/**
 * 管理员端功能管理
 */
class AdminManager {
    constructor() {
        this.apiBase = '/api/admin';
        this.init();
    }
    
    async init() {
        this.updateCurrentTime();
        setInterval(() => this.updateCurrentTime(), 1000);
        await this.loadUserInfo();
        
        // 页面路由逻辑
        const path = window.location.pathname;
        if (path.includes('/dashboard')) {
            this.initDashboard();
        } else if (path.includes('/user_management')) {
            this.initUserManagement();
        } else if (path.includes('/student_management')) {
            this.initStudentManagement();
        } else if (path.includes('/teacher_management')) {
            this.initTeacherManagement();
        } else if (path.includes('/grade_statistics')) {
            this.initGradeStatistics();
        } else if (path.includes('/system_settings')) {
            this.initSystemSettings();
        } else if (path.includes('/data_export')) {
            this.initDataExport();
        } else if (path.includes('/operation_logs')) {
            this.initOperationLogs();
        }

        // Logout
        const logoutBtn = document.getElementById('logoutBtn');
        if (logoutBtn) {
            logoutBtn.addEventListener('click', async (e) => {
                e.preventDefault();
                if (confirm('确定要退出登录吗？')) {
                    try {
                        const res = await fetch('/api/auth/logout', { method: 'POST' });
                        const result = await res.json();
                        if (result.success) {
                            alert('退出登录成功');
                            window.location.href = '/login';
                        } else {
                            alert(result.message || '退出登录失败');
                        }
                    } catch (e) {
                        console.error('Logout failed', e);
                        alert('退出登录出错: ' + e.message);
                    }
                }
            });
        }
    }
    
    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;
                
                const nameEls = document.querySelectorAll('#adminName, #userName');
                nameEls.forEach(el => el.textContent = user.name || '管理员');
            }
        } catch (error) {
            console.error('Load user info failed:', error);
        }
    }
    
    // ================= Dashboard =================
    async initDashboard() {
        try {
            const res = await fetch(`${this.apiBase}/stats`);
            const result = await res.json();
            
            if (result.success) {
                const stats = result.data;
                if (document.getElementById('totalUsers')) document.getElementById('totalUsers').textContent = stats.users;
                if (document.getElementById('totalStudents')) document.getElementById('totalStudents').textContent = stats.students;
                if (document.getElementById('totalTeachers')) document.getElementById('totalTeachers').textContent = stats.teachers;
                if (document.getElementById('totalCourses')) document.getElementById('totalCourses').textContent = stats.courses;
            }
        } catch (e) {
            console.error('Load stats failed', e);
        }
    }

    // ================= User Management =================
    async initUserManagement() {
        this.currentPage = 1;
        this.pageSize = 10;
        
        // Bind Filter Events
        document.getElementById('search').addEventListener('input', () => this.loadUsers());
        document.getElementById('roleFilter').addEventListener('change', () => this.loadUsers());
        
        // Bind Modal Events
        const modalEl = document.getElementById('userModal');
        this.userModal = new bootstrap.Modal(modalEl);
        
        document.getElementById('addUserBtn').addEventListener('click', () => {
            document.getElementById('userForm').reset();
            document.getElementById('userModalTitle').textContent = '新增用户';
            document.getElementById('isEdit').value = 'false';
            document.getElementById('userId').readOnly = false;
            this.userModal.show();
        });
        
        document.getElementById('saveUserBtn').addEventListener('click', () => this.saveUser());
        
