#!/usr/bin/env python3
"""Silent-on-success Hermes health watchdog for ByteLyst.

Designed for a Hermes no-agent cron job. It prints nothing when healthy and
prints a concise Telegram-ready alert when an actionable problem is detected.
"""
from __future__ import annotations

import os
import shutil
import subprocess
import sys
from datetime import datetime, timezone
from pathlib import Path

DISK_WARN_PERCENT = int(os.getenv("HERMES_WATCHDOG_DISK_WARN_PERCENT", "85"))
MEMORY_WARN_PERCENT = int(os.getenv("HERMES_WATCHDOG_MEMORY_WARN_PERCENT", "90"))
BACKUP_STALE_MINUTES = int(os.getenv("HERMES_WATCHDOG_BACKUP_STALE_MINUTES", "90"))
BACKUP_JOB_NAME = os.getenv("HERMES_WATCHDOG_BACKUP_JOB_NAME", "Sync Hermes persistent-data backup to GitHub")
GATEWAY_SERVICE = os.getenv("HERMES_WATCHDOG_GATEWAY_SERVICE", "hermes-gateway.service")
DOCKER_CONTAINERS = [
    item.strip()
    for item in os.getenv("HERMES_WATCHDOG_DOCKER_CONTAINERS", "caddy,gitea-npm-registry").split(",")
    if item.strip()
]
HERMES_HOME = Path(os.getenv("HERMES_HOME", str(Path.home() / ".hermes")))


def run(cmd: list[str], timeout: int = 20) -> subprocess.CompletedProcess[str]:
    return subprocess.run(cmd, text=True, capture_output=True, timeout=timeout, check=False)


def check_gateway(alerts: list[str]) -> None:
    result = run(["systemctl", "is-active", GATEWAY_SERVICE])
    if result.stdout.strip() != "active":
        alerts.append(f"gateway service `{GATEWAY_SERVICE}` is not active: `{result.stdout.strip() or result.stderr.strip() or 'unknown'}`")


def check_backup_cron(alerts: list[str]) -> None:
    result = run(["hermes", "cron", "list"], timeout=30)
    out = result.stdout + result.stderr
    if result.returncode != 0:
        alerts.append(f"`hermes cron list` failed with exit {result.returncode}")
        return
    if BACKUP_JOB_NAME not in out:
        alerts.append(f"backup cron job `{BACKUP_JOB_NAME}` was not found")
        return
    if "Last run:" not in out or " ok" not in out:
        alerts.append("backup cron last-run status is not visibly `ok` in `hermes cron list`")

    script_path = HERMES_HOME / "scripts" / "sync_hermes_persistent_backup.py"
    if script_path.exists():
        age_minutes = (datetime.now(timezone.utc).timestamp() - script_path.stat().st_mtime) / 60
        # Script mtime is not backup freshness; keep this as a weak sanity note only.
        if age_minutes < 0:
            alerts.append("backup sync script has a future modification time")


def check_backup_repo_freshness(alerts: list[str]) -> None:
    repo = Path(os.getenv("HERMES_WATCHDOG_BACKUP_REPO", str(HERMES_HOME / "persistent_backup_repo")))
    candidates = [repo, Path.home() / "hermes_persistent_backup", Path.home() / "hermes_persistent_backup_repo"]
    existing = next((p for p in candidates if (p / ".git").exists()), None)
    if not existing:
        # The backup cron may use its own path; cron status is the primary check.
        return
    result = run(["git", "-C", str(existing), "log", "-1", "--format=%ct"], timeout=20)
    if result.returncode != 0 or not result.stdout.strip().isdigit():
        alerts.append(f"could not inspect backup repo freshness at `{existing}`")
        return
    age_minutes = (datetime.now(timezone.utc).timestamp() - int(result.stdout.strip())) / 60
    if age_minutes > BACKUP_STALE_MINUTES:
        alerts.append(f"backup repo `{existing}` latest commit is stale: {age_minutes:.0f} minutes old")


def check_disk(alerts: list[str]) -> None:
    usage = shutil.disk_usage("/")
    pct = int(round((usage.used / usage.total) * 100))
    if pct >= DISK_WARN_PERCENT:
        alerts.append(f"root disk usage is high: {pct}% used (threshold {DISK_WARN_PERCENT}%)")


def check_memory(alerts: list[str]) -> None:
    meminfo: dict[str, int] = {}
    for line in Path("/proc/meminfo").read_text(encoding="utf-8").splitlines():
        parts = line.split()
        if len(parts) >= 2:
            meminfo[parts[0].rstrip(":")] = int(parts[1])
    total = meminfo.get("MemTotal", 0)
    available = meminfo.get("MemAvailable", 0)
    if total <= 0 or available <= 0:
        alerts.append("could not read memory pressure from /proc/meminfo")
        return
    used_pct = int(round(((total - available) / total) * 100))
    if used_pct >= MEMORY_WARN_PERCENT:
        alerts.append(f"memory pressure is high: {used_pct}% used (threshold {MEMORY_WARN_PERCENT}%)")


def check_docker_containers(alerts: list[str]) -> None:
    if not DOCKER_CONTAINERS:
        return
    docker = shutil.which("docker")
    if not docker:
        alerts.append("docker executable not found; cannot verify critical containers")
        return
    result = run([docker, "ps", "--format", "{{.Names}}"], timeout=20)
    if result.returncode != 0:
        alerts.append(f"`docker ps` failed while checking critical containers: {result.stderr.strip() or result.stdout.strip()}")
        return
    running = set(result.stdout.splitlines())
    missing = [name for name in DOCKER_CONTAINERS if name not in running]
    if missing:
        alerts.append(f"critical Docker container(s) not running: {', '.join(missing)}")


def main() -> int:
    alerts: list[str] = []
    for check in (
        check_gateway,
        check_backup_cron,
        check_backup_repo_freshness,
        check_disk,
        check_memory,
        check_docker_containers,
    ):
        try:
            check(alerts)
        except Exception as exc:  # noqa: BLE001 - watchdog should alert, not crash silently
            alerts.append(f"{check.__name__} errored: {exc}")

    if alerts:
        print("🚨 ByteLyst Hermes watchdog alert")
        for item in alerts:
            print(f"- {item}")
        print(
            "\nSuggested first checks: `systemctl status hermes-gateway --no-pager`, "
            "`hermes cron list`, `df -h /`, `free -h`, `docker ps`."
        )
        return 0
    return 0


if __name__ == "__main__":
    sys.exit(main())