"use client";

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

/**
 * 有未保存修改时：关闭/刷新走 beforeunload；站内链接先确认再跳转。
 * 未修改时不打扰。hash 分类切换由调用方自行拦截。
 */
export default function useUnsavedGuard(dirty: boolean) {
  const router = useRouter();
  const pathname = usePathname();
  const dirtyRef = useRef(dirty);
  dirtyRef.current = dirty;
  const [pendingHref, setPendingHref] = useState<string | null>(null);

  useEffect(() => {
    const onBeforeUnload = (e: BeforeUnloadEvent) => {
      if (!dirtyRef.current) return;
      e.preventDefault();
      e.returnValue = "";
    };
    window.addEventListener("beforeunload", onBeforeUnload);
    return () => window.removeEventListener("beforeunload", onBeforeUnload);
  }, []);

  useEffect(() => {
    const onClick = (e: MouseEvent) => {
      if (!dirtyRef.current) return;
      if (e.defaultPrevented || e.button !== 0 || e.metaKey || e.ctrlKey || e.shiftKey || e.altKey) {
        return;
      }
      const target = e.target;
      if (!(target instanceof Element)) return;
      const a = target.closest("a[href]");
      if (!a) return;
      const href = a.getAttribute("href");
      if (!href || href.startsWith("#") || href.startsWith("mailto:") || href.startsWith("javascript:")) return;
      if (a.getAttribute("target") === "_blank") return;
      let url: URL;
      try {
        url = new URL(href, window.location.href);
      } catch {
        return;
      }
      if (url.origin !== window.location.origin) return;
      const next = `${url.pathname}${url.search}${url.hash}`;
      const cur = `${pathname}${window.location.search}${window.location.hash}`;
      if (next === cur) return;
      e.preventDefault();
      e.stopPropagation();
      setPendingHref(next);
    };
    document.addEventListener("click", onClick, true);
    return () => document.removeEventListener("click", onClick, true);
  }, [pathname]);

  const confirmLeave = () => {
    if (!pendingHref) return;
    const href = pendingHref;
    setPendingHref(null);
    router.push(href);
  };

  return {
    leaveOpen: pendingHref != null,
    confirmLeave,
    cancelLeave: () => setPendingHref(null),
  };
}