/*
 * Forge Mod Loader
 * Copyright (c) 2012-2013 cpw.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *
 * Contributors:
 *     cpw - implementation
 */

package org.ultramine.bootstrap.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.ListIterator;
import java.util.Locale;
import java.util.Properties;
import java.util.Stack;

/**
 * Generic implementation of version comparison.
 *
 * <p>Features:
 * <ul>
 * <li>mixing of '<code>-</code>' (dash) 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>snapshot</code></li>
 *     <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>(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 dash usually precedes a qualifier, and is always less important than something preceded with a dot.</li>
 * </ul></p>
 *
 * @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
	{
		final int INTEGER_ITEM = 0;
		final int STRING_ITEM = 1;
		final 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 BigInteger_ZERO = new BigInteger( "0" );

		private final BigInteger value;

		public static final IntegerItem ZERO = new IntegerItem();

		private IntegerItem()
		{
			this.value = BigInteger_ZERO;
		}

		public IntegerItem( String str )
		{
			this.value = new BigInteger( str );
		}

		@Override
		public int getType()
		{
			return INTEGER_ITEM;
		}

		@Override
		public boolean isNull()
		{
			return BigInteger_ZERO.equals( value );
		}

		@Override
		public int compareTo( Item item )
		{
			if ( item == null )
			{
				return BigInteger_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() );
			}
		}

		@Override
		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" };

		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;
				}
			}
			this.value = ALIASES.getProperty( value , value );
		}

		@Override
		public int getType()
		{
			return STRING_ITEM;
		}

		@Override
		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 );
		}

		@Override
		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() );
			}
		}

		@Override
		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
	{
		/**
		 *
		 */
		private static final long serialVersionUID = 1L;

		@Override
		public int getType()
		{
			return LIST_ITEM;
		}

		@Override
		public boolean isNull()
		{
			return ( size() == 0 );
		}

		void normalize()
		{
			for( ListIterator<Item> iterator = listIterator( size() ); iterator.hasPrevious(); )
			{
				Item item = iterator.previous();
				if ( item.isNull() )
				{
					iterator.remove(); // remove null trailing items: 0, "", empty list
				}
				else
				{
					break;
				}
			}
		}

		@Override
		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 ? -1 * r.compareTo( l ) : l.compareTo( r );

						if ( result != 0 )
						{
							return result;
						}
					}

					return 0;

				default:
					throw new RuntimeException( "invalid item: " + item.getClass() );
			}
		}

		@Override
		public String toString()
		{
			StringBuilder buffer = new StringBuilder( "(" );
			for( Iterator<Item> iter = iterator(); iter.hasNext(); )
			{
				buffer.append( iter.next() );
				if ( iter.hasNext() )
				{
					buffer.append( ',' );
				}
			}
			buffer.append( ')' );
			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<Item>();
		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;

				if ( isDigit )
				{
					list.normalize(); // 1.0-* = 1-*

					if ( ( i + 1 < version.length() ) && Character.isDigit( version.charAt( i + 1 ) ) )
					{
						// new ListItem only if previous were digits and new char is a digit,
						// ie need to differentiate only 1.1 from 1-1
						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;
				}

				isDigit = true;
			}
			else
			{
				if ( isDigit && i > startIndex )
				{
					list.add( parseItem( true, version.substring( startIndex, i ) ) );
					startIndex = i;
				}

				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 );
	}

	@Override
	public int compareTo( ComparableVersion o )
	{
		return items.compareTo( o.items );
	}

	@Override
	public String toString()
	{
		return value;
	}

	@Override
	public boolean equals( Object o )
	{
		return ( o instanceof ComparableVersion ) && canonical.equals( ( (ComparableVersion) o ).canonical );
	}

	@Override
	public int hashCode()
	{
		return canonical.hashCode();
	}
}