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/**
 * Copyright (c) 2000-2009 Liferay, Inc. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.liferay.portal.kernel.util;

import com.liferay.portal.kernel.log.Log;
import com.liferay.portal.kernel.log.LogFactoryUtil;

import java.text.NumberFormat;

import java.util.HashMap;
import java.util.Map;

/**
 * View Source
 *
 * @author Brian Wing Shun Chan
 *
 */
public class MathUtil {

	public static int base2Log(long x) {
		return _base2LogValues.get(x);
	}

	public static long base2Pow(int x) {
		if (x == 0) {
			return 1;
		}
		else {
			return 2L << (x - 1);
		}
	}

	public static int factorial(int x) {
		if (x < 0) {
			return 0;
		}

		int factorial = 1;

		while (x > 1) {
			factorial = factorial * x;
			x = x - 1;
		}

		return factorial;
	}

	public static double format(double x, int max, int min) {
		NumberFormat nf = NumberFormat.getInstance();

		nf.setMaximumFractionDigits(max);
		nf.setMinimumFractionDigits(min);

		try {
			Number number = nf.parse(nf.format(x));

			x = number.doubleValue();
		}
		catch (Exception e) {
			_log.error(e.getMessage());
		}

		return x;
	}

	public static boolean isEven(int x) {
		if ((x % 2) == 0) {
			return true;
		}

		return false;
	}

	public static boolean isOdd(int x) {
		return !isEven(x);
	}

	public static int[] generatePrimes(int max) {
		if (max < 2) {
			return new int[0];
		}
		else {
			boolean[] crossedOut = new boolean[max + 1];

			for (int i = 2; i < crossedOut.length; i++) {
				crossedOut[i] = false;
			}

			int limit = (int)Math.sqrt(crossedOut.length);

			for (int i = 2; i <= limit; i++) {
				if (!crossedOut[i]) {
					for (int multiple = 2 * i; multiple < crossedOut.length;
							multiple += i) {

						crossedOut[multiple] = true;
					}
				}
			}

			int uncrossedCount = 0;

			for (int i = 2; i < crossedOut.length; i++) {
				if (!crossedOut[i]) {
					uncrossedCount++;
				}
			}

			int[] result = new int[uncrossedCount];

			for (int i = 2, j = 0; i < crossedOut.length; i++) {
				if (!crossedOut[i]) {
					result[j++] = i;
				}
			}

			return result;
		}
	}

	private static Log _log = LogFactoryUtil.getLog(MathUtil.class);

	private static Map _base2LogValues =
		new HashMap();

	static {
		_base2LogValues.put(0L, Integer.MIN_VALUE);

		for (int i = 0; i < 63; i++) {
			_base2LogValues.put(base2Pow(i), i);
		}
	}

}