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package net.sf.cuf.model.state;

import net.sf.cuf.state.SimpleState;
import net.sf.cuf.state.MutableState;
import net.sf.cuf.model.ValueModel;

import javax.swing.event.ChangeListener;
import javax.swing.event.ChangeEvent;

/**
 * A ValueState object wraps a ValueModel as a MutableState.
 * The true/false state of a MutableState is mapped to setting the value
 * of the ValueModel to Boolean.TRUE/Boolean.FALSE.
 * The isInitialized()/reset() semantics are mapped to setting
 * the value of the ValueModel to null.
 */
public class ValueState extends SimpleState implements MutableState, ChangeListener
{
    /** string we consider as true */
    private static final String TRUE = Boolean.TRUE.toString();

    /** the ValueModel we wrap, never null */
    private ValueModel   mModel;
    
    /**
     * If the property is null (default), then a value of null in the value model means
     * that the state will be not {@link #isInitialized()}.
     * If the property is {@link Boolean#TRUE}, then a value of null
     * in the value model means that the state is enabled.
     * If the property is {@link Boolean#FALSE}, then a value of null
     * in the value model means that the state is disabled.
     */
    private Boolean         mMeaningOfNull;

    /**
     * We wrap a ValueModel as a MutableState object.
     * @param pModel model we wrap, must not be null
     * @throws IllegalArgumentException if pModel is null
     */
    public ValueState(final ValueModel pModel)
    {
        if (pModel==null)
            throw new IllegalStateException("model must not be null");

        mModel= pModel;
        propagateModelToState();
        mModel.addChangeListener(this);
    }

    /**
     * Sets the state, the wrapped ValueModel will be set to Boolean.TRUE or Boolean.FALSE.
     * @param pEnabled true if the state gets enabled
     */
    public void setEnabled(final boolean pEnabled)
    {
        mInSetEnabled= true;
        try
        {
            mModel.setValue(pEnabled);
            super.setEnabled(pEnabled);
        }
        finally
        {
            mInSetEnabled= false;
        }
    }

    /**
     * Sets the state with a reason object. The reason object
     * may be null, and is returned to a getChangeReason() call
     * during the callback.
     * @param pEnabled true if the state gets enabled
     * @param pReason null or reason for the change
     */
    public void setEnabled(final boolean pEnabled, final Object pReason)
    {
        mModel.setValue(pEnabled);
        super.setEnabled(pEnabled, pReason);
    }

    /**
     * Resets a MutableState to not initilized. Calling this
     * method will not trigger a notification of the
     * (State) listeners. The value of the ValueModel will
     * be set to null.
     */
    public void reset()
    {
        mModel.setValue(null);
        super.reset();
    }

    /**
     * configures the behaviour of the state when the
     * value model has the value null.
     * If the parameter is null (default), then a value of null in the value model means
     * that the state will be not {@link #isInitialized()}.
     * If the parameter is {@link Boolean#TRUE}, then a value of null
     * in the value model means that the state is enabled.
     * If the parameter is {@link Boolean#FALSE}, then a value of null
     * in the value model means that the state is disabled.
     * 
     * @param pMeaningOfNull the meaning of null
     */
    public void setMeaningOfNull(final Boolean pMeaningOfNull)
    {
        mMeaningOfNull = pMeaningOfNull;
        propagateModelToState();
    }
    
    /**
     * @return the meaning of null
     * @see #setMeaningOfNull(Boolean)
     */
    public Boolean getMeaningOfNull()
    {
        return mMeaningOfNull;
    }
    
    /**
     * Invoked when the target of the listener has changed its state.
     *
     * @param pEvent  a ChangeEvent object
     */
    public void stateChanged(final ChangeEvent pEvent)
    {
        if (inSetEnabled())
        {
            return;
        }
        propagateModelToState();
    }

    /**
     * Small helper that propagates the value of the ValueModel to our state.
     */
    private void propagateModelToState()
    {
        if (mModel.getValue()==null)
        {
            if (mMeaningOfNull==null)
            {
                super.reset();
            }
            else
            {
                super.setEnabled(mMeaningOfNull, mModel);
            }
        }
        else
        {
            super.setEnabled(getModelAsBoolean(mModel), mModel);
        }
    }

    /**
     * Small helper to get the boolean value of the value of a ValueModel.
     * @param pModel the model we examine, must not be null
     * @return true if pModel is Boolean.TRUE or "true", false otherwise
     */
    private boolean getModelAsBoolean(final ValueModel pModel)
    {
        Object value= pModel.getValue();
        if (value==null)
        {
            return false;
        }
        if (value instanceof Boolean)
        {
            return (Boolean) value;
        }
        return value.toString().equals(TRUE);
    }
}