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/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.scenes.scene2d.interpolators;

import com.badlogic.gdx.scenes.scene2d.Interpolator;
import com.badlogic.gdx.utils.Pool;

/** An interpolator where the rate of change starts out slowly and then accelerates over time.
 * 
 * @author Moritz Post  */
public class AccelerateInterpolator implements Interpolator {

	private static final float DEFAULT_FACTOR = 1.0f;

	private static final Pool pool = new Pool(4, 100) {
		@Override
		protected AccelerateInterpolator newObject () {
			return new AccelerateInterpolator();
		}
	};

	private float factor;

	private double doubledFactor;

	AccelerateInterpolator () {
		// hide constructor
	}

	/** Gets a new {@link AccelerateInterpolator} from a maintained pool of {@link Interpolator}s.
	 * 
	 * @param factor the factor controlling the rate of change
	 * @return the obtained {@link AccelerateInterpolator} */
	public static AccelerateInterpolator $ (float factor) {
		AccelerateInterpolator inter = pool.obtain();
		inter.factor = factor;
		inter.doubledFactor = factor * 2;
		return inter;
	}

	/** Gets a new {@link AccelerateInterpolator} from a maintained pool of {@link Interpolator}s.
	 * 
	 * The initial factor is set to {@value AccelerateInterpolator#DEFAULT_FACTOR}.
	 * 
	 * @return the obtained {@link AccelerateInterpolator} */
	public static AccelerateInterpolator $ () {
		return $(DEFAULT_FACTOR);
	}

	@Override
	public void finished () {
		pool.free(this);
	}

	public float getInterpolation (float input) {
		if (factor == 1.0f) {
			return input * input;
		} else {
			return (float)Math.pow(input, doubledFactor);
		}
	}

	@Override
	public Interpolator copy () {
		return $(factor);
	}
}