        // Initial Load
        await this.loadUsers();
    }
    
    async loadUsers() {
        const search = document.getElementById('search').value;
        const role = document.getElementById('roleFilter').value;
        const tbody = document.getElementById('userTableBody');
        
        tbody.innerHTML = '<tr><td colspan="6" class="text-center py-5">加载中...</td></tr>';
        
        try {
            const query = new URLSearchParams({
                page: this.currentPage,
                limit: this.pageSize,
                search,
                role
            });
            
            const res = await fetch(`${this.apiBase}/users?${query}`);
            const result = await res.json();
            
            if (result.success) {
                this.renderUserTable(result.data, result.pagination);
            } else {
                tbody.innerHTML = `<tr><td colspan="6" class="text-center text-danger">${result.message}</td></tr>`;
            }
        } catch (e) {
            console.error(e);
            tbody.innerHTML = '<tr><td colspan="6" class="text-center text-danger">加载失败</td></tr>';
        }
    }
    
    renderUserTable(users, pagination) {
        const tbody = document.getElementById('userTableBody');
        
        if (users.length === 0) {
            tbody.innerHTML = '<tr><td colspan="6" class="text-center py-5 text-muted">暂无用户</td></tr>';
            return;
        }
        
        tbody.innerHTML = users.map(u => `
            <tr>
                <td class="ps-4 fw-bold">${u.id}</td>
                <td>${u.name}</td>
                <td><span class="badge bg-${this.getRoleBadgeColor(u.role)}">${this.getRoleName(u.role)}</span></td>
                <td>${u.class || '-'}</td>
                <td>${new Date(u.created_at).toLocaleDateString()}</td>
                <td class="text-end pe-4">
                    <button class="btn btn-sm btn-outline-primary me-1 btn-edit-user" data-user='${JSON.stringify(u).replace(/'/g, "&apos;")}'>
                        <i class="fas fa-edit"></i>
                    </button>
                    <button class="btn btn-sm btn-outline-danger btn-delete-user" data-id="${u.id}">
                        <i class="fas fa-trash"></i>
                    </button>
                </td>
            </tr>
        `).join('');
        
        // Bind Action Buttons
        document.querySelectorAll('.btn-edit-user').forEach(btn => {
            btn.addEventListener('click', () => {
                const user = JSON.parse(btn.dataset.user);
                this.openEditUserModal(user);
            });
        });
        
        document.querySelectorAll('.btn-delete-user').forEach(btn => {
            btn.addEventListener('click', () => {
                if(confirm('确定要删除该用户吗？此操作不可恢复。')) {
                    this.deleteUser(btn.dataset.id);
                }
            });
        });
        
        this.renderPagination(pagination);
    }
    
    getRoleBadgeColor(role) {
        switch(role) {
            case 'admin': return 'danger';
            case 'teacher': return 'info';
            case 'student': return 'success';
            default: return 'secondary';
        }
    }
    
    getRoleName(role) {
        switch(role) {
            case 'admin': return '管理员';
            case 'teacher': return '教师';
            case 'student': return '学生';
            default: role;
        }
    }
    
    renderPagination(pagination) {
        const el = document.getElementById('pagination');
        let html = '';
        
        if (pagination.page > 1) {
            html += `<li class="page-item"><a class="page-link" href="#" onclick="window.adminManager.changePage(${pagination.page - 1})">上一页</a></li>`;
        } else {
            html += `<li class="page-item disabled"><a class="page-link" href="#">上一页</a></li>`;
        }
        
        for (let i = 1; i <= pagination.pages; i++) {
            html += `<li class="page-item ${i === pagination.page ? 'active' : ''}"><a class="page-link" href="#" onclick="window.adminManager.changePage(${i})">${i}</a></li>`;
        }
        
        if (pagination.page < pagination.pages) {
            html += `<li class="page-item"><a class="page-link" href="#" onclick="window.adminManager.changePage(${pagination.page + 1})">下一页</a></li>`;
        } else {
            html += `<li class="page-item disabled"><a class="page-link" href="#">下一页</a></li>`;
        }
        
        el.innerHTML = html;
    }
    
    changePage(page) {
        this.currentPage = page;
        this.loadUsers();
    }
    
    openEditUserModal(user) {
        document.getElementById('userForm').reset();
        document.getElementById('userModalTitle').textContent = '编辑用户';
        document.getElementById('isEdit').value = 'true';
        document.getElementById('userId').value = user.id;
        document.getElementById('userId').readOnly = true;
        document.getElementById('userNameInput').value = user.name;
        document.getElementById('userRole').value = user.role;
        document.getElementById('userClass').value = user.class || '';
        this.userModal.show();
    }
    
    async saveUser() {
        const form = document.getElementById('userForm');
        const formData = new FormData(form);
        const data = Object.fromEntries(formData.entries());
        const isEdit = data.isEdit === 'true';
        
