Servant pattern

patterns/behavioral/servant.py

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+"""
+Implementation of the Servant design pattern.
+
+The Servant design pattern is a behavioral pattern used to offer functionality
+to a group of classes without requiring them to inherit from a base class.
+
+This pattern involves creating a Servant class that provides certain services
+or functionalities. These services are used by other classes which do not need
+to be related through a common parent class. It is particularly useful in
+scenarios where adding the desired functionality through inheritance is impractical
+or would lead to a rigid class hierarchy.
+
+This pattern is characterized by the following:
+
+- A Servant class that provides specific services or actions.
+- Client classes that need these services, but do not derive from the Servant class.
+- The use of the Servant class by the client classes to perform actions on their behalf.
+
+References:
+- https://en.wikipedia.org/wiki/Servant_(design_pattern)
+"""
+import math
+
+class Position:
+    """Representation of a 2D position with x and y coordinates."""
+
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+class Circle:
+    """Representation of a circle defined by a radius and a position."""
+
+    def __init__(self, radius, position: Position):
+        self.radius = radius
+        self.position = position
+
+class Rectangle:
+    """Representation of a rectangle defined by width, height, and a position."""
+
+    def __init__(self, width, height, position: Position):
+        self.width = width
+        self.height = height
+        self.position = position
+
+
+class GeometryTools:
+    """
+    Servant class providing geometry-related services, including area and
+    perimeter calculations and position updates.
+    """
+
+    @staticmethod
+    def calculate_area(shape):
+        """
+        Calculate the area of a given shape.
+
+        Args:
+            shape: The geometric shape whose area is to be calculated.
+
+        Returns:
+            The area of the shape.
+
+        Raises:
+            ValueError: If the shape type is unsupported.
+        """
+        if isinstance(shape, Circle):
+            return math.pi * shape.radius ** 2
+        elif isinstance(shape, Rectangle):
+            return shape.width * shape.height
+        else:
+            raise ValueError("Unsupported shape type")
+
+    @staticmethod
+    def calculate_perimeter(shape):
+        """
+        Calculate the perimeter of a given shape.
+
+        Args:
+            shape: The geometric shape whose perimeter is to be calculated.
+
+        Returns:
+            The perimeter of the shape.
+
+        Raises:
+            ValueError: If the shape type is unsupported.
+        """
+        if isinstance(shape, Circle):
+            return 2 * math.pi * shape.radius
+        elif isinstance(shape, Rectangle):
+            return 2 * (shape.width + shape.height)
+        else:
+            raise ValueError("Unsupported shape type")
+
+    @staticmethod
+    def move_to(shape, new_position: Position):
+        """
+        Move a given shape to a new position.
+
+        Args:
+            shape: The geometric shape to be moved.
+            new_position: The new position to move the shape to.
+        """
+        shape.position = new_position
+        print(f"Moved to ({shape.position.x}, {shape.position.y})")
+
+
+def main():
+    """
+    >>> servant = GeometryTools()
+    >>> circle = Circle(5, Position(0, 0))
+    >>> rectangle = Rectangle(3, 4, Position(0, 0))
+    >>> servant.calculate_area(circle)
+    78.53981633974483
+    >>> servant.calculate_perimeter(rectangle)
+    14
+    >>> servant.move_to(circle, Position(3, 4))
+    Moved to (3, 4)
+    >>> servant.move_to(rectangle, Position(5, 6))
+    Moved to (5, 6)
+    """
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()

tests/behavioral/test_servant.py

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+from patterns.behavioral.servant import GeometryTools, Circle, Rectangle, Position
+import pytest
+import math
+
+
+@pytest.fixture
+def circle():
+    return Circle(3, Position(0, 0))
+
+@pytest.fixture
+def rectangle():
+    return Rectangle(4, 5, Position(0, 0))
+
+
+def test_calculate_area(circle, rectangle):
+    assert GeometryTools.calculate_area(circle) == math.pi * 3 ** 2
+    assert GeometryTools.calculate_area(rectangle) == 4 * 5
+
+    with pytest.raises(ValueError):
+        GeometryTools.calculate_area("invalid shape")
+
+def test_calculate_perimeter(circle, rectangle):
+    assert GeometryTools.calculate_perimeter(circle) == 2 * math.pi * 3
+    assert GeometryTools.calculate_perimeter(rectangle) == 2 * (4 + 5)
+
+    with pytest.raises(ValueError):
+        GeometryTools.calculate_perimeter("invalid shape")
+
+
+def test_move_to(circle, rectangle):
+    new_position = Position(1, 1)
+    GeometryTools.move_to(circle, new_position)
+    assert circle.position == new_position
+
+    new_position = Position(1, 1)
+    GeometryTools.move_to(rectangle, new_position)
+    assert rectangle.position == new_position