/**
 * Web Vitals 采集（A11y + 性能）
 *
 * 仲裁：所有前端应用必须采集 Web Vitals
 * 端点：NEXT_PUBLIC_WEB_VITALS_ENDPOINT（默认 /api/admin/web-vitals）
 */
import { onLCP, onCLS, onFCP, onINP, onTTFB } from "web-vitals";

type Metric = { name: string; value: number; rating: string; id: string };

const ENDPOINT =
  process.env.NEXT_PUBLIC_WEB_VITALS_ENDPOINT ?? "/api/admin/web-vitals";

function sendMetric(metric: Metric): void {
  if (typeof navigator === "undefined") return;
  const body = JSON.stringify({
    name: metric.name,
    value: metric.value,
    rating: metric.rating,
    id: metric.id,
    page: window.location.pathname,
    ts: Date.now(),
  });
  // 使用 sendBeacon 避免阻塞卸载
  if (navigator.sendBeacon) {
    navigator.sendBeacon(ENDPOINT, body);
  } else {
    void fetch(ENDPOINT, { method: "POST", body, keepalive: true }).catch(
      () => {
        // 忽略上报失败
      },
    );
  }
}

export function initWebVitals(): void {
  if (typeof window === "undefined") return;
  onLCP((m) => sendMetric(m as unknown as Metric));
  onCLS((m) => sendMetric(m as unknown as Metric));
  onFCP((m) => sendMetric(m as unknown as Metric));
  onINP((m) => sendMetric(m as unknown as Metric));
  onTTFB((m) => sendMetric(m as unknown as Metric));
}