twitter.py

#!/usr/bin/python
#
# Copyright 2007 Google Inc. All Rights Reserved.

'''A library that provides a python interface to the Twitter API'''

__author__ = 'dewitt@google.com'
__version__ = '0.5'


import base64
import md5
import os
from django.utils import simplejson
import sys
import tempfile
import time
import urllib
import urllib2
import urlparse
import twitter

from google.appengine.ext import db
from google.appengine.api import urlfetch

class TwitterError(Exception):
  '''Base class for Twitter errors'''


class Status(object):
  '''A class representing the Status structure used by the twitter API.

  The Status structure exposes the following properties:

    status.created_at
    status.created_at_in_seconds # read only
    status.id
    status.text
    status.relative_created_at # read only
    status.user
  '''
  def __init__(self,
               created_at=None,
               id=None,
               text=None,
               user=None,
               from_user=None,
               from_user_id=None,
               source=None,
               profile_image_url=None,
               now=None):
    '''An object to hold a Twitter status message.

    This class is normally instantiated by the twitter.Api class and
    returned in a sequence.

    Note: Dates are posted in the form "Sat Jan 27 04:17:38 +0000 2007"

    Args:
      created_at: The time this status message was posted
      id: The unique id of this status message
      text: The text of this status message
      relative_created_at:
        A human readable string representing the posting time
      user:
        A twitter.User instance representing the person posting the message
      now:
        The current time, if the client choses to set it.  Defaults to the
        wall clock time.
    '''
    self.created_at = created_at
    self.id = id
    self.text = text
    self.user = user
    self.from_user = from_user
    self.from_user_id = from_user_id
    self.to_user = from_user
    self.to_user_id = from_user_id
    self.source = source
    self.profile_image_url = profile_image_url
    self.now = now

  def GetCreatedAt(self):
    '''Get the time this status message was posted.

    Returns:
      The time this status message was posted
    '''
    return self._created_at

  def SetCreatedAt(self, created_at):
    '''Set the time this status message was posted.

    Args:
      created_at: The time this status message was created
    '''
    self._created_at = created_at

  created_at = property(GetCreatedAt, SetCreatedAt,
                        doc='The time this status message was posted.')

  def GetCreatedAtInSeconds(self):
    '''Get the time this status message was posted, in seconds since the epoch.

    Returns:
      The time this status message was posted, in seconds since the epoch.
    '''
    # api.Search returns times in another format; use that for now
    return time.mktime(time.strptime(self.created_at, '%a, %d %b %Y %H:%M:%S +0000'))
    #return time.mktime(time.strptime(self.created_at, '%a %b %d %H:%M:%S +0000 %Y'))

  created_at_in_seconds = property(GetCreatedAtInSeconds,
                                   doc="The time this status message was "
                                       "posted, in seconds since the epoch")

  def GetId(self):
    '''Get the unique id of this status message.

    Returns:
      The unique id of this status message
    '''
    return self._id

  def SetId(self, id):
    '''Set the unique id of this status message.

    Args:
      id: The unique id of this status message
    '''
    self._id = id

  id = property(GetId, SetId,
                doc='The unique id of this status message.')

  def GetText(self):
    '''Get the text of this status message.

    Returns:
      The text of this status message.
    '''
    return self._text

  def SetText(self, text):
    '''Set the text of this status message.

    Args:
      text: The text of this status message
    '''
    self._text = text

  text = property(GetText, SetText,
                  doc='The text of this status message')

  def GetRelativeCreatedAt(self):
    '''Get a human redable string representing the posting time

    Returns:
      A human readable string representing the posting time
    '''
    fudge = 1.25
    delta  = int(self.now) - int(self.created_at_in_seconds)

    if delta < (1 * fudge):
      return 'about a second ago'
    elif delta < (60 * (1/fudge)):
      return 'about %d seconds ago' % (delta)
    elif delta < (60 * fudge):
      return 'about a minute ago'
    elif delta < (60 * 60 * (1/fudge)):
      return 'about %d minutes ago' % (delta / 60)
    elif delta < (60 * 60 * fudge):
      return 'about an hour ago'
    elif delta < (60 * 60 * 24 * (1/fudge)):
      return 'about %d hours ago' % (delta / (60 * 60))
    elif delta < (60 * 60 * 24 * fudge):
      return 'about a day ago'
    else:
      return 'about %d days ago' % (delta / (60 * 60 * 24))
#     if delta < (1 * fudge):
#       return 'for nogle sekunder siden'
#     elif delta < (60 * (1/fudge)):
#       return 'for %d sekunder siden' % (delta)
#     elif delta < (60 * fudge):
#       return 'for omkring et minut siden'
#     elif delta < (60 * 60 * (1/fudge)):
#       return 'for %d minutter siden' % (delta / 60)
#     elif delta < (60 * 60 * fudge):
#       return 'for omkring en time siden'
#     elif delta < (60 * 60 * 24 * (1/fudge)):
#       return 'for %d timer siden' % (delta / (60 * 60))
#     elif delta < (60 * 60 * 24 * fudge):
#       return 'for omkring en dag siden'
#     else:
#       return 'for %d dage siden' % (delta / (60 * 60 * 24))

  relative_created_at = property(GetRelativeCreatedAt,
                                 doc='Get a human readable string representing'
                                     'the posting time')

  def GetUser(self):
    '''Get a twitter.User reprenting the entity posting this status message.

