#!/usr/bin/env python3
"""
Simple uptime/health monitor.
Checks the deployed app's /health endpoint every 30 seconds,
logs the result, and writes a rolling JSON history file that
the dashboard (or anything else) can read.

Usage:
    python monitor.py --url https://your-app.ghaymah.systems
    python monitor.py --url http://localhost:3000 --interval 30
"""

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

LOG_FILE = Path("monitor.log")
HISTORY_FILE = Path("monitor_history.json")
MAX_HISTORY = 200  # keep the last N checks


def now_iso():
    return datetime.now(timezone.utc).isoformat()


def load_history():
    if HISTORY_FILE.exists():
        try:
            return json.loads(HISTORY_FILE.read_text())
        except json.JSONDecodeError:
            return []
    return []


def save_history(history):
    HISTORY_FILE.write_text(json.dumps(history[-MAX_HISTORY:], indent=2))


def log_line(message):
    line = f"[{now_iso()}] {message}"
    print(line)
    with LOG_FILE.open("a", encoding="utf-8") as f:
        f.write(line + "\n")


def check_health(base_url, timeout, health_path="/health"):
    url = base_url.rstrip("/") + health_path
    start = time.monotonic()
    try:
        req = urllib.request.Request(url, headers={"User-Agent": "ghaymah-monitor/1.0"})
        with urllib.request.urlopen(req, timeout=timeout) as resp:
            elapsed_ms = round((time.monotonic() - start) * 1000, 2)
            status_code = resp.getcode()
            raw = resp.read().decode("utf-8", errors="ignore")
            try:
                body = json.loads(raw)
            except json.JSONDecodeError:
                # Not a JSON API (e.g. static site returning plain "ok") -
                # any 200 response is considered healthy.
                body = {"raw": raw.strip()[:200]}
            healthy = status_code == 200
            return {
                "timestamp": now_iso(),
                "healthy": healthy,
                "status_code": status_code,
                "response_time_ms": elapsed_ms,
                "detail": body,
            }
    except (urllib.error.URLError, urllib.error.HTTPError, TimeoutError, Exception) as exc:
        elapsed_ms = round((time.monotonic() - start) * 1000, 2)
        return {
            "timestamp": now_iso(),
            "healthy": False,
            "status_code": None,
            "response_time_ms": elapsed_ms,
            "error": str(exc),
        }


def main():
    parser = argparse.ArgumentParser(description="Health monitor for the deployed API")
    parser.add_argument("--url", required=True, help="Base URL of the deployed app, e.g. https://myapp.ghaymah.systems")
    parser.add_argument("--health-path", default="/health", help="Path to check (default: /health)")
    parser.add_argument("--interval", type=int, default=30, help="Seconds between checks (default: 30)")
    parser.add_argument("--timeout", type=int, default=5, help="Request timeout in seconds (default: 5)")
    parser.add_argument("--once", action="store_true", help="Run a single check and exit (useful for testing)")
    args = parser.parse_args()

    history = load_history()
    consecutive_failures = 0

    log_line(f"Starting monitor for {args.url} (interval={args.interval}s)")

    while True:
        result = check_health(args.url, args.timeout, args.health_path)
        history.append(result)
        save_history(history)

        if result["healthy"]:
            consecutive_failures = 0
            log_line(f"OK   status={result['status_code']} response_time={result['response_time_ms']}ms")
        else:
            consecutive_failures += 1
            reason = result.get("error", f"status_code={result.get('status_code')}")
            log_line(f"FAIL consecutive_failures={consecutive_failures} reason={reason}")
            if consecutive_failures == 3:
                log_line("ALERT: app has failed 3 consecutive health checks")

        if args.once:
            break
        time.sleep(args.interval)


if __name__ == "__main__":
    main()