/*

  * 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.id.serial;

 import org.apache.commons.id.AbstractStringIdentifierGenerator;

 import java.io.Serializable;

 /**

  * <code>AlphanumericGenerator</code> is an identifier generator

  * that generates an incrementing number in base 36 as a String

  * object.

  *

  * <p>All generated ids have the same length (padding with 0's on the left),

  * which is determined by the <code>size</code> parameter passed to the constructor.<p>

  *

  * <p>The <code>wrap</code> property determines whether or not the sequence wraps

  * when it reaches the largest value that can be represented in <code>size</code>

  * base 36 digits. If <code>wrap</code> is false and the the maximum representable

  * value is exceeded, an IllegalStateException is thrown</p>

  *

  * @author Commons-Id team

  * @version $Id: AlphanumericGenerator.java 480488 2006-11-29 08:57:26Z bayard $

  */

 public class AlphanumericGenerator extends AbstractStringIdentifierGenerator implements Serializable {

     /**

      * <code>serialVersionUID</code> is the serializable UID for the binary version of the class.

      */

     private static final long serialVersionUID = 20060120L;

     /**

      * Should the counter wrap.

      */

     private boolean wrapping = true;

     /**

      * The counter.

      */

     private char[] count = null;

     /**

      * 'z' char

      */

     private static final char Z_CHAR = 'z';

     /**

      * '9' char

      */

     private static final char NINE_CHAR = '9';

     /**

      * Constructor with a default size for the alphanumeric identifier.

      *

      * @param wrap should the factory wrap when it reaches the maximum

      *  long value (or throw an exception)

      */

     public AlphanumericGenerator(boolean wrap) {

         this(wrap, DEFAULT_ALPHANUMERIC_IDENTIFIER_SIZE);

     }

     /**

      * Constructor.

      *

      * @param wrap should the factory wrap when it reaches the maximum

      *  long value (or throw an exception)

      * @param size  the size of the identifier

      */

     public AlphanumericGenerator(boolean wrap, int size) {

         super();

         this.wrapping = wrap;

         if (size < 1) {

             throw new IllegalArgumentException("The size must be at least one");

         }

         this.count = new char[size];

         for (int i = 0; i < size; i++) {

             count[i] = '0';  // zero

         }

     }

     /**

      * Construct with a counter, that will start at the specified

      * alphanumeric value.</p>

      *

      * @param wrap should the factory wrap when it reaches the maximum

      * value (or throw an exception)

      * @param initialValue the initial value to start at

      */

     public AlphanumericGenerator(boolean wrap, String initialValue) {

         super();

         this.wrapping = wrap;

         this.count = initialValue.toCharArray();

         for (int i = 0; i < this.count.length; i++) {

             char ch = this.count[i];

             if (ch >= '0' && ch <= '9') continue;

             if (ch >= 'a' && ch <= 'z') continue;

             throw new IllegalArgumentException(

                     "character " + this.count[i] + " is not valid");

         }

     }

     public long maxLength() {

         return this.count.length;

     }

     public long minLength() {

         return this.count.length;

     }

     /**

      * Getter for property wrap.

      *

      * @return <code>true</code> if this generator is set up to wrap.

      *

      */

     public boolean isWrap() {

         return wrapping;

     }

     /**

      * Sets the wrap property.

      *

      * @param wrap value for the wrap property

      *

      */

     public void setWrap(boolean wrap) {

         this.wrapping = wrap;

     }

     /**

      * Returns the (constant) size of the strings generated by this generator.

      *

      * @return the size of generated identifiers

      */

     public int getSize() {

         return this.count.length;

     }

     public synchronized String nextStringIdentifier() {

         for (int i = count.length - 1; i >= 0; i--) {

             switch (count[i]) {

                 case Z_CHAR:  // z

                     if (i == 0 && !wrapping) {

                         throw new IllegalStateException

                         ("The maximum number of identifiers has been reached");

                     }

                     count[i] = '0';

                     break;

                 case NINE_CHAR:  // 9

                     count[i] = 'a';

                     i = -1;

                     break;

                 default:

                     count[i]++;

                     i = -1;

                     break;

             }

         }

         return new String(count);

     }

 }