#!/usr/bin/env python3
"""Minimal SLO burn rate tracker for Prometheus."""

import argparse
import sys
from datetime import datetime, timedelta

import yaml
from prometheus_api_client import PrometheusConnect
from rich.console import Console
from rich.table import Table

console = Console()


def load_config(path: str) -> dict:
    with open(path) as f:
        return yaml.safe_load(f)


def evaluate_slo(prom: PrometheusConnect, slo: dict, window: str) -> dict:
    result = prom.custom_query(slo["query"])
    if not result:
        return {"name": slo["name"], "value": None, "target": slo["target"], "ok": False}
    value = float(result[0]["value"][1])
    return {
        "name": slo["name"],
        "value": value,
        "target": slo["target"],
        "ok": value >= slo["target"],
    }


def main():
    parser = argparse.ArgumentParser(description="SLO burn rate tracker")
    parser.add_argument("--config", required=True)
    parser.add_argument("--prometheus", default="http://localhost:9090")
    parser.add_argument("--window", default="7d")
    args = parser.parse_args()

    cfg = load_config(args.config)
    prom = PrometheusConnect(url=args.prometheus, disable_ssl=True)

    table = Table(title=f"SLO Status ({args.window} window)")
    table.add_column("SLO", style="cyan")
    table.add_column("Target", justify="right")
    table.add_column("Current", justify="right")
    table.add_column("Status", justify="center")

    all_ok = True
    for slo in cfg.get("slos", []):
        result = evaluate_slo(prom, slo, args.window)
        status = "[green]OK[/green]" if result["ok"] else "[red]BURNING[/red]"
        value_str = f"{result['value']:.4f}" if result["value"] is not None else "n/a"
        table.add_row(result["name"], str(result["target"]), value_str, status)
        if not result["ok"]:
            all_ok = False

    console.print(table)
    sys.exit(0 if all_ok else 1)


if __name__ == "__main__":
    main()


def burn_rate(error_rate: float, window_hours: float, target: float) -> float:
    """Calculate burn rate: how fast the error budget is being consumed."""
    budget = 1.0 - target
    if budget == 0:
        return float("inf")
    return error_rate / budget * (window_hours / (30 * 24))