"""Jobs and one tick that runs them (AD-12).

Every job reads the database for what is due and is safe to repeat, so a missed or doubled
tick does no harm. Each run is recorded for the Admin status page.
"""

from __future__ import annotations

import logging
from collections.abc import Callable
from dataclasses import dataclass
from datetime import datetime, timedelta

from django.utils import timezone

from portal.mailer import services as mailer

from .models import JobRun

logger = logging.getLogger(__name__)

KEEP_RUNS_DAYS = 7


@dataclass(frozen=True)
class Job:
    name: str
    run: Callable[[datetime], object]  # returns something printable as the run's summary


# The order is the order they run in. Later entries add jobs here.
JOBS: tuple[Job, ...] = (Job("mail.flush", lambda now: mailer.flush(now)),)


def tick(now: datetime | None = None, jobs: tuple[Job, ...] | None = None) -> None:
    """Run every job once. A failing job is recorded and does not stop the others."""
    now = now or timezone.now()
    for job in JOBS if jobs is None else jobs:
        run = JobRun.objects.create(job=job.name, started_at=now)
        try:
            detail = str(job.run(now))
            status = JobRun.Status.OK
        except Exception as exc:
            logger.exception("Job %s failed", job.name)
            detail, status = type(exc).__name__, JobRun.Status.ERROR
        run.status, run.detail, run.finished_at = status, detail[:200], timezone.now()
        run.save(update_fields=["status", "detail", "finished_at"])
    JobRun.objects.filter(started_at__lt=now - timedelta(days=KEEP_RUNS_DAYS)).delete()