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/*******************************************************************************
 * Copyright (c) 2003, 2007 s IT Solutions AT Spardat GmbH .
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     s IT Solutions AT Spardat GmbH - initial API and implementation
 *******************************************************************************/

// @(#) $Id: TestUtil.java 2089 2007-11-28 13:56:13Z s3460 $
package at.spardat.xma.test;

import java.io.FileReader;
import java.io.FileWriter;
import java.util.Random;


/**
 * Provides some utility-Methods to generate test-data. Contains a random
 * number generator, which is able to reproduce the same sequence of random numbers
 * over multiple runs of an application, dependent on a system property.
 * 
 * @author YSD, 02.05.2003 21:32:50
 */
public class TestUtil {

    /**
     * Generiert einen String einer besimmten L?nge mit zuf?lligen
     * Ziffern-Inhalt.
     *
     * @param len die L?nge des Returnwerts
     * @return String der L?nge len der nur aus Ziffern besteht.
     */
    public static String randomDigitString (int len) {
        StringBuffer        b = new StringBuffer(len);
        for (int i=0; ilen aus [a-z].
     */
    public static String randomString (int len) {
        StringBuffer        b = new StringBuffer(len);
        for (int i=0; iminLen up to maxLen.
     */
    public static String randomString (int minLen, int maxLen) {
        return randomString (randomInt (minLen, maxLen));
    }
    
    /**
     * Returns a random String whose length is also random and
     * ranges from minLen up to maxLen. This
     * method also returns null with a probability of 0.1.
     */
    public static String randomNullString (int minLen, int maxLen) {
        if (draw(0.1)) return null;
        return randomString (randomInt (minLen, maxLen));
    }
    

    /**
     * Returns random number in the range [low, high]
     */
    public static int randomInt (int low, int high) {
        if (high < low) throw new IllegalArgumentException();
        if (low == high) return low;
        return getRandom().nextInt(high-low+1)+low;
    }

    /**
     * Returns a random number in the range [low, high]
     */
    public static double randomDouble (double low, double high) {
        if (high < low) throw new IllegalArgumentException();
        if (low == high) return low;
        return getRandom().nextDouble() * (high-low) + low;
    }

    /**
     * Liefert Zufallsboolean
     */
    public static boolean randomBool () {
        return getRandom().nextBoolean();
    }
    
    /**
     * Returns a boolean that is true with a provided
     * probability.
     * 
     * @param probality value ranging from 0.0 to 1.0.
     * @return true with the specified probability.
     */
    public static boolean draw (double probality) {
        return getRandom().nextDouble() < probality;
    }

    private static Random       random_;

    /**
     * Get the singleton random number generator. Dependent upon the
     * system-property LASTSEED, it is seeded by an number read
     * from the file lastseed.txt or the seed is taken from the current
     * time and written to the file. 
     *
     * Thereby we are able to reproduce a sequence of random numbers
     * over multiple runs of a JUnit testRunner.
     */
    public synchronized static Random getRandom () {
        if (random_ == null) {
            // look up system property LASTSEED
            if (System.getProperty("LASTSEED") == null) {
                // create Random-Generator based on current time
                long        time = System.currentTimeMillis();
                try {
                    writeSeedToFile(time);
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
                random_ = new Random(time);
            } else {
                // get the last seed from file
                long        seed = 0;
                try {
                    seed = getLastSeedFromFile();
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
                random_ = new Random(seed);
            }
        }
        return random_;
    }

    private static String       SEED_FILE = "lastSeed.txt";

    /**
     * Returns the last seed written to the file lastSeed.txt
     */
    private static long getLastSeedFromFile () throws Exception {
        FileReader          fr = new FileReader(SEED_FILE);
        StringBuffer        buf = new StringBuffer();
        int                 lastChar;
        while ((lastChar = fr.read()) != -1)
            buf.append((char)lastChar);
        fr.close();
        return Long.parseLong(buf.toString());
    }

    /**
     * Writes the seed to the file lastSeed.txt
     */
    private static void writeSeedToFile(long seed) throws Exception {
        FileWriter          fw = new FileWriter(SEED_FILE);
        fw.write(String.valueOf(seed));
        fw.close();
    }

}