Create a Button Component

j5/components/__init__.py

@@ -1,6 +1,7 @@
 """This module contains components, which are the smallest logical element of hardware."""
 
 from .base import Component
+from .button import Button, ButtonInterface
 from .led import LED, LEDInterface
 
-__all__ = ["Component", "LED", "LEDInterface"]
+__all__ = ["Component", "Button", "ButtonInterface", "LED", "LEDInterface"]

j5/components/button.py

@@ -0,0 +1,43 @@
+"""Classes for Button."""
+
+from abc import ABCMeta, abstractmethod
+
+from j5.boards import Board
+from j5.components import Component
+
+
+class ButtonInterface(metaclass=ABCMeta):
+    """An interface containing the methods required for a button."""
+
+    @abstractmethod
+    def get_button_state(self, board: Board, identifier: int) -> bool:
+        """Set the state of a button."""
+        raise NotImplementedError  # pragma: no cover
+
+    @abstractmethod
+    def wait_until_button_pressed(self, board: Board, identifier: int) -> bool:
+        """Halt the program until this button is pushed."""
+        raise NotImplementedError  # pragma: no cover
+
+
+class Button(Component):
+    """A button."""
+
+    def __init__(self, identifier: int, board: Board, backend: ButtonInterface) -> None:
+        self._board = board
+        self._backend = backend
+        self._identifier = identifier
+
+    @staticmethod
+    def interface_class():
+        """Get the interface class that is required to use this component."""
+        return ButtonInterface
+
+    @property
+    def is_pressed(self) -> bool:
+        """Get the current pushed state of the button."""
+        return self._backend.get_button_state(self._board, self._identifier)
+
+    def wait_until_button_pressed(self):
+        """Halt the program until this button is pushed."""
+        self._backend.wait_until_button_pressed(self._board, self._identifier)

tests/components/test_button.py

@@ -0,0 +1,81 @@
+"""Tests for the Button Classes."""
+from time import sleep, time
+from typing import List, Type
+
+from j5.backends import Backend
+from j5.boards import Board
+from j5.components.button import Button, ButtonInterface
+
+
+class MockButtonDriver(ButtonInterface):
+    """A testing driver for the button component."""
+
+    def get_button_state(self, board: Board, identifier: int) -> bool:
+        """Get the state of the button."""
+        return False  # Never pushed.
+
+    def wait_until_button_pressed(self, board: Board, identifier: int) -> bool:
+        """Wait until the button was pressed."""
+        sleep(0.2)  # The mock driver always presses the button after 0.2s
+
+
+class MockButtonBoard(Board):
+    """A testing board for the button."""
+
+    @property
+    def name(self) -> str:
+        """The name of this board."""
+        return "Testing Button Board"
+
+    @property
+    def serial(self) -> str:
+        """The serial number of this board."""
+        return "SERIAL"
+
+    def make_safe(self):
+        """Make this board safe."""
+        pass
+
+    @staticmethod
+    def supported_components() -> List[Type['Component']]:
+        """List the types of component that this Board supports."""
+        return [Button]
+
+    @staticmethod
+    def discover(backend: Backend) -> List['Board']:
+        """Detect all of the boards on a given backend."""
+        return []
+
+
+def test_button_interface_implementation():
+    """Test that we can implement the button interface."""
+    MockButtonDriver()
+
+
+def test_button_instantiation():
+    """Test that we can instantiate a button."""
+    Button(0, MockButtonBoard(), MockButtonDriver())
+
+
+def test_button_state():
+    """Test that we can get the state of the button."""
+    button = Button(0, MockButtonBoard(), MockButtonDriver())
+
+    assert not button.is_pressed
+
+
+def test_button_wait_until_pressed():
+    """Test that the button takes at 0.2 secs to be pressed."""
+    button = Button(0, MockButtonBoard(), MockButtonDriver())
+    start_time = time()
+    button.wait_until_button_pressed()
+    end_time = time()
+    time_taken = end_time - start_time
+
+    assert time_taken > 0.2
+    assert time_taken < 2
+
+
+def test_button_interface_class():
+    """Test that the Button Interface class is a ButtonInterface."""
+    assert Button.interface_class() == ButtonInterface