        // Validation
        if (!data.id || !data.name || !data.role) {
            alert('请填写必填字段');
            return;
        }
        
        if (data.role === 'student' && !data.class) {
            alert('学生角色必须填写班级');
            return;
        }
        
        try {
            let res;
            if (isEdit) {
                res = await fetch(`${this.apiBase}/users/${data.id}`, {
                    method: 'PUT',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
            } else {
                res = await fetch(`${this.apiBase}/users`, {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
            }
            
            const result = await res.json();
            
            if (result.success) {
                alert(isEdit ? '更新成功' : '创建成功');
                this.userModal.hide();
                this.loadUsers();
            } else {
                alert(result.message || '操作失败');
            }
        } catch (e) {
            console.error(e);
            alert('系统错误');
        }
    }
    
    async deleteUser(id) {
        try {
            const res = await fetch(`${this.apiBase}/users/${id}`, { method: 'DELETE' });
            const result = await res.json();
            
            if (result.success) {
                alert('删除成功');
                this.loadUsers();
            } else {
                alert(result.message || '删除失败');
            }
        } catch (e) {
            console.error(e);
            alert('系统错误');
        }
    }

    // ================= Student Management =================
    async initStudentManagement() {
        this.studentCurrentPage = 1;
        this.studentPageSize = 10;
        
        // Bind Filter Events
        document.getElementById('studentSearch').addEventListener('input', () => this.loadStudents());
        
        // Bind Modal Events
        const modalEl = document.getElementById('studentModal');
        this.studentModal = new bootstrap.Modal(modalEl);
        
        document.getElementById('addStudentBtn').addEventListener('click', () => {
            document.getElementById('studentForm').reset();
            document.getElementById('studentModalTitle').textContent = '新增学生';
            document.getElementById('studentIsEdit').value = 'false';
            document.getElementById('studentId').readOnly = false;
            this.studentModal.show();
        });
        
        document.getElementById('saveStudentBtn').addEventListener('click', () => this.saveStudent());
        
        // Initial Load
        await this.loadStudents();
    }
    
    async loadStudents() {
        const search = document.getElementById('studentSearch').value;
        const tbody = document.getElementById('studentTableBody');
        
        tbody.innerHTML = '<tr><td colspan="7" class="text-center py-5">加载中...</td></tr>';
        
        try {
            const query = new URLSearchParams({
                page: this.studentCurrentPage,
                limit: this.studentPageSize,
                search
            });
            
            const res = await fetch(`${this.apiBase}/students?${query}`);
            const result = await res.json();
            
            if (result.success) {
                this.renderStudentTable(result.data, result.pagination);
            } else {
                tbody.innerHTML = `<tr><td colspan="7" class="text-center text-danger">${result.message}</td></tr>`;
            }
        } catch (e) {
            console.error(e);
            tbody.innerHTML = '<tr><td colspan="7" class="text-center text-danger">加载失败</td></tr>';
        }
    }
    
    renderStudentTable(students, pagination) {
        const tbody = document.getElementById('studentTableBody');
        
        if (students.length === 0) {
            tbody.innerHTML = '<tr><td colspan="7" class="text-center py-5 text-muted">暂无学生</td></tr>';
            return;
        }
        
