#!/usr/bin/env python3
"""Observe backup health, retain alert episodes, and refresh both delivery channels."""

import argparse
import importlib.util
import json
from datetime import UTC, datetime
from pathlib import Path

from backup_alerts import MAX_EVENTS, drain

spec = importlib.util.spec_from_file_location(
    "backup_health", Path(__file__).with_name("check-paired-backup-health.py"))
health = importlib.util.module_from_spec(spec)
spec.loader.exec_module(health)
PENDING = {"multiple_pending_captures", "pending_requires_review", "backup_stalled"}


def observations(report):
    reasons = set(report["reasons"])
    return {"pending_backup": bool(reasons & PENDING), "backup_stale": "backup_stale" in reasons,
            "backup_failed": bool(reasons - PENDING - {"backup_stale"})}


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--execute", action="store_true")
    parser.add_argument("--state-dir", type=Path, required=True)
    parser.add_argument("--mirror-receipt", type=Path, required=True)
    parser.add_argument("--alert-state-dir", type=Path, required=True)
    parser.add_argument("--minimum-free-bytes", type=int, required=True)
    parser.add_argument("--maximum-state-bytes", type=int, required=True)
    parser.add_argument("--hub-base", required=True)
    parser.add_argument("--alertmanager-base", required=True)
    args = parser.parse_args()
    now = datetime.now(UTC)
    report = health.check(args.state_dir, args.mirror_receipt, now,
                          min_free_bytes=args.minimum_free_bytes,
                          max_state_bytes=args.maximum_state_bytes)
    if sum(1 for _ in args.alert_state_dir.glob("*.json")) >= MAX_EVENTS * 3 // 4:
        report["reasons"] = sorted(set(report["reasons"]) | {"alert_journal_near_capacity"})
        report["status"] = "unhealthy"
    if not args.execute:
        print(json.dumps(report))
        return int(report["status"] != "healthy")
    try:
        delivery = drain(args.alert_state_dir, args.hub_base, args.alertmanager_base,
                         now=now, observations=observations(report),
                         recovered_capture=report.get("captured_at")
                         if report["status"] == "healthy" else None)
    except Exception as error:
        delivery = {"status": "alert_delivery_requires_review",
                    "failure_type": type(error).__name__}
    print(json.dumps({"health": report, "delivery": delivery}))
    # The unit measures successful monitoring, not backup health. A delivered
    # unhealthy observation must not trigger a second generic failure every hour.
    return int(delivery["status"] != "channel_handoffs_verified")


if __name__ == "__main__":
    raise SystemExit(main())