text: #!/usr/bin/env python
  #
  # Copyright (C) 2009 Google Inc.
  #
  # 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.
  
  
  # This module is used for version 2 of the Google Data APIs.
  
  
  """Provides auth related token classes and functions for Google Data APIs.
  
  Token classes represent a user's authorization of this app to access their
  data. Usually these are not created directly but by a GDClient object.
  
  ClientLoginToken
  AuthSubToken
  SecureAuthSubToken
  OAuthHmacToken
  OAuthRsaToken
  TwoLeggedOAuthHmacToken
  TwoLeggedOAuthRsaToken
  
  Functions which are often used in application code (as opposed to just within
  the gdata-python-client library) are the following:
  
  generate_auth_sub_url
  authorize_request_token
  
  The following are helper functions which are used to save and load auth token
  objects in the App Engine datastore. These should only be used if you are using
  this library within App Engine:
  
  ae_load
  ae_save
  """
  
  
  import time
  import random
  import urllib
  import atom.http_core
  
  
  __author__ = 'j.s@google.com (Jeff Scudder)'
  
  
  PROGRAMMATIC_AUTH_LABEL = 'GoogleLogin auth='
  AUTHSUB_AUTH_LABEL = 'AuthSub token='
  
  
  # This dict provides the AuthSub and OAuth scopes for all services by service
  # name. The service name (key) is used in ClientLogin requests.
  AUTH_SCOPES = {
      'cl': ( # Google Calendar API
          'https://www.google.com/calendar/feeds/',
          'http://www.google.com/calendar/feeds/'),
      'gbase': ( # Google Base API
          'http://base.google.com/base/feeds/',
          'http://www.google.com/base/feeds/'),
      'blogger': ( # Blogger API
          'http://www.blogger.com/feeds/',),
      'codesearch': ( # Google Code Search API
          'http://www.google.com/codesearch/feeds/',),
      'cp': ( # Contacts API
          'https://www.google.com/m8/feeds/',
          'http://www.google.com/m8/feeds/'),
      'finance': ( # Google Finance API
          'http://finance.google.com/finance/feeds/',),
      'health': ( # Google Health API
          'https://www.google.com/health/feeds/',),
      'writely': ( # Documents List API
          'https://docs.google.com/feeds/',
          'http://docs.google.com/feeds/'),
      'lh2': ( # Picasa Web Albums API
          'http://picasaweb.google.com/data/',),
      'apps': ( # Google Apps Provisioning API
          'http://www.google.com/a/feeds/',
          'https://www.google.com/a/feeds/',
          'http://apps-apis.google.com/a/feeds/',
          'https://apps-apis.google.com/a/feeds/'),
      'weaver': ( # Health H9 Sandbox
          'https://www.google.com/h9/feeds/',),
      'wise': ( # Spreadsheets Data API
          'https://spreadsheets.google.com/feeds/',
          'http://spreadsheets.google.com/feeds/'),
      'sitemaps': ( # Google Webmaster Tools API
          'https://www.google.com/webmasters/tools/feeds/',),
      'youtube': ( # YouTube API
          'http://gdata.youtube.com/feeds/api/',
          'http://uploads.gdata.youtube.com/feeds/api',
          'http://gdata.youtube.com/action/GetUploadToken'),
      'books': ( # Google Books API
          'http://www.google.com/books/feeds/',),
      'analytics': ( # Google Analytics API
          'https://www.google.com/analytics/feeds/',),
      'jotspot': ( # Google Sites API
          'http://sites.google.com/feeds/',
          'https://sites.google.com/feeds/'),
      'local': ( # Google Maps Data API
          'http://maps.google.com/maps/feeds/',),
      'code': ( # Project Hosting Data API
          'http://code.google.com/feeds/issues',)}
  
  
  
  class Error(Exception):
    pass
  
  
  class UnsupportedTokenType(Error):
    """Raised when token to or from blob is unable to convert the token."""
    pass
  
  
  # ClientLogin functions and classes.
  def generate_client_login_request_body(email, password, service, source,
      account_type='HOSTED_OR_GOOGLE', captcha_token=None,
      captcha_response=None):
    """Creates the body of the autentication request
  
    See http://code.google.com/apis/accounts/AuthForInstalledApps.html#Request
    for more details.
  
    Args:
      email: str
      password: str
      service: str
      source: str
      account_type: str (optional) Defaul is 'HOSTED_OR_GOOGLE', other valid
          values are 'GOOGLE' and 'HOSTED'
      captcha_token: str (optional)
      captcha_response: str (optional)
  
    Returns:
      The HTTP body to send in a request for a client login token.
    """
    # Create a POST body containing the user's credentials.
    request_fields = {'Email': email,
                      'Passwd': password,
                      'accountType': account_type,
                      'service': service,
                      'source': source}
    if captcha_token and captcha_response:
      # Send the captcha token and response as part of the POST body if the
      # user is responding to a captch challenge.
      request_fields['logintoken'] = captcha_token
      request_fields['logincaptcha'] = captcha_response
    return urllib.urlencode(request_fields)
  
  
  GenerateClientLoginRequestBody = generate_client_login_request_body
  
  
  def get_client_login_token_string(http_body):
    """Returns the token value for a ClientLoginToken.
  
    Reads the token from the server's response to a Client Login request and
    creates the token value string to use in requests.
  
    Args:
      http_body: str The body of the server's HTTP response to a Client Login
          request
  
    Returns:
      The token value string for a ClientLoginToken.
    """
    for response_line in http_body.splitlines():
      if response_line.startswith('Auth='):
        # Strip off the leading Auth= and return the Authorization value.
        return response_line[5:]
    return None
  
  
  GetClientLoginTokenString = get_client_login_token_string
  
  
  def get_captcha_challenge(http_body,
      captcha_base_url='http://www.google.com/accounts/'):
    """Returns the URL and token for a CAPTCHA challenge issued by the server.
  
