/**
 * 教师端功能管理
 */
class TeacherManager {
    constructor() {
        this.apiBase = '/api/teacher';
        this.init();
    }
    
    async init() {
        this.updateCurrentTime();
        setInterval(() => this.updateCurrentTime(), 1000);
        await this.loadUserInfo();
        
        // 页面路由逻辑
        if (document.getElementById('courseList')) {
            this.initDashboard();
        }
        if (document.getElementById('studentTableBody') && document.getElementById('courseSelect')) {
            this.initGradeEntry();
        }
        if (document.getElementById('gradeTableBody')) {
            this.initGradeManagement();
        }
        if (document.getElementById('profileForm')) {
            this.initProfilePage();
        }
    }
    
    updateCurrentTime() {
        const timeElement = document.getElementById('currentTime');
        if (timeElement) {
            const now = new Date();
            const options = { 
                year: 'numeric', month: 'long', day: 'numeric',
                hour: '2-digit', minute: '2-digit', second: '2-digit'
            };
            timeElement.textContent = now.toLocaleString('zh-CN', options);
        }
    }

    async loadUserInfo() {
        try {
            const res = await fetch('/api/auth/me');
            const result = await res.json();
            if (result.success && result.data.user) {
                const user = result.data.user;
                this.user = user;
                
                // Update Sidebar
                const nameEls = document.querySelectorAll('#teacherName, #userName, #profileName');
                const idEls = document.querySelectorAll('#teacherId, #profileId, #inputTeacherId');
                
                nameEls.forEach(el => el.textContent = user.name);
                idEls.forEach(el => {
                    if (el.tagName === 'INPUT') el.value = user.id;
                    else el.textContent = user.id;
                });
                
                // Profile Page Specific
                const inputName = document.getElementById('inputName');
                const inputClass = document.getElementById('inputClass');
                if (inputName) inputName.value = user.name;
                if (inputClass) inputClass.value = user.class || '';
            }
        } catch (error) {
            console.error('Load user info failed:', error);
        }
    }
    
    // ================= Dashboard =================
    async initDashboard() {
        await Promise.all([
            this.loadCourses(),
            this.loadManagedClasses()
        ]);
        this.initAddCourse();
        this.initEditCourse();
    }

    async loadManagedClasses() {
        const managedClassesSection = document.getElementById('managedClassesSection');
        const managedClassList = document.getElementById('managedClassList');
        const classCountEl = document.getElementById('classCount');
        
        if (!managedClassList) return;

        try {
            const res = await fetch(`${this.apiBase}/my-classes`);
            const result = await res.json();
            
            if (result.success && result.data.classes.length > 0) {
                const classes = result.data.classes;
                classCountEl.textContent = classes.length;
                managedClassesSection.style.display = 'block';
                
                managedClassList.innerHTML = classes.map(c => `
                    <div class="col-md-6 col-xl-4 mb-3">
                        <div class="card h-100 border-0 shadow-sm">
                            <div class="card-body d-flex align-items-center">
                                <div class="bg-info bg-opacity-10 text-info rounded p-3 me-3">
                                    <i class="fas fa-users fa-lg"></i>
                                </div>
                                <div>
                                    <h6 class="mb-1 fw-bold">${c.class_name}</h6>
                                    <p class="text-muted small mb-0">${c.major || '专业未设置'} | ${c.grade}级</p>
                                </div>
                            </div>
                        </div>
                    </div>
                `).join('');
            } else {
                classCountEl.textContent = '0';
                managedClassesSection.style.display = 'none';
            }
        } catch (e) {
            console.error('Load managed classes failed', e);
        }
    }

    async loadCourses() {
        try {
            const response = await fetch(`${this.apiBase}/courses`);
            const result = await response.json();
            
            if (result.success) {
                this.courses = result.data.courses;
                this.renderDashboard(this.courses);
            }
        } catch (error) {
            console.error('Fetch courses failed:', error);
        }
    }

    renderDashboard(courses) {
        const courseList = document.getElementById('courseList');
        if (!courseList) return;
        
        if (!courses || courses.length === 0) {
            courseList.innerHTML = '<div class="col-12 text-center py-5 text-muted">暂无负责课程</div>';
            return;
        }
        
