// Copied from https://github.com/ToxicBakery/ViewPagerTransforms
@SuppressWarnings("WeakerAccess")
public abstract class BaseTransformer implements PageTransformer {

  public static final float DAMPING_RATIO_NO_BOUNCY = 1f;

  /**
   * Called each {@link #transformPage(View, float)}.
   *
   * @param view the view
   * @param position the position
   */
  protected abstract void onTransform(View view, float position);

  @Override
  public void transformPage(@NonNull View view, float position) {
    onPreTransform(view, position);
    onTransform(view, position);
    onPostTransform(view, position);
  }

  /**
   * If the position offset of a fragment is less than negative one or greater than one, returning true will set the
   * visibility of the fragment to {@link View#GONE}. Returning false will force the fragment to {@link View#VISIBLE}.
   *
   * @return hideOffscreenPages
   */
  protected boolean hideOffscreenPages() {
    return true;
  }

  /**
   * Indicates if the default animations of the view pager should be used.
   *
   * @return isPagingEnabled
   */
  protected boolean isPagingEnabled() {
    return false;
  }

  /**
   * Called each {@link #transformPage(View, float)} before {{@link #onTransform(View, float)} is called.
   *
   * @param view the view
   * @param position the position
   */
  protected void onPreTransform(@NonNull View view, float position) {
    float alpha = 0.0f;
    float width = (float) view.getWidth();
    view.setRotationX(0.0f);
    view.setRotationY(0.0f);
    view.setRotation(0.0f);
    view.setScaleX(DAMPING_RATIO_NO_BOUNCY);
    view.setScaleY(DAMPING_RATIO_NO_BOUNCY);
    view.setPivotX(0.0f);
    view.setPivotY(0.0f);
    view.setTranslationY(0.0f);
    view.setTranslationX(isPagingEnabled() ? 0.0f : (-width) * position);
    if (hideOffscreenPages()) {
      if (position > -1.0f && position < DAMPING_RATIO_NO_BOUNCY) {
        alpha = DAMPING_RATIO_NO_BOUNCY;
      }
      view.setAlpha(alpha);
      view.setEnabled(false);
      return;
    }
    view.setEnabled(true);
    view.setAlpha(DAMPING_RATIO_NO_BOUNCY);
  }

  /**
   * Called each {@link #transformPage(View, float)} call after {@link #onTransform(View, float)} is finished.
   *
   * @param view the view
   * @param position the position
   */
  protected void onPostTransform(@NonNull View view, float position) {}
}