/*
 * 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.lang3;

import net.lax1dude.eaglercraft.v1_8.EaglercraftRandom;

/**
 * <p>
 * Utility library that supplements the standard {@link EaglercraftRandom} class.
 * </p>
 *
 * <p>
 * Caveat: Instances of {@link EaglercraftRandom} are not cryptographically secure.
 * </p>
 *
 * <p>
 * Please note that the Apache Commons project provides a component dedicated to
 * pseudo-random number generation, namely
 * <a href="https://commons.apache.org/rng">Commons RNG</a>, that may be a
 * better choice for applications with more stringent requirements (performance
 * and/or correctness).
 * </p>
 *
 * @since 3.3
 */
public class RandomUtils {

	/**
	 * Random object used by random method. This has to be not local to the random
	 * method so as to not return the same value in the same millisecond.
	 */
	private static final EaglercraftRandom RANDOM = new EaglercraftRandom();

	/**
	 * <p>
	 * {@code RandomUtils} instances should NOT be constructed in standard
	 * programming. Instead, the class should be used as
	 * {@code RandomUtils.nextBytes(5);}.
	 * </p>
	 *
	 * <p>
	 * This constructor is public to permit tools that require a JavaBean instance
	 * to operate.
	 * </p>
	 */
	public RandomUtils() {
	}

	/**
	 * <p>
	 * Returns a random boolean value
	 * </p>
	 *
	 * @return the random boolean
	 * @since 3.5
	 */
	public static boolean nextBoolean() {
		return RANDOM.nextBoolean();
	}

	/**
	 * <p>
	 * Creates an array of random bytes.
	 * </p>
	 *
	 * @param count the size of the returned array
	 * @return the random byte array
	 * @throws IllegalArgumentException if {@code count} is negative
	 */
	public static byte[] nextBytes(final int count) {
		Validate.isTrue(count >= 0, "Count cannot be negative.");

		final byte[] result = new byte[count];
		RANDOM.nextBytes(result);
		return result;
	}

	/**
	 * <p>
	 * Returns a random integer within the specified range.
	 * </p>
	 *
	 * @param startInclusive the smallest value that can be returned, must be
	 *                       non-negative
	 * @param endExclusive   the upper bound (not included)
	 * @throws IllegalArgumentException if {@code startInclusive > endExclusive} or
	 *                                  if {@code startInclusive} is negative
	 * @return the random integer
	 */
	public static int nextInt(final int startInclusive, final int endExclusive) {
		Validate.isTrue(endExclusive >= startInclusive, "Start value must be smaller or equal to end value.");
		Validate.isTrue(startInclusive >= 0, "Both range values must be non-negative.");

		if (startInclusive == endExclusive) {
			return startInclusive;
		}

		return startInclusive + RANDOM.nextInt(endExclusive - startInclusive);
	}

	/**
	 * <p>
	 * Returns a random int within 0 - Integer.MAX_VALUE
	 * </p>
	 *
	 * @return the random integer
	 * @see #nextInt(int, int)
	 * @since 3.5
	 */
	public static int nextInt() {
		return nextInt(0, Integer.MAX_VALUE);
	}

	/**
	 * <p>
	 * Returns a random long within the specified range.
	 * </p>
	 *
	 * @param startInclusive the smallest value that can be returned, must be
	 *                       non-negative
	 * @param endExclusive   the upper bound (not included)
	 * @throws IllegalArgumentException if {@code startInclusive > endExclusive} or
	 *                                  if {@code startInclusive} is negative
	 * @return the random long
	 */
	public static long nextLong(final long startInclusive, final long endExclusive) {
		Validate.isTrue(endExclusive >= startInclusive, "Start value must be smaller or equal to end value.");
		Validate.isTrue(startInclusive >= 0, "Both range values must be non-negative.");

		if (startInclusive == endExclusive) {
			return startInclusive;
		}

		return startInclusive + nextLong(endExclusive - startInclusive);
	}

	/**
	 * <p>
	 * Returns a random long within 0 - Long.MAX_VALUE
	 * </p>
	 *
	 * @return the random long
	 * @see #nextLong(long, long)
	 * @since 3.5
	 */
	public static long nextLong() {
		return nextLong(Long.MAX_VALUE);
	}

	/**
	 * Generates a {@code long} value between 0 (inclusive) and the specified value
	 * (exclusive).
	 *
	 * @param n Bound on the random number to be returned. Must be positive.
	 * @return a random {@code long} value between 0 (inclusive) and {@code n}
	 *         (exclusive).
	 */
	private static long nextLong(final long n) {
		// Extracted from o.a.c.rng.core.BaseProvider.nextLong(long)
		long bits;
		long val;
		do {
			bits = RANDOM.nextLong() >>> 1;
			val = bits % n;
		} while (bits - val + (n - 1) < 0);

		return val;
	}

	/**
	 * <p>
	 * Returns a random double within the specified range.
	 * </p>
	 *
	 * @param startInclusive the smallest value that can be returned, must be
	 *                       non-negative
	 * @param endExclusive   the upper bound (not included)
	 * @throws IllegalArgumentException if {@code startInclusive > endExclusive} or
	 *                                  if {@code startInclusive} is negative
	 * @return the random double
	 */
	public static double nextDouble(final double startInclusive, final double endExclusive) {
		Validate.isTrue(endExclusive >= startInclusive, "Start value must be smaller or equal to end value.");
		Validate.isTrue(startInclusive >= 0, "Both range values must be non-negative.");

		if (startInclusive == endExclusive) {
			return startInclusive;
		}

		return startInclusive + ((endExclusive - startInclusive) * RANDOM.nextDouble());
	}

	/**
	 * <p>
	 * Returns a random double within 0 - Double.MAX_VALUE
	 * </p>
	 *
	 * @return the random double
	 * @see #nextDouble(double, double)
	 * @since 3.5
	 */
	public static double nextDouble() {
		return nextDouble(0, Double.MAX_VALUE);
	}

	/**
	 * <p>
	 * Returns a random float within the specified range.
	 * </p>
	 *
	 * @param startInclusive the smallest value that can be returned, must be
	 *                       non-negative
	 * @param endExclusive   the upper bound (not included)
	 * @throws IllegalArgumentException if {@code startInclusive > endExclusive} or
	 *                                  if {@code startInclusive} is negative
	 * @return the random float
	 */
	public static float nextFloat(final float startInclusive, final float endExclusive) {
		Validate.isTrue(endExclusive >= startInclusive, "Start value must be smaller or equal to end value.");
		Validate.isTrue(startInclusive >= 0, "Both range values must be non-negative.");

		if (startInclusive == endExclusive) {
			return startInclusive;
		}

		return startInclusive + ((endExclusive - startInclusive) * RANDOM.nextFloat());
	}

	/**
	 * <p>
	 * Returns a random float within 0 - Float.MAX_VALUE
	 * </p>
	 *
	 * @return the random float
	 * @see #nextFloat(float, float)
	 * @since 3.5
	 */
	public static float nextFloat() {
		return nextFloat(0, Float.MAX_VALUE);
	}
}