    Args:
      http_body: str The body of the HTTP response from the server which
          contains the CAPTCHA challenge.
      captcha_base_url: str This function returns a full URL for viewing the
          challenge image which is built from the server's response. This
          base_url is used as the beginning of the URL because the server
          only provides the end of the URL. For example the server provides
          'Captcha?ctoken=Hi...N' and the URL for the image is
          'http://www.google.com/accounts/Captcha?ctoken=Hi...N'
  
    Returns:
      A dictionary containing the information needed to repond to the CAPTCHA
      challenge, the image URL and the ID token of the challenge. The
      dictionary is in the form:
      {'token': string identifying the CAPTCHA image,
       'url': string containing the URL of the image}
      Returns None if there was no CAPTCHA challenge in the response.
    """
    contains_captcha_challenge = False
    captcha_parameters = {}
    for response_line in http_body.splitlines():
      if response_line.startswith('Error=CaptchaRequired'):
        contains_captcha_challenge = True
      elif response_line.startswith('CaptchaToken='):
        # Strip off the leading CaptchaToken=
        captcha_parameters['token'] = response_line[13:]
      elif response_line.startswith('CaptchaUrl='):
        captcha_parameters['url'] = '%s%s' % (captcha_base_url,
            response_line[11:])
    if contains_captcha_challenge:
      return captcha_parameters
    else:
      return None
  
  
  GetCaptchaChallenge = get_captcha_challenge
  
  
  class ClientLoginToken(object):
  
    def __init__(self, token_string):
      self.token_string = token_string
  
    def modify_request(self, http_request):
      http_request.headers['Authorization'] = '%s%s' % (PROGRAMMATIC_AUTH_LABEL,
          self.token_string)
  
    ModifyRequest = modify_request
  
  
  # AuthSub functions and classes.
  def _to_uri(str_or_uri):
    if isinstance(str_or_uri, (str, unicode)):
      return atom.http_core.Uri.parse_uri(str_or_uri)
    return str_or_uri
  
  
  def generate_auth_sub_url(next, scopes, secure=False, session=True,
      request_url=atom.http_core.parse_uri(
          'https://www.google.com/accounts/AuthSubRequest'),
      domain='default', scopes_param_prefix='auth_sub_scopes'):
    """Constructs a URI for requesting a multiscope AuthSub token.
  
    The generated token will contain a URL parameter to pass along the
    requested scopes to the next URL. When the Google Accounts page
    redirects the broswser to the 'next' URL, it appends the single use
    AuthSub token value to the URL as a URL parameter with the key 'token'.
    However, the information about which scopes were requested is not
    included by Google Accounts. This method adds the scopes to the next
    URL before making the request so that the redirect will be sent to
    a page, and both the token value and the list of scopes for which the token
    was requested.
  
    Args:
      next: atom.http_core.Uri or string The URL user will be sent to after
            authorizing this web application to access their data.
      scopes: list containint strings or atom.http_core.Uri objects. The URLs
              of the services to be accessed. Could also be a single string
              or single atom.http_core.Uri for requesting just one scope.
      secure: boolean (optional) Determines whether or not the issued token
              is a secure token.
      session: boolean (optional) Determines whether or not the issued token
               can be upgraded to a session token.
      request_url: atom.http_core.Uri or str The beginning of the request URL.
                   This is normally
                   'http://www.google.com/accounts/AuthSubRequest' or
                   '/accounts/AuthSubRequest'
      domain: The domain which the account is part of. This is used for Google
              Apps accounts, the default value is 'default' which means that
              the requested account is a Google Account (@gmail.com for
              example)
      scopes_param_prefix: str (optional) The requested scopes are added as a
                           URL parameter to the next URL so that the page at
                           the 'next' URL can extract the token value and the
                           valid scopes from the URL. The key for the URL
                           parameter defaults to 'auth_sub_scopes'
  
    Returns:
      An atom.http_core.Uri which the user's browser should be directed to in
      order to authorize this application to access their information.
    """
    if isinstance(next, (str, unicode)):
      next = atom.http_core.Uri.parse_uri(next)
    # If the user passed in a string instead of a list for scopes, convert to
    # a single item tuple.
    if isinstance(scopes, (str, unicode, atom.http_core.Uri)):
      scopes = (scopes,)
    scopes_string = ' '.join([str(scope) for scope in scopes])
    next.query[scopes_param_prefix] = scopes_string
  
    if isinstance(request_url, (str, unicode)):
      request_url = atom.http_core.Uri.parse_uri(request_url)
    request_url.query['next'] = str(next)
    request_url.query['scope'] = scopes_string
    if session:
      request_url.query['session'] = '1'
    else:
      request_url.query['session'] = '0'
    if secure:
      request_url.query['secure'] = '1'
    else:
      request_url.query['secure'] = '0'
    request_url.query['hd'] = domain
    return request_url
  
  
  def auth_sub_string_from_url(url, scopes_param_prefix='auth_sub_scopes'):
    """Finds the token string (and scopes) after the browser is redirected.
  
    After the Google Accounts AuthSub pages redirect the user's broswer back to
    the web application (using the 'next' URL from the request) the web app must
    extract the token from the current page's URL. The token is provided as a
    URL parameter named 'token' and if generate_auth_sub_url was used to create
    the request, the token's valid scopes are included in a URL parameter whose
    name is specified in scopes_param_prefix.
  
    Args:
      url: atom.url.Url or str representing the current URL. The token value
           and valid scopes should be included as URL parameters.
      scopes_param_prefix: str (optional) The URL parameter key which maps to
                           the list of valid scopes for the token.
  
