(() => {
    'use strict';

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

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

    // ---- DOM refs ----
    const pageTitle = document.getElementById('page-title');
    const btnLogout = document.getElementById('btn-logout');
    const menuToggle = document.getElementById('menu-toggle');
    const sidebar = document.querySelector('.sidebar');
    const sidebarOverlay = document.getElementById('sidebar-overlay');

    // Users
    const usersTbody = document.getElementById('users-tbody');
    const createForm = document.getElementById('create-form');
    const createAlert = document.getElementById('create-alert');

    // Groups
    const groupsTbody = document.getElementById('groups-tbody');
    const createGroupForm = document.getElementById('create-group-form');
    const createGroupAlert = document.getElementById('create-group-alert');
    const newGroupEfSelect = document.getElementById('new-group-ef');
    const filterEfSelect = document.getElementById('filter-ef');

    // Education Forms
    const efTbody = document.getElementById('ef-tbody');
    const createEfForm = document.getElementById('create-ef-form');
    const createEfAlert = document.getElementById('create-ef-alert');

    const navItems = document.querySelectorAll('.nav-item[data-tab]');
    const tabContents = document.querySelectorAll('.tab-content');

    // ---- State ----
    let allGroups = [];
    let allEducationForms = [];

    // ---- Tab Switching ----
    const TAB_TITLES = {
        users: 'Управление пользователями',
        groups: 'Управление группами',
        'edu-forms': 'Формы обучения',
    };

    navItems.forEach(item => {
        item.addEventListener('click', (e) => {
            e.preventDefault();
            switchTab(item.dataset.tab);
        });
    });

    function switchTab(tab) {
        navItems.forEach(n => n.classList.remove('active'));
        document.querySelector(`.nav-item[data-tab="${tab}"]`)?.classList.add('active');

        tabContents.forEach(tc => tc.style.display = 'none');
        const target = document.getElementById('tab-' + tab);
        if (target) target.style.display = '';

        pageTitle.textContent = TAB_TITLES[tab] || '';

        if (tab === 'users') loadUsers();
        if (tab === 'groups') { loadEducationForms().then(() => loadGroups()); }
        if (tab === 'edu-forms') loadEducationForms();

        sidebar.classList.remove('open');
        sidebarOverlay.classList.remove('open');
    }

    // ---- Mobile Menu ----
    menuToggle.addEventListener('click', () => {
        sidebar.classList.toggle('open');
        sidebarOverlay.classList.toggle('open');
    });
    sidebarOverlay.addEventListener('click', () => {
        sidebar.classList.remove('open');
        sidebarOverlay.classList.remove('open');
    });

    // ---- Helpers ----
    const ROLE_LABELS = { ADMIN: 'Администратор', TEACHER: 'Преподаватель', STUDENT: 'Студент' };
    const ROLE_BADGE = { ADMIN: 'badge-admin', TEACHER: 'badge-teacher', STUDENT: 'badge-student' };

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

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

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

    // ============================================================
    //  USERS
    // ============================================================

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

    function renderUsers(users) {
        if (!users.length) {
            usersTbody.innerHTML = '<tr><td colspan="4" class="loading-row">Нет пользователей</td></tr>';
            return;
        }
        usersTbody.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="${u.id}">Удалить</button></td>
        <td><button class="btn-delete" data-role="${u.role}">Добавить занятие</button></td>
      </tr>`).join('');
    }

    createForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        hideAlert(createAlert);
        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(createAlert, '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(createAlert, `Пользователь "${data.username}" создан`, 'success');
                createForm.reset();
                loadUsers();
            } else {
                showAlert(createAlert, data.message || 'Ошибка создания', 'error');
            }
        } catch (e) { showAlert(createAlert, 'Ошибка соединения', 'error'); }
    });

    usersTbody.addEventListener('click', async (e) => {
        const btn = e.target.closest('.btn-delete');
        if (!btn) return;
        if (!confirm('Удалить пользователя?')) return;
        try {
            const res = await fetch('/api/users/' + btn.dataset.id, {
                method: 'DELETE',
                headers: { 'Authorization': 'Bearer ' + token },
            });
            if (res.ok) loadUsers();
            else alert('Ошибка удаления');
        } catch (e) { alert('Ошибка соединения'); }
    });

    // ============================================================
    //  EDUCATION FORMS
    // ============================================================

    async function loadEducationForms() {
        try {
            const res = await fetch('/api/education-forms', {
                headers: { 'Authorization': 'Bearer ' + token },
            });
            allEducationForms = await res.json();
            renderEfTable(allEducationForms);
            populateEfSelects(allEducationForms);
        } catch (e) {
            efTbody.innerHTML = '<tr><td colspan="3" class="loading-row">Ошибка загрузки</td></tr>';
        }
    }

    function renderEfTable(forms) {
        if (!forms.length) {
            efTbody.innerHTML = '<tr><td colspan="3" class="loading-row">Нет форм обучения</td></tr>';
            return;
        }
        efTbody.innerHTML = forms.map(ef => `
      <tr>
        <td>${ef.id}</td>
        <td>${escapeHtml(ef.name)}</td>
        <td><button class="btn-delete" data-id="${ef.id}">Удалить</button></td>
      </tr>`).join('');
    }

    function populateEfSelects(forms) {
        // Group creation select
        const currentVal = newGroupEfSelect.value;
        newGroupEfSelect.innerHTML = forms.map(ef =>
            `<option value="${ef.id}">${escapeHtml(ef.name)}</option>`
        ).join('');
        if (currentVal && forms.find(f => f.id == currentVal)) {
            newGroupEfSelect.value = currentVal;
        }