    Returns:
      A twitter.User reprenting the entity posting this status message
    '''
    return self._user

  def SetUser(self, user):
    '''Set a twitter.User reprenting the entity posting this status message.

    Args:
      user: A twitter.User reprenting the entity posting this status message
    '''
    self._user = user

  user = property(GetUser, SetUser,
                  doc='A twitter.User reprenting the entity posting this '
                      'status message')

  def GetNow(self):
    '''Get the wallclock time for this status message.

    Used to calculate relative_created_at.  Defaults to the time
    the object was instantiated.

    Returns:
      Whatever the status instance believes the current time to be,
      in seconds since the epoch.
    '''
    if self._now is None:
      self._now = time.mktime(time.gmtime())
    return self._now

  def SetNow(self, now):
    '''Set the wallclock time for this status message.

    Used to calculate relative_created_at.  Defaults to the time
    the object was instantiated.

    Args:
      now: The wallclock time for this instance.
    '''
    self._now = now

  now = property(GetNow, SetNow,
                 doc='The wallclock time for this status instance.')


  def __ne__(self, other):
    return not self.__eq__(other)

  def __eq__(self, other):
    try:
      return other and \
             self.created_at == other.created_at and \
             self.id == other.id and \
             self.text == other.text and \
             self.user == other.user
    except AttributeError:
      return False

  def __str__(self):
    '''A string representation of this twitter.Status instance.

    The return value is the same as the JSON string representation.

    Returns:
      A string representation of this twitter.Status instance.
    '''
    return self.AsJsonString()

  def AsJsonString(self):
    '''A JSON string representation of this twitter.Status instance.

    Returns:
      A JSON string representation of this twitter.Status instance
   '''
    return simplejson.dumps(self.AsDict(), sort_keys=True)

  def AsDict(self):
    '''A dict representation of this twitter.Status instance.

    The return value uses the same key names as the JSON representation.

    Return:
      A dict representing this twitter.Status instance
    '''
    data = {}
    if self.created_at:
      data['created_at'] = self.created_at
    if self.id:
      data['id'] = self.id
    if self.text:
      data['text'] = self.text
    if self.user:
      data['user'] = self.user.AsDict()
    return data

  @staticmethod
  def NewFromJsonDict(data):
    '''Create a new instance based on a JSON dict.

    Args:
      data: A JSON dict, as converted from the JSON in the twitter API
    Returns:
      A twitter.Status instance
    '''
    if 'user' in data:
      user = User.NewFromJsonDict(data['user'])
    else:
      user = None
    return Status(created_at=data.get('created_at', None),
                  id=data.get('id', None),
                  text=data.get('text', None),
                  from_user=data.get('from_user', None),
                  from_user_id=data.get('from_user_id', None),
                  source=data.get('source', None),
                  profile_image_url=data.get('profile_image_url', None),
                  user=user)


class User(object):
  '''A class representing the User structure used by the twitter API.

  The User structure exposes the following properties:

    user.id
    user.name
    user.screen_name
    user.location
    user.description
    user.profile_image_url
    user.url
    user.status
  '''
  def __init__(self,
               id=None,
               name=None,
               screen_name=None,
               location=None,
               description=None,
               profile_image_url=None,
               url=None,
               status=None):
    self.id = id
    self.name = name
    self.screen_name = screen_name
    self.location = location
    self.description = description
    self.profile_image_url = profile_image_url
    self.url = url
    self.status = status


  def GetId(self):
    '''Get the unique id of this user.

    Returns:
      The unique id of this user
    '''
    return self._id

  def SetId(self, id):
    '''Set the unique id of this user.

    Args:
      id: The unique id of this user.
    '''
    self._id = id

  id = property(GetId, SetId,
                doc='The unique id of this user.')

  def GetName(self):
    '''Get the real name of this user.

    Returns:
      The real name of this user
    '''
    return self._name

  def SetName(self, name):
    '''Set the real name of this user.

    Args:
      name: The real name of this user
    '''
    self._name = name

  name = property(GetName, SetName,
                  doc='The real name of this user.')

  def GetScreenName(self):
    '''Get the short username of this user.

    Returns:
      The short username of this user
    '''
    return self._screen_name

  def SetScreenName(self, screen_name):
    '''Set the short username of this user.

    Args:
      screen_name: the short username of this user
    '''
    self._screen_name = screen_name

  screen_name = property(GetScreenName, SetScreenName,
                         doc='The short username of this user.')

  def GetLocation(self):
    '''Get the geographic location of this user.

    Returns:
      The geographic location of this user
    '''
    return self._location

  def SetLocation(self, location):
    '''Set the geographic location of this user.

    Args:
      location: The geographic location of this user
    '''
    self._location = location

  location = property(GetLocation, SetLocation,
                      doc='The geographic location of this user.')

  def GetDescription(self):
    '''Get the short text description of this user.

    Returns:
      The short text description of this user
    '''
    return self._description

  def SetDescription(self, description):
    '''Set the short text description of this user.

    Args:
      description: The short text description of this user
    '''
    self._description = description

  description = property(GetDescription, SetDescription,
                         doc='The short text description of this user.')

  def GetUrl(self):
    '''Get the homepage url of this user.

    Returns:
      The homepage url of this user
    '''
    return self._url

  def SetUrl(self, url):
    '''Set the homepage url of this user.