    Returns:
      A tuple containing the token value as a string, and a tuple of scopes
      (as atom.http_core.Uri objects) which are URL prefixes under which this
      token grants permission to read and write user data.
      (token_string, (scope_uri, scope_uri, scope_uri, ...))
      If no scopes were included in the URL, the second value in the tuple is
      None. If there was no token param in the url, the tuple returned is
      (None, None)
    """
    if isinstance(url, (str, unicode)):
      url = atom.http_core.Uri.parse_uri(url)
    if 'token' not in url.query:
      return (None, None)
    token = url.query['token']
    # TODO: decide whether no scopes should be None or ().
    scopes = None # Default to None for no scopes.
    if scopes_param_prefix in url.query:
      scopes = tuple(url.query[scopes_param_prefix].split(' '))
    return (token, scopes)
  
  
  AuthSubStringFromUrl = auth_sub_string_from_url
  
  
  def auth_sub_string_from_body(http_body):
    """Extracts the AuthSub token from an HTTP body string.
  
    Used to find the new session token after making a request to upgrade a
    single use AuthSub token.
  
    Args:
      http_body: str The repsonse from the server which contains the AuthSub
          key. For example, this function would find the new session token
          from the server's response to an upgrade token request.
  
    Returns:
      The raw token value string to use in an AuthSubToken object.
    """
    for response_line in http_body.splitlines():
      if response_line.startswith('Token='):
        # Strip off Token= and return the token value string.
        return response_line[6:]
    return None
  
  
  class AuthSubToken(object):
  
    def __init__(self, token_string, scopes=None):
      self.token_string = token_string
      self.scopes = scopes or []
  
    def modify_request(self, http_request):
      """Sets Authorization header, allows app to act on the user's behalf."""
      http_request.headers['Authorization'] = '%s%s' % (AUTHSUB_AUTH_LABEL,
          self.token_string)
  
    ModifyRequest = modify_request
  
    def from_url(str_or_uri):
      """Creates a new AuthSubToken using information in the URL.
  
      Uses auth_sub_string_from_url.
  
      Args:
        str_or_uri: The current page's URL (as a str or atom.http_core.Uri)
                    which should contain a token query parameter since the
                    Google auth server redirected the user's browser to this
                    URL.
      """
      token_and_scopes = auth_sub_string_from_url(str_or_uri)
      return AuthSubToken(token_and_scopes[0], token_and_scopes[1])
  
    from_url = staticmethod(from_url)
    FromUrl = from_url
  
    def _upgrade_token(self, http_body):
      """Replaces the token value with a session token from the auth server.
  
      Uses the response of a token upgrade request to modify this token. Uses
      auth_sub_string_from_body.
      """
      self.token_string = auth_sub_string_from_body(http_body)
  
  
  # Functions and classes for Secure-mode AuthSub
  def build_auth_sub_data(http_request, timestamp, nonce):
    """Creates the data string which must be RSA-signed in secure requests.
  
    For more details see the documenation on secure AuthSub requests:
    http://code.google.com/apis/accounts/docs/AuthSub.html#signingrequests
  
    Args:
      http_request: The request being made to the server. The Request's URL
          must be complete before this signature is calculated as any changes
          to the URL will invalidate the signature.
      nonce: str Random 64-bit, unsigned number encoded as an ASCII string in
          decimal format. The nonce/timestamp pair should always be unique to
          prevent replay attacks.
      timestamp: Integer representing the time the request is sent. The
          timestamp should be expressed in number of seconds after January 1,
          1970 00:00:00 GMT.
    """
    return '%s %s %s %s' % (http_request.method, str(http_request.uri),
                            str(timestamp), nonce)
  
  
  def generate_signature(data, rsa_key):
    """Signs the data string for a secure AuthSub request."""
    import base64
    try:
      from tlslite.utils import keyfactory
    except ImportError:
      from gdata.tlslite.utils import keyfactory
    private_key = keyfactory.parsePrivateKey(rsa_key)
    signed = private_key.hashAndSign(data)
    # Python2.3 and lower does not have the base64.b64encode function.
    if hasattr(base64, 'b64encode'):
      return base64.b64encode(signed)
    else:
      return base64.encodestring(signed).replace('\n', '')
  
  
  class SecureAuthSubToken(AuthSubToken):
  
    def __init__(self, token_string, rsa_private_key, scopes=None):
      self.token_string = token_string
      self.scopes = scopes or []
      self.rsa_private_key = rsa_private_key
  
    def from_url(str_or_uri, rsa_private_key):
      """Creates a new SecureAuthSubToken using information in the URL.
  
      Uses auth_sub_string_from_url.
  
      Args:
        str_or_uri: The current page's URL (as a str or atom.http_core.Uri)
            which should contain a token query parameter since the Google auth
            server redirected the user's browser to this URL.
        rsa_private_key: str the private RSA key cert used to sign all requests
            made with this token.
      """
      token_and_scopes = auth_sub_string_from_url(str_or_uri)
      return SecureAuthSubToken(token_and_scopes[0], rsa_private_key,
                                token_and_scopes[1])
  
    from_url = staticmethod(from_url)
    FromUrl = from_url
  
    def modify_request(self, http_request):
      """Sets the Authorization header and includes a digital signature.
  
      Calculates a digital signature using the private RSA key, a timestamp
      (uses now at the time this method is called) and a random nonce.
  
      Args:
        http_request: The atom.http_core.HttpRequest which contains all of the
            information needed to send a request to the remote server. The
            URL and the method of the request must be already set and cannot be
            changed after this token signs the request, or the signature will
            not be valid.
      """
      timestamp = str(int(time.time()))
      nonce = ''.join([str(random.randint(0, 9)) for i in xrange(15)])
      data = build_auth_sub_data(http_request, timestamp, nonce)
      signature = generate_signature(data, self.rsa_private_key)
      http_request.headers['Authorization'] = (
          '%s%s sigalg="rsa-sha1" data="%s" sig="%s"' % (AUTHSUB_AUTH_LABEL,
              self.token_string, data, signature))
  
    ModifyRequest = modify_request
  
  
  # OAuth functions and classes.
  RSA_SHA1 = 'RSA-SHA1'
  HMAC_SHA1 = 'HMAC-SHA1'
  
  
  def build_oauth_base_string(http_request, consumer_key, nonce, signaure_type,
                              timestamp, version, next='oob', token=None,
                              verifier=None):
    """Generates the base string to be signed in the OAuth request.
  