        courseList.innerHTML = courses.map(course => `
            <div class="col-md-6 col-xl-4 mb-4">
                <div class="card h-100 border-0 shadow-sm course-card">
                    <div class="card-body p-4">
                        <div class="d-flex justify-content-between align-items-start mb-3">
                            <span class="badge bg-primary bg-opacity-10 text-primary">
                                <i class="fas fa-book me-1"></i> ${course.course_code || 'CODE'}
                            </span>
                            <div class="d-flex gap-2">
                                <button class="btn btn-link text-secondary p-0 btn-edit-course" 
                                    data-id="${course.id}">
                                    <i class="fas fa-edit"></i>
                                </button>
                                <span class="text-muted small">${course.credit} 学分</span>
                            </div>
                        </div>
                        <h5 class="card-title fw-bold mb-2">${course.course_name}</h5>
                        <p class="card-text text-secondary small mb-4">
                            <i class="fas fa-users me-1"></i> ${course.class_name || '班级未指定'}
                        </p>
                        <div class="d-grid gap-2">
                            <a href="/teacher/grade_entry?courseId=${course.id}" class="btn btn-outline-primary btn-sm">
                                <i class="fas fa-edit me-1"></i> 成绩录入
                            </a>
                            <a href="/teacher/grade_management?courseId=${course.id}" class="btn btn-primary btn-sm">
                                <i class="fas fa-tasks me-1"></i> 成绩管理
                            </a>
                        </div>
                    </div>
                </div>
            </div>
        `).join('');
        
        document.getElementById('courseCount').textContent = courses.length;
        // Calculate total students
        const totalStudents = courses.reduce((sum, c) => sum + (c.student_count || 0), 0);
        document.getElementById('totalStudents').textContent = totalStudents;
    }

    initAddCourse() {
        const btn = document.getElementById('addCourseBtn');
        const modalEl = document.getElementById('addCourseModal');
        const saveBtn = document.getElementById('saveCourseBtn');
        
        if (!btn || !modalEl) return;
        
        const modal = new bootstrap.Modal(modalEl);
        
        btn.addEventListener('click', async () => {
            // Load classes
            try {
                const res = await fetch(`${this.apiBase}/classes`);
                const result = await res.json();
                if (result.success) {
                    const select = document.getElementById('classSelect');
                    select.innerHTML = '<option value="">请选择班级...</option>' + 
                        result.data.classes.map(c => `<option value="${c.id}">${c.class_name}</option>`).join('');
                }
            } catch (e) {
                console.error('Load classes failed', e);
            }
            modal.show();
        });
        
        saveBtn.addEventListener('click', async () => {
            const form = document.getElementById('addCourseForm');
            const formData = new FormData(form);
            const data = Object.fromEntries(formData.entries());
            
            try {
                const res = await fetch(`${this.apiBase}/courses`, {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
                const result = await res.json();
                
                if (result.success) {
                    alert('课程创建成功');
                    modal.hide();
                    this.loadCourses();
                    form.reset();
                } else {
                    alert(result.message || '创建失败');
                }
            } catch (e) {
                console.error('Create course failed', e);
                alert('系统错误');
            }
        });
    }

    initEditCourse() {
        const modalEl = document.getElementById('editCourseModal');
        if (!modalEl) return;
        
        const modal = new bootstrap.Modal(modalEl);
        const updateBtn = document.getElementById('updateCourseBtn');
        
        // Use event delegation for dynamically created edit buttons
        document.addEventListener('click', async (e) => {
            const btn = e.target.closest('.btn-edit-course');
            if (!btn) return;
            
            const courseId = btn.dataset.id;
            if (!this.courses) return;
            const courseData = this.courses.find(c => c.id == courseId);
            
            if (!courseData) return;
            
            // Fill form
            document.getElementById('editCourseId').value = courseData.id;
            document.getElementById('editCourseName').value = courseData.course_name;
            document.getElementById('editCourseCode').value = courseData.course_code;
            document.getElementById('editCourseCredit').value = courseData.credit;
            document.getElementById('editSemester').value = courseData.semester;
            
