class AttendanceTracker {
    public function __construct() {
        // ... (existing code) ...
        add_action('wp_ajax_submit_course_hold_request', array($this, 'submit_course_hold_request'));
        add_action('wp_ajax_update_course_hold_status', array($this, 'update_course_hold_status'));
        add_action('wp_ajax_admin_apply_course_hold', array($this, 'admin_apply_course_hold'));
        add_action('admin_init', array($this, 'export_course_hold_report'));
    }

    public function create_db_tables() {
        // ... (existing code) ...

        $course_hold_table = $wpdb->prefix . 'attendance_tracker_course_holds';
        $course_hold_sql = "CREATE TABLE $course_hold_table (
            id mediumint(9) NOT NULL AUTO_INCREMENT,
            user_id bigint(20) NOT NULL,
            start_date date NOT NULL,
            end_date date NOT NULL,
            reason text NOT NULL,
            status enum('pending', 'approved', 'rejected') DEFAULT 'pending',
            created_at datetime DEFAULT CURRENT_TIMESTAMP,
            updated_at datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            PRIMARY KEY  (id)
        ) $charset_collate;";
        dbDelta($course_hold_sql);
    }

    public function add_admin_menu() {
        // ... (existing code) ...
        add_submenu_page('attendance-tracker', 'Course Hold Requests', 'Course Hold Requests', 'edit_pages', 'course-hold-requests', array($this, 'course_hold_requests_page'));
        add_submenu_page('attendance-tracker', 'Course Hold Reports', 'Hold Reports', 'edit_pages', 'course-hold-reports', array($this, 'course_hold_reports_page'));
    }

    public function mark_attendance() {
        // ... (existing code) ...

        $current_hold = $this->get_current_course_hold($user_id);
        if ($current_hold && $current_hold->status == 'approved') {
            $today = current_time('Y-m-d');
            if ($today >= $current_hold->start_date && $today <= $current_hold->end_date) {
                wp_send_json_error('Your course is currently on hold');
            }
        }

        // ... (rest of the existing code)
    }

    public function submit_course_hold_request() {
        check_ajax_referer('attendance_tracker_nonce', 'nonce');

        $user_id = get_current_user_id();
        $start_date = sanitize_text_field($_POST['start_date']);
        $end_date = sanitize_text_field($_POST['end_date']);
        $reason = sanitize_textarea_field($_POST['reason']);

        $result = $this->insert_course_hold_request($user_id, $start_date, $end_date, $reason);

        if ($result) {
            wp_send_json_success('Course hold request submitted successfully');
        } else {
            wp_send_json_error('Failed to submit course hold request');
        }
    }

    public function update_course_hold_status() {
        check_ajax_referer('update_course_hold_status', 'nonce');

        if (!current_user_can('edit_pages')) {
            wp_send_json_error('Permission denied');
        }

        $request_id = intval($_POST['request_id']);
        $status = sanitize_text_field($_POST['status']);

        global $wpdb;
        $table_name = $wpdb->prefix . 'attendance_tracker_course_holds';

        $result = $wpdb->update(
            $table_name,
            array('status' => $status),
            array('id' => $request_id),
            array('%s'),
            array('%d')
        );

        if ($result !== false) {
            wp_send_json_success('Course hold status updated successfully');
        } else {
            wp_send_json_error('Failed to update course hold status');
        }
    }

    public function admin_apply_course_hold() {
        check_ajax_referer('admin_apply_course_hold', 'nonce');

        if (!current_user_can('edit_users')) {
            wp_send_json_error('Permission denied');
        }

        $user_id = intval($_POST['user_id']);
        $start_date = sanitize_text_field($_POST['start_date']);
        $end_date = sanitize_text_field($_POST['end_date']);
        $reason = sanitize_textarea_field($_POST['reason']);

        $result = $this->insert_course_hold_request($user_id, $start_date, $end_date, $reason, 'approved');

        if ($result) {
            wp_send_json_success('Course hold applied successfully');
        } else {
            wp_send_json_error('Failed to apply course hold');
        }
    }

    private function insert_course_hold_request($user_id, $start_date, $end_date, $reason, $status = 'pending') {
        global $wpdb;
        $table_name = $wpdb->prefix . 'attendance_tracker_course_holds';

        return $wpdb->insert(
            $table_name,
            array(
                'user_id' => $user_id,
                'start_date' => date('Y-m-d', strtotime($start_date)),
                'end_date' => date('Y-m-d', strtotime($end_date)),
                'reason' => $reason,
                'status' => $status
            ),
            array('%d', '%s', '%s', '%s', '%s')
        );
    }

    private function get_current_course_hold($user_id) {
        global $wpdb;
        $table_name = $wpdb->prefix . 'attendance_tracker_course_holds';

