--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/soc/views/helpers/request_helpers.py	Tue Sep 23 23:20:23 2008 +0000
@@ -0,0 +1,87 @@
+#!/usr/bin/python2.5
+#
+# Copyright 2008 the Melange authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Helpers for manipulating HTTP requests.
+"""
+
+__authors__ = [
+  '"Todd Larsen" <tlarsen@google.com>',
+  ]
+
+
+def getSingleIndexedParamValue(request, param_name, values=()):
+  """Returns a value indexed by a query parameter in the HTTP request.
+  
+  Args:
+    request: the Django HTTP request object
+    param_name: name of the query parameter in the HTTP request
+    values: list (or tuple) of ordered values; one of which is
+      retrieved by the index value of the param_name argument in
+      the HTTP request
+      
+  Returns:
+    None if the query parameter was not present, was not an integer, or
+      was an integer that is not a valid [0..len(values)-1] index into
+      the values list.
+    Otherwise, returns values[int(param_name value)]
+  """
+  value_idx = request.GET.get(param_name)
+  
+  if isinstance(value_idx, (tuple, list)):
+    # keep only the first argument if multiple are present
+    value_idx = value_idx[0]
+
+  try:
+    # GET parameter 'param_name' should be an integer value index
+    value_idx = int(value_idx)
+  except:
+    # ignore bogus or missing parameter values, so return None (no message)
+    return None
+    
+  if value_idx < 0:
+    # value index out of range, so return None (no value)
+    return None
+
+  if value_idx >= len(values):
+    # value index out of range, so return None (no value)
+    return None
+
+  # return value associated with valid value index
+  return values[value_idx]
+
+
+def getSingleIndexedParamValueIfMissing(value, request, param_name,
+                                        values=()):
+  """Returns missing value indexed by a query parameter in the HTTP request.
+  
+  Args:
+    value: an existing value, or a "False" value such as None
+    request, param_name, values: see getSingleIndexParamValue()
+    
+  Returns:
+    value, if value is "non-False"
+    Otherwise, returns getSingleIndexedParamValue() result.
+  """
+  if value:
+    # value already present, so return it
+    return value
+
+  return getSingleIndexedParamValue(request, param_name, values=values)
+
+
+# TODO(tlarsen):  write getMultipleIndexParamValues() that returns a
+#   list of values if present, omitting those values that are
+#   out of range