changed the example to implement undo feature

Author: hojatm-huma

patterns/behavioral/command.py

@@ -6,6 +6,12 @@
 it is pressed. To achieve this you implement a command object with the `execute`
 method for each menu item and pass to it.
 
+*About the example
+We have a menu containing two items. Each item accept a file name, one hides the file
+and the other deletes it. Both items have undo option.
+Each item is a MenuItem class that accept corresponding command as input and executes
+its `execute` method when it is pressed.
+
 *TL;DR
 Object oriented implementation of callback functions.
 
@@ -14,33 +20,65 @@
 https://docs.djangoproject.com/en/2.1/ref/request-response/#httprequest-objects
 """
 
+import os
+
 
-class Command:
+class HideFileCommand:
     """
-    The interface that commands implement. This is used to abstract invoker from
-    the command is going to handle the job.
+    A command to hide a file given its name
     """
 
-    def execute(self):
-        raise NotImplementedError()
+    def __init__(self):
+        # an array of files hidden, to undo them as needed
+        self._hidden_files = []
 
+    def execute(self, filename):
+        if os.path.isfile(filename):
+            print(f'hiding {filename}')
 
-class MakeBoldCommand(Command):
-    """
-    A simple command to bold a text.
-    """
+            os.rename(filename, f'.{filename}')
+            self._hidden_files.append(filename)
+        else:
+            print(f'{filename} dose not exists to hide')
+
+    def undo(self):
+        if len(self._hidden_files) > 0:
+            filename = self._hidden_files.pop()
 
-    def execute(self):
-        print('I am making it bold.')
+            print(f'un-hiding {filename}')
 
+            os.rename(f'.{filename}', filename)
 
-class MakeItalicCommand(Command):
+
+class DeleteFileCommand:
     """
-    A simple command to italic a text.
+    A command to delete a file given its name
     """
 
-    def execute(self):
-        print('I am making it italic.')
+    def __init__(self):
+        # an array of deleted files, to undo them as needed
+        self._deleted_files = []
+
+        # create a directory to store deleted files
+        if not os.path.exists('bin'):
+            os.makedirs('bin')
+
+    def execute(self, filename):
+        if os.path.isfile(filename):
+            print(f'deleting {filename}')
+
+            os.rename(filename, f'bin/{filename}')
+            self._deleted_files.append(filename)
+        else:
+            print(f'{filename} dose not exists to delete')
+
+    def undo(self):
+        if len(self._deleted_files) > 0:
+            filename = self._deleted_files.pop()
+
+            print(f'un-deleting {filename}')
+
+            os.rename(f'bin/{filename}', filename)
 
 
 class MenuItem:
@@ -51,24 +89,42 @@ class MenuItem:
     def __init__(self, command):
         self._command = command
 
-    def on_press(self):
-        self._command.execute()
+    def on_do_press(self, filename):
+        self._command.execute(filename)
+
+    def on_undo_press(self):
+        self._command.undo()
 
 
 def main():
     """
-    >>> item1 = MenuItem(MakeBoldCommand())
+    >>> item1 = MenuItem(DeleteFileCommand())
 
-    >>> item2 = MenuItem(MakeItalicCommand())
+    >>> item2 = MenuItem(HideFileCommand())
 
-    >>> item1.on_press()
-    I am making it bold.
+    # create a file named `test-file` to work with
+    >>> test_file_name = 'test-file'
+    >>> open(test_file_name, 'w').close()
 
-    >>> item2.on_press()
-    I am making it italic.
+    # deleting `test-file`
+    >>> item1.on_do_press(test_file_name)
+    deleting test-file
+
+    # hiding `test-file` but it dose not exists
+    >>> item2.on_do_press(test_file_name)
+    test-file dose not exists to hide
+
+    # un-deleting `test-file`
+    >>> item1.on_undo_press()
+    un-deleting test-file
+
+    # hiding `test-file`
+    >>> item2.on_do_press(test_file_name)
+    hiding test-file
     """
 
 
 if __name__ == "__main__":
     import doctest
+
     doctest.testmod()