import React, { useEffect, useMemo, useState } from 'react';
import { Loader2, RefreshCw, ShieldCheck, UserCheck, UserX, Users } from 'lucide-react';
import { adminApi, ManagedUser } from '../services/api';
import { useAuth } from '../context/AuthContext';
import { useToast } from '../context/ToastContext';
import { useNavigate } from 'react-router-dom';

const roleLabel: Record<ManagedUser['role'], string> = {
  admin: 'Superadmin',
  instructor: 'Instrutor',
  student: 'Aluno',
};

export const SuperAdmin: React.FC = () => {
  const { user } = useAuth();
  const { showToast } = useToast();
  const navigate = useNavigate();
  const [users, setUsers] = useState<ManagedUser[]>([]);
  const [isLoading, setIsLoading] = useState(true);
  const [updatingUserId, setUpdatingUserId] = useState<string | null>(null);
  const [query, setQuery] = useState('');

  const loadUsers = async () => {
    setIsLoading(true);
    try {
      const response = await adminApi.listUsers();
      setUsers(response.data);
    } catch {
      showToast('Não foi possível carregar os usuários.', 'error');
    } finally {
      setIsLoading(false);
    }
  };

  useEffect(() => {
    void loadUsers();
  }, []);

  const filteredUsers = useMemo(() => {
    const normalized = query.trim().toLowerCase();
    if (!normalized) return users;
    return users.filter((account) =>
      account.name.toLowerCase().includes(normalized) || account.email.toLowerCase().includes(normalized),
    );
  }, [query, users]);

  const updateUser = async (account: ManagedUser, update: Partial<Pick<ManagedUser, 'role' | 'isActive'>>) => {
    setUpdatingUserId(account.id);
    try {
      const response = await adminApi.updateUser(account.id, update);
      setUsers((current) => current.map((item) => item.id === account.id ? response.data : item));
      showToast('Usuário atualizado.', 'success');
    } catch {
      showToast('Não foi possível atualizar este usuário.', 'error');
    } finally {
      setUpdatingUserId(null);
    }
  };

  const activeUsers = users.filter((account) => account.isActive).length;
  const instructorUsers = users.filter((account) => account.role === 'instructor' && account.isActive).length;

  return (
    <main className="min-h-screen pt-28 pb-20 px-6 md:px-12 max-w-[1440px] mx-auto">
      <div className="flex flex-col md:flex-row md:items-end md:justify-between gap-6 mb-10">
        <div>
          <div className="flex items-center gap-2 text-orange-400 text-xs font-bold uppercase tracking-wider mb-3">
            <ShieldCheck className="w-4 h-4" /> Superadmin
          </div>
          <h1 className="text-3xl md:text-4xl font-bold text-white">Painel Administrativo</h1>
          <p className="text-gray-400 mt-2">Gerencie os acessos da plataforma. Cursos e aulas continuam no Painel do Instrutor.</p>
        </div>
        <div className="flex flex-wrap gap-3">
          <button
            onClick={() => navigate('/gerenciar')}
            className="inline-flex items-center justify-center gap-2 rounded-full px-5 py-3 text-sm font-semibold bg-orange-500 hover:bg-orange-600 text-white transition-colors"
          >
            Gerenciar cursos
          </button>
          <button
            onClick={() => void loadUsers()}
            className="inline-flex items-center justify-center gap-2 rounded-full px-5 py-3 text-sm font-semibold bg-white/10 hover:bg-white/15 text-white transition-colors"
          >
            <RefreshCw className="w-4 h-4" /> Atualizar
          </button>
        </div>
      </div>

      <div className="grid grid-cols-1 sm:grid-cols-3 gap-4 mb-8">
        <StatCard icon={<Users className="w-5 h-5" />} label="Usuários cadastrados" value={users.length} />
        <StatCard icon={<UserCheck className="w-5 h-5" />} label="Contas ativas" value={activeUsers} />
        <StatCard icon={<ShieldCheck className="w-5 h-5" />} label="Instrutores ativos" value={instructorUsers} />
      </div>