    Args:
      http_request: The request being made to the server. The Request's URL
          must be complete before this signature is calculated as any changes
          to the URL will invalidate the signature.
      consumer_key: Domain identifying the third-party web application. This is
          the domain used when registering the application with Google. It
          identifies who is making the request on behalf of the user.
      nonce: Random 64-bit, unsigned number encoded as an ASCII string in decimal
          format. The nonce/timestamp pair should always be unique to prevent
          replay attacks.
      signaure_type: either RSA_SHA1 or HMAC_SHA1
      timestamp: Integer representing the time the request is sent. The
          timestamp should be expressed in number of seconds after January 1,
          1970 00:00:00 GMT.
      version: The OAuth version used by the requesting web application. This
          value must be '1.0' or '1.0a'. If not provided, Google assumes version
          1.0 is in use.
      next: The URL the user should be redirected to after granting access
          to a Google service(s). It can include url-encoded query parameters.
          The default value is 'oob'. (This is the oauth_callback.)
      token: The string for the OAuth request token or OAuth access token.
      verifier: str Sent as the oauth_verifier and required when upgrading a
          request token to an access token.
    """
    # First we must build the canonical base string for the request.
    params = http_request.uri.query.copy()
    params['oauth_consumer_key'] = consumer_key
    params['oauth_nonce'] = nonce
    params['oauth_signature_method'] = signaure_type
    params['oauth_timestamp'] = str(timestamp)
    if next is not None:
      params['oauth_callback'] = str(next)
    if token is not None:
      params['oauth_token'] = token
    if version is not None:
      params['oauth_version'] = version
    if verifier is not None:
      params['oauth_verifier'] = verifier
    # We need to get the key value pairs in lexigraphically sorted order.
    sorted_keys = None
    try:
      sorted_keys = sorted(params.keys())
    # The sorted function is not available in Python2.3 and lower
    except NameError:
      sorted_keys = params.keys()
      sorted_keys.sort()
    pairs = []
    for key in sorted_keys:
      pairs.append('%s=%s' % (urllib.quote(key, safe='~'),
                              urllib.quote(params[key], safe='~')))
    # We want to escape /'s too, so use safe='~'
    all_parameters = urllib.quote('&'.join(pairs), safe='~')
    normailzed_host = http_request.uri.host.lower()
    normalized_scheme = (http_request.uri.scheme or 'http').lower()
    non_default_port = None
    if (http_request.uri.port is not None
        and ((normalized_scheme == 'https' and http_request.uri.port != 443)
             or (normalized_scheme == 'http' and http_request.uri.port != 80))):
      non_default_port = http_request.uri.port
    path = http_request.uri.path or '/'
    request_path = None
    if not path.startswith('/'):
      path = '/%s' % path
    if non_default_port is not None:
      # Set the only safe char in url encoding to ~ since we want to escape /
      # as well.
      request_path = urllib.quote('%s://%s:%s%s' % (
          normalized_scheme, normailzed_host, non_default_port, path), safe='~')
    else:
      # Set the only safe char in url encoding to ~ since we want to escape /
      # as well.
      request_path = urllib.quote('%s://%s%s' % (
          normalized_scheme, normailzed_host, path), safe='~')
    # TODO: ensure that token escaping logic is correct, not sure if the token
    # value should be double escaped instead of single.
    base_string = '&'.join((http_request.method.upper(), request_path,
                            all_parameters))
    # Now we have the base string, we can calculate the oauth_signature.
    return base_string
  
  
  def generate_hmac_signature(http_request, consumer_key, consumer_secret,
                              timestamp, nonce, version, next='oob',
                              token=None, token_secret=None, verifier=None):
    import hmac
    import base64
    base_string = build_oauth_base_string(
        http_request, consumer_key, nonce, HMAC_SHA1, timestamp, version,
        next, token, verifier=verifier)
    hash_key = None
    hashed = None
    if token_secret is not None:
      hash_key = '%s&%s' % (urllib.quote(consumer_secret, safe='~'),
                            urllib.quote(token_secret, safe='~'))
    else:
      hash_key = '%s&' % urllib.quote(consumer_secret, safe='~')
    try:
      import hashlib
      hashed = hmac.new(hash_key, base_string, hashlib.sha1)
    except ImportError:
      import sha
      hashed = hmac.new(hash_key, base_string, sha)
    # Python2.3 does not have base64.b64encode.
    if hasattr(base64, 'b64encode'):
      return base64.b64encode(hashed.digest())
    else:
      return base64.encodestring(hashed.digest()).replace('\n', '')
  
  
  def generate_rsa_signature(http_request, consumer_key, rsa_key,
                             timestamp, nonce, version, next='oob',
                             token=None, token_secret=None, verifier=None):
    import base64
    try:
      from tlslite.utils import keyfactory
    except ImportError:
      from gdata.tlslite.utils import keyfactory
    base_string = build_oauth_base_string(
        http_request, consumer_key, nonce, RSA_SHA1, timestamp, version,
        next, token, verifier=verifier)
    private_key = keyfactory.parsePrivateKey(rsa_key)
    # Sign using the key
    signed = private_key.hashAndSign(base_string)
    # Python2.3 does not have base64.b64encode.
    if hasattr(base64, 'b64encode'):
      return base64.b64encode(signed)
    else:
      return base64.encodestring(signed).replace('\n', '')
  
  
  def generate_auth_header(consumer_key, timestamp, nonce, signature_type,
                           signature, version='1.0', next=None, token=None,
                           verifier=None):
    """Builds the Authorization header to be sent in the request.
  
