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 assignTeacherForm = document.getElementById('assign-teacher-form');
    const assignTeacherSelect = document.getElementById('assign-teacher-select');
    const assignSubjectSelect = document.getElementById('assign-subject-select');
    const teacherSubjectsTbody = document.getElementById('teacher-subjects-tbody');

    let allSubjects = [];
    let allTeachers = [];

    async function loadInitialData() {
        await Promise.all([loadSubjects(), loadTeachers()]);
        await loadTeacherSubjects();
    }

    async function loadSubjects() {
        try {
            allSubjects = await api.get('/api/subjects');
            renderSubjects(allSubjects);
            populateSubjectSelect(allSubjects);
        } catch (e) {
            if (subjectsTbody) subjectsTbody.innerHTML = '<tr><td colspan="3" class="loading-row">Ошибка загрузки</td></tr>';
        }
    }

    function renderSubjects(subjects) {
        if (!subjects || !subjects.length) {
            subjectsTbody.innerHTML = '<tr><td colspan="3" class="loading-row">Нет дисциплин</td></tr>';
            return;
        }
        subjectsTbody.innerHTML = subjects.map(s => `
      <tr>
        <td>${s.id}</td>
        <td>${escapeHtml(s.name)}</td>
        <td><button class="btn-delete" data-id="${s.id}">Удалить</button></td>
      </tr>`).join('');
    }

    function populateSubjectSelect(subjects) {
        if (!assignSubjectSelect) return;
        const currentVal = assignSubjectSelect.value;
        assignSubjectSelect.innerHTML = '<option value="">Выберите дисциплину</option>' +
            subjects.map(s => `<option value="${s.id}">${escapeHtml(s.name)}</option>`).join('');
        if (currentVal && subjects.find(s => s.id == currentVal)) {
            assignSubjectSelect.value = currentVal;
        }
    }

    async function loadTeachers() {
        try {
            allTeachers = await api.get('/api/users/teachers');
            populateTeacherSelect(allTeachers);
        } catch (e) {
            if (assignTeacherSelect) assignTeacherSelect.innerHTML = '<option value="">Ошибка загрузки</option>';
        }
    }

    function populateTeacherSelect(teachers) {
        if (!assignTeacherSelect) return;
        const currentVal = assignTeacherSelect.value;
        if (!teachers || !teachers.length) {
            assignTeacherSelect.innerHTML = '<option value="">Нет преподавателей</option>';
            return;
        }
        assignTeacherSelect.innerHTML = '<option value="">Выберите преподавателя</option>' +
            teachers.map(t => `<option value="${t.id}">${escapeHtml(t.username)}</option>`).join('');
        if (currentVal && teachers.find(t => t.id == currentVal)) {
            assignTeacherSelect.value = currentVal;
        }
    }

    async function loadTeacherSubjects() {
        try {
            const tsData = await api.get('/api/teacher-subjects');
            renderTeacherSubjects(tsData);
        } catch (e) {
            if (teacherSubjectsTbody) teacherSubjectsTbody.innerHTML = '<tr><td colspan="3" class="loading-row">Ошибка загрузки</td></tr>';
        }
    }

    function renderTeacherSubjects(tsArray) {
        if (!tsArray || !tsArray.length) {
            teacherSubjectsTbody.innerHTML = '<tr><td colspan="3" class="loading-row">Нет привязок</td></tr>';
            return;
        }
        teacherSubjectsTbody.innerHTML = tsArray.map(ts => `
      <tr>
        <td>${escapeHtml(ts.username)}</td>
        <td>${escapeHtml(ts.subjectName)}</td>
        <td><button class="btn-delete" data-user-id="${ts.userId}" data-subject-id="${ts.subjectId}">Удалить</button></td>
      </tr>`).join('');
    }

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

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

    subjectsTbody.addEventListener('click', async (e) => {
        const btn = e.target.closest('.btn-delete');
        if (!btn) return;
        if (!confirm('Удалить дисциплину?')) return;
        try {
            await api.delete('/api/subjects/' + btn.dataset.id);
            loadSubjects();
            loadTeacherSubjects(); // May have deleted a subject that was assigned
        } catch (e) { alert(e.message || 'Ошибка удаления'); }
    });

    assignTeacherForm.addEventListener('submit', async (e) => {
        e.preventDefault();
        hideAlert('assign-teacher-alert');
        const userId = assignTeacherSelect.value;
        const subjectId = assignSubjectSelect.value;
        if (!userId) { showAlert('assign-teacher-alert', 'Выберите преподавателя', 'error'); return; }
        if (!subjectId) { showAlert('assign-teacher-alert', 'Выберите дисциплину', 'error'); return; }

        try {
            await api.post('/api/teacher-subjects', { userId: Number(userId), subjectId: Number(subjectId) });
            showAlert('assign-teacher-alert', 'Привязка создана', 'success');
            loadTeacherSubjects();
        } catch (e) { showAlert('assign-teacher-alert', e.message || 'Ошибка привязки', 'error'); }
    });

    teacherSubjectsTbody.addEventListener('click', async (e) => {
        const btn = e.target.closest('.btn-delete');
        if (!btn) return;
        if (!confirm('Удалить привязку?')) return;
        try {
            await api.delete('/api/teacher-subjects', {
                userId: Number(btn.dataset.userId),
                subjectId: Number(btn.dataset.subjectId)
            });
            loadTeacherSubjects();
        } catch (e) { alert(e.message || 'Ошибка удаления'); }
    });

    loadInitialData();
}