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 cc.squirreljme.debugger;

import java.util.Arrays;

/**
 * Tally tracker.
 *
 * @since 2024/01/19
 */
public final class TallyTracker
{
    /** Tally listeners. */
    private volatile TallyListener[] _listeners;
    
    /** The current value. */
    private volatile int _value;
    
    /**
     * Adds a tally listener.
     *
     * @param __listener The listener to add.
     * @throws NullPointerException On null arguments.
     * @since 2024/01/19
     */
    public void addListener(TallyListener __listener)
        throws NullPointerException
    {
        if (__listener == null)
            throw new NullPointerException("NARG");
        
        synchronized (this)
        {
            // Expand array?
            TallyListener[] current = this._listeners;
            if (current != null)
                current = Arrays.copyOf(current, current.length + 1);
            else
                current = new TallyListener[1];
            
            // Set last to the new listener
            current[current.length - 1] = __listener;
            
            // Store for future usage
            this._listeners = current;
        }
    }
    
    /**
     * Decrements the tally by one.
     *
     * @since 2024/01/26
     */
    public void decrement()
    {
        // The changed values
        int oldValue;
        int newValue;
        
        // Increment it
        TallyListener[] listeners;
        synchronized (this)
        {
            // Get listeners to use
            listeners = this._listeners;
            
            // Get old and then increment to the new
            oldValue = this._value;
            if (oldValue > 0)
                newValue = oldValue - 1;
            else
                newValue = 0;
            
            // Store the new value
            this._value = newValue;
        }
        
        // Send to all listeners
        this.__notify(listeners, oldValue, newValue);
    }
    
    /**
     * Returns the current value.
     *
     * @return The current tally value.
     * @since 2024/01/19
     */
    public int get()
    {
        synchronized (this)
        {
            return this._value;
        }
    }
    
    /**
     * Increments the tally by one.
     *
     * @since 2024/01/19
     */
    public void increment()
    {
        // The changed values
        int oldValue;
        int newValue;
        
        // Increment it
        TallyListener[] listeners;
        synchronized (this)
        {
            // Get listeners to use
            listeners = this._listeners;
            
            // Get old and then increment to the new
            oldValue = this._value;
            newValue = oldValue + 1;
            
            // Store the new value
            this._value = newValue;
        }
        
        // Send to all listeners
        this.__notify(listeners, oldValue, newValue);
    }
    
    /**
     * Sets to the given value.
     *
     * @param __value The value to set to.
     * @since 2024/01/26
     */
    public void set(int __value)
    {
        // The changed values
        int oldValue;
        int newValue;
        
        // Increment it
        TallyListener[] listeners;
        synchronized (this)
        {
            // Get listeners to use
            listeners = this._listeners;
            
            // Get old and then increment to the new
            oldValue = this._value;
            newValue = (__value >= 0 ? __value : 0);
            
            // Store the new value
            this._value = newValue;
        }
        
        // Send to all listeners
        this.__notify(listeners, oldValue, newValue);
    }
    
    /**
     * Notifies the given listeners.
     *
     * @param __listeners The listeners to notify.
     * @param __oldValue The old value.
     * @param __newValue The new value.
     * @since 2024/01/26
     */
    private void __notify(TallyListener[] __listeners,
        int __oldValue, int __newValue)
    {
        // Send to all listeners
        if (__listeners != null && __oldValue != __newValue)
            for (TallyListener listener : __listeners)
                if (listener != null)
                    listener.updateTally(this, __oldValue, __newValue);
    }
}