"use client";

import Link from "next/link";
import { useCallback, useEffect, useMemo, useState } from "react";
import { listInviteCodesAPI, listUsersAPI, type InviteCodeItem, type UserItem } from "@/lib/api";
import { useAuth } from "@/hooks/use-auth";

export default function AdminPage() {
  const { user } = useAuth();
  const [users, setUsers] = useState<UserItem[]>([]);
  const [invites, setInvites] = useState<InviteCodeItem[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState("");

  const loadData = useCallback(async () => {
    if (user?.role !== "admin") return;
    setLoading(true);
    setError("");
    try {
      const [userRows, inviteRows] = await Promise.all([listUsersAPI(), listInviteCodesAPI()]);
      setUsers(userRows);
      setInvites(inviteRows);
    } catch (err) {
      setError(err instanceof Error ? err.message : "管理数据加载失败");
    } finally {
      setLoading(false);
    }
  }, [user?.role]);

  useEffect(() => {
    loadData();
  }, [loadData]);

  const stats = useMemo(() => {
    const activeUsers = users.filter((item) => item.is_active).length;
    const disabledUsers = users.length - activeUsers;
    const activeInvites = invites.filter((item) => item.is_active).length;
    const remainingInvites = invites.reduce((sum, item) => sum + Math.max(0, (item.max_uses || 0) - (item.used_count || 0)), 0);
    return { activeUsers, disabledUsers, activeInvites, remainingInvites };
  }, [invites, users]);

  if (user?.role !== "admin") {
    return <NoAccess />;
  }

  return (
    <div className="max-w-7xl mx-auto px-4 md:px-8 pt-6 pb-20 md:pb-10 space-y-5">
      <header className="flex flex-col gap-3 md:flex-row md:items-end md:justify-between">
        <div>
          <div className="text-[10px] font-semibold uppercase tracking-[0.22em] text-amber-400">Admin Console</div>
          <h1 className="mt-2 text-2xl font-bold tracking-tight text-text-primary">系统管理</h1>
          <p className="mt-1 text-sm text-text-muted">账号访问和注册入口分开管理，减少误操作。</p>
        </div>
        <button
          onClick={loadData}
          className="rounded-xl border border-border-subtle bg-surface-2 px-4 py-2 text-xs text-text-secondary hover:text-text-primary"
        >
          刷新概览
        </button>
      </header>

      {error ? <div className="glass-card-static border-red-500/15 px-4 py-2.5 text-xs text-red-300">{error}</div> : null}

      <section className="grid grid-cols-2 gap-3 lg:grid-cols-4">
        <StatCard label="启用用户" value={loading ? "-" : stats.activeUsers} />
        <StatCard label="停用用户" value={loading ? "-" : stats.disabledUsers} />
        <StatCard label="启用邀请码" value={loading ? "-" : stats.activeInvites} />
        <StatCard label="剩余注册名额" value={loading ? "-" : stats.remainingInvites} />
      </section>

      <section className="grid grid-cols-1 gap-4 lg:grid-cols-2">
        <AdminEntryCard
          href="/admin/users"
          title="用户管理"
          description="查看账号、禁用账号、重置密码。适合处理访问权限和账号生命周期。"
          primary={`${stats.activeUsers} 个启用账号`}
          secondary={`${stats.disabledUsers} 个停用账号`}
          loading={loading}
        />
        <AdminEntryCard
          href="/admin/invites"
          title="邀请码管理"
          description="创建邀请码、控制启停、查看使用量。适合管理新用户注册入口。"
          primary={`${stats.activeInvites} 个启用邀请码`}
          secondary={`${stats.remainingInvites} 个剩余名额`}
          loading={loading}
        />
      </section>
    </div>
  );
}

function NoAccess() {
  return (
    <div className="max-w-5xl mx-auto px-4 md:px-8 pt-8 pb-20">
      <div className="glass-card-static p-6 text-sm text-text-secondary">当前账号没有系统管理权限。</div>
    </div>
  );
}

function StatCard({ label, value }: { label: string; value: string | number }) {
  return (
    <div className="glass-card-static p-4">
      <div className="text-[10px] text-text-muted">{label}</div>
      <div className="mt-2 font-mono text-2xl font-bold tabular-nums text-text-primary">{value}</div>
    </div>
  );
}

function AdminEntryCard({
  href,
  title,
  description,
  primary,
  secondary,
  loading,
}: {
  href: string;
  title: string;
  description: string;
  primary: string;
  secondary: string;
  loading: boolean;
}) {
  return (
    <Link href={href} className="glass-card-static block p-5 transition-colors hover:border-amber-500/20">
      <div className="flex items-start justify-between gap-4">
        <div>
          <h2 className="text-lg font-bold tracking-tight text-text-primary">{title}</h2>
          <p className="mt-2 max-w-xl text-sm leading-6 text-text-muted">{description}</p>
        </div>
        <span className="rounded-xl border border-border-subtle bg-surface-2 px-3 py-1.5 text-xs text-text-secondary">进入</span>
      </div>
      <div className="mt-5 grid grid-cols-2 gap-3">
        <div className="rounded-xl bg-surface-2 px-3 py-3">
          <div className="text-[10px] text-text-muted">当前状态</div>
          <div className="mt-1 text-sm font-semibold text-text-primary">{loading ? "加载中" : primary}</div>
        </div>
        <div className="rounded-xl bg-surface-2 px-3 py-3">
          <div className="text-[10px] text-text-muted">补充信息</div>
          <div className="mt-1 text-sm font-semibold text-text-primary">{loading ? "加载中" : secondary}</div>
        </div>
      </div>
    </Link>
  );
}