Add change method

CHANGELOG

@@ -1,5 +1,6 @@
 - 0.1.1
 	* Add optional, pluggable verifier to protect state transition
+	* Add change method for atomic simultaneous set and unset
 - 0.1.0
 	* Release version bump
 - 0.0.19:

shep/persist.py

@@ -14,8 +14,8 @@ class PersistedState(State):
     :type logger: object
     """
 
-    def __init__(self, factory, bits, logger=None):
+    def __init__(self, factory, bits, logger=None, verifier=None):
-        super(PersistedState, self).__init__(bits, logger=logger)
+        super(PersistedState, self).__init__(bits, logger=logger, verifier=verifier)
         self.__store_factory = factory
         self.__stores = {}
 
@@ -78,6 +78,26 @@ class PersistedState(State):
         return to_state
 
 
+    def change(self, key, bits_set, bits_unset):
+        """Persist a new state for a key or key/content.
+
+        See shep.state.State.unset
+        """
+        from_state = self.state(key)
+        k_from = self.name(from_state)
+
+        to_state = super(PersistedState, self).change(key, bits_set, bits_unset)
+
+        k_to = self.name(to_state)
+        self.__ensure_store(k_to)
+
+        contents = self.__stores[k_from].get(key)
+        self.__stores[k_to].add(key, contents)
+        self.__stores[k_from].remove(key)
+
+        return to_state
+
+
     def move(self, key, to_state):
         """Persist a new state for a key or key/content.
 

shep/state.py

@@ -332,7 +332,7 @@ class State:
         if self.verifier != None:
             r = self.verifier(self, from_state, to_state)
             if r != None:
-                raise StateTransitionInvalid('{} -> {}: {}'.format(from_state, to_state, r))
+                raise StateTransitionInvalid(r)
 
         self.__add_state_list(to_state, key)
         current_state_list.pop(idx) 
@@ -404,6 +404,28 @@ class State:
         return self.__move(key, current_state, to_state)
 
 
+    def change(self, key, sets, unsets):
+        current_state = self.__keys_reverse.get(key)
+        if current_state == None:
+            raise StateItemNotFound(key)
+        to_state = current_state | sets
+        to_state &= ~unsets & self.__limit
+
+        if sets == 0:
+            to_state = current_state & (~unsets)
+            if to_state == current_state:
+                raise ValueError('invalid change by unsets for state {}: {}'.format(key, unsets))
+
+        if to_state == getattr(self, self.base_state_name):
+            raise ValueError('State {} for {} cannot be reverted to {}'.format(current_state, key, self.base_state_name))
+
+        new_state = self.__reverse.get(to_state)
+        if new_state == None:
+            raise StateInvalid('resulting to state is unknown: {}'.format(to_state))
+
+        return self.__move(key, current_state, to_state)
+
+
     def state(self, key):
         """Return the current numeric state for the given content key.
         

tests/test_file.py

@@ -74,6 +74,40 @@ class TestStateReport(unittest.TestCase):
             os.stat(fp)
    
   
+    def test_change(self):
+        self.states.alias('inky', self.states.FOO | self.states.BAR)
+        self.states.put('abcd', state=self.states.FOO, contents='foo')
+        self.states.change('abcd', self.states.BAR, 0)
+        
+        fp = os.path.join(self.d, 'INKY', 'abcd')
+        f = open(fp, 'r')
+        v = f.read()
+        f.close()
+
+        fp = os.path.join(self.d, 'FOO', 'abcd')
+        with self.assertRaises(FileNotFoundError):
+            os.stat(fp)
+
+        fp = os.path.join(self.d, 'BAR', 'abcd')
+        with self.assertRaises(FileNotFoundError):
+            os.stat(fp)
+
+        self.states.change('abcd', 0, self.states.BAR)
+
+        fp = os.path.join(self.d, 'FOO', 'abcd')
+        f = open(fp, 'r')
+        v = f.read()
+        f.close()
+
+        fp = os.path.join(self.d, 'INKY', 'abcd')
+        with self.assertRaises(FileNotFoundError):
+            os.stat(fp)
+
+        fp = os.path.join(self.d, 'BAR', 'abcd')
+        with self.assertRaises(FileNotFoundError):
+            os.stat(fp)
+
+
     def test_set(self):
         self.states.alias('xyzzy', self.states.FOO | self.states.BAR)
         self.states.put('abcd', state=self.states.FOO, contents='foo')

tests/test_state.py

@@ -106,5 +106,35 @@ class TestState(unittest.TestCase):
         self.assertEqual(states.from_name('foo'), states.FOO)
 
 
+
+    def test_change(self):
+        states = State(3)
+        states.add('foo')
+        states.add('bar')
+        states.add('baz')
+        states.alias('inky', states.FOO | states.BAR)
+        states.alias('pinky', states.FOO | states.BAZ)
+        states.put('abcd')
+        states.next('abcd')
+        states.set('abcd', states.BAR)
+        states.change('abcd', states.BAZ, states.BAR)
+        self.assertEqual(states.state('abcd'), states.PINKY)
+
+
+    def test_change_onezero(self):
+        states = State(3)
+        states.add('foo')
+        states.add('bar')
+        states.add('baz')
+        states.alias('inky', states.FOO | states.BAR)
+        states.alias('pinky', states.FOO | states.BAZ)
+        states.put('abcd')
+        states.next('abcd')
+        states.change('abcd', states.BAR, 0)
+        self.assertEqual(states.state('abcd'), states.INKY)
+        states.change('abcd', 0, states.BAR)
+        self.assertEqual(states.state('abcd'), states.FOO)
+
+
 if __name__ == '__main__':
     unittest.main()