Button.pde

class Button extends SceneElement implements InputReceiver {
  // ----- Fields

  private final int borderRoundness = 10;
  private final Vec2Int size;
  private final String text;
  private final Runnable callback;
  private Color fillColor;

  private final Color initialColor;
  private boolean currentlyHovered;
  private boolean clicked;
  private float clickedTimer;
  private boolean executeCallbackPending;

  // ----- Constructors

  public Button(Vec2Int size, String text, Color fillColor, Runnable callback) {
    this.size = size;
    this.text = text;
    this.fillColor = fillColor;
    this.callback = callback;

    initialColor = fillColor;
  }

  // ----- Methods

  @Override
  public void draw() {
    rectMode(CENTER);
    fill(fillColor);
    stroke(0);
    strokeWeight(2);
    rect(0, 0, size.x, size.y, borderRoundness);

    fill(0);
    textAlign(CENTER, CENTER);
    textSize(min(size.x * .25f, size.y * .75f));
    text(text, 0, 0);

    handleHover();
    handleClick();
  }

  @Override
  public void onInput(InputAction action, Object param) {
    switch (action) {
    case HOVER_ON:
      if (param == this)
        currentlyHovered = true;
      break;
    case CLICKED:
      if (param == this)
        clicked = true;
      break;
    case MOUSE_RELEASED:
      onMouseReleased();
      break;
    default:
      return;
    };
  }

  @Override
  public RectCollider getCollider() {
    return new RectCollider(
      new Vec2Int(width / 2 + position.x, height / 2 + position.y),
      new Vec2Int(size.x * scale, size.y * scale)
    );
  }

  private void handleHover() {
    if (currentlyHovered && scale == 1f) {
      TweenEngineHelpers.tween(this, SceneElementTweenAccessor.SCALE_ID, .1f)
        .target(1.05f)
        .ease(TweenEquations.easeInOutSine)
        .start(tweenManager);
    }

    if (!currentlyHovered) {
      TweenEngineHelpers.tween(this, SceneElementTweenAccessor.SCALE_ID, .1f)
        .target(1f)
        .ease(TweenEquations.easeInOutSine)
        .start(tweenManager);
    }

    currentlyHovered = false;
  }

  private void handleClick() {
    if (!clicked) return;

    clickedTimer += 1f / frameRate;
    float t = clickedTimer * 9f;
    if (t < 1) {
      fillColor = Color.gradient(initialColor, Color.brighten(initialColor, .75f), t);
      return;
    }

    if (executeCallbackPending) callback.run();
  }

  private void onMouseReleased() {
    if (!clicked) return;

    if (currentlyHovered) {
      executeCallbackPending = true;
    } else {
      fillColor = initialColor;
      clicked = false;
      clickedTimer = 0f;
    }
  }
}