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package net.sf.cuf.model.state;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

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

import net.sf.cuf.model.ValueModel;
import net.sf.cuf.state.AbstractState;

/**
 * The RegExpState is a state that is enabled if value model has a string value
 * that matches the given regular expression. If the value model has a string
 * value that does not match the regular expression or a value of different
 * type (not a CharSequence), this state is disabled.
 */
public class RegExpState extends AbstractState implements ChangeListener
{
    
    /**
     * the value model we are responsible for, never null
     */
    private ValueModel mTrigger;
    
    /**
     * the compiled pattern for checking the value
     */
    private Pattern mPattern;
    
    /**
     * Creates a new RegExpState for the given value model and
     * the given regular expression pattern
     * @param pTrigger the trigger value model whose value is observed and checked, must not be null
     * @param pRegExpr the regular expression pattern, must not be null
     */
    public RegExpState(final ValueModel pTrigger, final String pRegExpr)
    {
        if (pTrigger==null)
        {
            throw new IllegalArgumentException( "pTrigger must not be null");
        }
        if (pRegExpr==null)
        {
            throw new IllegalArgumentException( "pRegExpr must not be null");
        }
        mTrigger = pTrigger;
        mPattern = Pattern.compile( pRegExpr);
        
        mIsInitialized = true;
        mTrigger.addChangeListener( this);
        checkTriggerValue();
    }
    
    /**
     * called when our trigger changes
     * {@inheritDoc}
     */
    public void stateChanged(final ChangeEvent pE)
    {
        checkTriggerValue();
    }

    /**
     * checks the value of our trigger and computes this state value
     */
    private void checkTriggerValue()
    {
        boolean newIsEnabled = false;
        Object value = mTrigger.getValue();
        if (value instanceof CharSequence)
        {
            Matcher matcher= mPattern.matcher((CharSequence)value);
            newIsEnabled = matcher.matches();
        }
        if (newIsEnabled!=mIsEnabled)
        {
            mIsEnabled = newIsEnabled;
            fireStateChanged();
        }
    }
}