SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// 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 cc.squirreljme.jdwp.host;

import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.Deque;

/**
 * Represents a value for storage.
 *
 * @since 2021/03/17
 */
public final class JDWPHostValue
    implements AutoCloseable
{
    /** Free value queue. */
    private final Reference<Deque<JDWPHostValue>> _freeValues;
    
    /** Is this open? */
    private volatile boolean _isOpen;
    
    /** The set value. */
    private volatile Object _value;
    
    /** Is this set? */
    private volatile boolean _isSet;
    
    /**
     * Initializes the value storage.
     * 
     * @param __freeValues The free values queue, to go when closed.
     * @throws NullPointerException On null arguments.
     * @since 2021/03/19
     */
    JDWPHostValue(Deque<JDWPHostValue> __freeValues)
        throws NullPointerException
    {
        if (__freeValues == null)
            throw new NullPointerException("NARG");
        
        this._freeValues = new WeakReference<>(__freeValues);
    }
    
    /**
     * {@inheritDoc}
     * @since 2021/03/17
     */
    @SuppressWarnings("SynchronizationOnLocalVariableOrMethodParameter")
    @Override
    public void close()
    {
        if (this._isOpen)
        {
            // Clear to closed
            this._isOpen = true;
            this._isSet = false;
            this._value = null;
            
            // Recycle this back in the queue
            Deque<JDWPHostValue> queue = this._freeValues.get();
            if (queue != null)
                synchronized (queue)
                {
                    queue.add(this);
                }
        }
    }
    
    /**
     * Returns the value.
     * 
     * @return The value.
     * @throws IllegalStateException If no value was set or this was closed.
     * @since 2021/03/17
     */
    public Object get()
        throws IllegalStateException
    {
        synchronized (this)
        {
            // Must be open
            this.__checkOpen();
            
            /* {@squirreljme.error AG0j Value not set.} */
            if (!this._isSet)
                throw new IllegalStateException("AG0j");
            
            return this._value;
        }
    }
    
    /**
     * Checks if the value has been set.
     * 
     * @return If this is set.
     * @throws IllegalStateException If this is not open.
     * @since 2021/04/30
     */
    public boolean isSet()
        throws IllegalStateException
    {
        synchronized (this)
        {
            // Must be open
            this.__checkOpen();
            
            return this._isSet;
        }
    }
    
    /**
     * Sets the value.
     * 
     * @param __val The value to set.
     * @throws IllegalStateException If a value is already set or this is
     * not open.
     * @since 2021/03/19
     */
    public void set(Object __val)
        throws IllegalStateException
    {
        synchronized (this)
        {
            // Must be open
            this.__checkOpen();
            
            /* {@squirreljme.error AG0k Value already set.} */
            if (this._isSet)
                throw new IllegalStateException("AG0k");
            
            this._value = __val;
            this._isSet = true;
        }
    }
    
    /**
     * {@inheritDoc}
     * @since 2021/04/30
     */
    @Override
    public final String toString()
    {
        synchronized (this)
        {
            if (!this._isSet)
                return "<UNSET>";
            return String.valueOf(this._value);
        }
    }
    
    /**
     * Checks if the value is open.
     * 
     * @throws IllegalStateException If it is not open.
     * @since 2021/03/19
     */
    void __checkOpen()
        throws IllegalStateException
    {
        /* {@squirreljme.error AG0i Value not open.} */
        if (!this._isOpen)
            throw new IllegalStateException("AG0i");
    }
    
    /**
     * Resets this value.
     * 
     * @return {@code this}.
     * @since 2021/03/19
     */
    final JDWPHostValue __resetToOpen()
    {
        synchronized (this)
        {
            // Set to open
            this._isOpen = true;
            this._isSet = false;
            this._value = null;
            
            return this;
        }
    }
}