        tbody.innerHTML = students.map(s => `
            <tr>
                <td class="ps-4 fw-bold">${s.id}</td>
                <td>${s.name}</td>
                <td>${s.class || '-'}</td>
                <td>${s.major || '-'}</td>
                <td>${s.grade || '-'}</td>
                <td>${s.contact_info || '-'}</td>
                <td class="text-end pe-4">
                    <button class="btn btn-sm btn-outline-primary me-1 btn-edit-student" data-student='${JSON.stringify(s).replace(/'/g, "&apos;")}'>
                        <i class="fas fa-edit"></i>
                    </button>
                    <button class="btn btn-sm btn-outline-danger btn-delete-student" data-id="${s.id}">
                        <i class="fas fa-trash"></i>
                    </button>
                </td>
            </tr>
        `).join('');
        
        // Bind Action Buttons
        document.querySelectorAll('.btn-edit-student').forEach(btn => {
            btn.addEventListener('click', () => {
                const student = JSON.parse(btn.dataset.student);
                this.openEditStudentModal(student);
            });
        });
        
        document.querySelectorAll('.btn-delete-student').forEach(btn => {
            btn.addEventListener('click', () => {
                if(confirm('确定要删除该学生吗？这将同时删除其用户账号。')) {
                    this.deleteStudent(btn.dataset.id);
                }
            });
        });
        
        this.renderStudentPagination(pagination);
    }
    
    renderStudentPagination(pagination) {
        const el = document.getElementById('studentPagination');
        let html = '';
        
        if (pagination.page > 1) {
            html += `<li class="page-item"><a class="page-link" href="#" onclick="window.adminManager.changeStudentPage(${pagination.page - 1})">上一页</a></li>`;
        } else {
            html += `<li class="page-item disabled"><a class="page-link" href="#">上一页</a></li>`;
        }
        
        for (let i = 1; i <= pagination.pages; i++) {
            html += `<li class="page-item ${i === pagination.page ? 'active' : ''}"><a class="page-link" href="#" onclick="window.adminManager.changeStudentPage(${i})">${i}</a></li>`;
        }
        
        if (pagination.page < pagination.pages) {
            html += `<li class="page-item"><a class="page-link" href="#" onclick="window.adminManager.changeStudentPage(${pagination.page + 1})">下一页</a></li>`;
        } else {
            html += `<li class="page-item disabled"><a class="page-link" href="#">下一页</a></li>`;
        }
        
        el.innerHTML = html;
    }
    
    changeStudentPage(page) {
        this.studentCurrentPage = page;
        this.loadStudents();
    }
    
    openEditStudentModal(student) {
        document.getElementById('studentForm').reset();
        document.getElementById('studentModalTitle').textContent = '编辑学生';
        document.getElementById('studentIsEdit').value = 'true';
        document.getElementById('studentId').value = student.id;
        document.getElementById('studentId').readOnly = true;
        document.getElementById('studentNameInput').value = student.name;
        document.getElementById('studentClass').value = student.class || '';
        document.getElementById('studentMajor').value = student.major || '';
        document.getElementById('studentGrade').value = student.grade || '';
        document.getElementById('studentContact').value = student.contact_info || '';
        this.studentModal.show();
    }
    
    async saveStudent() {
        const form = document.getElementById('studentForm');
        const formData = new FormData(form);
        const data = Object.fromEntries(formData.entries());
        const isEdit = data.isEdit === 'true';
        
        // Validation
        if (!data.id || !data.name || !data.class) {
            alert('学号、姓名和班级为必填项');
            return;
        }
        
        try {
            let res;
            if (isEdit) {
                res = await fetch(`${this.apiBase}/students/${data.id}`, {
                    method: 'PUT',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
            } else {
                res = await fetch(`${this.apiBase}/students`, {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
            }
            
            const result = await res.json();
            
            if (result.success) {
                alert(isEdit ? '更新成功' : '创建成功');
                this.studentModal.hide();
                this.loadStudents();
            } else {
                alert(result.message || '操作失败');
            }
        } catch (e) {
            console.error(e);
            alert('系统错误');
        }
    }
    
    async deleteStudent(id) {
        try {
            const res = await fetch(`${this.apiBase}/students/${id}`, { method: 'DELETE' });
            const result = await res.json();
            
            if (result.success) {
                alert('删除成功');
                this.loadStudents();
            } else {
                alert(result.message || '删除失败');
            }
        } catch (e) {
            console.error(e);
            alert('系统错误');
        }
    }