            // Load classes and select current one
            try {
                const res = await fetch(`${this.apiBase}/classes`);
                const result = await res.json();
                if (result.success) {
                    const select = document.getElementById('editClassSelect');
                    select.innerHTML = '<option value="">请选择班级...</option>' + 
                        result.data.classes.map(c => `<option value="${c.id}" ${c.id == courseData.class_id ? 'selected' : ''}>${c.class_name}</option>`).join('');
                }
            } catch (e) {
                console.error('Load classes failed', e);
            }
            
            modal.show();
        });
        
        updateBtn.addEventListener('click', async () => {
            const form = document.getElementById('editCourseForm');
            const formData = new FormData(form);
            const data = Object.fromEntries(formData.entries());
            const courseId = data.id;
            
            try {
                const res = await fetch(`${this.apiBase}/courses/${courseId}`, {
                    method: 'PUT',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
                const result = await res.json();
                
                if (result.success) {
                    alert('课程更新成功');
                    modal.hide();
                    this.loadCourses();
                } else {
                    alert(result.message || '更新失败');
                }
            } catch (e) {
                console.error('Update course failed', e);
                alert('系统错误');
            }
        });
    }

    // ================= Grade Entry =================
    async initGradeEntry() {
        const courseSelect = document.getElementById('courseSelect');
        
        // Load Courses for Select
        try {
            const response = await fetch(`${this.apiBase}/courses`);
            const result = await response.json();
            if (result.success) {
                courseSelect.innerHTML = '<option value="">请选择课程...</option>' + 
                    result.data.courses.map(c => `<option value="${c.id}">${c.course_name} (${c.class_name || '未指定班级'})</option>`).join('');
                
                // Check URL params
                const params = new URLSearchParams(window.location.search);
                const courseId = params.get('courseId');
                if (courseId) {
                    courseSelect.value = courseId;
                    this.loadStudentsForGradeEntry(courseId);
                }
            }
        } catch (e) { console.error(e); }
        
        courseSelect.addEventListener('change', (e) => {
            if (e.target.value) {
                this.loadStudentsForGradeEntry(e.target.value);
            } else {
                document.getElementById('studentTableBody').innerHTML = '<tr><td colspan="7" class="text-center py-5 text-muted">请选择课程以加载学生列表</td></tr>';
            }
        });
    }
    
    async loadStudentsForGradeEntry(courseId) {
        const tbody = document.getElementById('studentTableBody');
        tbody.innerHTML = '<tr><td colspan="7" class="text-center py-5"><div class="spinner-border text-primary" role="status"></div><div class="mt-2">加载中...</div></td></tr>';
        
        // Since we don't have a direct "get students by course" API that returns grades yet,
        // we might need to rely on what we have.
        // Actually, we need to fetch students enrolled in the class of this course.
        // AND fetch their existing grades for this course.
        // For simplicity, let's assume we have an endpoint or we modify `getGradeStatistics` or similar?
        // No, we should probably add `GET /api/teacher/course/:id/students`?
        // Or just use `GET /api/teacher/grades?courseId=X`.
        
        // Let's assume `GET /api/teacher/grades?courseId=X` returns the list of students with their grades (or null if no grade).
        // I need to implement this backend logic if it's missing.
        // For now, I'll simulate or try to use what I have.
        // I'll add `getCourseGrades` to TeacherController.
        
        // Wait, I can't modify backend endlessly.
        // Let's check `TeacherController.js` again.
        // It has `addScore`.
        // It does NOT have `getCourseGrades`.
        // I need to add it to support this view.
        
