# Copyright 2015 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""General functions which are useful throughout this project."""

import base64
import binascii
import json
import logging
import os
import re
import time

from apiclient import discovery
from apiclient import errors
from google.appengine.api import memcache
from google.appengine.api import urlfetch
from google.appengine.api import urlfetch_errors
from google.appengine.api import users
from google.appengine.ext import ndb
from oauth2client import client

from dashboard import stored_object

SHERIFF_DOMAINS_KEY = 'sheriff_domains_key'
IP_WHITELIST_KEY = 'ip_whitelist'
SERVICE_ACCOUNT_KEY = 'service_account'
EMAIL_SCOPE = 'https://www.googleapis.com/auth/userinfo.email'
_PROJECT_ID_KEY = 'project_id'
_DEFAULT_CUSTOM_METRIC_VAL = 1


def _GetNowRfc3339():
  """Returns the current time formatted per RFC 3339."""
  return time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime())


def TickMonitoringCustomMetric(metric_name):
  """Increments the stackdriver custom metric with the given name.

  This is used for cron job monitoring; if these metrics stop being received
  an alert mail is sent. For more information on custom metrics, see
  https://cloud.google.com/monitoring/custom-metrics/using-custom-metrics

  Args:
    metric_name: The name of the metric being monitored.
  """
  credentials = client.GoogleCredentials.get_application_default()
  monitoring = discovery.build(
      'cloudmonitoring', 'v2beta2', credentials=credentials)
  now = _GetNowRfc3339()
  project_id = stored_object.Get(_PROJECT_ID_KEY)
  desc = {
      'project': project_id,
      'metric': 'custom.cloudmonitoring.googleapis.com/%s' % metric_name
  }
  point = {
      'start': now,
      'end': now,
      'int64Value': _DEFAULT_CUSTOM_METRIC_VAL
  }
  write_request = monitoring.timeseries().write(
      project=project_id,
      body={'timeseries': [{'timeseriesDesc': desc, 'point': point}]})
  write_request.execute()


def TestPath(key):
  """Returns the test path for a Test from an ndb.Key.

  A "test path" is just a convenient string representation of an ndb.Key.
  Each test path corresponds to one ndb.Key, which can be used to get an
  entity.

  Args:
    key: An ndb.Key where all IDs are string IDs.

  Returns:
    A test path string.
  """
  return '/'.join(key.flat()[1::2])


def TestSuiteName(test_key):
  """Returns the test suite name for a given Test key."""
  pairs = test_key.pairs()
  if len(pairs) < 3:
    return None
  return pairs[2][1]


def TestKey(test_path):
  """Returns the ndb.Key that corresponds to a test path."""
  if test_path is None:
    return None
  path_parts = test_path.split('/')
  if path_parts is None:
    return None
  key_list = [('Master', path_parts[0])]
  if len(path_parts) > 1:
    key_list += [('Bot', path_parts[1])]
  if len(path_parts) > 2:
    key_list += [('Test', x) for x in path_parts[2:]]
  return ndb.Key(pairs=key_list)


def TestMatchesPattern(test, pattern):
  """Checks whether a test matches a test path pattern.

  Args:
    test: A Test entity or a Test key.
    pattern: A test path which can include wildcard characters (*).

  Returns:
    True if it matches, False otherwise.
  """
  if not test:
    return False
  if type(test) is ndb.Key:
    test_path = TestPath(test)
  else:
    test_path = test.test_path
  test_path_parts = test_path.split('/')
  pattern_parts = pattern.split('/')
  if len(test_path_parts) != len(pattern_parts):
    return False
  for test_path_part, pattern_part in zip(test_path_parts, pattern_parts):
    if not _MatchesPatternPart(pattern_part, test_path_part):
      return False
  return True


def _MatchesPatternPart(pattern_part, test_path_part):
  """Checks whether a pattern (possibly with a *) matches the given string.

  Args:
    pattern_part: A string which may contain a wildcard (*).
    test_path_part: Another string.

