/*******************************************************************************
 * Copyright (c) 2012, 2013 Original authors and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Original authors and others - initial API and implementation
 ******************************************************************************/
package org.eclipse.nebula.widgets.nattable.extension.builder.util;

import static org.eclipse.nebula.widgets.nattable.util.ObjectUtils.isNotNull;

import java.text.DecimalFormat;
import java.text.ParseException;

import org.eclipse.nebula.widgets.nattable.data.convert.DisplayConverter;
import org.eclipse.nebula.widgets.nattable.data.convert.IDisplayConverter;

/**
 * Converts between data source and display values for numeric data.
 */
public class DisplayConverters {

    /**
     * Convert using the FormatterFactory. (Typically Broker and Book columns)
     *
     * @see BrokerFormatter
     * @see BookFormatter
     */
    public static IDisplayConverter getDoubleDisplayConverter(
            final String pattern) {
        return new DisplayConverter() {
            private final DecimalFormat formatter = isNotNull(pattern) ? new DecimalFormat(
                    pattern) : new DecimalFormat();

            public Object canonicalToDisplayValue(Object canonicalValue) {
                if (isNotNull(canonicalValue)) {
                    return formatter.format(canonicalValue);
                }
                return canonicalValue;
            }

            public Object displayToCanonicalValue(Object displayValue) {
                try {
                    if (isNotNull(displayValue)) {
                        return formatter.parse(displayValue.toString())
                                .doubleValue();
                    }
                } catch (ParseException e) {
                    System.err
                            .println("Error while converting the followiung to canonical value: "
                                    + displayValue);
                    e.printStackTrace(System.err);
                }
                return displayValue;
            }
        };
    }
}