    Args:
      url: The homepage url of this user
    '''
    self._url = url

  url = property(GetUrl, SetUrl,
                 doc='The homepage url of this user.')

  def GetProfileImageUrl(self):
    '''Get the url of the thumbnail of this user.

    Returns:
      The url of the thumbnail of this user
    '''
    return self._profile_image_url

  def SetProfileImageUrl(self, profile_image_url):
    '''Set the url of the thumbnail of this user.

    Args:
      profile_image_url: The url of the thumbnail of this user
    '''
    self._profile_image_url = profile_image_url

  profile_image_url= property(GetProfileImageUrl, SetProfileImageUrl,
                              doc='The url of the thumbnail of this user.')

  def GetStatus(self):
    '''Get the latest twitter.Status of this user.

    Returns:
      The latest twitter.Status of this user
    '''
    return self._status

  def SetStatus(self, status):
    '''Set the latest twitter.Status of this user.

    Args:
      status: The latest twitter.Status of this user
    '''
    self._status = status

  status = property(GetStatus, SetStatus,
                  doc='The latest twitter.Status of this user.')

  def __ne__(self, other):
    return not self.__eq__(other)

  def __eq__(self, other):
    try:
      return other and \
             self.id == other.id and \
             self.name == other.name and \
             self.screen_name == other.screen_name and \
             self.location == other.location and \
             self.description == other.description and \
             self.profile_image_url == other.profile_image_url and \
             self.url == other.url and \
             self.status == other.status
    except AttributeError:
      return False

  def __str__(self):
    '''A string representation of this twitter.User instance.

    The return value is the same as the JSON string representation.

    Returns:
      A string representation of this twitter.User instance.
    '''
    return self.AsJsonString()

  def AsJsonString(self):
    '''A JSON string representation of this twitter.User instance.

    Returns:
      A JSON string representation of this twitter.User instance
   '''
    return simplejson.dumps(self.AsDict(), sort_keys=True)

  def AsDict(self):
    '''A dict representation of this twitter.User instance.

    The return value uses the same key names as the JSON representation.

    Return:
      A dict representing this twitter.User instance
    '''
    data = {}
    if self.id:
      data['id'] = self.id
    if self.name:
      data['name'] = self.name
    if self.screen_name:
      data['screen_name'] = self.screen_name
    if self.location:
      data['location'] = self.location
    if self.description:
      data['description'] = self.description
    if self.profile_image_url:
      data['profile_image_url'] = self.profile_image_url
    if self.url:
      data['url'] = self.url
    if self.status:
      data['status'] = self.status.AsDict()
    return data

  @staticmethod
  def NewFromJsonDict(data):
    '''Create a new instance based on a JSON dict.

    Args:
      data: A JSON dict, as converted from the JSON in the twitter API
    Returns:
      A twitter.User instance
    '''
    if 'status' in data:
      status = Status.NewFromJsonDict(data['status'])
    else:
      status = None
    return User(id=data.get('id', None),
                name=data.get('name', None),
                screen_name=data.get('screen_name', None),
                location=data.get('location', None),
                description=data.get('description', None),
                profile_image_url=data.get('profile_image_url', None),
                url=data.get('url', None),
                status=status)

class DirectMessage(object):
  '''A class representing the DirectMessage structure used by the twitter API.

  The DirectMessage structure exposes the following properties:

    direct_message.id
    direct_message.created_at
    direct_message.created_at_in_seconds # read only
    direct_message.sender_id
    direct_message.sender_screen_name
    direct_message.recipient_id
    direct_message.recipient_screen_name
    direct_message.text
  '''

  def __init__(self,
               id=None,
               created_at=None,
               sender_id=None,
               sender_screen_name=None,
               recipient_id=None,
               recipient_screen_name=None,
               text=None):
    '''An object to hold a Twitter direct message.

    This class is normally instantiated by the twitter.Api class and
    returned in a sequence.

    Note: Dates are posted in the form "Sat Jan 27 04:17:38 +0000 2007"

    Args:
      id: The unique id of this direct message
      created_at: The time this direct message was posted
      sender_id: The id of the twitter user that sent this message
      sender_screen_name: The name of the twitter user that sent this message
      recipient_id: The id of the twitter that received this message
      recipient_screen_name: The name of the twitter that received this message
      text: The text of this direct message
    '''
    self.id = id
    self.created_at = created_at
    self.sender_id = sender_id
    self.sender_screen_name = sender_screen_name
    self.recipient_id = recipient_id
    self.recipient_screen_name = recipient_screen_name
    self.text = text

  def GetId(self):
    '''Get the unique id of this direct message.

    Returns:
      The unique id of this direct message
    '''
    return self._id

  def SetId(self, id):
    '''Set the unique id of this direct message.

    Args:
      id: The unique id of this direct message
    '''
    self._id = id

  id = property(GetId, SetId,
                doc='The unique id of this direct message.')

  def GetCreatedAt(self):
    '''Get the time this direct message was posted.

    Returns:
      The time this direct message was posted
    '''
    return self._created_at

  def SetCreatedAt(self, created_at):
    '''Set the time this direct message was posted.

    Args:
      created_at: The time this direct message was created
    '''
    self._created_at = created_at

  created_at = property(GetCreatedAt, SetCreatedAt,
                        doc='The time this direct message was posted.')

  def GetCreatedAtInSeconds(self):
    '''Get the time this direct message was posted, in seconds since the epoch.

