1 files changed, 106 insertions, 0 deletions

diff --git a/foundry/utils.py b/foundry/utils.py
new file mode 100644
index 0000000..b5d58b6
--- /dev/null
+++ b/foundry/utils.py
@@ -0,0 +1,106 @@
+# vim: set filencoding=utf8
+"""
+Random Stuff
+
+@author: Mike Crute (mcrute@gmail.com)
+@organization: SoftGroup Interactive, Inc.
+@date: May 02, 2010
+
+Random stuff that doesn't deserve it's own module
+but is still needed for the rest of the program.
+"""
+
+class frozendict(dict):
+    """
+    A frozen dictionary implementation can not be modified once
+    it has been constructed, much like a tuple. Frozen dictionaries
+    are hashable.
+    """
+
+    def __new__(cls, indict):
+        inst = dict.__new__(cls)
+        inst.__hash = hash(tuple(sorted(indict.items())))
+        inst.__slots__ = indict.keys()
+        dict.__init__(inst, indict)
+        return inst
+
+    @property
+    def __blocked(self):
+        raise AttributeError("Can't modify frozendict instance.")
+
+    __delitem__ = __setitem__ = clear = pop = __blocked
+    popitem = setdefault = update = __blocked
+
+    __hash__ = lambda self: self.__hash
+    __repr__ = lambda self: "frozendict({1})".format(dict.__repr__(self))
+
+
+def implements(interface, debug=False):
+    """
+    Verify that a class conforms to a specified interface.
+    This decorator is not perfect, for example it can not
+    check exceptions or return values. But it does ensure
+    that all public methods exist and their arguments
+    conform to the interface.
+
+    The debug flag allows overriding checking of the runtime
+    flag for testing purposes, it should never be set in
+    production code.
+
+    NOTE: This decorator does nothing if -d is not passed
+    to the Python runtime.
+    """
+    import sys
+    if not sys.flags.debug and not debug:
+        return lambda func: func
+
+    # Defer this import until we know we're supposed to run
+    import inspect
+
+    def get_filtered_members(item):
+        "Gets non-private or non-protected symbols."
+        return dict([(key, value) for key, value in inspect.getmembers(item)
+                if not key.startswith('_')])
+
+    def build_contract(item):
+        """
+        Builds a function contract string. The contract
+        string will ignore the name of positional params
+        but will consider the name of keyword arguments.
+        """
+        argspec = inspect.getargspec(item)
+
+        if argspec.defaults:
+            num_keywords = len(argspec.defaults)
+            args = ['_'] * (len(argspec.args) - num_keywords)
+            args.extend(argspec.args[num_keywords-1:])
+        else:
+            args = ['_'] * len(argspec.args)
+
+        if argspec.varargs:
+            args.append('*args')
+
+        if argspec.keywords:
+            args.append('**kwargs')
+
+        return ', '.join(args)
+
+    def tester(klass):
+        "Verifies conformance to the interface."
+        interface_elements = get_filtered_members(interface)
+        class_elements = get_filtered_members(klass)
+
+        for key, value in interface_elements.items():
+            assert key in class_elements, \
+                    "{0!r} is required but missing.".format(key)
+
+            if inspect.isfunction(value) or inspect.ismethod(value):
+                contract = build_contract(value)
+                implementation = build_contract(class_elements[key])
+
+                assert implementation == contract, \
+                        "{0!r} doesn't conform to interface.".format(key)
+
+        return klass
+
+    return tester