--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_utils/tales.py	Thu Feb 19 00:46:48 2015 +0100
@@ -0,0 +1,80 @@
+#
+# Copyright (c) 2008-2015 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+
+__docformat__ = 'restructuredtext'
+
+
+# import standard library
+import re
+
+# import interfaces
+from pyams_utils.interfaces.tales import ITALESExtension
+
+# import packages
+from chameleon.astutil import Symbol
+from chameleon.codegen import template
+from chameleon.tales import StringExpr
+from zope.contentprovider.tales import addTALNamespaceData
+
+
+class ContextExprMixin(object):
+    """Mixin-class for expression compilers."""
+
+    transform = None
+
+    def __call__(self, target, engine):
+        # Make call to superclass to assign value to target
+        assignment = super(ContextExprMixin, self).__call__(target, engine)
+        transform = template("target = transform(econtext, target)",
+                             target=target,
+                             transform=self.transform)
+        return assignment + transform
+
+
+FUNCTION_EXPRESSION = re.compile('(.+)\((.+)\)')
+
+
+def render_extension(econtext, name):
+    name = name.strip()
+
+    context = econtext.get('context')
+    request = econtext.get('request')
+    view = econtext.get('view')
+
+    func_match = FUNCTION_EXPRESSION.match(name)
+    if func_match:
+        name, argument = func_match.groups()
+        arg_value = econtext.get(argument, argument)
+    else:
+        arg_value = None
+
+    registry = request.registry
+    extension = registry.queryMultiAdapter((context, request, view), ITALESExtension, name=name)
+    if extension is None:
+        extension = registry.queryMultiAdapter((context, request), ITALESExtension, name=name)
+    if extension is None:
+        extension = registry.queryAdapter(context, ITALESExtension, name=name)
+
+    # provide a useful error message, if the extension was not found.
+    if extension is None:
+        return None
+
+    # Insert the data gotten from the context
+    addTALNamespaceData(extension, econtext)
+
+    return extension.render(arg_value)
+
+
+class ExtensionExpr(ContextExprMixin, StringExpr):
+    """extension: TALES expression"""
+
+    transform = Symbol(render_extension)