import android.animation.TimeInterpolator;
import android.view.animation.LinearInterpolator;

/**
 * Maps time into another interpolator so that the animation plays, and then reverses.
 * i.e. time maps like so:
 * [0..0.5, 0.5..1] maps to [0..1, 1..0]
 */
public final class AutoReverseInterpolator implements TimeInterpolator {

    private final TimeInterpolator inner;

    /**
     * Decorator constructor, use if you don't want a linear interpolation.
     * @param inner
     */
    public AutoReverseInterpolator(TimeInterpolator inner) {
        this.inner = inner;
    }

    /**
     * Linear interpolation constructor.
     */
    public AutoReverseInterpolator() {
        this(new LinearInterpolator());
    }

    @Override
    public float getInterpolation(float input) {
        input *= 2;
        if (input > 1) {
            input = 2 - input;
        }
        return inner.getInterpolation(input);
    }
}