package org.apache.maven.artifact.versioning;
   
   /*
    * 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.
   */
  
  import java.math.BigInteger;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Locale;
  import java.util.Properties;
  import java.util.Stack;
  
  /**
   * <p>
   * Generic implementation of version comparison.
   * </p>
   * 
   * Features:
   * <ul>
   * <li>mixing of '<code>-</code>' (hyphen) and '<code>.</code>' (dot) separators,</li>
   * <li>transition between characters and digits also constitutes a separator:
   *     <code>1.0alpha1 =&gt; [1, 0, alpha, 1]</code></li>
   * <li>unlimited number of version components,</li>
   * <li>version components in the text can be digits or strings,</li>
   * <li>strings are checked for well-known qualifiers and the qualifier ordering is used for version ordering.
   *     Well-known qualifiers (case insensitive) are:<ul>
   *     <li><code>alpha</code> or <code>a</code></li>
   *     <li><code>beta</code> or <code>b</code></li>
   *     <li><code>milestone</code> or <code>m</code></li>
   *     <li><code>rc</code> or <code>cr</code></li>
   *     <li><code>snapshot</code></li>
   *     <li><code>(the empty string)</code> or <code>ga</code> or <code>final</code></li>
   *     <li><code>sp</code></li>
   *     </ul>
   *     Unknown qualifiers are considered after known qualifiers, with lexical order (always case insensitive),
   *   </li>
   * <li>a hyphen usually precedes a qualifier, and is always less important than something preceded with a dot.</li>
   * </ul>
   *
   * @see <a href="https://cwiki.apache.org/confluence/display/MAVENOLD/Versioning">"Versioning" on Maven Wiki</a>
   * @author <a href="mailto:kenney@apache.org">Kenney Westerhof</a>
   * @author <a href="mailto:hboutemy@apache.org">Hervé Boutemy</a>
   */
  public class ComparableVersion
      implements Comparable<ComparableVersion>
  {
      private String value;
  
      private String canonical;
  
      private ListItem items;
  
      private interface Item
      {
          int INTEGER_ITEM = 0;
          int STRING_ITEM = 1;
          int LIST_ITEM = 2;
  
          int compareTo( Item item );
  
          int getType();
  
          boolean isNull();
      }
  
      /**
       * Represents a numeric item in the version item list.
       */
      private static class IntegerItem
          implements Item
      {
          private static final BigInteger BIG_INTEGER_ZERO = new BigInteger( "0" );
  
          private final BigInteger value;
  
          public static final IntegerItem ZERO = new IntegerItem();
  
          private IntegerItem()
          {
              this.value = BIG_INTEGER_ZERO;
          }
 
         public IntegerItem( String str )
         {
             this.value = new BigInteger( str );
         }
 
         public int getType()
         {
             return INTEGER_ITEM;
         }
 
         public boolean isNull()
         {
             return BIG_INTEGER_ZERO.equals( value );
         }
 
         public int compareTo( Item item )
         {
             if ( item == null )
             {
                 return BIG_INTEGER_ZERO.equals( value ) ? 0 : 1; // 1.0 == 1, 1.1 > 1
             }
 
             switch ( item.getType() )
             {
                 case INTEGER_ITEM:
                     return value.compareTo( ( (IntegerItem) item ).value );
 
                 case STRING_ITEM:
                     return 1; // 1.1 > 1-sp
 
                 case LIST_ITEM:
                     return 1; // 1.1 > 1-1
 
                 default:
                     throw new RuntimeException( "invalid item: " + item.getClass() );
             }
         }
 
         public String toString()
         {
             return value.toString();
         }
     }
 
     /**
      * Represents a string in the version item list, usually a qualifier.
      */
     private static class StringItem
         implements Item
     {
         private static final String[] QUALIFIERS = { "alpha", "beta", "milestone", "rc", "snapshot", "", "sp" };
 
         @SuppressWarnings( "checkstyle:constantname" )
         private static final List<String> _QUALIFIERS = Arrays.asList( QUALIFIERS );
 
         private static final Properties ALIASES = new Properties();
         static
         {
             ALIASES.put( "ga", "" );
             ALIASES.put( "final", "" );
             ALIASES.put( "cr", "rc" );
         }
 