  Returns:
    True if it matches, False otherwise.
  """
  if pattern_part == '*' or pattern_part == test_path_part:
    return True
  if '*' not in pattern_part:
    return False
  # Escape any other special non-alphanumeric characters.
  pattern_part = re.escape(pattern_part)
  # There are not supposed to be any other asterisk characters, so all
  # occurrences of backslash-asterisk can now be replaced with dot-asterisk.
  re_pattern = re.compile('^' + pattern_part.replace('\\*', '.*') + '$')
  return re_pattern.match(test_path_part)


def TimestampMilliseconds(datetime):
  """Returns the number of milliseconds since the epoch."""
  return int(time.mktime(datetime.timetuple()) * 1000)


def GetTestContainerKey(test):
  """Gets the TestContainer key for the given Test.

  Args:
    test: Either a Test entity or its ndb.Key.

  Returns:
    ndb.Key('TestContainer', test path)
  """
  test_path = None
  if type(test) is ndb.Key:
    test_path = TestPath(test)
  else:
    test_path = test.test_path
  return ndb.Key('TestContainer', test_path)


def GetMulti(keys):
  """Gets a list of entities from a list of keys.

  If this user is logged in, this is the same as ndb.get_multi. However, if the
  user is logged out and any of the data is internal only, an AssertionError
  will be raised.

  Args:
    keys: A list of ndb entity keys.

  Returns:
    A list of entities, but no internal_only ones if the user is not logged in.
  """
  if IsInternalUser():
    return ndb.get_multi(keys)
  # Not logged in. Check each key individually.
  entities = []
  for key in keys:
    try:
      entities.append(key.get())
    except AssertionError:
      continue
  return entities


def MinimumAlertRange(alerts):
  """Returns the intersection of the revision ranges for a set of alerts.

  Args:
    alerts: An iterable of Alerts (Anomaly or StoppageAlert entities).

  Returns:
    A pair (start, end) if there is a valid minimum range,
    or None if the ranges are not overlapping.
  """
  ranges = [(a.start_revision, a.end_revision) for a in alerts if a]
  return MinimumRange(ranges)


def MinimumRange(ranges):
  """Returns the intersection of the given ranges, or None."""
  if not ranges:
    return None
  starts, ends = zip(*ranges)
  start, end = (max(starts), min(ends))
  if start > end:
    return None
  return start, end


def IsInternalUser():
  """Checks whether the user should be able to see internal-only data."""
  username = users.get_current_user()
  if not username:
    return False
  cached = GetCachedIsInternalUser(username)
  if cached is not None:
    return cached
  is_internal_user = IsGroupMember(identity=username, group='googlers')
  SetCachedIsInternalUser(username, is_internal_user)
  return is_internal_user


def GetCachedIsInternalUser(username):
  return memcache.get(_IsInternalUserCacheKey(username))


def SetCachedIsInternalUser(username, value):
  memcache.add(_IsInternalUserCacheKey(username), value, time=60*60*24)


def _IsInternalUserCacheKey(username):
  return 'is_internal_user_%s' % username


def IsGroupMember(identity, group):
  """Checks if a user is a group member of using chrome-infra-auth.appspot.com.

  Args:
    identity: User email address.
    group: Group name.

  Returns:
    True if confirmed to be a member, False otherwise.
  """
  try:
    discovery_url = ('https://chrome-infra-auth.appspot.com'
                     '/_ah/api/discovery/v1/apis/{api}/{apiVersion}/rest')
    service = discovery.build(
        'auth', 'v1', discoveryServiceUrl=discovery_url,
        credentials=ServiceAccountCredentials())
    request = service.membership(identity=identity, group=group)
    response = request.execute()
    return response['is_member']
  except (errors.HttpError, KeyError, AttributeError) as e:
    logging.error('Failed to check membership of %s: %s', identity, e)
    return False


def ServiceAccountCredentials():
  """Returns the Credentials of the service account if available."""
  account_details = stored_object.Get(SERVICE_ACCOUNT_KEY)
  if not account_details:
    logging.error('Service account credentials not found.')
    return None
  return client.SignedJwtAssertionCredentials(
      service_account_name=account_details['client_email'],
      private_key=account_details['private_key'],
      scope=EMAIL_SCOPE)


def IsValidSheriffUser():
  """Checks whether the user should be allowed to triage alerts."""
  user = users.get_current_user()
  sheriff_domains = stored_object.Get(SHERIFF_DOMAINS_KEY)
  return user and sheriff_domains and any(
      user.email().endswith('@' + domain) for domain in sheriff_domains)


def GetIpWhitelist():
  """Returns a list of IP address strings in the whitelist."""
  return stored_object.Get(IP_WHITELIST_KEY)


def BisectConfigPythonString(config):
  """Turns a bisect config dict into a properly formatted Python string.