    Args:
      consumer_key: Identifies the application making the request (str).
      timestamp:
      nonce:
      signature_type: One of either HMAC_SHA1 or RSA_SHA1
      signature: The HMAC or RSA signature for the request as a base64
          encoded string.
      version: The version of the OAuth protocol that this request is using.
          Default is '1.0'
      next: The URL of the page that the user's browser should be sent to
          after they authorize the token. (Optional)
      token: str The OAuth token value to be used in the oauth_token parameter
          of the header.
      verifier: str The OAuth verifier which must be included when you are
          upgrading a request token to an access token.
    """
    params = {
        'oauth_consumer_key': consumer_key,
        'oauth_version': version,
        'oauth_nonce': nonce,
        'oauth_timestamp': str(timestamp),
        'oauth_signature_method': signature_type,
        'oauth_signature': signature}
    if next is not None:
      params['oauth_callback'] = str(next)
    if token is not None:
      params['oauth_token'] = token
    if verifier is not None:
      params['oauth_verifier'] = verifier
    pairs = [
        '%s="%s"' % (
            k, urllib.quote(v, safe='~')) for k, v in params.iteritems()]
    return 'OAuth %s' % (', '.join(pairs))
  
  
  REQUEST_TOKEN_URL = 'https://www.google.com/accounts/OAuthGetRequestToken'
  ACCESS_TOKEN_URL = 'https://www.google.com/accounts/OAuthGetAccessToken'
  
  
  def generate_request_for_request_token(
      consumer_key, signature_type, scopes, rsa_key=None, consumer_secret=None,
      auth_server_url=REQUEST_TOKEN_URL, next='oob', version='1.0'):
    """Creates request to be sent to auth server to get an OAuth request token.
  
    Args:
      consumer_key:
      signature_type: either RSA_SHA1 or HMAC_SHA1. The rsa_key must be
          provided if the signature type is RSA but if the signature method
          is HMAC, the consumer_secret must be used.
      scopes: List of URL prefixes for the data which we want to access. For
          example, to request access to the user's Blogger and Google Calendar
          data, we would request
          ['http://www.blogger.com/feeds/',
           'https://www.google.com/calendar/feeds/',
           'http://www.google.com/calendar/feeds/']
      rsa_key: Only used if the signature method is RSA_SHA1.
      consumer_secret: Only used if the signature method is HMAC_SHA1.
      auth_server_url: The URL to which the token request should be directed.
          Defaults to 'https://www.google.com/accounts/OAuthGetRequestToken'.
      next: The URL of the page that the user's browser should be sent to
          after they authorize the token. (Optional)
      version: The OAuth version used by the requesting web application.
          Defaults to '1.0a'
  
    Returns:
      An atom.http_core.HttpRequest object with the URL, Authorization header
      and body filled in.
    """
    request = atom.http_core.HttpRequest(auth_server_url, 'POST')
    # Add the requested auth scopes to the Auth request URL.
    if scopes:
      request.uri.query['scope'] = ' '.join(scopes)
  
    timestamp = str(int(time.time()))
    nonce = ''.join([str(random.randint(0, 9)) for i in xrange(15)])
    signature = None
    if signature_type == HMAC_SHA1:
      signature = generate_hmac_signature(
          request, consumer_key, consumer_secret, timestamp, nonce, version,
          next=next)
    elif signature_type == RSA_SHA1:
      signature = generate_rsa_signature(
          request, consumer_key, rsa_key, timestamp, nonce, version, next=next)
    else:
      return None
  
    request.headers['Authorization'] = generate_auth_header(
        consumer_key, timestamp, nonce, signature_type, signature, version,
        next)
    request.headers['Content-Length'] = '0'
    return request
  
  
  def generate_request_for_access_token(
      request_token, auth_server_url=ACCESS_TOKEN_URL):
    """Creates a request to ask the OAuth server for an access token.
  
    Requires a request token which the user has authorized. See the
    documentation on OAuth with Google Data for more details:
    http://code.google.com/apis/accounts/docs/OAuth.html#AccessToken
  
    Args:
      request_token: An OAuthHmacToken or OAuthRsaToken which the user has
          approved using their browser.
      auth_server_url: (optional) The URL at which the OAuth access token is
          requested. Defaults to
          https://www.google.com/accounts/OAuthGetAccessToken
  
    Returns:
      A new HttpRequest object which can be sent to the OAuth server to
      request an OAuth Access Token.
    """
    http_request = atom.http_core.HttpRequest(auth_server_url, 'POST')
    http_request.headers['Content-Length'] = '0'
    return request_token.modify_request(http_request)
  
  
  def oauth_token_info_from_body(http_body):
    """Exracts an OAuth request token from the server's response.
  
    Returns:
      A tuple of strings containing the OAuth token and token secret. If
      neither of these are present in the body, returns (None, None)
    """
    token = None
    token_secret = None
    for pair in http_body.split('&'):
      if pair.startswith('oauth_token='):
        token = urllib.unquote(pair[len('oauth_token='):])
      if pair.startswith('oauth_token_secret='):
        token_secret = urllib.unquote(pair[len('oauth_token_secret='):])
    return (token, token_secret)
  
  
  def hmac_token_from_body(http_body, consumer_key, consumer_secret,
                           auth_state):
    token_value, token_secret = oauth_token_info_from_body(http_body)
    token = OAuthHmacToken(consumer_key, consumer_secret, token_value,
                           token_secret, auth_state)
    return token
  
  
  def rsa_token_from_body(http_body, consumer_key, rsa_private_key,
                          auth_state):
    token_value, token_secret = oauth_token_info_from_body(http_body)
    token = OAuthRsaToken(consumer_key, rsa_private_key, token_value,
                          token_secret, auth_state)
    return token
  
  
  DEFAULT_DOMAIN = 'default'
  OAUTH_AUTHORIZE_URL = 'https://www.google.com/accounts/OAuthAuthorizeToken'
  
  
  def generate_oauth_authorization_url(
      token, next=None, hd=DEFAULT_DOMAIN, hl=None, btmpl=None,
      auth_server=OAUTH_AUTHORIZE_URL):
    """Creates a URL for the page where the request token can be authorized.
  