        try {
            // Placeholder: I will add this endpoint in next step.
            const res = await fetch(`${this.apiBase}/grades?courseId=${courseId}`);
            const result = await res.json();
            
            if (result.success) {
                this.renderGradeEntryTable(result.data.grades);
            } else {
                tbody.innerHTML = `<tr><td colspan="7" class="text-center text-danger">${result.message}</td></tr>`;
            }
        } catch (e) {
            tbody.innerHTML = `<tr><td colspan="7" class="text-center text-danger">加载失败: ${e.message}</td></tr>`;
        }
    }
    
    renderGradeEntryTable(grades) {
        const tbody = document.getElementById('studentTableBody');
        if (!grades || grades.length === 0) {
            tbody.innerHTML = '<tr><td colspan="7" class="text-center py-5 text-muted">该课程暂无学生</td></tr>';
            return;
        }
        
        tbody.innerHTML = grades.map(g => `
            <tr>
                <td>${g.student_id}</td>
                <td>${g.student_name}</td>
                <td><input type="number" class="form-control form-control-sm" value="${g.usual_score || ''}" placeholder="平时"></td>
                <td><input type="number" class="form-control form-control-sm" value="${g.midterm_score || ''}" placeholder="期中"></td>
                <td><input type="number" class="form-control form-control-sm" value="${g.final_score || ''}" placeholder="期末"></td>
                <td>${g.total_score || '-'}</td>
                <td>
                    <button class="btn btn-sm btn-primary save-grade-btn" data-student-id="${g.student_id}">
                        <i class="fas fa-save"></i> 保存
                    </button>
                </td>
            </tr>
        `).join('');
        
        // Bind save events
        document.querySelectorAll('.save-grade-btn').forEach(btn => {
            btn.addEventListener('click', (e) => this.saveGrade(e.target.closest('tr'), btn.dataset.studentId));
        });
    }
    
    async saveGrade(row, studentId) {
        const inputs = row.querySelectorAll('input');
        const usual = inputs[0].value;
        const midterm = inputs[1].value;
        const final = inputs[2].value;
        const courseId = document.getElementById('courseSelect').value;
        
        // Simple calculation for total score preview (Backend should do the real one)
        const total = (usual * 0.3 + midterm * 0.3 + final * 0.4).toFixed(1); // Example weights
        
        try {
            const res = await fetch(`${this.apiBase}/grades`, {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({
                    studentId,
                    courseId,
                    usual_score: usual,
                    midterm_score: midterm,
                    final_score: final,
                    score: total // Passing total score as 'score' for compatibility with existing API
                })
            });
            
            const result = await res.json();
            if (result.success) {
                // Update total cell
                row.cells[5].textContent = total;
                // Show success feedback
                const btn = row.querySelector('.save-grade-btn');
                const originalText = btn.innerHTML;
                btn.innerHTML = '<i class="fas fa-check"></i> 已保存';
                btn.classList.remove('btn-primary');
                btn.classList.add('btn-success');
                setTimeout(() => {
                    btn.innerHTML = originalText;
                    btn.classList.add('btn-primary');
                    btn.classList.remove('btn-success');
                }, 2000);
            } else {
                alert(result.message || '保存失败');
            }
        } catch (e) {
            console.error(e);
            alert('保存失败');
        }
    }

    // ================= Grade Management =================
    async initGradeManagement() {
        // Similar logic to Grade Entry but Read-Only or Filter focused
        // Fetch courses for filter
         try {
            const response = await fetch(`${this.apiBase}/courses`);
            const result = await response.json();
            if (result.success) {
                const select = document.getElementById('courseSelectFilter');
                select.innerHTML = '<option value="">全部课程</option>' + 
                    result.data.courses.map(c => `<option value="${c.id}">${c.course_name}</option>`).join('');
            }
        } catch (e) { console.error(e); }
        
        document.getElementById('searchBtn').addEventListener('click', () => this.searchGrades());
        
        // Check URL params
        const params = new URLSearchParams(window.location.search);
        if (params.get('courseId')) {
            document.getElementById('courseSelectFilter').value = params.get('courseId');
            this.searchGrades();
        }
    }
    
    async searchGrades() {
        const courseId = document.getElementById('courseSelectFilter').value;
        const studentName = document.getElementById('studentNameFilter').value;
        const tbody = document.getElementById('gradeTableBody');
        
        tbody.innerHTML = '<tr><td colspan="7" class="text-center py-5"><div class="spinner-border text-primary"></div></td></tr>';
        
        try {
            let url = `${this.apiBase}/grades?`;
            if (courseId) url += `courseId=${courseId}&`;
            if (studentName) url += `studentName=${studentName}`;
            
            const res = await fetch(url);
            const result = await res.json();
            