      <section className="rounded-2xl border border-white/10 bg-zinc-950/80 overflow-hidden">
        <div className="p-5 border-b border-white/10 flex flex-col sm:flex-row gap-4 sm:items-center sm:justify-between">
          <h2 className="text-lg font-bold text-white">Usuários</h2>
          <input
            value={query}
            onChange={(event) => setQuery(event.target.value)}
            placeholder="Buscar por nome ou e-mail"
            className="w-full sm:w-80 rounded-xl bg-zinc-900 border border-white/10 px-4 py-2.5 text-sm text-white placeholder:text-gray-500 focus:outline-none focus:border-orange-500"
          />
        </div>

        {isLoading ? (
          <div className="h-64 flex items-center justify-center"><Loader2 className="w-8 h-8 animate-spin text-orange-400" /></div>
        ) : filteredUsers.length === 0 ? (
          <div className="h-48 flex items-center justify-center text-sm text-gray-500">Nenhum usuário encontrado.</div>
        ) : (
          <div className="overflow-x-auto">
            <table className="w-full min-w-[760px] text-left text-sm">
              <thead className="bg-white/[0.03] text-xs uppercase tracking-wider text-gray-500">
                <tr>
                  <th className="px-5 py-4">Usuário</th>
                  <th className="px-5 py-4">Perfil</th>
                  <th className="px-5 py-4">Status</th>
                  <th className="px-5 py-4">Cadastro</th>
                </tr>
              </thead>
              <tbody className="divide-y divide-white/5">
                {filteredUsers.map((account) => {
                  const isCurrentUser = account.id === user?.id;
                  const isUpdating = updatingUserId === account.id;
                  return (
                    <tr key={account.id} className="text-gray-300">
                      <td className="px-5 py-4">
                        <div className="font-semibold text-white">{account.name}</div>
                        <div className="text-xs text-gray-500 mt-1">{account.email}</div>
                      </td>
                      <td className="px-5 py-4">
                        <select
                          value={account.role}
                          disabled={isCurrentUser || isUpdating}
                          onChange={(event) => void updateUser(account, { role: event.target.value as ManagedUser['role'] })}
                          className="rounded-lg bg-zinc-900 border border-white/10 px-3 py-2 text-xs text-white disabled:opacity-50"
                        >
                          {Object.entries(roleLabel).map(([role, label]) => <option key={role} value={role}>{label}</option>)}
                        </select>
                      </td>
                      <td className="px-5 py-4">
                        <button
                          disabled={isCurrentUser || isUpdating}
                          onClick={() => void updateUser(account, { isActive: !account.isActive })}
                          className={`inline-flex items-center gap-2 rounded-full px-3 py-2 text-xs font-semibold disabled:opacity-50 ${
                            account.isActive ? 'bg-emerald-500/15 text-emerald-400 hover:bg-emerald-500/25' : 'bg-red-500/15 text-red-400 hover:bg-red-500/25'
                          }`}
                        >
                          {account.isActive ? <UserCheck className="w-3.5 h-3.5" /> : <UserX className="w-3.5 h-3.5" />}
                          {account.isActive ? 'Ativo' : 'Desativado'}
                        </button>
                      </td>
                      <td className="px-5 py-4 text-xs text-gray-500">{new Intl.DateTimeFormat('pt-BR').format(new Date(account.createdAt))}</td>
                    </tr>
                  );
                })}
              </tbody>
            </table>
          </div>
        )}
      </section>
    </main>
  );
};

const StatCard: React.FC<{ icon: React.ReactNode; label: string; value: number }> = ({ icon, label, value }) => (
  <div className="rounded-2xl border border-white/10 bg-zinc-950/80 p-5">
    <div className="flex items-center gap-2 text-orange-400 mb-3">{icon}<span className="text-xs font-semibold uppercase tracking-wider">{label}</span></div>
    <div className="text-3xl font-bold text-white">{value}</div>
  </div>
);