(() => {
    'use strict';

    const token = localStorage.getItem('token');
    const role = localStorage.getItem('role');

    if (!token || role !== 'ADMIN') {
        window.location.href = '/';
        return;
    }

    const tbody = document.getElementById('users-tbody');
    const createForm = document.getElementById('create-form');
    const createAlert = document.getElementById('create-alert');
    const btnLogout = document.getElementById('btn-logout');

    const ROLE_LABELS = {
        ADMIN: 'Администратор',
        TEACHER: 'Преподаватель',
        STUDENT: 'Студент',
    };

    const ROLE_BADGE = {
        ADMIN: 'badge-admin',
        TEACHER: 'badge-teacher',
        STUDENT: 'badge-student',
    };

    // ---- Load Users ----
    async function loadUsers() {
        try {
            const res = await fetch('/api/users', {
                headers: { 'Authorization': 'Bearer ' + token },
            });
            const users = await res.json();
            renderUsers(users);
        } catch (e) {
            tbody.innerHTML = '<tr><td colspan="4" class="loading-row">Ошибка загрузки</td></tr>';
        }
    }

    function renderUsers(users) {
        if (!users.length) {
            tbody.innerHTML = '<tr><td colspan="4" class="loading-row">Нет пользователей</td></tr>';
            return;
        }

        tbody.innerHTML = users.map(u => `
      <tr>
        <td>${u.id}</td>
        <td>${escapeHtml(u.username)}</td>
        <td><span class="badge ${ROLE_BADGE[u.role] || ''}">${ROLE_LABELS[u.role] || u.role}</span></td>
        <td><button class="btn-delete" data-id="${u.id}">Удалить</button></td>
      </tr>
    `).join('');
    }

    function escapeHtml(str) {
        const div = document.createElement('div');
        div.textContent = str;
        return div.innerHTML;
    }

    // ---- Create User ----
    createForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        hideAlert();

        const username = document.getElementById('new-username').value.trim();
        const password = document.getElementById('new-password').value;
        const role = document.getElementById('new-role').value;

        if (!username || !password) {
            showAlert('Заполните все поля', 'error');
            return;
        }

        try {
            const res = await fetch('/api/users', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                    'Authorization': 'Bearer ' + token,
                },
                body: JSON.stringify({ username, password, role }),
            });

            const data = await res.json();

            if (res.ok) {
                showAlert(`Пользователь "${data.username}" создан`, 'success');
                createForm.reset();
                loadUsers();
            } else {
                showAlert(data.message || 'Ошибка создания', 'error');
            }
        } catch (e) {
            showAlert('Ошибка соединения', 'error');
        }
    });

    // ---- Delete User ----
    tbody.addEventListener('click', async (e) => {
        const btn = e.target.closest('.btn-delete');
        if (!btn) return;

        const id = btn.dataset.id;
        if (!confirm('Удалить пользователя?')) return;

        try {
            const res = await fetch('/api/users/' + id, {
                method: 'DELETE',
                headers: { 'Authorization': 'Bearer ' + token },
            });

            if (res.ok) {
                loadUsers();
            } else {
                alert('Ошибка удаления');
            }
        } catch (e) {
            alert('Ошибка соединения');
        }
    });

    // ---- Logout ----
    btnLogout.addEventListener('click', () => {
        localStorage.removeItem('token');
        localStorage.removeItem('role');
        window.location.href = '/';
    });

    // ---- Helpers ----
    function showAlert(msg, type) {
        createAlert.className = 'form-alert ' + type;
        createAlert.textContent = msg;
    }

    function hideAlert() {
        createAlert.className = 'form-alert';
        createAlert.textContent = '';
    }

    // Init
    loadUsers();
})();