    Returns:
      The time this direct message was posted, in seconds since the epoch.
    '''
    return time.mktime(time.strptime(self.created_at, '%a %b %d %H:%M:%S +0000 %Y'))

  created_at_in_seconds = property(GetCreatedAtInSeconds,
                                   doc="The time this direct message was "
                                       "posted, in seconds since the epoch")

  def GetSenderId(self):
    '''Get the unique sender id of this direct message.

    Returns:
      The unique sender id of this direct message
    '''
    return self._sender_id

  def SetSenderId(self, sender_id):
    '''Set the unique sender id of this direct message.

    Args:
      sender id: The unique sender id of this direct message
    '''
    self._sender_id = sender_id

  sender_id = property(GetSenderId, SetSenderId,
                doc='The unique sender id of this direct message.')

  def GetSenderScreenName(self):
    '''Get the unique sender screen name of this direct message.

    Returns:
      The unique sender screen name of this direct message
    '''
    return self._sender_screen_name

  def SetSenderScreenName(self, sender_screen_name):
    '''Set the unique sender screen name of this direct message.

    Args:
      sender_screen_name: The unique sender screen name of this direct message
    '''
    self._sender_screen_name = sender_screen_name

  sender_screen_name = property(GetSenderScreenName, SetSenderScreenName,
                doc='The unique sender screen name of this direct message.')

  def GetRecipientId(self):
    '''Get the unique recipient id of this direct message.

    Returns:
      The unique recipient id of this direct message
    '''
    return self._recipient_id

  def SetRecipientId(self, recipient_id):
    '''Set the unique recipient id of this direct message.

    Args:
      recipient id: The unique recipient id of this direct message
    '''
    self._recipient_id = recipient_id

  recipient_id = property(GetRecipientId, SetRecipientId,
                doc='The unique recipient id of this direct message.')

  def GetRecipientScreenName(self):
    '''Get the unique recipient screen name of this direct message.

    Returns:
      The unique recipient screen name of this direct message
    '''
    return self._recipient_screen_name

  def SetRecipientScreenName(self, recipient_screen_name):
    '''Set the unique recipient screen name of this direct message.

    Args:
      recipient_screen_name: The unique recipient screen name of this direct message
    '''
    self._recipient_screen_name = recipient_screen_name

  recipient_screen_name = property(GetRecipientScreenName, SetRecipientScreenName,
                doc='The unique recipient screen name of this direct message.')

  def GetText(self):
    '''Get the text of this direct message.

    Returns:
      The text of this direct message.
    '''
    return self._text

  def SetText(self, text):
    '''Set the text of this direct message.

    Args:
      text: The text of this direct message
    '''
    self._text = text

  text = property(GetText, SetText,
                  doc='The text of this direct message')

  def __ne__(self, other):
    return not self.__eq__(other)

  def __eq__(self, other):
    try:
      return other and \
          self.id == other.id and \
          self.created_at == other.created_at and \
          self.sender_id == other.sender_id and \
          self.sender_screen_name == other.sender_screen_name and \
          self.recipient_id == other.recipient_id and \
          self.recipient_screen_name == other.recipient_screen_name and \
          self.text == other.text
    except AttributeError:
      return False

  def __str__(self):
    '''A string representation of this twitter.DirectMessage instance.

    The return value is the same as the JSON string representation.

    Returns:
      A string representation of this twitter.DirectMessage instance.
    '''
    return self.AsJsonString()

  def AsJsonString(self):
    '''A JSON string representation of this twitter.DirectMessage instance.

    Returns:
      A JSON string representation of this twitter.DirectMessage instance
   '''
    return simplejson.dumps(self.AsDict(), sort_keys=True)

  def AsDict(self):
    '''A dict representation of this twitter.DirectMessage instance.

    The return value uses the same key names as the JSON representation.

    Return:
      A dict representing this twitter.DirectMessage instance
    '''
    data = {}
    if self.id:
      data['id'] = self.id
    if self.created_at:
      data['created_at'] = self.created_at
    if self.sender_id:
      data['sender_id'] = self.sender_id
    if self.sender_screen_name:
      data['sender_screen_name'] = self.sender_screen_name
    if self.recipient_id:
      data['recipient_id'] = self.recipient_id
    if self.recipient_screen_name:
      data['recipient_screen_name'] = self.recipient_screen_name
    if self.text:
      data['text'] = self.text
    return data

  @staticmethod
  def NewFromJsonDict(data):
    '''Create a new instance based on a JSON dict.

    Args:
      data: A JSON dict, as converted from the JSON in the twitter API
    Returns:
      A twitter.DirectMessage instance
    '''
    return DirectMessage(created_at=data.get('created_at', None),
                         recipient_id=data.get('recipient_id', None),
                         sender_id=data.get('sender_id', None),
                         text=data.get('text', None),
                         sender_screen_name=data.get('sender_screen_name', None),
                         id=data.get('id', None),
                         recipient_screen_name=data.get('recipient_screen_name', None))

class Api(object):
  '''A python interface into the Twitter API

  By default, the Api caches results for 1 minute.

