implemented command pattern.

pypatterns/behavioral/command.py

@@ -0,0 +1,94 @@
+from abc import ABCMeta, abstractmethod
+
+
+class InvalidActionException(Exception):
+    """
+    Exception for when an invalid action is called on a Receiver.
+    """
+    pass
+
+
+class InvalidInvokerCommandException(Exception):
+    """
+    Exception for when an invalid command is given to an Invoker to execute.
+    """
+
+
+class Receiver(object, metaclass=ABCMeta):
+    """
+    Abstract receiver class as part of the Command pattern.
+    """
+    def action(self, name, *args, **kwargs):
+        """
+        Delegates which method to be called for a desired action.
+
+        @param name: The name of the action to execute.
+        @type name: str
+        @param args: Any arguments for the action.
+        @param kwargs: Any keyword arguments for the action.
+        """
+        try:
+            return getattr(self, name)(*args, **kwargs)
+        except AttributeError:
+            raise InvalidActionException
+
+
+class Command(object, metaclass=ABCMeta):
+    """
+    Abstract Command class as part of the Command pattern.
+    """
+    def __init__(self, receiver):
+        """
+        Initialize a new command instance.
+
+        @param receiver: The receiver for this command to use.
+        @type receiver: Receiver
+        """
+        self._receiver = receiver
+
+    @abstractmethod
+    def execute(self):
+        """
+        Abstract method for executing an action.
+        """
+        pass
+
+    @abstractmethod
+    def unexecute(self):
+        """
+        Abstract method for unexecuting an action.
+        """
+        pass
+
+
+class Invoker(object, metaclass=ABCMeta):
+    """
+    Abstract Invoker class as part of the Command pattern.
+    """
+    def __init__(self, valid_commands):
+        """
+        Initialize a new Invoker instance.
+
+        @param valid_commands: A list of command classes this invoker can handle.
+        """
+        self._history = []
+        self._valid_commands = valid_commands
+
+    def execute(self, command):
+        """
+        Execute a command.
+
+        @param command: A command for the invoker to execute.
+        @type command: Command
+        """
+        if command.__class__ not in self._valid_commands:
+            raise InvalidInvokerCommandException
+        else:
+            self._history.append(command)
+            return command.execute()
+
+    def undo(self):
+        """
+        Undo the last command.
+        """
+        return self._history.pop().unexecute()

