#!/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
import simplejson
import sys
import tempfile
import time
import urllib
import urllib2
import urlparse
import twitter

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,
               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.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.
    '''
    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))

  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),
                  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 = _FileCache()
    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 _GetOpener(self, url, username=None, password=None):
    if username and password:
      self._AddAuthorizationHeader(username, password)
      handler = self._urllib.HTTPBasicAuthHandler()
      (scheme, netloc, path, params, query, fragment) = urlparse.urlparse(url)
      handler.add_password(Api._API_REALM, netloc, username, password)
      opener = self._urllib.build_opener(handler)
    else:
      opener = self._urllib.build_opener()
    opener.addheaders = self._request_headers.items()
    return opener

  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)

    # Get a url opener that can handle basic auth
    opener = self._GetOpener(url, username=self._username, password=self._password)

    encoded_post_data = self._EncodePostData(post_data)

    # Open and return the URL immediately if we're not going to cache
    if encoded_post_data or no_cache or not self._cache or not self._cache_timeout:
      url_data = opener.open(url, encoded_post_data).read()
    else:
      # Unique keys are a combination of the url and the username
      if self._username:
        key = self._username + ':' + url
      else:
        key = url

      # See if it has been cached before
      last_cached = self._cache.GetCachedTime(key)

      # If the cached version is outdated then fetch another and store it
      if not last_cached or time.time() >= last_cached + self._cache_timeout:
        url_data = opener.open(url, encoded_post_data).read()
        self._cache.Set(key, url_data)
      else:
        url_data = self._cache.Get(key)

    # Always return the latest version
    return url_data

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 \
        os.getlogin() 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])