SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// Multi-Phasic Applications: SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package java.util;

import cc.squirreljme.runtime.cldc.debug.Debugging;
import java.lang.ref.WeakReference;

/**
 * Iterator over weak hash map entry keys.
 *
 * @since 2023/02/09
 */
final class __WeakHashMapIterator__<K, V>
    implements Iterator<Map.Entry<K, V>>
{
    /** The iterator this is using. */
    private final Iterator<Map.Entry<__WeakHashMapKey__<K>, V>> _iterator;
    
    /** Is there an entry waiting for us? */
    private __WeakHashMapEntry__<K, V> _waiting;
    
    /**
     * Initializes the iterator.
     * 
     * @param __iterator The iterator over entries.
     * @throws NullPointerException On null arguments.
     * @since 2023/02/09
     */
    __WeakHashMapIterator__(
        Iterator<Map.Entry<__WeakHashMapKey__<K>, V>> __iterator)
        throws NullPointerException
    {
        if (__iterator == null)
            throw new NullPointerException("NARG");
        
        this._iterator = __iterator;
    }
    
    /**
     * {@inheritDoc}
     * @since 2023/02/09
     */
    @Override
    public boolean hasNext()
    {
        try
        {
            // There has to be something waiting for us here, since we delete
            // entries on iteration we need to check this
            this.__next();
            
            // If this is here then we have something waiting
            return true;
        }
        
        // If this happens, then there is actually nothing
        catch (NoSuchElementException ignored)
        {
            return false;
        }
    }
    
    /**
     * {@inheritDoc}
     * @since 2023/02/09
     */
    @Override
    public Map.Entry<K, V> next()
        throws NoSuchElementException
    {
        // Pop in next, if there is one... will return the waiting item
        __WeakHashMapEntry__<K, V> result = this.__next();
        
        // We took what was waiting, so remove that now
        this._waiting = null;
        
        return result;
    }
    
    /**
     * {@inheritDoc}
     * @since 2023/02/09
     */
    @Override
    public void remove()
        throws IllegalStateException, UnsupportedOperationException
    {
        this._iterator.remove();
    }
    
    /**
     * Queues the next item
     * 
     * @return The next entry, will be {@link #_waiting}.
     * @since 2023/02/09
     */
    private __WeakHashMapEntry__<K, V> __next()
    {
        // If there is something already waiting, do that
        if (this._waiting != null)
            return this._waiting;
        
        // Keep poking the iterator for new entries, if there are any
        Iterator<Map.Entry<__WeakHashMapKey__<K>, V>> iterator =
            this._iterator;
        for (;;)
        {
            // Get next entry, if this fails we stop as the iteration is empty
            Map.Entry<__WeakHashMapKey__<K>, V> next = iterator.next();
            
            // Get the details here
            __WeakHashMapKey__<K> wrappedKey = next.getKey();
            WeakReference<K> ref = wrappedKey._ref;
            
            // If reference is null, then this key represents null
            if (ref == null)
                return new __WeakHashMapEntry__<>(null, next);
            
            // Get the key, if it is null then we just got it GCed
            K key = ref.get();
            if (key == null)
            {
                // Just remove this from the set now...
                iterator.remove();
                
                // Try again because we cannot continue here...
                continue;
            }
            
            // Wrap it and set a waiting down
            this._waiting = new __WeakHashMapEntry__<>(key, next);
            return this._waiting;
        }
    }
}