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package net.sf.cuf.model;

/**
 * A ValueHolder object holds a value (any Object). The value can
 * be changed via setValue() and accessed vai getValue(). Whenever
 * the value changes, all interested listeners are notified.
 * @param  the type of the value we hold
 */
public class ValueHolder extends AbstractValueModel implements ValueModel, DelegateAccess
{
    /** our value, may be null */
    private T  mValue;

    /**
     * Create a new holder with NULL as its value.
     */
    public ValueHolder()
    {
        this(null);
    }

    /**
     * Create a new holder with the handed object as its value.
     * @param pValue the value we hold, may be null
     */
    public ValueHolder(final T pValue)
    {
        super();
        mValue= pValue;
    }

    /**
     * Returns always true
     * @return true
     */
    public boolean isEditable()
    {
        return true;
    }

    /**
     * Set a new value, this will fire a ChangeEvent if the new value
     * is different from the old value.
     * @param pValue the new value (null is o.k.)
     * @param pIsSetForced true if a forced setValue should be done
     */
    public void setValue(final T pValue, final boolean pIsSetForced)
    {
        checkDisposed();
        // optimize only if there is no forced update
        if (!pIsSetForced)
        {
            if ((mValue != null ? mValue.equals(pValue) : pValue == null || pValue.equals(mValue)))
            {
                // nothing changed
                return;
            }
        }

        mValue= pValue;
        setInSetValue(true, pIsSetForced);
        try
        {
            fireStateChanged();
        }
        finally
        {
            setInSetValue(false, pIsSetForced);
        }
    }

    /**
     * Get the current value, during a callback this is the new value.
     * @return null or the value object
     */
    public T getValue()
    {
        checkDisposed();
        return mValue;
    }

    /**
     * Transform the handed value to a new value.
     * This should not change the current value or trigger any updates.
     * @param pValue the value we should assume as our value
     * @return pValue
     */
    public Object getValue(final Object pValue)
    {
        checkDisposed();
        return pValue;
    }
}