/***********************************************************************************************************************************************************************
 * File Name: users.ctrl.js (staff)
 * Type of Program: Controller
 * Description: Staff-scoped user endpoints.
 *              A staff member can only see users who belong to at least one
 *              of the same groups the staff member belongs to.
 ***********************************************************************************************************************************************************************/
const { Op } = require('sequelize');
const mdl_Users = require('../../models/users/users.mdl');
const { mdl_UserGroups, mdl_UserGroupMembers } = require('../../models/users/user_groups.mdl');

/**
 * GET /api/staff/users
 * Returns all users who share at least one group with the requesting staff member.
 * Supports optional query: ?group_id=27 or ?group_code=CG2027
 */
const getUsers = async (req, res) => {
  try {
    const staffUserId = req.user.user_id;
    const { group_id, group_code, page = 1, limit = 20 } = req.query;
    const offset = (parseInt(page) - 1) * parseInt(limit);

    // 1. Find the groups the staff member belongs to
    const staffMemberships = await mdl_UserGroupMembers.findAll({
      where: { user_id: staffUserId },
      attributes: ['group_id'],
      raw: true,
    });

    let scopedGroupIds = staffMemberships.map(m => m.group_id);

    if (scopedGroupIds.length === 0) {
      return res.status(200).json({ success: true, data: [], total: 0, page, limit });
    }

    // 2. Filter down to a specific group if requested
    if (group_id) {
      const gid = parseInt(group_id);
      if (!scopedGroupIds.includes(gid)) {
        return res.status(403).json({ success: false, message: 'You do not have access to this group.' });
      }
      scopedGroupIds = [gid];
    }

    if (group_code) {
      const group = await mdl_UserGroups.findOne({
        where: { group_code: group_code.toUpperCase().trim(), deletedAt: null },
        attributes: ['group_id'],
        raw: true,
      });
      if (!group || !scopedGroupIds.includes(group.group_id)) {
        return res.status(403).json({ success: false, message: 'You do not have access to this group.' });
      }
      scopedGroupIds = [group.group_id];
    }

    // 3. Find all user_ids in those groups (excluding the staff member themselves)
    const memberships = await mdl_UserGroupMembers.findAll({
      where: { group_id: { [Op.in]: scopedGroupIds } },
      attributes: ['user_id'],
      raw: true,
    });

    const userIds = [...new Set(memberships.map(m => m.user_id))].filter(id => id !== staffUserId);

    // 4. Fetch users
    const { count, rows } = await mdl_Users.findAndCountAll({
      where: { user_id: { [Op.in]: userIds } },
      attributes: [
        'user_id', 'email', 'is_active', 'is_verified',
        'acc_type', 'personal_info', 'createdAt',
      ],
      include: [
        {
          model: mdl_UserGroups,
          as: 'groups',
          attributes: ['group_id', 'name', 'group_code'],
          through: { attributes: ['joined_at'] },
          where: { group_id: { [Op.in]: scopedGroupIds } },
          required: true,
        },
      ],
      limit: parseInt(limit),
      offset,
      order: [['createdAt', 'DESC']],
    });

    return res.status(200).json({
      success: true,
      data: rows,
      total: count,
      page: parseInt(page),
      limit: parseInt(limit),
      totalPages: Math.ceil(count / parseInt(limit)),
    });
  } catch (err) {
    console.error('[staff/users] getUsers error:', err);
    return res.status(500).json({ success: false, message: 'Internal server error.' });
  }
};

/**
 * GET /api/staff/users/:user_id
 * Get a single user's profile — only if they share a group with the staff member.
 */
const getUserById = async (req, res) => {
  try {
    const staffUserId = req.user.user_id;
    const targetUserId = parseInt(req.params.user_id);

    // Get staff's groups
    const staffMemberships = await mdl_UserGroupMembers.findAll({
      where: { user_id: staffUserId },
      attributes: ['group_id'],
      raw: true,
    });
    const scopedGroupIds = staffMemberships.map(m => m.group_id);

    // Check target user shares a group
    const sharedMembership = await mdl_UserGroupMembers.findOne({
      where: {
        user_id: targetUserId,
        group_id: { [Op.in]: scopedGroupIds },
      },
    });

    if (!sharedMembership) {
      return res.status(403).json({ success: false, message: 'User not in your scope.' });
    }

    const user = await mdl_Users.findByPk(targetUserId, {
      attributes: ['user_id', 'email', 'is_active', 'is_verified', 'acc_type', 'personal_info', 'createdAt'],
      include: [
        {
          model: mdl_UserGroups,
          as: 'groups',
          attributes: ['group_id', 'name', 'group_code'],
          through: { attributes: ['joined_at'] },
        },
      ],
    });

    if (!user) return res.status(404).json({ success: false, message: 'User not found.' });

    return res.status(200).json({ success: true, data: user });
  } catch (err) {
    console.error('[staff/users] getUserById error:', err);
    return res.status(500).json({ success: false, message: 'Internal server error.' });
  }
};

module.exports = { getUsers, getUserById };