State change event emitter

shep/state.py

@@ -30,7 +30,7 @@ class State:
 
     base_state_name = 'NEW'
 
-    def __init__(self, bits, logger=None, verifier=None, check_alias=True):
+    def __init__(self, bits, logger=None, verifier=None, check_alias=True, event_callback=None):
         self.__bits = bits
         self.__limit = (1 << bits) - 1
         self.__c = 0
@@ -43,6 +43,7 @@ class State:
         self.modified_last = {}
         self.verifier = verifier
         self.check_alias = check_alias
+        self.event_callback = event_callback
 
 
     @classmethod
@@ -321,6 +322,9 @@ class State:
 
         self.register_modify(key)
         
+        if self.event_callback != None:
+            self.event_callback(key, state)
+
         return state
                                 
 
@@ -369,6 +373,9 @@ class State:
 
         self.register_modify(key)
 
+        if self.event_callback != None:
+            self.event_callback(key, to_state)
+
         return to_state
    
 

tests/test_state.py

@@ -13,6 +13,18 @@ logging.basicConfig(level=logging.DEBUG)
 logg = logging.getLogger()
 
 
+class MockCallback:
+
+    def __init__(self):
+        self.items = {}
+
+
+    def add(self, k, v):
+        if self.items.get(k) == None:
+            self.items[k] = []
+        self.items[k].append(v)
+
+
 class TestState(unittest.TestCase):
 
     def test_key_check(self):
@@ -177,5 +189,24 @@ class TestState(unittest.TestCase):
         self.assertGreater(a, b)
 
 
+    def test_event_callback(self):
+        cb = MockCallback()
+        states = State(3, event_callback=cb.add)
+        states.add('foo')
+        states.add('bar')
+        states.add('baz')
+        states.alias('xyzzy', states.FOO | states.BAR)
+        states.put('abcd')
+        states.set('abcd', states.FOO)
+        states.set('abcd', states.BAR)
+        states.change('abcd', states.BAZ, states.XYZZY)
+        events = cb.items['abcd']
+        self.assertEqual(len(events), 4)
+        self.assertEqual(events[0], states.NEW)
+        self.assertEqual(events[1], states.FOO)
+        self.assertEqual(events[2], states.XYZZY)
+        self.assertEqual(events[3], states.BAZ)
+
+
 if __name__ == '__main__':
     unittest.main()