/**
 * Copyright (C) 2010-2017 Gordon Fraser, Andrea Arcuri and EvoSuite
 * contributors
 *
 * This file is part of EvoSuite.
 *
 * EvoSuite is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3.0 of the License, or
 * (at your option) any later version.
 *
 * EvoSuite is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with EvoSuite. If not, see <http://www.gnu.org/licenses/>.
 */
/**
 * 
 */
package org.evosuite.runtime;

import java.util.UUID;

/**
 * <p>
 * Random class.
 * </p>
 * 
 * @author Gordon Fraser
 */
public class Random {

	private static boolean wasAccessed = false;

	/**
	 * We have a unique number that is increased every time a new random number
	 * is accessed
	 */
	private static int currentNumber = 0;

	/**
	 * Replacement function for nextInt
	 * 
	 * @return a int.
	 */
	public static int nextInt() {
		wasAccessed = true;
		return currentNumber++;
	}

	/**
	 * Replacement function for nextInt
	 * 
	 * @param max
	 *            a int.
	 * @return a int.
	 */
	public static int nextInt(int max) {
		wasAccessed = true;
		return currentNumber % max;
	}

	/**
	 * Replacement function for nextFloat
	 * 
	 * @return a float.
	 */
	public static float nextFloat() {
		wasAccessed = true;
		return (currentNumber++ % 10F) / 10F;
	}
	

	/**
	 * Replacement function for nextBytes
	 * @param bytes
	 */
	 public static void nextBytes(byte[] bytes) {
			wasAccessed = true;

		   for (int i = 0; i < bytes.length; )
		     for (int rnd = nextInt(), n = Math.min(bytes.length - i, 4);
		          n-- > 0; rnd >>= 8)
		       bytes[i++] = (byte)rnd;
		 }

	 
	/**
	 * Replacement function for nextDouble
	 * 
	 * @return a float.
	 */
	public static double nextDouble() {
		wasAccessed = true;
		return (currentNumber++ % 10.0) / 10.0;
	}

	/**
	 * Replacement function for nextGaussian
	 * 
	 * @return a double.
	 */
	public static double nextGaussian() {
		wasAccessed = true;
		return nextDouble();
	}
	
	/**
	 * Replacement function for nextBoolean
	 * 
	 * @return a boolean.
	 */
	public static boolean nextBoolean() {
		wasAccessed = true;
		return nextInt(1)!=0;
	}

	
	/**
	 * Replacement function for nextLong
	 * 
	 * @return a long.
	 */
	public static long nextLong() {
		wasAccessed = true;
		return currentNumber++;
	}

	/**
	 * Set the next random number to a value
	 * 
	 * @param number
	 *            a int.
	 */
	public static void setNextRandom(int number) {
		currentNumber = Math.abs(number);
	}

	/**
	 * Reset runtime to initial state
	 */
	public static void reset() {
		currentNumber = 0;
		wasAccessed = false;
	}

	/**
	 * Getter to check whether this runtime replacement was accessed during test
	 * execution
	 * 
	 * @return a boolean.
	 */
	public static boolean wasAccessed() {
		return wasAccessed;
	}

	/**
	 * Replacement for function java.util.UUID.randomUUID() 
	 * @return
	 */
    public static UUID randomUUID() {
		wasAccessed = true;

        byte[] randomBytes = new byte[16];
        nextBytes(randomBytes);
        randomBytes[6]  &= 0x0f;  /* clear version        */
        randomBytes[6]  |= 0x40;  /* set to version 4     */
        randomBytes[8]  &= 0x3f;  /* clear variant        */
        randomBytes[8]  |= 0x80;  /* set to IETF variant  */
        
        UUID newUUID = buildNewUUID(randomBytes);
        return newUUID;
    }

    /**
     * Replacement for creation of new UUID using byte[]
     * @param data
     * @return
     */
    private static UUID buildNewUUID(byte[] data) {
        long msb = 0;
        long lsb = 0;
        assert data.length == 16 : "data must be 16 bytes in length";
        for (int i=0; i<8; i++)
            msb = (msb << 8) | (data[i] & 0xff);
        for (int i=8; i<16; i++)
            lsb = (lsb << 8) | (data[i] & 0xff);
        UUID newUUID = new UUID(msb,lsb);
        return newUUID;
    }

    public static int getCurrentNumber() {
    	return currentNumber;
    }
}