         /**
          * A comparable value for the empty-string qualifier. This one is used to determine if a given qualifier makes
          * the version older than one without a qualifier, or more recent.
          */
         private static final String RELEASE_VERSION_INDEX = String.valueOf( _QUALIFIERS.indexOf( "" ) );
 
         private String value;
 
         public StringItem( String value, boolean followedByDigit )
         {
             if ( followedByDigit && value.length() == 1 )
             {
                 // a1 = alpha-1, b1 = beta-1, m1 = milestone-1
                 switch ( value.charAt( 0 ) )
                 {
                     case 'a':
                         value = "alpha";
                         break;
                     case 'b':
                         value = "beta";
                         break;
                     case 'm':
                         value = "milestone";
                         break;
                     default:
                 }
             }
             this.value = ALIASES.getProperty( value , value );
         }
 
         public int getType()
         {
             return STRING_ITEM;
         }
 
         public boolean isNull()
         {
             return ( comparableQualifier( value ).compareTo( RELEASE_VERSION_INDEX ) == 0 );
         }
 
         /**
          * Returns a comparable value for a qualifier.
          *
          * This method takes into account the ordering of known qualifiers then unknown qualifiers with lexical
          * ordering.
          *
          * just returning an Integer with the index here is faster, but requires a lot of if/then/else to check for -1
          * or QUALIFIERS.size and then resort to lexical ordering. Most comparisons are decided by the first character,
          * so this is still fast. If more characters are needed then it requires a lexical sort anyway.
          *
          * @param qualifier
          * @return an equivalent value that can be used with lexical comparison
          */
         public static String comparableQualifier( String qualifier )
         {
             int i = _QUALIFIERS.indexOf( qualifier );
 
             return i == -1 ? ( _QUALIFIERS.size() + "-" + qualifier ) : String.valueOf( i );
         }
 
         public int compareTo( Item item )
         {
             if ( item == null )
             {
                 // 1-rc < 1, 1-ga > 1
                 return comparableQualifier( value ).compareTo( RELEASE_VERSION_INDEX );
             }
             switch ( item.getType() )
             {
                 case INTEGER_ITEM:
                     return -1; // 1.any < 1.1 ?
 
                 case STRING_ITEM:
                     return comparableQualifier( value ).compareTo( comparableQualifier( ( (StringItem) item ).value ) );
 
                 case LIST_ITEM:
                     return -1; // 1.any < 1-1
 
                 default:
                     throw new RuntimeException( "invalid item: " + item.getClass() );
             }
         }
 
         public String toString()
         {
             return value;
         }
     }
 
     /**
      * Represents a version list item. This class is used both for the global item list and for sub-lists (which start
      * with '-(number)' in the version specification).
      */
     private static class ListItem
         extends ArrayList<Item>
         implements Item
     {
         public int getType()
         {
             return LIST_ITEM;
         }
 
         public boolean isNull()
         {
             return ( size() == 0 );
         }
 
         void normalize()
         {
             for ( int i = size() - 1; i >= 0; i-- )
             {
                 Item lastItem = get( i );
 
                 if ( lastItem.isNull() )
                 {
                     // remove null trailing items: 0, "", empty list
                     remove( i );
                 }
                 else if ( !( lastItem instanceof ListItem ) )
                 {
                     break;
                 }
             }
         }
 
         public int compareTo( Item item )
         {
             if ( item == null )
             {
                 if ( size() == 0 )
                 {
                     return 0; // 1-0 = 1- (normalize) = 1
                 }
                 Item first = get( 0 );
                 return first.compareTo( null );
             }
             switch ( item.getType() )
             {
                 case INTEGER_ITEM:
                     return -1; // 1-1 < 1.0.x
 
                 case STRING_ITEM:
                     return 1; // 1-1 > 1-sp
 
                 case LIST_ITEM:
                     Iterator<Item> left = iterator();
                     Iterator<Item> right = ( (ListItem) item ).iterator();
 
                     while ( left.hasNext() || right.hasNext() )
                     {
                         Item l = left.hasNext() ? left.next() : null;
                         Item r = right.hasNext() ? right.next() : null;
 
                         // if this is shorter, then invert the compare and mul with -1
                         int result = l == null ? ( r == null ? 0 : -1 * r.compareTo( l ) ) : l.compareTo( r );
 