    // ================= Teacher Management =================
    async initTeacherManagement() {
        this.teacherCurrentPage = 1;
        this.teacherPageSize = 10;
        
        // Bind Filter Events
        document.getElementById('teacherSearch').addEventListener('input', () => this.loadTeachers());
        
        // Bind Modal Events
        const modalEl = document.getElementById('teacherModal');
        this.teacherModal = new bootstrap.Modal(modalEl);
        
        document.getElementById('addTeacherBtn').addEventListener('click', () => {
            document.getElementById('teacherForm').reset();
            document.getElementById('teacherModalTitle').textContent = '新增教师';
            document.getElementById('teacherIsEdit').value = 'false';
            document.getElementById('teacherId').readOnly = false;
            this.teacherModal.show();
        });
        
        document.getElementById('saveTeacherBtn').addEventListener('click', () => this.saveTeacher());
        
        // Initial Load
        await this.loadTeachers();
    }
    
    async loadTeachers() {
        const search = document.getElementById('teacherSearch').value;
        const tbody = document.getElementById('teacherTableBody');
        
        tbody.innerHTML = '<tr><td colspan="6" class="text-center py-5">加载中...</td></tr>';
        
        try {
            const query = new URLSearchParams({
                page: this.teacherCurrentPage,
                limit: this.teacherPageSize,
                search
            });
            
            const res = await fetch(`${this.apiBase}/teachers?${query}`);
            const result = await res.json();
            
            if (result.success) {
                this.renderTeacherTable(result.data, result.pagination);
            } else {
                tbody.innerHTML = `<tr><td colspan="6" class="text-center text-danger">${result.message}</td></tr>`;
            }
        } catch (e) {
            console.error(e);
            tbody.innerHTML = '<tr><td colspan="6" class="text-center text-danger">加载失败</td></tr>';
        }
    }
    
    renderTeacherTable(teachers, pagination) {
        const tbody = document.getElementById('teacherTableBody');
        
        if (teachers.length === 0) {
            tbody.innerHTML = '<tr><td colspan="6" class="text-center py-5 text-muted">暂无教师</td></tr>';
            return;
        }
        
        tbody.innerHTML = teachers.map(t => `
            <tr>
                <td class="ps-4 fw-bold">${t.id}</td>
                <td>${t.name}</td>
                <td>${t.title || '-'}</td>
                <td>${t.department || '-'}</td>
                <td>${t.contact_info || '-'}</td>
                <td class="text-end pe-4">
                    <button class="btn btn-sm btn-outline-primary me-1 btn-edit-teacher" data-teacher='${JSON.stringify(t).replace(/'/g, "&apos;")}'>
                        <i class="fas fa-edit"></i>
                    </button>
                    <button class="btn btn-sm btn-outline-danger btn-delete-teacher" data-id="${t.id}">
                        <i class="fas fa-trash"></i>
                    </button>
                </td>
            </tr>
        `).join('');
        