  Example usage:

    To create an instance of the twitter.Api class, with no authentication:

      >>> import twitter
      >>> api = twitter.Api()

    To fetch the most recently posted public twitter status messages:

      >>> statuses = api.GetPublicTimeline()
      >>> print [s.user.name for s in statuses]
      [u'DeWitt', u'Kesuke Miyagi', u'ev', u'Buzz Andersen', u'Biz Stone'] #...

    To fetch a single user's public status messages, where "user" is either
    a Twitter "short name" or their user id.

      >>> statuses = api.GetUserTimeline(user)
      >>> print [s.text for s in statuses]

    To use authentication, instantiate the twitter.Api class with a
    username and password:

      >>> api = twitter.Api(username='twitter user', password='twitter pass')

    To fetch your friends (after being authenticated):

      >>> users = api.GetFriends()
      >>> print [u.name for u in users]

    To post a twitter status message (after being authenticated):

      >>> status = api.PostUpdate('I love python-twitter!')
      >>> print status.text
      I love python-twitter!

    There are many other methods, including:

      >>> api.PostDirectMessage(user, text)
      >>> api.GetUser(user)
      >>> api.GetReplies()
      >>> api.GetUserTimeline(user)
      >>> api.GetStatus(id)
      >>> api.DestroyStatus(id)
      >>> api.GetFriendsTimeline(user)
      >>> api.GetFriends(user)
      >>> api.GetFollowers()
      >>> api.GetFeatured()
      >>> api.GetDirectMessages()
      >>> api.PostDirectMessage(user, text)
      >>> api.DestroyDirectMessage(id)
      >>> api.DestroyFriendship(user)
      >>> api.CreateFriendship(user)
  '''

  DEFAULT_CACHE_TIMEOUT = 60 # cache for 1 minute

  _API_REALM = 'Twitter API'

  def __init__(self,
               username=None,
               password=None,
               input_encoding=None,
               request_headers=None):
    '''Instantiate a new twitter.Api object.

    Args:
      username: The username of the twitter account.  [optional]
      password: The password for the twitter account. [optional]
      input_encoding: The encoding used to encode input strings. [optional]
      request_header: A dictionary of additional HTTP request headers. [optional]
    '''
    self._cache = _DbCache()
    self._urllib = urllib2
    self._cache_timeout = Api.DEFAULT_CACHE_TIMEOUT
    self._InitializeRequestHeaders(request_headers)
    self._InitializeUserAgent()
    self._input_encoding = input_encoding
    self.SetCredentials(username, password)

  def GetPublicTimeline(self, since_id=None):
    '''Fetch the sequnce of public twitter.Status message for all users.

    Args:
      since_id:
        Returns only public statuses with an ID greater than (that is,
        more recent than) the specified ID. [Optional]

    Returns:
      An sequence of twitter.Status instances, one for each message
    '''
    parameters = {}
    if since_id:
      parameters['since_id'] = since_id
    url = 'http://twitter.com/statuses/public_timeline.json'
    json = self._FetchUrl(url,  parameters=parameters)
    data = simplejson.loads(json)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetFriendsTimeline(self, user=None, since=None):
    '''Fetch the sequence of twitter.Status messages for a user's friends

    The twitter.Api instance must be authenticated if the user is private.

    Args:
      user:
        Specifies the ID or screen name of the user for whom to return
        the friends_timeline.  If unspecified, the username and password
        must be set in the twitter.Api instance.  [optional]
      since:
        Narrows the returned results to just those statuses created
        after the specified HTTP-formatted date. [optional]

    Returns:
      A sequence of twitter.Status instances, one for each message
    '''
    if user:
      url = 'http://twitter.com/statuses/friends_timeline/%s.json' % user
    elif not user and not self._username:
      raise TwitterError("User must be specified if API is not authenticated.")
    else:
      url = 'http://twitter.com/statuses/friends_timeline.json'
    parameters = {}
    if since:
      parameters['since'] = since
    json = self._FetchUrl(url, parameters=parameters)
    data = simplejson.loads(json)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetUserTimeline(self, user=None, count=None, since=None):
    '''Fetch the sequence of public twitter.Status messages for a single user.

    The twitter.Api instance must be authenticated if the user is private.

    Args:
      user:
        either the username (short_name) or id of the user to retrieve.  If
        not specified, then the current authenticated user is used. [optional]
      count: the number of status messages to retrieve [optional]
      since:
        Narrows the returned results to just those statuses created
        after the specified HTTP-formatted date. [optional]

    Returns:
      A sequence of twitter.Status instances, one for each message up to count
    '''
    try:
      if count:
        int(count)
    except:
      raise TwitterError("Count must be an integer")
    parameters = {}
    if count:
      parameters['count'] = count
    if since:
      parameters['since'] = since
    if user:
      url = 'http://twitter.com/statuses/user_timeline/%s.json' % user
    elif not user and not self._username:
      raise TwitterError("User must be specified if API is not authenticated.")
    else:
      url = 'http://twitter.com/statuses/user_timeline.json'
    json = self._FetchUrl(url, parameters=parameters)
    data = simplejson.loads(json)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetStatus(self, id):
    '''Returns a single status message.

    The twitter.Api instance must be authenticated if the status message is private.

    Args:
      id: The numerical ID of the status you're trying to retrieve.

    Returns:
      A twitter.Status instance representing that status message
    '''
    try:
      if id:
        int(id)
    except:
      raise TwitterError("id must be an integer")
    url = 'http://twitter.com/statuses/show/%s.json' % id
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    return Status.NewFromJsonDict(data)

  def DestroyStatus(self, id):
    '''Destroys the status specified by the required ID parameter.

