def licences_query(users)
  return users unless params[:licence_ids]
  users_scope = users
  licence_ids = params[:licence_ids]

  if params[:licence_ids].is_a? String
    licence_ids = params[:licence_ids].split(',').map{|chr| chr.to_i}
  end

  # 4 - Door Supervision
  # 2 - CCTV
  # Return all users with Door Supervision if there is no CCTV selected
  # Otherwise, require exact match (else)
  if licence_ids.include?(4) && !licence_ids.include?(2) 
    users_scope = users_scope.joins("INNER JOIN guard_licences as #{rel} ON users.id=#{rel}.user_id")
                             .where("#{rel}.licence_id=4")
                             .where("#{rel}.status=?", 'active')
  else
    licence_ids.each_with_index do |licence_id, index|
      rel = "gl#{index}"
      users_scope = users_scope.joins("INNER JOIN guard_licences as #{rel} ON users.id=#{rel}.user_id")
                               .where("#{rel}.licence_id=?", licence_id)
                               .where("#{rel}.status=?", 'active')
    end          
  end

  users_scope
end