        // Bind Action Buttons
        document.querySelectorAll('.btn-edit-teacher').forEach(btn => {
            btn.addEventListener('click', () => {
                const teacher = JSON.parse(btn.dataset.teacher);
                this.openEditTeacherModal(teacher);
            });
        });
        
        document.querySelectorAll('.btn-delete-teacher').forEach(btn => {
            btn.addEventListener('click', () => {
                if(confirm('确定要删除该教师吗？这将同时删除其用户账号。')) {
                    this.deleteTeacher(btn.dataset.id);
                }
            });
        });
        
        this.renderTeacherPagination(pagination);
    }
    
    renderTeacherPagination(pagination) {
        const el = document.getElementById('teacherPagination');
        let html = '';
        
        if (pagination.page > 1) {
            html += `<li class="page-item"><a class="page-link" href="#" onclick="window.adminManager.changeTeacherPage(${pagination.page - 1})">上一页</a></li>`;
        } else {
            html += `<li class="page-item disabled"><a class="page-link" href="#">上一页</a></li>`;
        }
        
        for (let i = 1; i <= pagination.pages; i++) {
            html += `<li class="page-item ${i === pagination.page ? 'active' : ''}"><a class="page-link" href="#" onclick="window.adminManager.changeTeacherPage(${i})">${i}</a></li>`;
        }
        
        if (pagination.page < pagination.pages) {
            html += `<li class="page-item"><a class="page-link" href="#" onclick="window.adminManager.changeTeacherPage(${pagination.page + 1})">下一页</a></li>`;
        } else {
            html += `<li class="page-item disabled"><a class="page-link" href="#">下一页</a></li>`;
        }
        
        el.innerHTML = html;
    }
    
    changeTeacherPage(page) {
        this.teacherCurrentPage = page;
        this.loadTeachers();
    }
    
    openEditTeacherModal(teacher) {
        document.getElementById('teacherForm').reset();
        document.getElementById('teacherModalTitle').textContent = '编辑教师';
        document.getElementById('teacherIsEdit').value = 'true';
        document.getElementById('teacherId').value = teacher.id;
        document.getElementById('teacherId').readOnly = true;
        document.getElementById('teacherNameInput').value = teacher.name;
        document.getElementById('teacherDepartment').value = teacher.department || '';
        document.getElementById('teacherTitle').value = teacher.title || '';
        document.getElementById('teacherContact').value = teacher.contact_info || '';
        this.teacherModal.show();
    }
    
    async saveTeacher() {
        const form = document.getElementById('teacherForm');
        const formData = new FormData(form);
        const data = Object.fromEntries(formData.entries());
        const isEdit = data.isEdit === 'true';
        
        // Validation
        if (!data.id || !data.name) {
            alert('工号和姓名为必填项');
            return;
        }
        
        try {
            let res;
            if (isEdit) {
                res = await fetch(`${this.apiBase}/teachers/${data.id}`, {
                    method: 'PUT',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
            } else {
                res = await fetch(`${this.apiBase}/teachers`, {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(data)
                });
            }
            
            const result = await res.json();
            
            if (result.success) {
                alert(isEdit ? '更新成功' : '创建成功');
                this.teacherModal.hide();
                this.loadTeachers();
            } else {
                alert(result.message || '操作失败');
            }
        } catch (e) {
            console.error(e);
            alert('系统错误');
        }
    }
    
    async deleteTeacher(id) {
        try {
            const res = await fetch(`${this.apiBase}/teachers/${id}`, { method: 'DELETE' });
            const result = await res.json();
            
            if (result.success) {
                alert('删除成功');
                this.loadTeachers();
            } else {
                alert(result.message || '删除失败');
            }
        } catch (e) {
            console.error(e);
            alert('系统错误');
        }
    }

    // ================= Grade Statistics =================
    async initGradeStatistics() {
        try {
            const res = await fetch(`${this.apiBase}/grade-stats`);
            const result = await res.json();
            
            if (result.success) {
                const stats = result.data;
                this.renderGradeStatsTable(stats);
                this.renderGradeCharts(stats);
            }
        } catch (e) {
            console.error(e);
        }
    }
    
    renderGradeStatsTable(stats) {
        const tbody = document.getElementById('gradeStatsBody');
        if (!tbody) return;
        
        if (stats.length === 0) {
            tbody.innerHTML = '<tr><td colspan="8" class="text-center py-5 text-muted">暂无数据</td></tr>';
            return;
        }
        
