# -*- coding: utf-8 -*-
# Copyright 2023 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utilities for working with URLs."""
from __future__ import annotations

import re
from urllib import parse


def _validate_url_part(part: str) -> None:
  if not re.fullmatch('[a-zA-Z0-9_-]*', part):
    raise ValueError(
        '"{}" is outside the restricted character set'.format(part)
    )


def _validate_url_query_or_fragment(part: str) -> None:
  for key, values in parse.parse_qs(part).items():
    _validate_url_part(key)
    for value in values:
      _validate_url_part(value)


def sanitize_sheets_url(url: str) -> str:
  """Sanitize a Sheets URL.

  Run some saftey checks to check whether `url` is a Sheets URL. This is not a
  general-purpose URL sanitizer. Rather, it makes use of the fact that we know
  the URL has to be for Sheets so we can make a few assumptions about (e.g. the
  domain).

  Args:
    url: The url to sanitize.

  Returns:
    The sanitized url.

  Raises:
    ValueError: If `url` does not match the expected restrictions for a Sheets
    URL.
  """
  parse_result = parse.urlparse(url)
  if parse_result.scheme != 'https':
    raise ValueError(
        'Scheme for Sheets url must be "https", got "{}"'.format(
            parse_result.scheme
        )
    )
  if parse_result.netloc not in ('docs.google.com', 'sheets.googleapis.com'):
    raise ValueError(
        'Domain for Sheets url must be "docs.google.com", got "{}"'.format(
            parse_result.netloc
        )
    )

  # Path component.
  try:
    for fragment in parse_result.path.split('/'):
      _validate_url_part(fragment)
  except ValueError as exc:
    raise ValueError(
        'Invalid path for Sheets url, got "{}"'.format(parse_result.path)
    ) from exc

  # Params component.
  if parse_result.params:
    raise ValueError(
        'Params component must be empty, got "{}"'.format(parse_result.params)
    )

  # Query component.
  try:
    _validate_url_query_or_fragment(parse_result.query)
  except ValueError as exc:
    raise ValueError(
        'Invalid query for Sheets url, got "{}"'.format(parse_result.query)
    ) from exc

  # Fragment component.
  try:
    _validate_url_query_or_fragment(parse_result.fragment)
  except ValueError as exc:
    raise ValueError(
        'Invalid fragment for Sheets url, got "{}"'.format(
            parse_result.fragment
        )
    ) from exc

  return url