    The twitter.Api instance must be authenticated and thee
    authenticating user must be the author of the specified status.

    Args:
      id: The numerical ID of the status you're trying to destroy.

    Returns:
      A twitter.Status instance representing the destroyed status message
    '''
    try:
      if id:
        int(id)
    except:
      raise TwitterError("id must be an integer")
    url = 'http://twitter.com/statuses/destroy/%s.json' % id
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    return Status.NewFromJsonDict(data)

  def PostUpdate(self, text):
    '''Post a twitter status message from the authenticated user.

    The twitter.Api instance must be authenticated.

    Args:
      text: The message text to be posted.  Must be less than 140 characters.

    Returns:
      A twitter.Status instance representing the message posted
    '''
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    if len(text) > 140:
      raise TwitterError("Text must be less than or equal to 140 characters.")
    url = 'http://twitter.com/statuses/update.json'
    data = {'status': text}
    json = self._FetchUrl(url, post_data=data)
    data = simplejson.loads(json)
    return Status.NewFromJsonDict(data)

  def GetReplies(self):
    '''Get a sequence of status messages representing the 20 most recent
    replies (status updates prefixed with @username) to the authenticating
    user.

    Returns:
      A sequence of twitter.Status instances, one for each reply to the user.
    '''
    url = 'http://twitter.com/statuses/replies.json'
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetFriends(self, user=None):
    '''Fetch the sequence of twitter.User instances, one for each friend.

    Args:
      user: the username or id of the user whose friends you are fetching.  If
      not specified, defaults to the authenticated user. [optional]

    The twitter.Api instance must be authenticated.

    Returns:
      A sequence of twitter.User instances, one for each friend
    '''
    if not self._username:
      raise TwitterError("twitter.Api instance must be authenticated")
    if user:
      url = 'http://twitter.com/statuses/friends/%s.json' % user
    else:
      url = 'http://twitter.com/statuses/friends.json'
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    return [User.NewFromJsonDict(x) for x in data]

  def GetFollowers(self):
    '''Fetch the sequence of twitter.User instances, one for each follower

    The twitter.Api instance must be authenticated.

    Returns:
      A sequence of twitter.User instances, one for each follower
    '''
    if not self._username:
      raise TwitterError("twitter.Api instance must be authenticated")
    url = 'http://twitter.com/statuses/followers.json'
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    return [User.NewFromJsonDict(x) for x in data]

  def GetFeatured(self):
    '''Fetch the sequence of twitter.User instances featured on twitter.com

    The twitter.Api instance must be authenticated.

    Returns:
      A sequence of twitter.User instances
    '''
    url = 'http://twitter.com/statuses/featured.json'
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    return [User.NewFromJsonDict(x) for x in data]

  def GetUser(self, user):
    '''Returns a single user.

    The twitter.Api instance must be authenticated.

    Args:
      user: The username or id of the user to retrieve.

    Returns:
      A twitter.User instance representing that user
    '''
    url = 'http://twitter.com/users/show/%s.json' % user
    json = self._FetchUrl(url)
    data = simplejson.loads(json)

    return User.NewFromJsonDict(data)

  def GetDirectMessages(self, since=None):
    '''Returns a list of the direct messages sent to the authenticating user.

    The twitter.Api instance must be authenticated.

    Args:
      since:
        Narrows the returned results to just those statuses created
        after the specified HTTP-formatted date. [optional]

    Returns:
      A sequence of twitter.DirectMessage instances
    '''
    url = 'http://twitter.com/direct_messages.json'
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    parameters = {}
    if since:
      parameters['since'] = since
    json = self._FetchUrl(url, parameters=parameters)
    data = simplejson.loads(json)
    return [DirectMessage.NewFromJsonDict(x) for x in data]

  def PostDirectMessage(self, user, text):
    '''Post a twitter direct message from the authenticated user

    The twitter.Api instance must be authenticated.

    Args:
      user: The ID or screen name of the recipient user.
      text: The message text to be posted.  Must be less than 140 characters.

    Returns:
      A twitter.DirectMessage instance representing the message posted
    '''
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    url = 'http://twitter.com/direct_messages/new.json'
    data = {'text': text, 'user': user}
    json = self._FetchUrl(url, post_data=data)
    data = simplejson.loads(json)
    return DirectMessage.NewFromJsonDict(data)

  def DestroyDirectMessage(self, id):
    '''Destroys the direct message specified in the required ID parameter.

    The twitter.Api instance must be authenticated, and the
    authenticating user must be the recipient of the specified direct
    message.

    Args:
      id: The id of the direct message to be destroyed

    Returns:
      A twitter.DirectMessage instance representing the message destroyed
    '''
    url = 'http://twitter.com/direct_messages/destroy/%s.json' % id
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    return DirectMessage.NewFromJsonDict(data)

  def CreateFriendship(self, user):
    '''Befriends the user specified in the user parameter as the authenticating user.

    The twitter.Api instance must be authenticated.

    Args:
      The ID or screen name of the user to befriend.
    Returns:
      A twitter.User instance representing the befriended user.
    '''
    url = 'http://twitter.com/friendships/create/%s.json' % user
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    return User.NewFromJsonDict(data)

  def DestroyFriendship(self, user):
    '''Discontinues friendship with the user specified in the user parameter.

