"""The backup check, daily at 07:15 site time.

BACKUP_DIR is this stack's backup folder on the host (/var/backups/packetstation/<stack>/), mounted read-only.
The host's backup script writes `*.dump` files and the `last-success` and `last-failure` markers there. The
check raises the `backup_stale` condition (subject: the stack) when the newest dump is missing, empty or older
than 26 hours, or when `last-failure` is newer than `last-success`. Otherwise it resolves it. It only reads.
"""

from __future__ import annotations

from datetime import UTC, datetime, time
from pathlib import Path

from ...feed.config import FeedSettings
from .. import jobs
from . import Counts, JobContext, JobSpec, seconds_until

AT = time(7, 15)
NAME = "backup-check"
MAX_AGE_HOURS = 26.0
SUCCESS = "last-success"
FAILURE = "last-failure"


def _mtime(p: Path) -> datetime | None:
    try:
        return datetime.fromtimestamp(p.stat().st_mtime, UTC)
    except OSError:
        return None


def inspect(folder: Path, now: datetime | None = None) -> tuple[Counts, list[str]]:
    """(counts, problems) for a backup folder. No problems means the backups are fine."""
    now = now or datetime.now(UTC)
    counts: Counts = {"folder": str(folder), "dumps": 0, "newest": None, "age_hours": None, "size": None}
    if not folder.is_dir():
        return counts, [f"The backup folder {folder} is not there."]
    dumps: list[tuple[datetime, Path, int]] = []
    for p in folder.glob("*.dump"):
        try:
            st = p.stat()
        except OSError:
            continue
        if p.is_file():
            dumps.append((datetime.fromtimestamp(st.st_mtime, UTC), p, st.st_size))
    counts["dumps"] = len(dumps)
    problems: list[str] = []
    if not dumps:
        problems.append("No backup dump is in the folder.")
    else:
        at, path, size = max(dumps, key=lambda d: (d[0], d[1].name))
        age = (now - at).total_seconds() / 3600
        counts.update(newest=path.name, newest_at=at.isoformat(), age_hours=round(age, 1), size=size)
        if size == 0:
            problems.append(f"The newest dump {path.name} is empty.")
        if age > MAX_AGE_HOURS:
            problems.append(f"The newest dump {path.name} is {age:.0f} hours old.")
    ok_at, fail_at = _mtime(folder / SUCCESS), _mtime(folder / FAILURE)
    counts["last_success"] = ok_at.isoformat() if ok_at else None
    counts["last_failure"] = fail_at.isoformat() if fail_at else None
    if fail_at is not None and (ok_at is None or fail_at > ok_at):
        problems.append("The last backup run failed (last-failure is newer than last-success).")
    return counts, problems


def run(ctx: JobContext) -> Counts:
    stack = str(ctx.settings.stack)
    counts, problems = inspect(Path(ctx.settings.backup_dir))
    counts["problems"] = problems
    title = f"Backup failed or stale ({stack})"
    with ctx.conn.transaction():
        if problems:
            jobs.raise_event(
                ctx.conn,
                "backup_stale",
                subject=stack,
                title=title,
                body="\n".join(problems),
                detail={k: v for k, v in counts.items() if k != "problems"},
                severity="critical",
                condition=True,
            )
        else:
            jobs.resolve_event(ctx.conn, "backup_stale", subject=stack, title=title)
    return counts


def cadence(_: FeedSettings, now_site: datetime) -> int:
    return seconds_until(now_site, AT)


SPEC = JobSpec(name=NAME, run=run, cadence=cadence, pausable=False)