manage/backend/src/media_library_viewer_api/routers/monitoring.py

"""Monitoring router — observability stack status (Alertmanager + Prometheus)."""

from __future__ import annotations

import logging
from typing import Any

from fastapi import APIRouter, Body, Depends

from media_library_viewer_api.config import get_settings
from media_library_viewer_api.dependencies import get_settings_store
from media_library_viewer_api.services.settings_store import SettingsStore
from media_library_viewer_api.services.targets import build_node_exporter_targets

logger = logging.getLogger(__name__)


def _alertmanager_client() -> Any:
    """Return a simple HTTP client for the configured Alertmanager URL."""
    import requests

    settings = get_settings()
    return requests.Session(), settings.alertmanager_url


def _webhook_client() -> Any:
    """Return a simple HTTP client for the optional webhook receiver URL."""
    import requests

    settings = get_settings()
    return requests.Session(), settings.alertmanager_webhook_url


def _summary_from_alerts(alerts: list[dict[str, Any]]) -> dict[str, Any]:
    """Build a UI-friendly summary from Alertmanager /api/v1/alerts payload."""
    by_severity: dict[str, int] = {}
    open_alerts: list[dict[str, Any]] = []
    for alert in alerts:
        labels = alert.get("labels") or {}
        annotations = alert.get("annotations") or {}
        severity = labels.get("severity", "unknown")
        by_severity[severity] = by_severity.get(severity, 0) + 1
        open_alerts.append(
            {
                "name": labels.get("alertname", "unknown"),
                "severity": severity,
                "category": labels.get("category", ""),
                "job_name": labels.get("job_name", labels.get("job", "")),
                "summary": annotations.get("summary", ""),
                "description": annotations.get("description", ""),
                "active_since": alert.get("startsAt"),
                "state": alert.get("status", "firing"),
                "labels": labels,
            }
        )
    open_alerts.sort(key=lambda a: (a["severity"] not in {"critical", "warning"}, a["severity"], a["name"]))
    return {
        "total": len(open_alerts),
        "by_severity": by_severity,
        "alerts": open_alerts[:50],
    }


router = APIRouter(prefix="/api/monitoring", tags=["monitoring"])


@router.get("/machines")
def get_machines(store: SettingsStore = Depends(get_settings_store)) -> list[dict[str, Any]]:
    """Return enabled monitoring machines for the UI."""
    return [m for m in store.list_machines() if m.get("enabled")]


@router.get("/prometheus-targets")
def get_prometheus_targets(store: SettingsStore = Depends(get_settings_store)) -> list[dict[str, Any]]:
    """Return Prometheus file-SD targets for remote Node Exporters.

    The backend writes these targets to a JSON file that Prometheus reads via
    file_sd_configs. This endpoint returns the same list live from the store so
    the UI can preview which machines will be scraped.
    """
    targets = build_node_exporter_targets(store)
    logger.info("Prometheus targets requested count=%s", len(targets))
    return targets


@router.get("/alerts")
def get_alertmanager_alerts() -> dict[str, Any]:
    """Return a summary of active Alertmanager alerts for the UI.

    Proxies the Alertmanager `/api/v1/alerts` endpoint and reshapes the payload
    into a stable, UI-friendly format. If Alertmanager is unreachable, the
    endpoint returns an empty summary and logs the failure so the UI can still
    render a health card instead of an error page.
    """
    session, base_url = _alertmanager_client()
    try:
        response = session.get(f"{base_url}/api/v1/alerts", timeout=5)
        response.raise_for_status()
        data = response.json()
    except Exception:
        logger.exception("Failed to fetch Alertmanager alerts from %s", base_url)
        return {"total": 0, "by_severity": {}, "alerts": [], "error": "alertmanager_unreachable"}

    if data.get("status") != "success":
        return {"total": 0, "by_severity": {}, "alerts": [], "error": data.get("error", "unknown")}

    summary = _summary_from_alerts(data.get("data", []))
    logger.info("Alertmanager alerts requested total=%s", summary["total"])
    return summary


@router.get("/alertmanager-status")
def get_alertmanager_status() -> dict[str, Any]:
    """Return Alertmanager cluster/status for the UI health card.

    Uses the Alertmanager `/api/v2/status` endpoint and exposes only the high-
    level fields the UI needs: uptime, version, and whether the cluster is
    healthy.
    """
    session, base_url = _alertmanager_client()
    try:
        response = session.get(f"{base_url}/api/v2/status", timeout=5)
        response.raise_for_status()
        data = response.json()
    except Exception:
        logger.exception("Failed to fetch Alertmanager status from %s", base_url)
        return {"up": False, "version": "", "uptime": ""}

    cluster = data.get("cluster") or {}
    status = data.get("clusterStatus") or {}
    return {
        "up": True,
        "version": data.get("versionInfo", {}).get("version", ""),
        "uptime": status.get("createdAt", ""),
        "name": "",
        "peers": [p.get("name", "") for p in cluster.get("peers", [])],
    }


@router.post("/alertmanager-webhook")
def receive_alertmanager_webhook(payload: dict[str, Any] = Body(...)) -> dict[str, str]:
    """Receive alerts from Alertmanager and optionally forward to a webhook URL.

    This endpoint is the receiver referenced by the optional `webhook_configs`
    block in Alertmanager. It logs the payload for audit/debug purposes and, if
    `ALERTMANAGER_WEBHOOK_URL` is configured, forwards the alert JSON verbatim.
    Forwarding is best-effort: a failure to reach the downstream webhook does
    not fail this endpoint, so Alertmanager sees a successful delivery.
    """
    alerts = payload.get("alerts", [])
    logger.info(
        "Received Alertmanager webhook with %s alert(s), status=%s",
        len(alerts),
        payload.get("status", "unknown"),
    )

    session, webhook_url = _webhook_client()
    if webhook_url:
        try:
            response = session.post(webhook_url, json=payload, timeout=10)
            response.raise_for_status()
            logger.info("Forwarded Alertmanager webhook to %s", webhook_url)
        except Exception:
            logger.exception("Failed to forward Alertmanager webhook to %s", webhook_url)
    else:
        logger.debug("No ALERTMANAGER_WEBHOOK_URL configured; webhook stored in logs only")

    return {"status": "received"}