import { api } from '../api.js';
import { escapeHtml, showAlert, hideAlert } from '../utils.js';

export async function initSubjects() {
    const subjectsTbody = document.getElementById('subjects-tbody');
    const createSubjectForm = document.getElementById('create-subject-form');
    const newSubjectDeptSelect = document.getElementById('new-subject-department');

    // Модалка управления преподавателями
    const modalManageTeachers = document.getElementById('modal-manage-teachers');
    const modalManageTeachersClose = document.getElementById('modal-manage-teachers-close');
    const subjectTeachersContext = document.getElementById('subject-teachers-context');
    const manageTeacherSubjectForm = document.getElementById('manage-teacher-subject-form');
    const manageTsSubjectIdInput = document.getElementById('manage-ts-subject-id');
    const manageTsTeacherSelect = document.getElementById('manage-ts-teacher-select');
    const manageTsTbody = document.getElementById('manage-ts-tbody');

    let allSubjects = [];
    let allTeachers = [];
    let allDepartments = [];
    let teacherSubjects = [];

    bindEvents();
    await loadInitialData();

    function bindEvents() {
        createSubjectForm.addEventListener('submit', createSubject);
        subjectsTbody.addEventListener('click', handleSubjectsTableClick);

        manageTeacherSubjectForm.addEventListener('submit', saveTeacherAssignment);
        manageTsTbody.addEventListener('click', handleTeacherAssignmentTableClick);

        modalManageTeachersClose.addEventListener('click', () => modalManageTeachers.classList.remove('open'));
        modalManageTeachers.addEventListener('click', (e) => {
            if (e.target === modalManageTeachers) modalManageTeachers.classList.remove('open');
        });
    }

    async function loadInitialData() {
        try {
            [allTeachers, allDepartments] = await Promise.all([
                api.get('/api/users/teachers'),
                api.get('/api/departments')
            ]);
            populateDepartmentsSelect();
            await loadSubjects();
        } catch (e) {
            subjectsTbody.innerHTML = `<tr><td colspan="6" class="loading-row">Ошибка загрузки справочников: ${escapeHtml(e.message)}</td></tr>`;
        }
    }

    function populateDepartmentsSelect() {
        newSubjectDeptSelect.innerHTML = '<option value="">Выберите кафедру</option>' +
            allDepartments.map(d => {
                const name = d.departmentName || d.name || 'Без названия';
                const code = d.departmentCode || d.code || d.id;
                return `<option value="${d.id}">${escapeHtml(name)} (${escapeHtml(String(code))})</option>`;
            }).join('');
    }

    async function loadSubjects() {
        subjectsTbody.innerHTML = '<tr><td colspan="6" class="loading-row">Загрузка...</td></tr>';
        try {
            [allSubjects, teacherSubjects] = await Promise.all([
                api.get('/api/subjects'),
                api.get('/api/teacher-subjects')
            ]);
            renderSubjects();
        } catch (e) {
            subjectsTbody.innerHTML = `<tr><td colspan="6" class="loading-row">Ошибка загрузки: ${escapeHtml(e.message)}</td></tr>`;
        }
    }

    function renderSubjects() {
        if (!allSubjects || !allSubjects.length) {
            subjectsTbody.innerHTML = '<tr><td colspan="6" class="loading-row">Нет дисциплин</td></tr>';
            return;
        }

        // Группируем преподавателей по дисциплинам
        const teachersBySubject = new Map();
        teacherSubjects.forEach(ts => {
            if (!teachersBySubject.has(ts.subjectId)) {
                teachersBySubject.set(ts.subjectId, []);
            }
            teachersBySubject.get(ts.subjectId).push(ts);
        });

        subjectsTbody.innerHTML = allSubjects.map(s => {
            const teachers = teachersBySubject.get(s.id) || [];
            const teachersHtml = teachers.length
                ? teachers.map(t => `<span class="badge badge-ef" style="margin: 0.1rem;">${escapeHtml(t.fullName || t.username)}</span>`).join('')
                : '<span class="text-muted"><small>Нет преподавателей</small></span>';

            return `
                <tr>
                    <td>${s.id}</td>
                    <td><strong>${escapeHtml(s.name)}</strong></td>
                    <td>${escapeHtml(s.code || '-')}</td>
                    <td>${escapeHtml(departmentLabel(s.departmentId))}</td>
                    <td><div style="display: flex; flex-wrap: wrap; gap: 0.25rem;">${teachersHtml}</div></td>
                    <td style="text-align: right; white-space: nowrap;">
                        <button class="btn btn-sm btn-secondary btn-manage-teachers" data-id="${s.id}">Преподаватели</button>
                        <button class="btn btn-sm btn-danger btn-delete-subject" data-id="${s.id}">Удалить</button>
                    </td>
                </tr>
            `;
        }).join('');
    }

    async function createSubject(e) {
        e.preventDefault();
        hideAlert('create-subject-alert');
        const name = document.getElementById('new-subject-name').value.trim();
        const code = document.getElementById('new-subject-code').value.trim();
        const departmentId = newSubjectDeptSelect.value;

        if (!name || !code || !departmentId) {
            showAlert('create-subject-alert', 'Заполните все поля', 'error');
            return;
        }