    The twitter.Api instance must be authenticated.

    Args:
      The ID or screen name of the user  with whom to discontinue friendship.
    Returns:
      A twitter.User instance representing the discontinued friend.
    '''
    url = 'http://twitter.com/friendships/destroy/%s.json' % user
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    return User.NewFromJsonDict(data)

  def SetCredentials(self, username, password):
    '''Set the username and password for this instance

    Args:
      username: The twitter username.
      password: The twitter password.
    '''
    self._username = username
    self._password = password

  def ClearCredentials(self):
    '''Clear the username and password for this instance
    '''
    self._username = None
    self._password = None

  def SetCache(self, cache):
    '''Override the default cache.  Set to None to prevent caching.

    Args:
      cache: an instance that supports the same API as the  twitter._FileCache
    '''
    self._cache = cache

  def SetUrllib(self, urllib):
    '''Override the default urllib implementation.

    Args:
      urllib: an instance that supports the same API as the urllib2 module
    '''
    self._urllib = urllib

  def SetCacheTimeout(self, cache_timeout):
    '''Override the default cache timeout.

    Args:
      cache_timeout: time, in seconds, that responses should be reused.
    '''
    self._cache_timeout = cache_timeout

  def SetUserAgent(self, user_agent):
    '''Override the default user agent

    Args:
      user_agent: a string that should be send to the server as the User-agent
    '''
    self._request_headers['User-Agent'] = user_agent

  def SetXTwitterHeaders(self, client, url, version):
    '''Set the X-Twitter HTTP headers that will be sent to the server.

    Args:
      client:
         The client name as a string.  Will be sent to the server as
         the 'X-Twitter-Client' header.
      url:
         The URL of the meta.xml as a string.  Will be sent to the server
         as the 'X-Twitter-Client-URL' header.
      version:
         The client version as a string.  Will be sent to the server
         as the 'X-Twitter-Client-Version' header.
    '''
    self._request_headers['X-Twitter-Client'] = client
    self._request_headers['X-Twitter-Client-URL'] = url
    self._request_headers['X-Twitter-Client-Version'] = version

  def _BuildUrl(self, url, path_elements=None, extra_params=None):
    # Break url into consituent parts
    (scheme, netloc, path, params, query, fragment) = urlparse.urlparse(url)

    # Add any additional path elements to the path
    if path_elements:
      # Filter out the path elements that have a value of None
      p = [i for i in path_elements if i]
      if not path.endswith('/'):
        path += '/'
      path += '/'.join(p)

    # Add any additional query parameters to the query string
    if extra_params and len(extra_params) > 0:
      extra_query = self._EncodeParameters(extra_params)
      # Add it to the existing query
      if query:
        query += '&' + extra_query
      else:
        query = extra_query

    # Return the rebuilt URL
    return urlparse.urlunparse((scheme, netloc, path, params, query, fragment))

  def _InitializeRequestHeaders(self, request_headers):
    if request_headers:
      self._request_headers = request_headers
    else:
      self._request_headers = {}

  def _InitializeUserAgent(self):
    user_agent = 'Python-urllib/%s (python-twitter/%s)' % \
                 (self._urllib.__version__, twitter.__version__)
    self.SetUserAgent(user_agent)

  def _AddAuthorizationHeader(self, username, password):
    if username and password:
      basic_auth = base64.encodestring('%s:%s' % (username, password))[:-1]
      self._request_headers['Authorization'] = 'Basic %s' % basic_auth

  def _RemoveAuthorizationHeader(self):
    if self._request_headers and 'Authorization' in self._request_headers:
      del self._request_headers['Authorization']


  def _Encode(self, s):
    if self._input_encoding:
      return unicode(s, self._input_encoding).encode('utf-8')
    else:
      return unicode(s).encode('utf-8')

  def _EncodeParameters(self, parameters):
    '''Return a string in key=value&key=value form

    Values of None are not included in the output string.

    Args:
      parameters:
        A dict of (key, value) tuples, where value is encoded as
        specified by self._encoding
    Returns:
      A URL-encoded string in "key=value&key=value" form
    '''
    if parameters is None:
      return None
    else:
      return urllib.urlencode(dict([(k, self._Encode(v)) for k, v in parameters.items() if v is not None]))

  def _EncodePostData(self, post_data):
    '''Return a string in key=value&key=value form

    Values are assumed to be encoded in the format specified by self._encoding,
    and are subsequently URL encoded.

    Args:
      post_data:
        A dict of (key, value) tuples, where value is encoded as
        specified by self._encoding
    Returns:
      A URL-encoded string in "key=value&key=value" form
    '''
    if post_data is None:
      return None
    else:
      return urllib.urlencode(dict([(k, self._Encode(v)) for k, v in post_data.items()]))

  def _FetchUrl(self,
                url,
                post_data=None,
                parameters=None,
                no_cache=None):
    """Fetch a URL, optionally caching for a specified time.

