"use client";

import { Suspense, useEffect, useRef, useState } from "react";
import { usePathname, useSearchParams } from "next/navigation";

// 版本由 Footer（RSC）从 package.json 注入；未正式设计版本号时传入空串，显示占位
const PLACEHOLDER = "—";

interface Metrics {
  page: number; // 页面：整页加载/客户端导航总耗时
  tpl: number; // 模板：服务端响应（SSR / RSC）耗时
}

// 硬加载：页面=loadEventEnd，模板≈TTFB（localhost 下基本等于服务端生成时间）
function readHardNav(): Metrics {
  const n = performance.getEntriesByType("navigation")[0] as
    | PerformanceNavigationTiming
    | undefined;
  if (!n) return { page: 0, tpl: 0 };
  return {
    page: Math.round((n.loadEventEnd || n.domComplete || n.responseEnd) - n.startTime),
    tpl: Math.max(0, Math.round(n.responseStart - n.requestStart)),
  };
}

function TimingInner({ version }: { version: string }) {
  const pathname = usePathname();
  const search = useSearchParams().toString();
  // 初始必须为 null：performance 仅客户端可读，直接参与首帧渲染会导致水合不一致
  const [metrics, setMetrics] = useState<Metrics | null>(null);
  // 记录一次站内链接点击，作为客户端导航计时起点
  const pending = useRef<{ start: number; path: string; search: string } | null>(null);

  // 挂载后读取硬加载指标；load 事件后 loadEventEnd 才有完整值，再补一次
  useEffect(() => {
    setMetrics(readHardNav());
    const apply = () => setMetrics(readHardNav());
    if (document.readyState !== "complete") {
      window.addEventListener("load", apply, { once: true });
      return () => window.removeEventListener("load", apply);
    }
  }, []);

  // 捕获阶段监听站内点击（不干预任何默认行为）
  useEffect(() => {
    const onClick = (e: MouseEvent) => {
      if (e.button !== 0 || e.metaKey || e.ctrlKey || e.shiftKey || e.altKey || e.defaultPrevented) return;
      const a = (e.target as HTMLElement).closest("a");
      if (!a || !a.href || a.target === "_blank" || a.hasAttribute("download")) return;
      let u: URL;
      try {
        u = new URL(a.href);
      } catch {
        return;
      }
      if (u.origin !== location.origin) return;
      pending.current = { start: performance.now(), path: u.pathname, search: u.search };
    };
    document.addEventListener("click", onClick, true);
    return () => document.removeEventListener("click", onClick, true);
  }, []);

  // 路由切换后两帧（绘制完成）结算；模板耗时取本次 RSC fetch 的资源条目
  useEffect(() => {
    const p = pending.current;
    if (!p) return;
    if (p.path !== pathname || p.search !== (search ? `?${search}` : "")) return;
    let raf2 = 0;
    const raf1 = requestAnimationFrame(() => {
      raf2 = requestAnimationFrame(() => {
        const page = Math.round(performance.now() - p.start);
        let tpl = 0;
        const resources = performance.getEntriesByType("resource") as PerformanceResourceTiming[];
        for (let i = resources.length - 1; i >= 0; i--) {
          const r = resources[i];
          if (
            r.initiatorType === "fetch" &&
            r.startTime >= p.start - 10 &&
            r.name.startsWith(location.origin + p.path)
          ) {
            tpl = Math.round(r.responseEnd - r.startTime);
            break;
          }
        }
        setMetrics((prev) => ({ page: Math.max(1, page), tpl: tpl || prev?.tpl || 0 }));
        pending.current = null;
      });
    });
    return () => {
      cancelAnimationFrame(raf1);
      cancelAnimationFrame(raf2);
    };
  }, [pathname, search]);

  return (
    <span
      className="inline-flex items-center gap-2 text-[12px] tabular-nums whitespace-nowrap"
      style={{ color: "var(--ink-3)" }}
    >
      <span>版本:{version || PLACEHOLDER}</span>
      <span aria-hidden="true">·</span>
      <span suppressHydrationWarning>页面:{metrics ? `${metrics.page}ms` : PLACEHOLDER}</span>
      <span aria-hidden="true">·</span>
      <span suppressHydrationWarning>模板:{metrics ? `${metrics.tpl}ms` : PLACEHOLDER}</span>
    </span>
  );
}

export default function FooterTiming({ version = "" }: { version?: string }) {
  return (
    <Suspense
      fallback={
        <span className="inline-flex items-center gap-2 text-[12px] tabular-nums whitespace-nowrap" style={{ color: "var(--ink-3)" }}>
          版本:{version || PLACEHOLDER}
          <span aria-hidden="true">·</span>
          页面:{PLACEHOLDER}
          <span aria-hidden="true">·</span>
          模板:{PLACEHOLDER}
        </span>
      }
    >
      <TimingInner version={version} />
    </Suspense>
  );
}