88 

    89 

    90 def isReferrerSelf(request,

    91                    expected_prefix=None, suffix=None):

    92   """Returns True if HTTP referrer path starts with the HTTP request path.

    93     

    94   Args:

    95     request: the Django HTTP request object; request.path is used if

    96       expected_path is not supplied (the most common usage)

    97     expected_prefix: optional HTTP path to use instead of the one in

    98       request.path; default is None (use request.path)

    99     suffix: suffix to remove from the HTTP request path before comparing

   100       it to the HTTP referrer path in the HTTP request object headers

   101       (this is often an link name, for example, that may be changing from

   102       a POST referrer to a GET redirect target) 

   103   

   104   Returns:

   105     True if HTTP referrer path begins with the HTTP request path (either

   106       request.path or expected_prefix instead if it was supplied), after

   107       any suffix was removed from that request path

   108     False otherwise

   109        

   110   """

   111   http_from = request.META.get('HTTP_REFERER')

   112       

   113   if not http_from:

   114     # no HTTP referrer, so cannot possibly start with expected prefix

   115     return False

   116 

   117   from_path = urlparse.urlparse(http_from).path

   118   

   119   if not expected_prefix:

   120     # use HTTP request path, since expected_prefix was not supplied

   121     expected_prefix = request.path

   122 

   123   if suffix:

   124     # remove suffix (such as a link name) before comparison

   125     chars_to_remove = len(suffix)

   126     

   127     if not suffix.startswith('/'):

   128       chars_to_remove = chars_to_remove + 1

   129 

   130     expected_prefix = expected_prefix[:-chars_to_remove]

   131 

   132   if not from_path.startswith(expected_prefix):

   133     # expected prefix did not match first part of HTTP referrer path

   134     return False

   135  

   136   # HTTP referrer started with (possibly truncated) expected prefix

   137   return True

   138 

   139 

   140 def replaceSuffix(path, old_suffix, new_suffix=None, params=None):

   141   """Replace the last part of a URL path with something else.

   142 

   143   Also appends an optional list of query parameters.  Used for

   144   replacing, for example, one link name at the end of a relative

   145   URL path with another.

   146 

   147   Args:

   148     path: HTTP request relative URL path (with no query arguments)

   149     old_suffix: expected suffix at the end of request.path component;

   150       if any False value (such as None), the empty string '' is used

   151     new_suffix: if non-False, appended to request.path along with a

   152       '/' separator (after removing old_suffix if necessary)

   153     params: an optional dictionary of query parameters to append to

   154       the redirect target; appended as ?<key1>=<value1>&<key2>=...

   155       

   156   Returns:

   157     /path/with/new_suffix?a=1&b=2

   158   """    

   159   if not old_suffix:

   160     old_suffix = ''

   161 

   162   old_suffix = '/' + old_suffix

   163 

   164   if path.endswith(old_suffix):

   165     # also removes any trailing '/' if old_suffix was empty

   166     path = path[:-len(old_suffix)]

   167 

   168   if new_suffix:

   169     # if present, appends new_suffix, after '/' separator

   170     path = '%s/%s' % (path, new_suffix)

   171 

   172   if params:

   173     # appends any query parameters, after a '?' and separated by '&'

   174     path = '%s?%s' % (path, '&'.join(

   175         ['%s=%s' % (p,v) for p,v in params.iteritems()]))

   176 

   177   return path