        return $wpdb->get_row($wpdb->prepare(
            "SELECT * FROM $table_name 
            WHERE user_id = %d 
            AND (status = 'pending' OR (status = 'approved' AND end_date >= CURDATE()))
            ORDER BY created_at DESC 
            LIMIT 1",
            $user_id
        ));
    }

    private function is_course_on_hold($user_id) {
        $current_hold = $this->get_current_course_hold($user_id);
        if ($current_hold && $current_hold->status == 'approved') {
            $today = current_time('Y-m-d');
            return ($today >= $current_hold->start_date && $today <= $current_hold->end_date);
        }
        return false;
    }

    public function course_hold_requests_page() {
        global $wpdb;
        $table_name = $wpdb->prefix . 'attendance_tracker_course_holds';
        $hold_requests = $wpdb->get_results("SELECT * FROM $table_name ORDER BY created_at DESC");
        
        include plugin_dir_path(__FILE__) . 'admin-course-hold-requests.php';
    }

    public function course_hold_reports_page() {
        $start_date = isset($_GET['start_date']) ? sanitize_text_field($_GET['start_date']) : '';
        $end_date = isset($_GET['end_date']) ? sanitize_text_field($_GET['end_date']) : '';
        $status = isset($_GET['status']) ? sanitize_text_field($_GET['status']) : '';

        global $wpdb;
        $table_name = $wpdb->prefix . 'attendance_tracker_course_holds';

        $query = "SELECT * FROM $table_name WHERE 1=1";
        $args = array();

        if (!empty($start_date)) {
            $query .= " AND start_date >= %s";
            $args[] = date('Y-m-d', strtotime($start_date));
        }

        if (!empty($end_date)) {
            $query .= " AND end_date <= %s";
            $args[] = date('Y-m-d', strtotime($end_date));
        }

        if (!empty($status)) {
            $query .= " AND status = %s";
            $args[] = $status;
        }

        $query .= " ORDER BY created_at DESC";

        if (!empty($args)) {
            $hold_requests = $wpdb->get_results($wpdb->prepare($query, $args));
        } else {
            $hold_requests = $wpdb->get_results($query);
        }

        include plugin_dir_path(__FILE__) . 'admin-course-hold-reports.php';
    }

    private function get_course_hold_statistics() {
        global $wpdb;
        $table_name = $wpdb->prefix . 'attendance_tracker_course_holds';

        $stats = $wpdb->get_results("
            SELECT 
                status, 
                COUNT(*) as count, 
                AVG(DATEDIFF(end_date, start_date)) as avg_duration
            FROM $table_name 
            GROUP BY status
        ");

        return $stats;
    }

    public function export_course_hold_report() {
        if (isset($_POST['action']) && $_POST['action'] == 'export_course_hold_report') {
            check_admin_referer('export_course_hold_report', 'export_nonce');

            $start_date = isset($_POST['start_date']) ? sanitize_text_field($_POST['start_date']) : '';
            $end_date = isset($_POST['end_date']) ? sanitize_text_field($_POST['end_date']) : '';
            $status = isset($_POST['status']) ? sanitize_text_field($_POST['status']) : '';

            global $wpdb;
            $table_name = $wpdb->prefix . 'attendance_tracker_course_holds';

            $query = "SELECT ch.*, u.display_name 
                      FROM $table_name ch
                      JOIN {$wpdb->users} u ON ch.user_id = u.ID 
                      WHERE 1=1";
            $args = array();

            if (!empty($start_date)) {
                $query .= " AND start_date >= %s";
                $args[] = date('Y-m-d', strtotime($start_date));
            }

            if (!empty($end_date)) {
                $query .= " AND end_date <= %s";
                $args[] = date('Y-m-d', strtotime($end_date));
            }

            if (!empty($status)) {
                $query .= " AND status = %s";
                $args[] = $status;
            }

            $query .= " ORDER BY created_at DESC";

            if (!empty($args)) {
                $hold_requests = $wpdb->get_results($wpdb->prepare($query, $args));
            } else {
                $hold_requests = $wpdb->get_results($query);
            }

            header('Content-Type: text/csv');
            header('Content-Disposition: attachment; filename="course_hold_report.csv"');

            $output = fopen('php://output', 'w');
            fputcsv($output, array('User', 'Start Date', 'End Date', 'Reason', 'Status', 'Requested On'));

            foreach ($hold_requests as $request) {
                fputcsv($output, array(
                    $request->display_name,
                    date('j-M-Y', strtotime($request->start_date)),
                    date('j-M-Y', strtotime($request->end_date)),
                    $request->reason,
                    ucfirst($request->status),
                    date('j-M-Y', strtotime($request->created_at))
                ));
            }

            fclose($output);
            exit;
        }
    }
}