            if (result.success && result.data.grades) {
                if (result.data.grades.length === 0) {
                     tbody.innerHTML = '<tr><td colspan="7" class="text-center py-5 text-muted">未找到相关成绩记录</td></tr>';
                     return;
                }
                
                tbody.innerHTML = result.data.grades.map(g => `
                    <tr>
                        <td>${g.course_name || '-'}</td>
                        <td>${g.student_id || '-'}</td>
                        <td>${g.student_name || '-'}</td>
                        <td>${g.total_score || '-'}</td>
                        <td>${g.grade_point || '-'}</td>
                        <td><span class="badge bg-${this.getBadgeColor(g.grade_level)}">${g.grade_level || '-'}</span></td>
                        <td>
                            <button class="btn btn-sm btn-outline-primary" onclick="window.location.href='/teacher/grade_entry?courseId=${g.course_id}'">
                                <i class="fas fa-edit"></i> 修改
                            </button>
                        </td>
                    </tr>
                `).join('');
            }
        } catch (e) {
            tbody.innerHTML = `<tr><td colspan="7" class="text-center text-danger">查询失败</td></tr>`;
        }
    }
    
    getBadgeColor(level) {
        if (!level) return 'secondary';
        if (level.startsWith('A')) return 'success';
        if (level.startsWith('B')) return 'info';
        if (level.startsWith('C')) return 'warning';
        if (level.startsWith('F')) return 'danger';
        return 'primary';
    }
    
    // ================= Profile =================
    initProfilePage() {
        const saveProfileBtn = document.getElementById('saveProfileBtn');
        if (saveProfileBtn) {
            saveProfileBtn.addEventListener('click', async () => {
                const name = document.getElementById('inputName').value;
                const className = document.getElementById('inputClass').value;
                try {
                    const res = await fetch('/api/auth/update-profile', {
                        method: 'PUT',
                        headers: { 'Content-Type': 'application/json' },
                        body: JSON.stringify({ name, class: className })
                    });
                    const result = await res.json();
                    if (result.success) {
                        alert('资料更新成功');
                        // 更新侧边栏和顶栏
                        const nameEls = document.querySelectorAll('#teacherName, #userName, #profileName');
                        nameEls.forEach(el => el.textContent = name);
                    } else {
                        alert(result.message || '更新失败');
                    }
                } catch (e) {
                    console.error('Update profile failed', e);
                    alert('系统错误');
                }
            });
        }

        const passwordForm = document.getElementById('passwordForm');
        if (passwordForm) {
            passwordForm.addEventListener('submit', async (e) => {
                e.preventDefault();
                
                const oldPassword = document.getElementById('oldPassword').value;
                const newPassword = document.getElementById('newPassword').value;
                const confirmPassword = document.getElementById('confirmPassword').value;
                const errorEl = document.getElementById('passwordError');
                
                // Hide previous error
                errorEl.style.display = 'none';
                
                // Basic validation
                if (newPassword !== confirmPassword) {
                    errorEl.textContent = '两次输入的新密码不一致';
                    errorEl.style.display = 'block';
                    return;
                }
                
                if (newPassword.length < 6) {
                    errorEl.textContent = '新密码长度至少为 6 位';
                    errorEl.style.display = 'block';
                    return;
                }

                try {
                    const res = await fetch('/api/auth/update-password', {
                        method: 'PUT',
                        headers: {
                            'Content-Type': 'application/json'
                        },
                        body: JSON.stringify({ oldPassword, newPassword })
                    });
                    
                    const result = await res.json();
                    if (result.success) {
                        alert('密码修改成功，请重新登录');
                        // Logout and redirect
                        await fetch('/api/auth/logout', { method: 'POST' });
                        window.location.href = '/login';
                    } else {
                        errorEl.textContent = result.message || '修改失败';
                        errorEl.style.display = 'block';
                    }
                } catch (err) {
                    console.error(err);
                    errorEl.textContent = '服务器错误，请稍后再试';
                    errorEl.style.display = 'block';
                }
            });
        }
    }
}

document.addEventListener('DOMContentLoaded', () => {
    window.teacherManager = new TeacherManager();
});