    Args:
      token: str The request token from the OAuth server.
      next: str (optional) URL the user should be redirected to after granting
          access to a Google service(s). It can include url-encoded query
          parameters.
      hd: str (optional) Identifies a particular hosted domain account to be
          accessed (for example, 'mycollege.edu'). Uses 'default' to specify a
          regular Google account ('username@gmail.com').
      hl: str (optional) An ISO 639 country code identifying what language the
          approval page should be translated in (for example, 'hl=en' for
          English). The default is the user's selected language.
      btmpl: str (optional) Forces a mobile version of the approval page. The
          only accepted value is 'mobile'.
      auth_server: str (optional) The start of the token authorization web
          page. Defaults to
          'https://www.google.com/accounts/OAuthAuthorizeToken'
  
    Returns:
      An atom.http_core.Uri pointing to the token authorization page where the
      user may allow or deny this app to access their Google data.
    """
    uri = atom.http_core.Uri.parse_uri(auth_server)
    uri.query['oauth_token'] = token
    uri.query['hd'] = hd
    if next is not None:
      uri.query['oauth_callback'] = str(next)
    if hl is not None:
      uri.query['hl'] = hl
    if btmpl is not None:
      uri.query['btmpl'] = btmpl
    return uri
  
  
  def oauth_token_info_from_url(url):
    """Exracts an OAuth access token from the redirected page's URL.
  
    Returns:
      A tuple of strings containing the OAuth token and the OAuth verifier which
      need to sent when upgrading a request token to an access token.
    """
    if isinstance(url, (str, unicode)):
      url = atom.http_core.Uri.parse_uri(url)
    token = None
    verifier = None
    if 'oauth_token' in url.query:
      token = urllib.unquote(url.query['oauth_token'])
    if 'oauth_verifier' in url.query:
      verifier = urllib.unquote(url.query['oauth_verifier'])
    return (token, verifier)
  
  
  def authorize_request_token(request_token, url):
    """Adds information to request token to allow it to become an access token.
  
    Modifies the request_token object passed in by setting and unsetting the
    necessary fields to allow this token to form a valid upgrade request.
  
    Args:
      request_token: The OAuth request token which has been authorized by the
          user. In order for this token to be upgraded to an access token,
          certain fields must be extracted from the URL and added to the token
          so that they can be passed in an upgrade-token request.
      url: The URL of the current page which the user's browser was redirected
          to after they authorized access for the app. This function extracts
          information from the URL which is needed to upgraded the token from
          a request token to an access token.
  
    Returns:
      The same token object which was passed in.
    """
    token, verifier = oauth_token_info_from_url(url)
    request_token.token = token
    request_token.verifier = verifier
    request_token.auth_state = AUTHORIZED_REQUEST_TOKEN
    return request_token
  
  
  AuthorizeRequestToken = authorize_request_token
  
  
  def upgrade_to_access_token(request_token, server_response_body):
    """Extracts access token information from response to an upgrade request.
  
    Once the server has responded with the new token info for the OAuth
    access token, this method modifies the request_token to set and unset
    necessary fields to create valid OAuth authorization headers for requests.
  
    Args:
      request_token: An OAuth token which this function modifies to allow it
          to be used as an access token.
      server_response_body: str The server's response to an OAuthAuthorizeToken
          request. This should contain the new token and token_secret which
          are used to generate the signature and parameters of the Authorization
          header in subsequent requests to Google Data APIs.
  
    Returns:
      The same token object which was passed in.
    """
    token, token_secret = oauth_token_info_from_body(server_response_body)
    request_token.token = token
    request_token.token_secret = token_secret
    request_token.auth_state = ACCESS_TOKEN
    request_token.next = None
    request_token.verifier = None
    return request_token
  
  
  UpgradeToAccessToken = upgrade_to_access_token
  
  
  REQUEST_TOKEN = 1
  AUTHORIZED_REQUEST_TOKEN = 2
  ACCESS_TOKEN = 3
  
  
  class OAuthHmacToken(object):
    SIGNATURE_METHOD = HMAC_SHA1
  
    def __init__(self, consumer_key, consumer_secret, token, token_secret,
                 auth_state, next=None, verifier=None):
      self.consumer_key = consumer_key
      self.consumer_secret = consumer_secret
      self.token = token
      self.token_secret = token_secret
      self.auth_state = auth_state
      self.next = next
      self.verifier = verifier # Used to convert request token to access token.
  
    def generate_authorization_url(
        self, google_apps_domain=DEFAULT_DOMAIN, language=None, btmpl=None,
        auth_server=OAUTH_AUTHORIZE_URL):
      """Creates the URL at which the user can authorize this app to access.
  
      Args:
        google_apps_domain: str (optional) If the user should be signing in
            using an account under a known Google Apps domain, provide the
            domain name ('example.com') here. If not provided, 'default'
            will be used, and the user will be prompted to select an account
            if they are signed in with a Google Account and Google Apps
            accounts.
        language: str (optional) An ISO 639 country code identifying what
            language the approval page should be translated in (for example,
            'en' for English). The default is the user's selected language.
        btmpl: str (optional) Forces a mobile version of the approval page. The
          only accepted value is 'mobile'.
        auth_server: str (optional) The start of the token authorization web
          page. Defaults to
          'https://www.google.com/accounts/OAuthAuthorizeToken'
      """
      return generate_oauth_authorization_url(
          self.token, hd=google_apps_domain, hl=language, btmpl=btmpl,
          auth_server=auth_server)
  
    GenerateAuthorizationUrl = generate_authorization_url
  
    def modify_request(self, http_request):
      """Sets the Authorization header in the HTTP request using the token.
  
