import json
import os
import sys
import urllib.request


def emit(key: str, value) -> None:
    print(f"{key}: {json.dumps(value)}")


def require_env(name: str) -> str:
    value = os.environ.get(name)
    if not value:
        print(f"Error: {name} environment variable is not set.", file=sys.stderr)
        sys.exit(1)
    return value


def main() -> None:
    host = require_env("HOST")
    port = require_env("PORT")
    url = f"http://{host}:{port}/healthz"

    req = urllib.request.Request(url, method="GET")
    with urllib.request.urlopen(req, timeout=10) as resp:
        status_code = resp.status
        body = resp.read().decode()

    emit("status_code", status_code)

    try:
        data = json.loads(body)
        emit("serving", data.get("status") == "SERVING")
    except json.JSONDecodeError:
        emit("serving", False)


if __name__ == "__main__":
    main()