Add LED animation classes

[SamCarlberg]

Also fixes a few CI things - spotbugs doesn't need to pass, and formatter diff stages work now

Using LEDs

Two things are needed in code to be able to use LEDs: an AddressableLED object, which is a WPI class that can write data out on a PWM port to control an LED strip, and an AddressableLEDBuffer, which is used to store the data for LED strips.

public class LEDSubsystem extends SubsystemBase {
  private final AddressableLED leds;
  private final AddressableLEDBuffer ledData;

  public LEDSubsystem() {
    leds = new AddressableLED(Constants.LEDConstants.ledPortNumber);
    leds.setLength(Constants.LEDConstants.ledLength);
    ledData = new AddressableLEDBuffer(Constants.LEDConstants.ledLength);
  }

  @Override
  public void periodic() {
    leds.setData(ledData);
  }
}

This is about as much as WPILib provides for us - if we want to do fancier things with LEDs, we'd need to write that ourselves:

public void setRed() {
  for (int ledIndex = 0; ledIndex < leds.getLength(); ledIndex ++) {
    ledData.setRGB(ledIndex, 255, 0, 0);
  }
}

If we want to do animated effects, that would be more complicated code, and would be repetitive (remember "Don't Repeat Yourself"?)

public void blinkRed() {
  if (WPIUtilJNI.now() % 2_000_000 < 1_000_000) {
    // blink "on" for the first half of a 2-second period
    // (WPIUtilJNI.now() returns a number in terms of microseconds, thus the 6 zeroes)
    for (int ledIndex = 0; ledIndex < leds.getLength(); ledIndex ++) {
      ledData.setRGB(ledIndex, 255, 0, 0);
    }
  } else {
    // blink "off" for the second half of the 2-second period
    for (int ledIndex = 0; ledIndex < leds.getLength(); ledIndex ++) {
      ledData.setRGB(ledIndex, 0, 0, 0);
    }
  }
}

Animating LEDs

To make it easier to manage animating LEDs without manually writing the color of each and every LED yourself, I've added a few classes to manage animations and building up more complex animations from simple ones. Animations require a reader and a writer to run - they deliberately don't work with LED data buffers directly, because that prevents animations from being efficiently chained together.

We can update the LED subsystem to work with animations - here, we add a dataView that animations can work with, and a method that runs an animation as a command. This lets us bind animations to button presses, robot state, or match timing just like any other command

public class LEDSubsystem extends SubsystemBase {
  private final AddressableLED leds;
  private final AddressableLEDBuffer ledData;

  // Use a view for compatibility with animations
  private final AddressableLEDBufferView dataView;

  public LEDSubsystem() {
    leds = new AddressableLED(Constants.LEDConstants.ledPortNumber);
    leds.setLength(Constants.LEDConstants.ledLength);
    ledData = new AddressableLEDBuffer(Constants.LEDConstants.ledLength);
    dataView = new AddressableLEDBufferView(ledData, 0, ledData.getLength());
  }

  @Override
  public void periodic() {
    leds.setData(ledData);
  }

  public Command runAnimation(Animation animation) {
    return run(() -> animation.update(dataView));
  }
}

Of course, we can also define some prebuilt commands in this subsystem:

public Command blinkRed() {
  return runAnimation(Animation.solid(Color.kRed).blink(Seconds.of(1));
}

public Command blinkBlue() {
  return runAnimation(Animation.solid(Color.kBlue).blink(Seconds.of(1));
}

And even make some fairly complicated animated patterns:

// A motionless rainbow flag - this will light up the LEDs in a rainbow pattern, but won't move
private static final Animation rainbowFlag =
  Animation.steps(
    Map.of(
      0.0 / 6, Color.Red,
      1.0 / 6, Color.kOrange,
      2.0 / 6, Color.kYellow,
      3.0 / 6, Color.kGreen,
      4.0 / 6, Color.kIndigo,
      5.0 / 6, Color.kViolet));

// But we can make it move! Use the "scrollAtRelativeSpeed" method to make it scroll across the LED strip
// This will make a full trip around every 2 seconds (50% per second)
private static final Animation rainbowFlagScroll =
  rainbowFlag.scrollAtRelativeSpeed(Percent.per(Second).of(50));

public Command rainbowFlagScroll() {
  return runAnimation(rainbowFlagScroll);
}

Be sure to look at the Animation class, there's a lot of helpful things in there.