        try {
            const data = await api.post('/api/subjects', {
                name,
                code,
                departmentId: Number(departmentId)
            });
            showAlert('create-subject-alert', `Дисциплина "${escapeHtml(data.name || name)}" создана`, 'success');
            createSubjectForm.reset();
            await loadSubjects();
        } catch (error) {
            showAlert('create-subject-alert', error.message || 'Ошибка создания', 'error');
        }
    }

    async function handleSubjectsTableClick(e) {
        const btnDelete = e.target.closest('.btn-delete-subject');
        const btnTeachers = e.target.closest('.btn-manage-teachers');

        if (btnDelete) {
            if (!confirm('Удалить дисциплину? Это удалит её привязки к преподавателям.')) return;
            try {
                await api.delete('/api/subjects/' + btnDelete.dataset.id);
                await loadSubjects();
            } catch (error) {
                alert(error.message || 'Ошибка удаления');
            }
        }

        if (btnTeachers) {
            const subjectId = btnTeachers.dataset.id;
            const subject = allSubjects.find(s => s.id == subjectId);
            if (subject) openTeachersModal(subject);
        }
    }

    // --- Управление привязками преподавателей к дисциплине ---
    function openTeachersModal(subject) {
        subjectTeachersContext.textContent = `${subject.code ? `${subject.code} · ` : ''}${subject.name}`;
        manageTsSubjectIdInput.value = subject.id;
        hideAlert('manage-ts-alert');
        modalManageTeachers.classList.add('open');
        renderSubjectTeachers(subject.id);
        populateTeachersSelect(subject.id);
    }

    function renderSubjectTeachers(subjectId) {
        const list = teacherSubjects.filter(ts => String(ts.subjectId) === String(subjectId));
        if (!list.length) {
            manageTsTbody.innerHTML = '<tr><td colspan="2" class="loading-row">Преподаватели не привязаны</td></tr>';
            return;
        }
        manageTsTbody.innerHTML = list.map(ts => `
            <tr>
                <td><strong>${escapeHtml(ts.fullName || ts.username)}</strong> <span class="text-muted">(${escapeHtml(ts.username)})</span></td>
                <td>
                    <button class="btn btn-sm btn-danger btn-delete-ts" data-user-id="${ts.userId}" data-subject-id="${ts.subjectId}">Удалить</button>
                </td>
            </tr>
        `).join('');
    }

    function populateTeachersSelect(subjectId) {
        // Показываем только тех преподавателей, которые еще не привязаны к этой дисциплине
        const assignedUserIds = new Set(
            teacherSubjects
                .filter(ts => String(ts.subjectId) === String(subjectId))
                .map(ts => String(ts.userId))
        );

        const availableTeachers = allTeachers.filter(t => !assignedUserIds.has(String(t.id)));

        if (!availableTeachers.length) {
            manageTsTeacherSelect.innerHTML = '<option value="">Все преподаватели привязаны</option>';
            return;
        }

        manageTsTeacherSelect.innerHTML = '<option value="">Выберите преподавателя</option>' +
            availableTeachers.map(t => `<option value="${t.id}">${escapeHtml(t.fullName || t.username)} (${escapeHtml(t.username)})</option>`).join('');
    }

    async function saveTeacherAssignment(e) {
        e.preventDefault();
        hideAlert('manage-ts-alert');
        const subjectId = manageTsSubjectIdInput.value;
        const userId = manageTsTeacherSelect.value;

        if (!userId) {
            showAlert('manage-ts-alert', 'Выберите преподавателя', 'error');
            return;
        }

        try {
            await api.post('/api/teacher-subjects', {
                userId: Number(userId),
                subjectId: Number(subjectId)
            });
            showAlert('manage-ts-alert', 'Преподаватель успешно привязан', 'success');
            
            // Перезагрузим привязки и обновим интерфейс
            teacherSubjects = await api.get('/api/teacher-subjects');
            renderSubjectTeachers(subjectId);
            populateTeachersSelect(subjectId);
            
            // Также обновим главную таблицу
            renderSubjects();
        } catch (error) {
            showAlert('manage-ts-alert', error.message || 'Ошибка привязки', 'error');
        }
    }

    async function handleTeacherAssignmentTableClick(e) {
        const btnDelete = e.target.closest('.btn-delete-ts');
        if (!btnDelete) return;
        if (!confirm('Удалить привязку преподавателя?')) return;
        const subjectId = manageTsSubjectIdInput.value;

        try {
            await api.delete('/api/teacher-subjects', {
                userId: Number(btnDelete.dataset.userId),
                subjectId: Number(btnDelete.dataset.subjectId)
            });
            
            // Перезагрузим привязки
            teacherSubjects = await api.get('/api/teacher-subjects');
            renderSubjectTeachers(subjectId);
            populateTeachersSelect(subjectId);
            
            // Обновим главную таблицу
            renderSubjects();
        } catch (error) {
            alert(error.message || 'Ошибка удаления привязки');
        }
    }

    // --- Вспомогательные функции ---
    function departmentLabel(departmentId) {
        const department = allDepartments.find(item => item.id == departmentId);
        if (!department) return departmentId || '-';
        return department.departmentName || department.name || departmentId;
    }
}