  Args:
    config: A bisect config dict (see start_try_job.GetBisectConfig)

  Returns:
    A config string suitable to store in a TryJob entity.
  """
  return 'config = %s\n' % json.dumps(
      config, sort_keys=True, indent=2, separators=(',', ': '))


def DownloadChromiumFile(path):
  """Downloads a file in the chromium/src repository.

  This function uses gitiles to fetch files. As of September 2015,
  gitiles supports fetching base-64 encoding of files. If it supports
  fetching plain text in the future, that may be simpler.

  Args:
    path: Path to a file in src repository, without a leading slash or "src/".

  Returns:
    The contents of the file as a string, or None.
  """
  base_url = 'https://chromium.googlesource.com/chromium/src/+/master/'
  url = '%s%s?format=TEXT' % (base_url, path)
  response = urlfetch.fetch(url)
  if response.status_code != 200:
    logging.error('Got %d fetching "%s".', response.status_code, url)
    return None
  try:
    plaintext_content = base64.decodestring(response.content)
  except binascii.Error:
    logging.error('Failed to decode "%s" from "%s".', response.content, url)
    return None
  return plaintext_content


def GetRequestId():
  """Returns the request log ID which can be used to find a specific log."""
  return os.environ.get('REQUEST_LOG_ID')


def Validate(expected, actual):
  """Generic validator for expected keys, values, and types.

  Values are also considered equal if |actual| can be converted to |expected|'s
  type.  For instance:
    _Validate([3], '3')  # Returns True.

  See utils_test.py for more examples.

  Args:
    expected: Either a list of expected values or a dictionary of expected
        keys and type.  A dictionary can contain a list of expected values.
    actual: A value.
  """
  def IsValidType(expected, actual):
    if type(expected) is type and type(actual) is not expected:
      try:
        expected(actual)
      except ValueError:
        return False
    return True

  def IsInList(expected, actual):
    for value in expected:
      try:
        if type(value)(actual) == value:
          return True
      except ValueError:
        pass
    return False

  if not expected:
    return
  expected_type = type(expected)
  actual_type = type(actual)
  if expected_type is list:
    if not IsInList(expected, actual):
      raise ValueError('Invalid value. Expected one of the following: '
                       '%s. Actual: %s.' % (','.join(expected), actual))
  elif expected_type is dict:
    if actual_type is not dict:
      raise ValueError('Invalid type. Expected: %s. Actual: %s.'
                       % (expected_type, actual_type))
    missing = set(expected.keys()) - set(actual.keys())
    if missing:
      raise ValueError('Missing the following properties: %s'
                       % ','.join(missing))
    for key in expected:
      Validate(expected[key], actual[key])
  elif not IsValidType(expected, actual):
    raise ValueError('Invalid type. Expected: %s. Actual: %s.' %
                     (expected, actual_type))


def FetchURL(request_url, skip_status_code=False):
  """Wrapper around URL fetch service to make request.

  Args:
    request_url: URL of request.
    skip_status_code: Skips return code check when True, default is False.

  Returns:
    Response object return by URL fetch, otherwise None when there's an error.
  """
  logging.info('URL being fetched: ' + request_url)
  try:
    response = urlfetch.fetch(request_url)
  except urlfetch_errors.DeadlineExceededError:
    logging.error('Deadline exceeded error checking %s', request_url)
    return None
  except urlfetch_errors.DownloadError as err:
    # DownloadError is raised to indicate a non-specific failure when there
    # was not a 4xx or 5xx status code.
    logging.error(err)
    return None
  if skip_status_code:
    return response
  elif response.status_code != 200:
    logging.error(
        'ERROR %s checking %s', response.status_code, request_url)
    return None
  return response