    Args:
      url: The URL to retrieve
      data: A dict of (str, unicode) key value pairs.  If set, POST will be used.
      parameters: A dict of key/value pairs that should added to
                  the query string. [OPTIONAL]
      username: A HTTP Basic Auth username for this request
      username: A HTTP Basic Auth password for this request
      no_cache: If true, overrides the cache on the current request

    Returns:
      A string containing the body of the response.
    """
    # Add key/value parameters to the query string of the url
    url = self._BuildUrl(url, extra_params=parameters)
    encoded_post_data = self._EncodePostData(post_data)
    result = urlfetch.fetch(url, payload=encoded_post_data, method=post_data and urlfetch.POST or urlfetch.GET, headers=self._request_headers)
    return result.content

  def Search(self, terms=None, from_user=None, to_user=None, hashtag=None, since_id=None, lang=None):
    '''Fetch the public twitter.Status messages hits for search terms.
    
    Uses the Twitter Search API:
    http://twitter.com/api
    
    Args:
    terms: a String of search terms separated by spaces
    Returns public statuses containing those terms
    from_user: the username of the sender
    to_user: the username of the recipient
    hashtag: containing a #tag
    since_id: only newer tweets since the specified id
    lang: the language desired (i.e. en for english)
    
    Returns:
    A sequence of twitter.Status instances, one for each message
    '''
    
    url = 'http://search.twitter.com/search.json'
    
    query = []
    if terms:
      query.append(terms)
    if from_user:
      query.append("from%%3A%s" % from_user)
    if to_user:
      query.append("to%%3A%s" % to_user)
    if hashtag:
      query.append("%%23%s" % hashtag)

    if not query:
      return None

    # the query is the first of several possible parameters
    params = {'q': "+".join(query)}
    if since_id:
      params['since_id'] = since_id
    if lang:
      params['lang'] = lang

    json = self._FetchUrl(url,  parameters=params)
    data = simplejson.loads(json)
    # data contains: results, (all parameters used),
    # results_per_page, query, total, max_id, and page
    return [Status.NewFromJsonDict(x) for x in data['results']] 

class _FileCacheError(Exception):
  '''Base exception class for FileCache related errors'''

class _FileCache(object):

  DEPTH = 3

  def __init__(self,root_directory=None):
    self._InitializeRootDirectory(root_directory)

  def Get(self,key):
    path = self._GetPath(key)
    if os.path.exists(path):
      return open(path).read()
    else:
      return None

  def Set(self,key,data):
    path = self._GetPath(key)
    directory = os.path.dirname(path)
    if not os.path.exists(directory):
      os.makedirs(directory)
    if not os.path.isdir(directory):
      raise _FileCacheError('%s exists but is not a directory' % directory)
    temp_fd, temp_path = tempfile.mkstemp()
    temp_fp = os.fdopen(temp_fd, 'w')
    temp_fp.write(data)
    temp_fp.close()
    if not path.startswith(self._root_directory):
      raise _FileCacheError('%s does not appear to live under %s' %
                            (path, self._root_directory))
    if os.path.exists(path):
      os.remove(path)
    os.rename(temp_path, path)

  def Remove(self,key):
    path = self._GetPath(key)
    if not path.startswith(self._root_directory):
      raise _FileCacheError('%s does not appear to live under %s' %
                            (path, self._root_directory ))
    if os.path.exists(path):
      os.remove(path)

  def GetCachedTime(self,key):
    path = self._GetPath(key)
    if os.path.exists(path):
      return os.path.getmtime(path)
    else:
      return None

  def _GetUsername(self):
    '''Attempt to find the username in a cross-platform fashion.'''
    return os.getenv('USER') or \
        os.getenv('LOGNAME') or \
        os.getenv('USERNAME') or \
        'nobody'

  def _GetTmpCachePath(self):
    username = self._GetUsername()
    cache_directory = 'python.cache_' + username
    return os.path.join(tempfile.gettempdir(), cache_directory)

  def _InitializeRootDirectory(self, root_directory):
    if not root_directory:
      root_directory = self._GetTmpCachePath()
    root_directory = os.path.abspath(root_directory)
    if not os.path.exists(root_directory):
      os.mkdir(root_directory)
    if not os.path.isdir(root_directory):
      raise _FileCacheError('%s exists but is not a directory' %
                            root_directory)
    self._root_directory = root_directory

  def _GetPath(self,key):
    hashed_key = md5.new(key).hexdigest()
    return os.path.join(self._root_directory,
                        self._GetPrefix(hashed_key),
                        hashed_key)

  def _GetPrefix(self,hashed_key):
    return os.path.sep.join(hashed_key[0:_FileCache.DEPTH])



class _DbCacheEntry(db.Model):
  value = db.TextProperty(required=True)
  timestamp = db.DateTimeProperty(required=True, auto_now=True)

class _DbCache(object):
  '''Simple cache on top of Google App engine's datastore'''
  def Get(self, key):
    entry = _DbCacheEntry.get_by_key_name(key)
    if entry:
      return entry.value
    else:
      return None
  
  def Set(self, key, data):
    entry = _DbCacheEntry.get_by_key_name(key)
    if not entry:
      entry = _DbCacheEntry(
          key_name = key,
          value = data)
    else:
      entry.value = data
    entry.put()
    
  def GetCachedTime(self, key):
    entry = _DbCacheEntry.get_by_key_name(key)
    if entry:
      try:
        # All cached data must be valid JSON, and if we mistakenly cache
        # error response, we should ignore them
        data = simplejson.loads(entry.value)
        if isinstance(data, dict) and data.has_key('error'):
          return None
      except:
        return None
    
      return time.mktime(entry.timestamp.timetuple())
    else:
      return None

    return None