tests/behavioral_tests/test_command.py

@@ -0,0 +1,190 @@
+from unittest import TestCase
+from pypatterns.behavioral.command import InvalidActionException, InvalidInvokerCommandException, \
+    Receiver, Command, Invoker
+
+
+class ReceiverTestCase(TestCase):
+    """
+    Unit testing class for the Receiver class.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class Thermostat(Receiver):
+
+            def raise_temp(self, amount):
+                return "Temperature raised by {0} degrees".format(amount)
+
+            def lower_temp(self, amount):
+                return "Temperature lowered by {0} degrees".format(amount)
+
+        self.thermostat = Thermostat()
+
+    def test_valid_action(self):
+        """
+        Test the action method with a valid action.
+
+        @raise AssertionError: If the test fails.
+        """
+        self.assertEquals("Temperature raised by 5 degrees", self.thermostat.action('raise_temp', 5))
+        self.assertEquals("Temperature lowered by 5 degrees", self.thermostat.action('lower_temp', 5))
+
+    def test_invalid_action(self):
+        """
+        Test the action method with an invalid action.
+
+        @raise AssertionError: If the test fails.
+        """
+        with self.assertRaises(InvalidActionException):
+            self.thermostat.action('foo')
+
+
+class CommandTestCase(TestCase):
+    """
+    Unit testing class for the Command class.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class Thermostat(Receiver):
+            def raise_temp(self, amount):
+                return "Temperature raised by {0} degrees".format(amount)
+
+            def lower_temp(self, amount):
+                return "Temperature lowered by {0} degrees".format(amount)
+
+        class RaiseTempCommand(Command):
+
+            def __init__(self, receiver, amount=5):
+                super().__init__(receiver)
+                self.amount = amount
+
+            def execute(self):
+                return self._receiver.action('raise_temp', self.amount)
+
+            def unexecute(self):
+                return self._receiver.action('lower_temp', self.amount)
+
+        class LowerTempCommand(Command):
+
+            def __init__(self, receiver, amount=5):
+                super().__init__(receiver)
+                self.amount = amount
+
+            def execute(self):
+                return self._receiver.action('lower_temp', self.amount)
+
+            def unexecute(self):
+                return self._receiver.action('raise_temp', self.amount)
+
+        self.thermostat = Thermostat()
+        self.raise_temp_command_class = RaiseTempCommand
+        self.lower_temp_command_class = LowerTempCommand
+
+    def test_execute(self):
+        """
+        Test the execute method.
+
+        @raise AssertionError: If the test fails.
+        """
+        raise_temp_command = self.raise_temp_command_class(self.thermostat, 10)
+        lower_temp_command = self.lower_temp_command_class(self.thermostat, 5)
+
+        self.assertEquals("Temperature raised by 10 degrees", raise_temp_command.execute())
+        self.assertEquals("Temperature lowered by 5 degrees", lower_temp_command.execute())
+
+
+class InvokerTestCase(TestCase):
+    """
+    Unit testing class for the Invoker class.
+    """
+    def setUp(self):
+        """
+        Initialize testing data.
+        """
+        class Thermostat(Receiver):
+            def raise_temp(self, amount):
+                return "Temperature raised by {0} degrees".format(amount)
+
+            def lower_temp(self, amount):
+                return "Temperature lowered by {0} degrees".format(amount)
+
+        class RaiseTempCommand(Command):
+            def __init__(self, receiver, amount=5):
+                super().__init__(receiver)
+                self.amount = amount
+
+            def execute(self):
+                return self._receiver.action('raise_temp', self.amount)
+
+            def unexecute(self):
+                return self._receiver.action('lower_temp', self.amount)
+
+        class LowerTempCommand(Command):
+            def __init__(self, receiver, amount=5):
+                super().__init__(receiver)
+                self.amount = amount
+
+            def execute(self):
+                return self._receiver.action('lower_temp', self.amount)
+
+            def unexecute(self):
+                return self._receiver.action('raise_temp', self.amount)
+
+        class Worker(Invoker):
+
+            def __init__(self):
+                super().__init__([LowerTempCommand, RaiseTempCommand])
+
+        self.worker = Worker()
+        self.receiver = Thermostat()
+        self.lower_temp_command = LowerTempCommand(self.receiver)
+        self.raise_temp_command = RaiseTempCommand(self.receiver)
+
+    def test_valid_execute(self):
+        """
+        Test the execute method with a valid command for the Worker Invoker.
+
+        @raise AssertionError: If the test fails.
+        """
+        self.assertEquals("Temperature lowered by 5 degrees", self.worker.execute(self.lower_temp_command))
+        self.assertEquals("Temperature raised by 5 degrees", self.worker.execute(self.raise_temp_command))
+
+    def test_invalid_execute(self):
+        """
+        Test the execute method with an invalid command for the Worker Invoker.
+
+        @raise AssertionError: If the test fails.
+        """
+        class Light(Receiver):
+
+            def turn_on(self):
+                return "Light turned on"
+
+            def turn_off(self):
+                return "Light turned off"
+
+        class TurnOnLightCommand(Command):
+
+            def execute(self):
+                return self._receiver.action('turn_on')
+
+            def unexecute(self):
+                return self._receiver.action('turn_off')
+
+        with self.assertRaises(InvalidInvokerCommandException):
+            self.worker.execute(TurnOnLightCommand(Light))
+
+    def test_undo(self):
+        """
+        Test the undo method.
+
+        @raise AssertionError: If the test fails.
+        """
+        self.worker.execute(self.raise_temp_command)
+
+        self.assertIn(self.raise_temp_command, self.worker._history)
+        self.assertEquals("Temperature lowered by 5 degrees", self.worker.undo())
+        self.assertNotIn(self.raise_temp_command, self.worker._history)