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Guise™ Internet application framework.
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/*
 * Copyright © 2005-2008 GlobalMentor, Inc. 
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.guise.framework.model;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyVetoException;

import static java.util.Objects.*;

import com.globalmentor.beans.GenericPropertyChangeEvent;

import io.guise.framework.validator.*;

/**
 * An abstract implementation of a model representing a value. A derived class need only implement the value access methods.
 * @param  The type of value contained in the model.
 * @author Garret Wilson
 */
public abstract class AbstractValueModel extends AbstractModel implements ValueModel {

	/** The validator for this model, or null if no validator is installed. */
	private Validator validator;

	@Override
	public Validator getValidator() {
		return validator;
	}

	@Override
	public void setValidator(final Validator newValidator) {
		if(validator != newValidator) { //if the value is really changing
			final Validator oldValidator = validator; //get the old value
			validator = newValidator; //actually change the value
			firePropertyChange(VALIDATOR_PROPERTY, oldValidator, newValidator); //indicate that the value changed
		}
	}

	/** The class representing the type of value this model can hold. */
	private final Class valueClass;

	@Override
	public Class getValueClass() {
		return valueClass;
	}

	/**
	 * Constructs a value model indicating the type of value it can hold.
	 * @param valueClass The class indicating the type of value held in the model.
	 * @throws NullPointerException if the given value class is null.
	 */
	public AbstractValueModel(final Class valueClass) {
		this.valueClass = requireNonNull(valueClass, "Value class cannot be null."); //store the value class
	}

	/**
	 * {@inheritDoc}
	 * 
	 * This version delegates to the validator, if one is installed.
	 * 
	 * @see #getValidator()
	 * @see #getValue()
	 */
	@Override
	public boolean isValidValue() {
		final Validator validator = getValidator(); //get the current validator
		return validator != null ? validator.isValid(getValue()) : true; //if we have a validator, make sure it thinks the value is valid
	}

	/**
	 * {@inheritDoc}
	 * 
	 * This version validates the current value if there is a validator installed.
	 * 
	 */
	@Override
	public void validateValue() throws ValidationException {
		final Validator validator = getValidator(); //get the currently installed validator, if there is one
		if(validator != null) { //if a validator is installed
			validator.validate(getValue()); //validate the current value, throwing an exception if anything is wrong
		}
	}

	/**
	 * Creates a property veto exception that represents a validation exception. The validation exception will be accessible via
	 * {@link PropertyVetoException#getCause()}. This is useful for converting a validation exception into a property veto exception in
	 * {@link ValueModel#setValue(Object)} if an installed validator deems a value invalid.
	 * @param  The type of property the change of which was vetoed because of invalidity.
	 * @param source The source of the property change event.
	 * @param validationException The validation exception that is the cause of the property veto.
	 * @param propertyName The name of the property the change of which was vetoed.
	 * @param oldValue The old value of the property.
	 * @param newValue The new value of the property.
	 * @return A property veto exception representing the validation error.
	 */
	public static  PropertyVetoException createPropertyVetoException(final Object source, final ValidationException validationException,
			final String propertyName, final VV oldValue, final VV newValue) {
		final PropertyChangeEvent propertyChangeEvent = new GenericPropertyChangeEvent(source, propertyName, oldValue, newValue); //create a new property change event
		final PropertyVetoException propertyVetoException = new PropertyVetoException(validationException.getMessage(), propertyChangeEvent); //create a new property veto exception with the message from the validation exception
		propertyVetoException.initCause(validationException); //indicate the cause of the property veto exception
		return propertyVetoException; //return the new property veto exception
	}

}