from peewee import SQL

def paginate(query, model, descending=False, page_token=None, limit=50, id_alias=None):
  """ Paginates the given query using an ID range, starting at the optional page_token.
      Returns a *list* of matching results along with an unencrypted page_token for the
      next page, if any. If descending is set to True, orders by the ID descending rather
      than ascending.
  """
  # Note: We use the id_alias for the order_by, but not the where below. The alias is necessary
  # for certain queries that use unions in MySQL, as it gets confused on which ID to order by.
  # The where clause, on the other hand, cannot use the alias because Postgres does not allow
  # aliases in where clauses.
  id_field = model.id
  if id_alias is not None:
    id_field = SQL(id_alias)

  if descending:
    query = query.order_by(id_field.desc())
  else:
    query = query.order_by(id_field)

  if page_token is not None:
    start_id = page_token.get('start_id')
    if start_id is not None:
      if descending:
        query = query.where(model.id <= start_id)
      else:
        query = query.where(model.id >= start_id)

  results = list(query)
  page_token = None
  if len(results) > limit:
    start_id = results[limit].id
    page_token = {
      'start_id': start_id
    }

  return results[0:limit], page_token