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import os
import sys


def FindOnPage(input_api, url, regex):
  """Given a url, download it and find the part matching a regex.
  Arguments:
    input_api: the limited set of input modules allowed in presubmit
    url: url to download
    regex: regex to match on
  Returns:
    A string extracted from the match, or None if no match or error.
  """
  try:
    connection = input_api.urllib2.urlopen(url)
    text = connection.read()
    connection.close()
    match = input_api.re.search(regex, text)
    if match:
      return match.group(1)
    else:
      return None
  except IOError, e:
    print str(e)
    return None


def CheckTreeIsOpen(input_api, output_api, url, url_text):
  """Similar to the one in presubmit_canned_checks except it shows an helpful
  status text instead.
  Arguments:
    input_api: the limited set of input modules allowed in presubmit
    output_api: the limited set of output modules allowed in presubmit
    url: url to get numerical tree status from
    url_text: url to get human readable tree status from
    regex: regex to match on
  Returns:
    A list of presubmit warnings.
  """
  assert(input_api.is_committing)
  # Check if tree is open.
  status = FindOnPage(input_api, url, '([0-9]+)')
  if status and int(status):
    return []
  # Try to find out what failed.
  message = FindOnPage(input_api, url_text,
                       r'\<div class\="Notice"\>(.*)\<\/div\>')
  if message:
    return [output_api.PresubmitPromptWarning("The tree is closed.",
                                              long_text=message.strip())]
  # Report unknown reason.
  return [output_api.PresubmitPromptWarning(
      "The tree status can't be checked.")]


def CheckChangeOnCommit(input_api, output_api):
  report = []
  report.extend(CheckTreeIsOpen(
      input_api, output_api,
      'http://o3d-status.appspot.com/status',
      'http://o3d-status.appspot.com/current'))
  return report