      Calculates an HMAC signature using the information in the token to
      indicate that the request came from this application and that this
      application has permission to access a particular user's data.
  
      Returns:
        The same HTTP request object which was passed in.
      """
      timestamp = str(int(time.time()))
      nonce = ''.join([str(random.randint(0, 9)) for i in xrange(15)])
      signature = generate_hmac_signature(
          http_request, self.consumer_key, self.consumer_secret, timestamp,
          nonce, version='1.0', next=self.next, token=self.token,
          token_secret=self.token_secret, verifier=self.verifier)
      http_request.headers['Authorization'] = generate_auth_header(
          self.consumer_key, timestamp, nonce, HMAC_SHA1, signature,
          version='1.0', next=self.next, token=self.token,
          verifier=self.verifier)
      return http_request
  
    ModifyRequest = modify_request
  
  
  class OAuthRsaToken(OAuthHmacToken):
    SIGNATURE_METHOD = RSA_SHA1
  
    def __init__(self, consumer_key, rsa_private_key, token, token_secret,
                 auth_state, next=None, verifier=None):
      self.consumer_key = consumer_key
      self.rsa_private_key = rsa_private_key
      self.token = token
      self.token_secret = token_secret
      self.auth_state = auth_state
      self.next = next
      self.verifier = verifier # Used to convert request token to access token.
  
    def modify_request(self, http_request):
      """Sets the Authorization header in the HTTP request using the token.
  
      Calculates an RSA signature using the information in the token to
      indicate that the request came from this application and that this
      application has permission to access a particular user's data.
  
      Returns:
        The same HTTP request object which was passed in.
      """
      timestamp = str(int(time.time()))
      nonce = ''.join([str(random.randint(0, 9)) for i in xrange(15)])
      signature = generate_rsa_signature(
          http_request, self.consumer_key, self.rsa_private_key, timestamp,
          nonce, version='1.0', next=self.next, token=self.token,
          token_secret=self.token_secret, verifier=self.verifier)
      http_request.headers['Authorization'] = generate_auth_header(
          self.consumer_key, timestamp, nonce, RSA_SHA1, signature,
          version='1.0', next=self.next, token=self.token,
          verifier=self.verifier)
      return http_request
  
    ModifyRequest = modify_request
  
  
  class TwoLeggedOAuthHmacToken(OAuthHmacToken):
  
    def __init__(self, consumer_key, consumer_secret, requestor_id):
      self.requestor_id = requestor_id
      OAuthHmacToken.__init__(
          self, consumer_key, consumer_secret, None, None, ACCESS_TOKEN,
          next=None, verifier=None)
  
    def modify_request(self, http_request):
      """Sets the Authorization header in the HTTP request using the token.
  
      Calculates an HMAC signature using the information in the token to
      indicate that the request came from this application and that this
      application has permission to access a particular user's data using 2LO.
  
      Returns:
        The same HTTP request object which was passed in.
      """
      http_request.uri.query['xoauth_requestor_id'] = self.requestor_id
      return OAuthHmacToken.modify_request(self, http_request)
  
    ModifyRequest = modify_request
  
  
  class TwoLeggedOAuthRsaToken(OAuthRsaToken):
  
    def __init__(self, consumer_key, rsa_private_key, requestor_id):
      self.requestor_id = requestor_id
      OAuthRsaToken.__init__(
          self, consumer_key, rsa_private_key, None, None, ACCESS_TOKEN,
          next=None, verifier=None)
  
    def modify_request(self, http_request):
      """Sets the Authorization header in the HTTP request using the token.
  
      Calculates an RSA signature using the information in the token to
      indicate that the request came from this application and that this
      application has permission to access a particular user's data using 2LO.
  
      Returns:
        The same HTTP request object which was passed in.
      """
      http_request.uri.query['xoauth_requestor_id'] = self.requestor_id
      return OAuthRsaToken.modify_request(self, http_request)
  
    ModifyRequest = modify_request
  
  
  def _join_token_parts(*args):
    """"Escapes and combines all strings passed in.
  
    Used to convert a token object's members into a string instead of
    using pickle.
  
    Note: A None value will be converted to an empty string.
  
    Returns:
      A string in the form 1x|member1|member2|member3...
    """
    return '|'.join([urllib.quote_plus(a or '') for a in args])
  
  
  def _split_token_parts(blob):
    """Extracts and unescapes fields from the provided binary string.
  
    Reverses the packing performed by _join_token_parts. Used to extract
    the members of a token object.
  
    Note: An empty string from the blob will be interpreted as None.
  
    Args:
      blob: str A string of the form 1x|member1|member2|member3 as created
          by _join_token_parts
  
    Returns:
      A list of unescaped strings.
    """
    return [urllib.unquote_plus(part) or None for part in blob.split('|')]
  
  
  def token_to_blob(token):
    """Serializes the token data as a string for storage in a datastore.
  
    Supported token classes: ClientLoginToken, AuthSubToken, SecureAuthSubToken,
    OAuthRsaToken, and OAuthHmacToken, TwoLeggedOAuthRsaToken,
    TwoLeggedOAuthHmacToken.
  
    Args:
      token: A token object which must be of one of the supported token classes.
  
    Raises:
      UnsupportedTokenType if the token is not one of the supported token
      classes listed above.
  
