21   '"Chen Lunpeng" <forever.clp@gmail.com>',

   121 def getNearestUsers(id=None, link_name=None):

   122   """Get User entities just before and just after the specified User.

   123     

   124   Args:

   125     id: a Google Account (users.User) object; default is None (not supplied)

   126     link_name: link name string; default is None (not supplied)

   127 

   128   Returns:

   129     User entities being those just before and just after the (possibly

   130     non-existent) User for given id or link_name,

   131       OR

   132     possibly None if query had no results or neither id or link_name were

   133     supplied.

   134   """

   135   if id:

   136     query = db.GqlQuery("SELECT * FROM User WHERE id > :1", id)

   137     return query.fetch(1)

   138 

   139   #if id not supplied, try link name.

   140   if link_name:

   141     query = db.GqlQuery("SELECT * FROM User WHERE link_name > :1", link_name)

   142     return query.fetch(1)

   143 

   144   return None

   145 

   146 

   147 def findNearestUsersOffset(width, id=None, link_name=None):

   148   """Finds offset of beginning of a range of Users around the nearest User.

   149   

   150   Args:

   151     limit: the width of the "found" window around the nearest User found 

   152     id: a Google Account (users.User) object, or None

   153     link_name: link name input in the Lookup form or None if not supplied.

   154     

   155   Returns:

   156     an offset into the list of Users that is width/2 less than the

   157     offset of the first User returned by getNearestUsers(), or zero if

   158     that offset would be less than zero

   159       OR

   160     None if there are no nearest Users or the offset of the beginning of

   161     the range cannot be found for some reason 

   162   """

   163   # find User "nearest" to supplied id (Google Account) or link_name

   164   nearest_users = getNearestUsers(id=id, link_name=link_name)

   165   

   166   if not nearest_users:

   167     # no "nearest" User, so indicate that with None

   168     return None

   169 

   170   nearest_user = nearest_users[0]

   171 

   172   # start search for beginning of nearest Users range at offset zero

   173   offset = 0

   174   users = getUsersForOffsetAndLimit(offset=offset, limit=width)

   175   

   176   while True:

   177     for user in users:

   178       if nearest_user.id == user.id:

   179         # nearest User found in current search range, so return a range start

   180         return max(0, (offset - (width/2)))

   181 

   182       offset = offset + 1

   183 

   184     # nearest User was not in the current search range, so fetch the next set

   185     users = getUsersForOffsetAndLimit(offset=offset, limit=width)

   186 

   187     if not users:

   188       # nearest User never found, so indicate that with None

   189       break

   190 

   191   return None

   192 

   193