        // Filter select
        const currentFilter = filterEfSelect.value;
        filterEfSelect.innerHTML = '<option value="">Все формы</option>' +
            forms.map(ef =>
                `<option value="${ef.id}">${escapeHtml(ef.name)}</option>`
            ).join('');
        if (currentFilter) filterEfSelect.value = currentFilter;
    }

    createEfForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        hideAlert(createEfAlert);
        const name = document.getElementById('new-ef-name').value.trim();
        if (!name) { showAlert(createEfAlert, 'Введите название', 'error'); return; }

        try {
            const res = await fetch('/api/education-forms', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json', 'Authorization': 'Bearer ' + token },
                body: JSON.stringify({ name }),
            });
            const data = await res.json();
            if (res.ok) {
                showAlert(createEfAlert, `Форма "${data.name}" создана`, 'success');
                createEfForm.reset();
                loadEducationForms();
            } else {
                showAlert(createEfAlert, data.message || 'Ошибка создания', 'error');
            }
        } catch (e) { showAlert(createEfAlert, 'Ошибка соединения', 'error'); }
    });

    efTbody.addEventListener('click', async (e) => {
        const btn = e.target.closest('.btn-delete');
        if (!btn) return;
        if (!confirm('Удалить форму обучения?')) return;
        try {
            const res = await fetch('/api/education-forms/' + btn.dataset.id, {
                method: 'DELETE',
                headers: { 'Authorization': 'Bearer ' + token },
            });
            if (res.ok) {
                loadEducationForms();
            } else {
                const data = await res.json();
                alert(data.message || 'Ошибка удаления');
            }
        } catch (e) { alert('Ошибка соединения'); }
    });

    // ============================================================
    //  GROUPS
    // ============================================================

    async function loadGroups() {
        try {
            const res = await fetch('/api/groups', {
                headers: { 'Authorization': 'Bearer ' + token },
            });
            allGroups = await res.json();
            applyGroupFilter();
        } catch (e) {
            groupsTbody.innerHTML = '<tr><td colspan="4" class="loading-row">Ошибка загрузки</td></tr>';
        }
    }

    function applyGroupFilter() {
        const filterId = filterEfSelect.value;
        const filtered = filterId
            ? allGroups.filter(g => g.educationFormId == filterId)
            : allGroups;
        renderGroups(filtered);
    }

    filterEfSelect.addEventListener('change', applyGroupFilter);

    function renderGroups(groups) {
        if (!groups.length) {
            groupsTbody.innerHTML = '<tr><td colspan="4" class="loading-row">Нет групп</td></tr>';
            return;
        }
        groupsTbody.innerHTML = groups.map(g => `
      <tr>
        <td>${g.id}</td>
        <td>${escapeHtml(g.name)}</td>
        <td><span class="badge badge-ef">${escapeHtml(g.educationFormName)}</span></td>
        <td><button class="btn-delete" data-id="${g.id}">Удалить</button></td>
      </tr>`).join('');
    }

    createGroupForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        hideAlert(createGroupAlert);
        const name = document.getElementById('new-group-name').value.trim();
        const educationFormId = newGroupEfSelect.value;
        if (!name) { showAlert(createGroupAlert, 'Введите название группы', 'error'); return; }
        if (!educationFormId) { showAlert(createGroupAlert, 'Выберите форму обучения', 'error'); return; }

        try {
            const res = await fetch('/api/groups', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json', 'Authorization': 'Bearer ' + token },
                body: JSON.stringify({ name, educationFormId: Number(educationFormId) }),
            });
            const data = await res.json();
            if (res.ok) {
                showAlert(createGroupAlert, `Группа "${data.name}" создана`, 'success');
                createGroupForm.reset();
                loadGroups();
            } else {
                showAlert(createGroupAlert, data.message || 'Ошибка создания', 'error');
            }
        } catch (e) { showAlert(createGroupAlert, 'Ошибка соединения', 'error'); }
    });

    groupsTbody.addEventListener('click', async (e) => {
        const btn = e.target.closest('.btn-delete');
        if (!btn) return;
        if (!confirm('Удалить группу?')) return;
        try {
            const res = await fetch('/api/groups/' + btn.dataset.id, {
                method: 'DELETE',
                headers: { 'Authorization': 'Bearer ' + token },
            });
            if (res.ok) loadGroups();
            else alert('Ошибка удаления');
        } catch (e) { alert('Ошибка соединения'); }
    });

    // ============================================================
    //  LOGOUT & INIT
    // ============================================================

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

    loadUsers();
})();