    Returns:
      A string represenging this token. The string can be converted back into
      an equivalent token object using token_from_blob. Note that any members
      which are set to '' will be set to None when the token is deserialized
      by token_from_blob.
    """
    if isinstance(token, ClientLoginToken):
      return _join_token_parts('1c', token.token_string)
    # Check for secure auth sub type first since it is a subclass of
    # AuthSubToken.
    elif isinstance(token, SecureAuthSubToken):
      return _join_token_parts('1s', token.token_string, token.rsa_private_key,
                               *token.scopes)
    elif isinstance(token, AuthSubToken):
      return _join_token_parts('1a', token.token_string, *token.scopes)
    elif isinstance(token, TwoLeggedOAuthRsaToken):
      return _join_token_parts(
          '1rtl', token.consumer_key, token.rsa_private_key, token.requestor_id)
    elif isinstance(token, TwoLeggedOAuthHmacToken):
      return _join_token_parts(
          '1htl', token.consumer_key, token.consumer_secret, token.requestor_id)
    # Check RSA OAuth token first since the OAuthRsaToken is a subclass of
    # OAuthHmacToken.
    elif isinstance(token, OAuthRsaToken):
      return _join_token_parts(
          '1r', token.consumer_key, token.rsa_private_key, token.token,
          token.token_secret, str(token.auth_state), token.next,
          token.verifier)
    elif isinstance(token, OAuthHmacToken):
      return _join_token_parts(
          '1h', token.consumer_key, token.consumer_secret, token.token,
          token.token_secret, str(token.auth_state), token.next,
          token.verifier)
    else:
      raise UnsupportedTokenType(
          'Unable to serialize token of type %s' % type(token))
  
  
  TokenToBlob = token_to_blob
  
  
  def token_from_blob(blob):
    """Deserializes a token string from the datastore back into a token object.
  
    Supported token classes: ClientLoginToken, AuthSubToken, SecureAuthSubToken,
    OAuthRsaToken, and OAuthHmacToken, TwoLeggedOAuthRsaToken,
    TwoLeggedOAuthHmacToken.
  
    Args:
      blob: string created by token_to_blob.
  
    Raises:
      UnsupportedTokenType if the token is not one of the supported token
      classes listed above.
  
    Returns:
      A new token object with members set to the values serialized in the
      blob string. Note that any members which were set to '' in the original
      token will now be None.
    """
    parts = _split_token_parts(blob)
    if parts[0] == '1c':
      return ClientLoginToken(parts[1])
    elif parts[0] == '1a':
      return AuthSubToken(parts[1], parts[2:])
    elif parts[0] == '1s':
      return SecureAuthSubToken(parts[1], parts[2], parts[3:])
    elif parts[0] == '1rtl':
      return TwoLeggedOAuthRsaToken(parts[1], parts[2], parts[3])
    elif parts[0] == '1htl':
      return TwoLeggedOAuthHmacToken(parts[1], parts[2], parts[3])
    elif parts[0] == '1r':
      auth_state = int(parts[5])
      return OAuthRsaToken(parts[1], parts[2], parts[3], parts[4], auth_state,
                           parts[6], parts[7])
    elif parts[0] == '1h':
      auth_state = int(parts[5])
      return OAuthHmacToken(parts[1], parts[2], parts[3], parts[4], auth_state,
                            parts[6], parts[7])
    else:
      raise UnsupportedTokenType(
          'Unable to deserialize token with type marker of %s' % parts[0])
  
  
  TokenFromBlob = token_from_blob
  
  
  def dump_tokens(tokens):
    return ','.join([token_to_blob(t) for t in tokens])
  
  
  def load_tokens(blob):
    return [token_from_blob(s) for s in blob.split(',')]
  
  
  def find_scopes_for_services(service_names=None):
    """Creates a combined list of scope URLs for the desired services.
  
    This method searches the AUTH_SCOPES dictionary.
    
    Args:
      service_names: list of strings (optional) Each name must be a key in the
                     AUTH_SCOPES dictionary. If no list is provided (None) then
                     the resulting list will contain all scope URLs in the
                     AUTH_SCOPES dict.
  
    Returns:
      A list of URL strings which are the scopes needed to access these services
      when requesting a token using AuthSub or OAuth.
    """
    result_scopes = []
    if service_names is None:
      for service_name, scopes in AUTH_SCOPES.iteritems():
        result_scopes.extend(scopes)
    else:
      for service_name in service_names:
        result_scopes.extend(AUTH_SCOPES[service_name])
    return result_scopes
  
  
  FindScopesForServices = find_scopes_for_services
  
  
  def ae_save(token, token_key):
    """Stores an auth token in the App Engine datastore.
  
    This is a convenience method for using the library with App Engine.
    Recommended usage is to associate the auth token with the current_user.
    If a user is signed in to the app using the App Engine users API, you
    can use
    gdata.gauth.ae_save(some_token, users.get_current_user().user_id())
    If you are not using the Users API you are free to choose whatever
    string you would like for a token_string.
  
    Args:
      token: an auth token object. Must be one of ClientLoginToken,
             AuthSubToken, SecureAuthSubToken, OAuthRsaToken, or OAuthHmacToken
             (see token_to_blob).
      token_key: str A unique identified to be used when you want to retrieve
                 the token. If the user is signed in to App Engine using the
                 users API, I recommend using the user ID for the token_key:
                 users.get_current_user().user_id()
    """
    import gdata.alt.app_engine
    key_name = ''.join(('gd_auth_token', token_key))
    return gdata.alt.app_engine.set_token(key_name, token_to_blob(token))
  
  
  AeSave = ae_save
  
  
  def ae_load(token_key):
    """Retrieves a token object from the App Engine datastore.
  
    This is a convenience method for using the library with App Engine.
    See also ae_save.
  
    Args:
      token_key: str The unique key associated with the desired token when it
                 was saved using ae_save.
  
    Returns:
      A token object if there was a token associated with the token_key or None
      if the key could not be found.
    """
    import gdata.alt.app_engine
    key_name = ''.join(('gd_auth_token', token_key))
    token_string = gdata.alt.app_engine.get_token(key_name)
    if token_string is not None:
      return token_from_blob(token_string)
    else:
      return None
  
  
  AeLoad = ae_load
  
  
  def ae_delete(token_key):
    """Removes the token object from the App Engine datastore."""
    import gdata.alt.app_engine
    key_name = ''.join(('gd_auth_token', token_key))
    gdata.alt.app_engine.delete_token(key_name)
  
  
  AeDelete = ae_delete
  