#!/usr/bin/env python3
"""
Lightweight uptime/health monitor.

Polls the target app's /health endpoint every CHECK_INTERVAL seconds,
logs status + response time, and writes the latest result to a JSON
file (status.json) that can be consumed by other tools or dashboards.

Usage:
    python health-check.py --url https://q1-deploy-monitor-cad54f6feeb3.hosted.ghaymah.systems/
    python health-check.py --url https://q1-deploy-monitor-cad54f6feeb3.hosted.ghaymah.systems/ --interval 30
"""

import argparse
import json
import logging
import time
import urllib.request
import urllib.error
from datetime import datetime, timezone

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(levelname)s] %(message)s",
    handlers=[
        logging.FileHandler("monitor.log"),
        logging.StreamHandler(),
    ],
)
log = logging.getLogger("monitor")

STATUS_FILE = "status.json"
FAILURE_THRESHOLD = 3  # consecutive failures before raising an "ALERT"


def check_health(url: str, timeout: float = 5.0):
    start = time.perf_counter()
    try:
        with urllib.request.urlopen(url, timeout=timeout) as resp:
            elapsed_ms = round((time.perf_counter() - start) * 1000, 2)
            body = json.loads(resp.read().decode())
            return {
                "ok": resp.status == 200,
                "http_status": resp.status,
                "response_time_ms": elapsed_ms,
                "body": body,
            }
    except urllib.error.HTTPError as e:
        elapsed_ms = round((time.perf_counter() - start) * 1000, 2)
        return {"ok": False, "http_status": e.code, "response_time_ms": elapsed_ms, "error": str(e)}
    except Exception as e:  # DNS errors, timeouts, connection refused, etc.
        elapsed_ms = round((time.perf_counter() - start) * 1000, 2)
        return {"ok": False, "http_status": None, "response_time_ms": elapsed_ms, "error": str(e)}


def write_status(result: dict, consecutive_failures: int):
    payload = {
        "timestamp": datetime.now(timezone.utc).isoformat(),
        "status": "healthy" if result["ok"] else "unhealthy",
        "http_status": result.get("http_status"),
        "response_time_ms": result.get("response_time_ms"),
        "consecutive_failures": consecutive_failures,
    }
    with open(STATUS_FILE, "w") as f:
        json.dump(payload, f, indent=2)


def main():
    parser = argparse.ArgumentParser(description="Poll /health endpoint on an interval.")
    parser.add_argument("--url", required=True, help="Base URL of the app, e.g. https://myapp.ghaymah.systems")
    parser.add_argument("--interval", type=int, default=30, help="Seconds between checks (default: 30)")
    args = parser.parse_args()

    health_url = args.url.rstrip("/") + "/health"
    log.info("Starting monitor for %s every %ss", health_url, args.interval)

    consecutive_failures = 0

    while True:
        result = check_health(health_url)
        write_status(result, consecutive_failures)

        if result["ok"]:
            if consecutive_failures > 0:
                log.info("Service RECOVERED after %d failed check(s).", consecutive_failures)
            consecutive_failures = 0
            log.info("OK  status=%s  response_time=%sms", result["http_status"], result["response_time_ms"])
        else:
            consecutive_failures += 1
            log.warning(
                "FAIL attempt=%d  status=%s  error=%s",
                consecutive_failures, result.get("http_status"), result.get("error"),
            )
            if consecutive_failures >= FAILURE_THRESHOLD:
                log.error("ALERT: %s has failed %d consecutive health checks!", args.url, consecutive_failures)

        time.sleep(args.interval)


if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        log.info("Monitor stopped by user.")