                         if ( result != 0 )
                         {
                             return result;
                         }
                     }
 
                     return 0;
 
                 default:
                     throw new RuntimeException( "invalid item: " + item.getClass() );
             }
         }
 
         public String toString()
         {
             StringBuilder buffer = new StringBuilder();
             for ( Item item : this )
             {
                 if ( buffer.length() > 0 )
                 {
                     buffer.append( ( item instanceof ListItem ) ? '-' : '.' );
                 }
                 buffer.append( item );
             }
             return buffer.toString();
         }
     }
 
     public ComparableVersion( String version )
     {
         parseVersion( version );
     }
 
     public final void parseVersion( String version )
     {
         this.value = version;
 
         items = new ListItem();
 
         version = version.toLowerCase( Locale.ENGLISH );
 
         ListItem list = items;
 
         Stack<Item> stack = new Stack<>();
         stack.push( list );
 
         boolean isDigit = false;
 
         int startIndex = 0;
 
         for ( int i = 0; i < version.length(); i++ )
         {
             char c = version.charAt( i );
 
             if ( c == '.' )
             {
                 if ( i == startIndex )
                 {
                     list.add( IntegerItem.ZERO );
                 }
                 else
                 {
                     list.add( parseItem( isDigit, version.substring( startIndex, i ) ) );
                 }
                 startIndex = i + 1;
             }
             else if ( c == '-' )
             {
                 if ( i == startIndex )
                 {
                     list.add( IntegerItem.ZERO );
                 }
                 else
                 {
                     list.add( parseItem( isDigit, version.substring( startIndex, i ) ) );
                 }
                 startIndex = i + 1;
 
                 list.add( list = new ListItem() );
                 stack.push( list );
             }
             else if ( Character.isDigit( c ) )
             {
                 if ( !isDigit && i > startIndex )
                 {
                     list.add( new StringItem( version.substring( startIndex, i ), true ) );
                     startIndex = i;
 
                     list.add( list = new ListItem() );
                     stack.push( list );
                 }
 
                 isDigit = true;
             }
             else
             {
                 if ( isDigit && i > startIndex )
                 {
                     list.add( parseItem( true, version.substring( startIndex, i ) ) );
                     startIndex = i;
 
                     list.add( list = new ListItem() );
                     stack.push( list );
                 }
 
                 isDigit = false;
             }
         }
 
         if ( version.length() > startIndex )
         {
             list.add( parseItem( isDigit, version.substring( startIndex ) ) );
         }
 
         while ( !stack.isEmpty() )
         {
             list = (ListItem) stack.pop();
             list.normalize();
         }
 
         canonical = items.toString();
     }
 
     private static Item parseItem( boolean isDigit, String buf )
     {
         return isDigit ? new IntegerItem( buf ) : new StringItem( buf, false );
     }
 
     public int compareTo( ComparableVersion o )
     {
         return items.compareTo( o.items );
     }
 
     public String toString()
     {
         return value;
     }
 
     public String getCanonical()
     {
         return canonical;
     }
 
     public boolean equals( Object o )
     {
         return ( o instanceof ComparableVersion ) && canonical.equals( ( (ComparableVersion) o ).canonical );
     }
 
     public int hashCode()
     {
         return canonical.hashCode();
     }
 
     /**
      * Main to test version parsing and comparison.
      *
      * @param args the version strings to parse and compare
      */
     public static void main( String... args )
     {
         System.out.println( "Display parameters as parsed by Maven (in canonical form) and comparison result:" );
         if ( args.length == 0 )
         {
             return;
         }
 
         ComparableVersion prev = null;
         int i = 1;
         for ( String version : args )
         {
             ComparableVersion c = new ComparableVersion( version );
 
             if ( prev != null )
             {
                 int compare = prev.compareTo( c );
                 System.out.println( "   " + prev.toString() + ' '
                     + ( ( compare == 0 ) ? "==" : ( ( compare < 0 ) ? "<" : ">" ) ) + ' ' + version );
             }
 
             System.out.println( String.valueOf( i++ ) + ". " + version + " == " + c.getCanonical() );
 
             prev = c;
         }
     }
 }