const Level = require('../models/level');
const Degree = require('../models/degree');

// GET /admin/level
exports.index = async (req, res) => {
  try {
    const levels = await Level.find();
    res.render('admin/level/index', {
      levels,
      user: req.session.user,
      layout: 'layouts/admin',
      title: 'Quản lý Cấp độ'
    });
  } catch (err) {
    console.error('levelController.index error:', err);
    req.flash('error', 'Đã xảy ra lỗi khi tải danh sách cấp độ');
    res.redirect('/admin/dashboard');
  }
};

// POST /admin/level/create
exports.create = async (req, res) => {
  try {
    const { type } = req.body;

    if (!type) {
      req.flash('error', 'Type is required');
      return res.redirect('back');
    }

    await Level.create({ type });
    req.flash('success', 'Level created');
    res.redirect('/admin/level');
  } catch (err) {
    console.error('levelController.create error:', err);
    req.flash('error', 'Đã xảy ra lỗi khi tạo cấp độ');
    res.redirect('back');
  }
};

// POST /admin/level/:id/edit
exports.update = async (req, res) => {
  try {
    const { id } = req.params;
    const { type } = req.body;

    await Level.findByIdAndUpdate(id, { type });
    req.flash('success', 'Level updated');
    res.redirect('/admin/level');
  } catch (err) {
    console.error('levelController.update error:', err);
    req.flash('error', 'Đã xảy ra lỗi khi cập nhật cấp độ');
    res.redirect('back');
  }
};

// POST /admin/level/:id/delete
exports.destroy = async (req, res) => {
  try {
    const { id } = req.params;
    const count = await Degree.countDocuments({ level: id });

    if (count > 0) {
      req.flash('error', 'Cannot delete: Level is referenced by existing degrees');
      return res.redirect('back');
    }

    await Level.findByIdAndDelete(id);
    req.flash('success', 'Level deleted');
    res.redirect('/admin/level');
  } catch (err) {
    console.error('levelController.destroy error:', err);
    req.flash('error', 'Đã xảy ra lỗi khi xóa cấp độ');
    res.redirect('back');
  }
};