"use client";

import Link from "next/link";
import { usePathname } from "next/navigation";
import { Fragment, useEffect, useState } from "react";
import {
  Home,
  BookOpen,
  PenSquare,
  MessageSquare,
  User as UserIcon,
} from "lucide-react";
import { apiChatUnreadSummary, type User } from "@/lib/api";
import { useAllowMessages } from "@/components/MessagesPolicyProvider";
import { useSiteBrand } from "@/components/SiteBrandProvider";
import { onDocumentVisible } from "@/lib/visibilityReconcile";
import { userPath, libraryPath } from "@/lib/urlStyle";
import { realtime, RT_CHAT_UNREAD } from "@/lib/realtime";
import type { RtChatUnreadData } from "@/lib/realtime";
import type { MobileTabKey } from "@/lib/mobileTabs";

/**
 * 移动端全局底部公共菜单（lg 以下显示）：
 * 按 SiteBrand.mobile_tabs 配置顺序渲染（消息在未登录/未开放时不显示）。
 * SiteChrome 只在启用 tab 的根路径渲染本组件，
 * 避免与聊天 / 发帖工作台的锁视口布局冲突。
 */
export default function MobileTabBar({
  user,
  initialChatUnread = 0,
}: {
  user: User | null;
  initialChatUnread?: number;
}) {
  const pathname = usePathname();
  const allowMessages = useAllowMessages();
  const { url_style: urlStyle, mobile_tabs: mobileTabs } = useSiteBrand();
  const libHref = libraryPath(urlStyle);
  const [chatUnread, setChatUnread] = useState(initialChatUnread);

  // 登录态经 router.refresh() 下发新 props 时校正徽标
  useEffect(() => {
    setChatUnread(initialChatUnread);
  }, [initialChatUnread]);

  // 实时未读：与 Header 同源（chat:unread 对全体成员推送；在当前会话页则忽略）
  useEffect(() => {
    if (!user || !allowMessages) return;
    const off = realtime.on<RtChatUnreadData>(RT_CHAT_UNREAD, (data) => {
      if (!data || typeof data.room_id !== "number") return;
      if (pathname === `/chat/${data.room_id}`) return;
      const delta = typeof data.delta === "number" ? data.delta : 1;
      setChatUnread((c) => Math.max(0, c + delta));
    });
    return off;
  }, [user, pathname, allowMessages]);

  // 会话内已读 / 回前台：合并对账（短时间多次同步只打一次 summary）
  useEffect(() => {
    if (!user || !allowMessages) return;
    let debounceTimer: ReturnType<typeof setTimeout> | null = null;
    const pullSummary = () => {
      apiChatUnreadSummary()
        .then((res) => setChatUnread(res.total || 0))
        .catch(() => {});
    };
    const onSync = () => {
      if (debounceTimer) clearTimeout(debounceTimer);
      debounceTimer = setTimeout(pullSummary, 250);
    };
    window.addEventListener("j13-chat-unread-sync", onSync);
    const offVisible = onDocumentVisible(pullSummary);
    return () => {
      if (debounceTimer) clearTimeout(debounceTimer);
      window.removeEventListener("j13-chat-unread-sync", onSync);
      offVisible();
    };
  }, [user, allowMessages]);

  const showMessages = !!user && allowMessages;

  const isActive = (match: (p: string) => boolean) =>
    !!pathname && match(pathname);

  // 配置已由 SiteBrandProvider normalize（白名单内子集，空回落全量）；数组顺序即展示顺序
  const tabNodes: Record<MobileTabKey, React.ReactNode> = {
    home: (
      <TabLink
        href="/"
        icon={<Home size={20} />}
        label="首页"
        active={isActive((p) => p === "/")}
      />
    ),
    library: (
      <TabLink
        href={libHref}
        icon={<BookOpen size={20} />}
        label="书库"
        active={isActive((p) => p === libHref)}
      />
    ),
    compose: (
      <TabLink
        href={user ? "/compose" : "/login"}
        icon={<PenSquare size={18} />}
        label="发帖"
        prominent
        active={false}
      />
    ),
    messages: showMessages ? (
      <TabLink
        href="/chat"
        icon={<MessageSquare size={20} />}
        label="消息"
        active={isActive((p) => p === "/chat")}
        badge={chatUnread > 0 ? (chatUnread > 99 ? "99+" : chatUnread) : 0}
      />
    ) : null,
    me: (
      <TabLink
        href={user ? userPath(urlStyle, user.id) : "/login"}
        icon={<UserIcon size={20} />}
        label="我的"
        active={!!user && isActive((p) => p === userPath(urlStyle, user.id))}
      />
    ),
  };

  return (
    <nav
      data-j13-tabbar
      className="lg:hidden fixed bottom-0 inset-x-0 z-50 border-t"
      aria-label="底部导航"
      style={{
        borderColor: "var(--line)",
        background: "color-mix(in srgb, var(--panel) 92%, transparent)",
        backdropFilter: "blur(14px)",
        WebkitBackdropFilter: "blur(14px)",
        paddingBottom: "env(safe-area-inset-bottom)",
      }}
    >
      <div className="flex items-stretch">
        {mobileTabs.map((key) =>
          tabNodes[key] ? <Fragment key={key}>{tabNodes[key]}</Fragment> : null,
        )}
      </div>
    </nav>
  );
}

function TabLink({
  href,
  icon,
  label,
  active,
  prominent = false,
  badge = 0,
}: {
  href: string;
  icon: React.ReactNode;
  label: string;
  active: boolean;
  prominent?: boolean;
  badge?: number | string;
}) {
  const ink = active ? "var(--accent)" : "var(--ink-2)";
  return (
    <Link
      href={href}
      prefetch={false}
      aria-label={label}
      aria-current={active ? "page" : undefined}
      className="flex-1 min-w-0 flex flex-col items-center justify-center gap-0.5 pt-2 pb-1.5 transition-colors"
      style={{ color: ink }}
    >
      {prominent ? (
        <span
          className="w-9 h-9 -mt-1 flex items-center justify-center rounded-full"
          style={{ background: "var(--accent)", color: "var(--accent-on)" }}
          aria-hidden="true"
        >
          {icon}
        </span>
      ) : (
        <span className="relative" aria-hidden="true">
          {icon}
          {badge ? (
            <span
              className="absolute -top-1.5 -right-2.5 min-w-[16px] h-[16px] px-1 text-[9.5px] font-medium flex items-center justify-center rounded-full"
              style={{
                background: "var(--clay)",
                color: "#fff",
                border: "2px solid var(--panel)",
              }}
            >
              {badge}
            </span>
          ) : null}
        </span>
      )}
      <span
        className={`text-[10px] leading-none ${
          prominent ? "mt-0.5" : ""
        } ${active ? "font-semibold" : "font-medium"}`}
      >
        {label}
      </span>
    </Link>
  );
}