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/*
 * Copyright 2008-2012 Sergey Skladchikov
 *
 * 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 org.gwt.advanced.client.datamodel;

import org.gwt.advanced.client.ui.SuggestionBoxListener;

/**
 * This is an implementation designed especially for the suggestion box widget.
 * The content of this widget depends on the expression value. Expression interpretation may be different
 * and must be defined in the {@link org.gwt.advanced.client.datamodel.ListCallbackHandler} implementation.
 *
 * @author Sergey Skladchikov
 * @since 1.2.0
 */
public class SuggestionBoxDataModel extends ComboBoxDataModel implements SuggestionBoxListener {
    /** an expression to suggest items for the list */
    private String expression;
    /** a callback handler to fill the list */
    private ListCallbackHandler handler;

    /**
     * Constructs the class and sets the expression value to null.
     * 
     * @param handler is a handler to fill data.
     */
    public SuggestionBoxDataModel(ListCallbackHandler handler) {
        this(null, handler);
    }

    /**
     * Constructs the class and performs filling via the handler.
     *
     * @param expression an expression to be used for filtering.
     * @param handler a callback handler to fill the list.
     */
    public SuggestionBoxDataModel(String expression, ListCallbackHandler handler) {
        this.expression = expression;
        this.handler = handler;

        fill();
    }

    /**
     * Getter for property 'expression'.
     *
     * @return Value for property 'expression'.
     */
    public String getExpression() {
        return expression;
    }

    /**
     * Setter for property 'expression'.
     *
     * @param expression Value to set for property 'expression'.
     */
    public void setExpression(String expression) {
        this.expression = expression;

        fireEvent(new SuggestionModelEvent(this, SuggestionModelEvent.EXPRESSION_CHANGED, expression));
    }

    /** {@inheritDoc} */
    public void onChange(String expression) {
        setExpression(expression);
        fill();
    }

    /**
     * Sets the callback handler that must fill the model with the values on demand.
     *
     * @param handler is a handler to set.
     */
    public void setHandler(ListCallbackHandler handler) {
        this.handler = handler;
    }

    /**
     * Getter for property 'handler'.
     *
     * @return Value for property 'handler'.
     */
    protected ListCallbackHandler getHandler() {
        return handler;
    }

    /**
     * This method fills the list with the values.
     */
    @SuppressWarnings({"unchecked"})
    protected void fill() {
        ListCallbackHandler handler = getHandler();
        if (handler != null)
            handler.fill(this);
    }
}