.utils.runtime_state import get_effective_settings

if TYPE_CHECKING:
    import aiosqlite

if TYPE_CHECKING:
    from fastapi import FastAPI

log: structlog.stdlib.BoundLogger = structlog.get_logger()

#: Stable APScheduler job id so the job can be replaced without duplicates.
JOB_ID: str = "blocklist_import"


async def _get_db(app: Any) -> tuple[aiosqlite.Connection, bool]:
    settings = get_effective_settings(app)
    db = await open_db(settings.database_path)
    return db, True


async def _run_import(app: Any) -> None:
    """APScheduler callback that imports all enabled blocklist sources.

    Reads shared resources from ``app.state`` and delegates to
    :func:`~app.services.blocklist_service.import_all`.

    Args:
        app: The :class:`fastapi.FastAPI` application instance passed via
            APScheduler ``kwargs``.
    """
    db, close_db = await _get_db(app)
    settings = get_effective_settings(app)
    http_session = app.state.http_session
    socket_path: str = settings.fail2ban_socket

    log.info("blocklist_import_starting")
    try:
        result = await blocklist_service.import_all(
            db,
            http_session,
            socket_path,
        )
        log.info(
            "blocklist_import_finished",
            total_imported=result.total_imported,
            total_skipped=result.total_skipped,
            errors=result.errors_count,
        )
    except Exception:
        log.exception("blocklist_import_unexpected_error")
    finally:
        if close_db:
            await db.close()


async def register(app: FastAPI) -> None:
    """Add (or replace) the blocklist import job in the application scheduler.

    Reads the persisted :class:`~app.models.blocklist.ScheduleConfig` from
    the database and translates it into the appropriate APScheduler trigger.

    Should be called inside the lifespan handler after the scheduler and
    database have been initialised.

    Args:
        app: The :class:`fastapi.FastAPI` application instance whose
            ``app.state.scheduler`` will receive the job.
    """
    db, close_db = await _get_db(app)
    try:
        config = await blocklist_service.get_schedule(db)
    finally:
        if close_db:
            await db.close()

    _apply_schedule(app, config)


def reschedule(app: FastAPI) -> None:
    """Re-register the blocklist import job with the latest schedule config.

    Called by the blocklist router after a schedule update so changes take
    effect immediately without a server restart.

    Args:
        app: The :class:`fastapi.FastAPI` application instance.
    """
    import asyncio  # noqa: PLC0415

    async def _do_reschedule() -> None:
        db, close_db = await _get_db(app)
        try:
            config = await blocklist_service.get_schedule(db)
        finally:
            if close_db:
                await db.close()
        _apply_schedule(app, config)

    asyncio.ensure_future(_do_reschedule())


def _apply_schedule(app: FastAPI, config: Any) -> None:
    """Add or replace the APScheduler cron/interval job for the given config.

    Args:
        app: FastAPI application instance.
        config: :class:`~app.models.blocklist.ScheduleConfig` to apply.
    """
    scheduler = app.state.scheduler

    kwargs: dict[str, Any] = {"app": app}
    trigger_type: str
    trigger_kwargs: dict[str, Any]

    if config.frequency == ScheduleFrequency.hourly:
        trigger_type = "interval"
        trigger_kwargs = {"hours": config.interval_hours}
    elif config.frequency == ScheduleFrequency.weekly:
        trigger_type = "cron"
        trigger_kwargs = {
            "day_of_week": config.day_of_week,
            "hour": config.hour,
            "minute": config.minute,
        }
    else:  # daily (default)
        trigger_type = "cron"
        trigger_kwargs = {
            "hour": config.hour,
            "minute": config.minute,
        }

    # Remove existing job if it exists, then add new one.
    if scheduler.get_job(JOB_ID):
        scheduler.remove_job(JOB_ID)

    scheduler.add_job(
        _run_import,
        trigger=trigger_type,
        id=JOB_ID,
        kwargs=kwargs,
        **trigger_kwargs,
    )
    log.info(
        "blocklist_import_scheduled",
        frequency=config.frequency,
        trigger=trigger_type,
        trigger_kwargs=trigger_kwargs,
    )