/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.math.transform;

import junit.framework.TestCase;

/**
 * JUnit Test for HadamardTransformerTest
 * 
 * @see org.apache.commons.math.transform.FastHadamardTransformer
 */
public final class FastHadamardTransformerTest extends TestCase {

	/**
	 * Test of transformer for the a 8-point FHT (means n=8)
	 */
	public void test8Points() {
		checkAllTransforms(new int[] { 1, 4, -2, 3, 0, 1, 4, -1 }, new int[] { 10, -4, 2, -4, 2, -12, 6, 8 });
	}

	/**
	 * Test of transformer for the a 4-points FHT (means n=4)
	 */
	public void test4Points() {
		checkAllTransforms(new int[] { 1, 2, 3, 4 }, new int[] { 10, -2, -4, 0 });
	}

	/**
	 * Test the inverse transform of an integer vector is not always an integer
	 * vector
	 */
	public void testNoIntInverse() {
		FastHadamardTransformer transformer = new FastHadamardTransformer();
		double[] x = transformer.inversetransform(new double[] { 0, 1, 0, 1 });
		assertEquals(0.5, x[0], 0);
		assertEquals(-0.5, x[1], 0);
		assertEquals(0.0, x[2], 0);
		assertEquals(0.0, x[3], 0);
	}

	/**
	 * Test of transformer for wrong number of points
	 */
	public void test3Points() {
		try {
			new FastHadamardTransformer().transform(new double[3]);
			fail("an exception should have been thrown");
		} catch (IllegalArgumentException iae) {
			// expected
		}
	}

	private void checkAllTransforms(int[] x, int[] y) {
		checkDoubleTransform(x, y);
		checkInverseDoubleTransform(x, y);
		checkIntTransform(x, y);
	}

	private void checkDoubleTransform(int[] x, int[] y) {
		// Initiate the transformer
		FastHadamardTransformer transformer = new FastHadamardTransformer();

		// check double transform
		double[] dX = new double[x.length];
		for (int i = 0; i < dX.length; ++i) {
			dX[i] = x[i];
		}
		double dResult[] = transformer.transform(dX);
		for (int i = 0; i < dResult.length; i++) {
			// compare computed results to precomputed results
			assertEquals((double) y[i], dResult[i]);
		}
	}

	private void checkIntTransform(int[] x, int[] y) {
		// Initiate the transformer
		FastHadamardTransformer transformer = new FastHadamardTransformer();

		// check integer transform
		int iResult[] = transformer.transform(x);
		for (int i = 0; i < iResult.length; i++) {
			// compare computed results to precomputed results
			assertEquals(y[i], iResult[i]);
		}

	}

	private void checkInverseDoubleTransform(int[] x, int[] y) {
		// Initiate the transformer
		FastHadamardTransformer transformer = new FastHadamardTransformer();

		// check double transform
		double[] dY = new double[y.length];
		for (int i = 0; i < dY.length; ++i) {
			dY[i] = y[i];
		}
		double dResult[] = transformer.inversetransform(dY);
		for (int i = 0; i < dResult.length; i++) {
			// compare computed results to precomputed results
			assertEquals((double) x[i], dResult[i]);
		}

	}

}