        tbody.innerHTML = stats.map(s => `
            <tr>
                <td class="ps-4 fw-bold">${s.course_code || '-'}</td>
                <td>${s.course_name}</td>
                <td>${s.teacher_name || '未分配'}</td>
                <td>${s.student_count}</td>
                <td><span class="fw-bold text-primary">${s.avg_score}</span></td>
                <td>${s.max_score || '-'}</td>
                <td>${s.min_score || '-'}</td>
                <td>
                    <div class="d-flex align-items-center">
                        <div class="progress flex-grow-1 me-2" style="height: 6px;">
                            <div class="progress-bar bg-${s.pass_rate >= 60 ? 'success' : 'danger'}" style="width: ${s.pass_rate}%"></div>
                        </div>
                        <span class="small">${s.pass_rate}%</span>
                    </div>
                </td>
            </tr>
        `).join('');
    }
    
    renderGradeCharts(stats) {
        if (!window.Chart) return;
        
        // 1. Course Average Scores Bar Chart
        const ctxBar = document.getElementById('courseAvgChart');
        if (ctxBar) {
            new Chart(ctxBar, {
                type: 'bar',
                data: {
                    labels: stats.map(s => s.course_name),
                    datasets: [{
                        label: '平均分',
                        data: stats.map(s => s.avg_score),
                        backgroundColor: 'rgba(78, 115, 223, 0.5)',
                        borderColor: 'rgba(78, 115, 223, 1)',
                        borderWidth: 1
                    }]
                },
                options: {
                    responsive: true,
                    scales: {
                        y: { beginAtZero: true, max: 100 }
                    }
                }
            });
        }
        
        // 2. Overall Pass Rate Pie Chart
        const ctxPie = document.getElementById('passRateChart');
        if (ctxPie) {
            const totalStudents = stats.reduce((sum, s) => sum + s.student_count, 0);
            const totalPass = stats.reduce((sum, s) => sum + parseInt(s.pass_count), 0);
            const totalFail = totalStudents - totalPass;
            
            new Chart(ctxPie, {
                type: 'doughnut',
                data: {
                    labels: ['及格', '不及格'],
                    datasets: [{
                        data: [totalPass, totalFail],
                        backgroundColor: ['#1cc88a', '#e74a3b'],
                        hoverOffset: 4
                    }]
                },
                options: {
                    responsive: true,
                    plugins: {
                        legend: { position: 'bottom' }
                    }
                }
            });
        }
    }

    // ================= System Settings =================
    async initSystemSettings() {
        const form = document.getElementById('basicSettingsForm');
        if (!form) return;

        // Load current settings
        try {
            const response = await fetch('/api/admin/settings');
            const result = await response.json();
            if (result.success) {
                const settings = result.data;
                const nameInput = form.querySelector('input[type="text"]');
                const semesterSelect = form.querySelector('select');
                const courseSwitch = document.getElementById('courseSelectionSwitch');
                const gradeSwitch = document.getElementById('gradeCheckSwitch');

                if (nameInput) nameInput.value = settings.system_name || '';
                if (semesterSelect) semesterSelect.value = settings.current_semester || '';
                if (courseSwitch) courseSwitch.checked = settings.allow_course_selection === '1';
                if (gradeSwitch) gradeSwitch.checked = settings.allow_grade_check === '1';
            }
        } catch (err) {
            console.error('加载设置失败:', err);
        }

        form.addEventListener('submit', async (e) => {
            e.preventDefault();
            const settings = {
                system_name: form.querySelector('input[type="text"]').value,
                current_semester: form.querySelector('select').value,
                allow_course_selection: document.getElementById('courseSelectionSwitch').checked ? '1' : '0',
                allow_grade_check: document.getElementById('gradeCheckSwitch').checked ? '1' : '0'
            };

            try {
                const response = await fetch('/api/admin/settings', {
                    method: 'POST',
                    headers: { 'Content-Type': 'application/json' },
                    body: JSON.stringify(settings)
                });
                const result = await response.json();
                if (result.success) {
                    alert('系统设置已保存');
                } else {
                    alert('保存失败: ' + result.message);
                }
            } catch (err) {
                alert('保存出错');
            }
        });
        
