"""Prometheus queries — node load lookups.

F-06 remediation: ``PROM_URL`` is now resolved from
``backend.config.EXTERNAL_CONFIG["prometheus_url"]`` (env-var
``FESTER_PROM_URL``) instead of being hardcoded.
"""

from __future__ import annotations

import logging
from typing import Optional

import requests

from backend.config import EXTERNAL_CONFIG

log = logging.getLogger(__name__)


def _prom_url() -> str:
    """Return the current Prometheus URL.

    Read at call time so tests / operators can monkey-patch the env
    var between requests without restarting the process.
    """
    import os
    return os.environ.get(
        "FESTER_PROM_URL",
        EXTERNAL_CONFIG.get("prometheus_url", "http://localhost:9090"),
    )


def get_node_load(node: str) -> float:
    """Return the 1-minute load average for ``node``.

    Falls back to 1.0 on any error (Prometheus down, metric missing,
    network error) so the scheduler always gets a usable number.
    """
    query = f'node_load1{{instance="{node}"}}'
    try:
        r = requests.get(
            f"{_prom_url()}/api/v1/query",
            params={"query": query},
            timeout=5,
        )
        r.raise_for_status()
        data = r.json()
        result = data.get("data", {}).get("result", [])
        if not result:
            log.debug("prometheus returned no data for %s", node)
            return 1.0
        return float(result[0]["value"][1])
    except Exception as e:
        log.debug("prometheus lookup failed for %s: %s", node, e)
        return 1.0