// This Source Code is in the Public Domain per: http://unlicense.org
package org.litesoft.util;

import java.util.*;

public class CopyOnWriteUniqueIdentityListManager<E>
{
    List<E> mEntries = Collections.emptyList();

    public synchronized List<E> getAll()
    {
        return mEntries;
    }

    public synchronized void removeAll()
    {
        mEntries = Collections.emptyList();
    }

    /**
     * @return True if pE actually added
     */
    public synchronized boolean add( E pE )
    {
        if ( (pE != null) && !contains( pE ) )
        {
            List<E> zNewList = new ArrayList<E>( mEntries );
            zNewList.add( pE );
            mEntries = Collections.unmodifiableList( zNewList );
            return true;
        }
        return false;
    }

    /**
     * @return True if pE actually removed
     */
    public synchronized boolean remove( E pE )
    {
        int zAt = indexOf( pE );
        if ( zAt != -1 )
        {
            if ( mEntries.size() == 1 )
            {
                mEntries = Collections.emptyList();
            }
            else
            {
                List<E> zNewList = new ArrayList<E>();
                int i = 0;
                for (; i < zAt; i++ )
                {
                    zNewList.add( mEntries.get( i ) );
                }
                while ( ++i < mEntries.size() )
                {
                    zNewList.add( mEntries.get( i ) );
                }
                mEntries = Collections.unmodifiableList( zNewList );
            }
            return true;
        }
        return false;
    }

    private int indexOf( E pE )
    {
        if ( pE != null )
        {
            List<E> zList = getAll();
            for ( int i = 0; i < zList.size(); i++ )
            {
                if ( pE == zList.get( i ) )
                {
                    return i;
                }
            }
        }
        return -1;
    }

    private boolean contains( E pE )
    {
        return -1 != indexOf( pE );
    }
}