        // Data Maintenance Buttons
        const backupBtn = document.querySelector('.btn-outline-primary i.fa-database')?.parentElement;
        const clearCacheBtn = document.querySelector('.btn-outline-warning i.fa-trash-alt')?.parentElement;
        const resetPassBtn = document.querySelector('.btn-outline-danger i.fa-history')?.parentElement;

        if (backupBtn) {
            backupBtn.addEventListener('click', async () => {
                if (!confirm('确定要立即备份数据库吗？')) return;
                try {
                    const res = await fetch('/api/admin/maintenance/backup', { method: 'POST' });
                    const result = await res.json();
                    if (result.success) alert('备份成功！文件已保存到 backups 目录: ' + result.data.filename);
                    else alert('备份失败: ' + result.message);
                } catch (err) { alert('请求失败'); }
            });
        }

        if (clearCacheBtn) {
            clearCacheBtn.addEventListener('click', async () => {
                try {
                    const res = await fetch('/api/admin/maintenance/clear-cache', { method: 'POST' });
                    const result = await res.json();
                    if (result.success) alert('系统缓存已清理');
                    else alert('清理失败');
                } catch (err) { alert('请求失败'); }
            });
        }

        if (resetPassBtn) {
            resetPassBtn.addEventListener('click', async () => {
                if (!confirm('确定要重置所有学生密码为 123456 吗？此操作不可撤销！')) return;
                try {
                    const res = await fetch('/api/admin/maintenance/reset-passwords', { method: 'POST' });
                    const result = await res.json();
                    if (result.success) alert('所有学生密码已重置为 123456');
                    else alert('重置失败');
                } catch (err) { alert('请求失败'); }
            });
        }
    }

    // ================= Data Export =================
    async initDataExport() {
        const studentExportBtn = document.getElementById('exportStudentsBtn');
        const teacherExportBtn = document.getElementById('exportTeachersBtn');
        const gradeExportBtn = document.getElementById('exportGradesBtn');

        if (studentExportBtn) {
            studentExportBtn.addEventListener('click', () => {
                window.location.href = '/api/admin/export/students';
            });
        }

        if (teacherExportBtn) {
            teacherExportBtn.addEventListener('click', () => {
                window.location.href = '/api/admin/export/teachers';
            });
        }

        if (gradeExportBtn) {
            gradeExportBtn.addEventListener('click', () => {
                window.location.href = '/api/admin/export/grades';
            });
        }
    }

    // ================= Operation Logs =================
    async initOperationLogs() {
        const tbody = document.getElementById('logsTableBody');
        if (!tbody) return;
        
        try {
            const response = await fetch('/api/admin/logs');
            const result = await response.json();
            if (result.success) {
                const logs = result.data;
                if (logs.length === 0) {
                    tbody.innerHTML = '<tr><td colspan="5" class="text-center py-4 text-muted">暂无操作日志</td></tr>';
                    return;
                }
                tbody.innerHTML = logs.map(log => `
                    <tr>
                        <td class="ps-4 text-muted">${log.created_at}</td>
                        <td class="fw-bold">${log.user_id} (${log.user_name || '未知'})</td>
                        <td><span class="badge bg-secondary">${log.operation_type}</span></td>
                        <td>${log.description}</td>
                        <td class="text-muted small">${log.ip_address || '-'}</td>
                    </tr>
                `).join('');
            }
        } catch (err) {
            console.error('获取日志失败:', err);
            tbody.innerHTML = '<tr><td colspan="5" class="text-center py-4 text-danger">加载失败</td></tr>';
        }
    }
}

document.addEventListener('DOMContentLoaded', () => {
    window.adminManager = new AdminManager();
});