/*
 * Copyright 2008 (C) Tom Parker <thpr@users.sourceforge.net>
 * 
 * This library 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 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library 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 General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package pcgen.rules.persistence.util;

import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;

import pcgen.rules.persistence.token.CDOMSecondaryToken;

/**
 * An Iterator that increments across the CDOMSecondaryTokens for a given Parent
 * Token name and within a given TokenFamily. This is primarily used when items
 * are "unparsed" (converted to LST), since it is necessary to increment across
 * ALL tokens in order to be able to ensure that the object is fully written to
 * a persistent format.
 * 
 * Note that this Iterator "corrects" for the fact that parent classes can also
 * be used, meaning if an LST Token is registered against CDOMObject.class it
 * can be used on Race.class or Ability.class, etc.
 * 
 * @param <C>
 *            The Class of object for which this TokenFamilySubIterator is
 *            iterating over tokens (will be the class of the object being
 *            loaded, such as Race or Ability)
 */
public class TokenFamilySubIterator<C> implements
		Iterator<CDOMSecondaryToken<? super C>>
{
	/**
	 * The Object class, "cached" due to common use
	 */
	private static final Class<Object> OBJECT_CLASS = Object.class;

	/**
	 * The next token to be returned by this TokenFamilySubIterator (Note: is only
	 * validly containing the next token when needNewToken is false)
	 */
	private CDOMSecondaryToken<? super C> nextToken = null;

	/**
	 * True if nextToken has been used and needs to be refreshed
	 */
	private boolean needNewToken = true;
	
	/**
	 * The "acting" class for which tokens are being retrieved. This can be
	 * either the class being loaded (e.g. Race) or a parent Class (e.g.
	 * CDOMObject).
	 */
	private Class<? super C> actingClass;

	/**
	 * The name of the parent token for which the CDOMSecondaryTokens are being
	 * returned.
	 */
	private final String parentToken;
	
	/**
	 * The underlying Iterator that is incrementing across the
	 * CDOMSecondaryTokens in the actingClass.
	 */
	private Iterator<CDOMSecondaryToken<? super C>> subIterator;
	
	/**
	 * The token names that have been used. This is necessary since a specific
	 * class (e.g. Race) can have a "local" version of a token. If that local
	 * version exists, then we MUST skip the version that is "more global" when
	 * we do this Iterator, otherwise this Iterator will provide tokens that are
	 * designed to be unreachable (And thus will produce errors)
	 */
	private final Set<String> used = new HashSet<>();

	/**
	 * Constructs a new TokenFamilySubIterator for the given Class and parent
	 * token name.
	 * 
	 * @param cl
	 *            The Class for which this TokenFamilySubIterator will return
	 *            CDOMSecondaryTokens.
	 * @param parentName
	 *            The name of the parent token for which the CDOMSecondaryTokens
	 *            will be returned
	 */
	public TokenFamilySubIterator(Class<C> cl, String parentName)
	{
		actingClass = cl;
		parentToken = parentName;
		subIterator = TokenFamily.CURRENT.getSubTokens(cl, parentToken)
				.iterator();
	}

	/**
	 * Returns the next CDOMSecondaryToken
	 * 
	 * @see java.util.Iterator#next()
	 */
	@Override
	public CDOMSecondaryToken<? super C> next()
	{
		setNext();
		if (nextToken == null)
		{
			throw new NoSuchElementException();
		}
		needNewToken = true;
		return nextToken;
	}

	/**
	 * Sets nextToken to be "valid", in the sense of determining the next token
	 * that this TokenFamilySubIterator needs to return.
	 */
	private void setNext()
	{
		if (needNewToken)
		{
			nextToken = getNext();
			if (nextToken != null)
			{
				String tokenName = nextToken.getTokenName();
				if (used.contains(tokenName))
				{
					/*
					 * Don't use a super-class token in write
					 */
					needNewToken = true;
					setNext();
				}
				else
				{
					used.add(nextToken.getTokenName());
				}
			}
		}
	}

	/**
	 * Returns the next eligible CDOMSecondaryToken.
	 * 
	 * Note the eligible token may not be valid for use if it is a token for a
	 * parent class and there was a more specific token already defined.
	 * 
	 * @return The next eligible CDOMSecondaryToken
	 */
	private CDOMSecondaryToken<? super C> getNext()
	{
		needNewToken = false;
		while (subIterator.hasNext())
		{
			CDOMSecondaryToken<? super C> tok = subIterator.next();
			return tok;
		}
		if (OBJECT_CLASS.equals(actingClass))
		{
			return null;
		}
		actingClass = actingClass.getSuperclass();
		Set<CDOMSecondaryToken<? super C>> st =
				TokenFamily.CURRENT.getSubTokens(actingClass, parentToken);
		subIterator = st.iterator();
		return getNext();
	}

	/**
	 * @see java.util.Iterator#hasNext()
	 */
	@Override
	public boolean hasNext()
	{
		setNext();
		return nextToken != null;
	}

	/**
	 * Unsupported
	 * 
	 * @see java.util.Iterator#remove()
	 */
	@Override
	public void remove()
	{
		throw new UnsupportedOperationException(
				"Iterator does not support remove");
	}
}