FilterFunction_listMultiply.java

/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2017, Open Source Geospatial Foundation (OSGeo)
 *    
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 */
package org.geotools.filter.function;

import java.util.regex.Pattern;
import org.geotools.filter.FunctionExpressionImpl;
import org.geotools.filter.capability.FunctionNameImpl;
import static org.geotools.filter.capability.FunctionNameImpl.parameter;
import org.opengis.filter.capability.FunctionName;
import org.opengis.filter.expression.Expression;

/**
 * Filter function to multiply a text list of numbers with a given factor.
 *
 * "1 2 3" * 2 = "2 4 6"
 *
 * @author Tobias Warneke
 */
public class FilterFunction_listMultiply extends FunctionExpressionImpl {

    public static FunctionName NAME = new FunctionNameImpl("listMultiply", String.class,
            parameter("factor", Number.class),
            parameter("list", String.class));

    public FilterFunction_listMultiply() {
        super(NAME);
    }

    private static final Pattern WHITE_SPACE_SPLIT = Pattern.compile("\\s+");

    @Override
    public Object evaluate(Object feature) {
        Number arg0;
        String arg1;

        try { // attempt to get value and perform conversion
            Object o = getExpression(0).evaluate(feature);
            if (o instanceof String) {
                arg0 = Double.valueOf((String) o);
            } else {
                arg0 = (Number) o;
            }
        } catch (Exception e) // probably a type error
        {
            throw new IllegalArgumentException(
                    "Filter Function problem for function listMultiply argument #0 - expected type Double (" + e.getMessage() + ")");
        }

        try {
            // attempt to get value and perform conversion
            final Expression exprArg1 = getExpression(1);
            if (exprArg1 == null) {
                return null;
            }

            Object data = exprArg1.evaluate(feature);
            if (data instanceof Number) {
                return ((Number) data).doubleValue() * arg0.doubleValue();
            }

            arg1 = (String) data;
        } catch (Exception e) // probably a type error
        {
            throw new IllegalArgumentException(
                    "Filter Function problem for function listMultiply argument #1 - expected type String (" + e.getMessage() + ")");
        }

        if (arg1 == null || arg1.isEmpty()) {
            return null;
        }

        String[] values = WHITE_SPACE_SPLIT.split(arg1);
        StringBuilder b = new StringBuilder();

        for (int i = 0; i < values.length; i++) {
            if ("".equals(values[i])) {
                continue;
            }
            if (b.length() != 0) {
                b.append(" ");
            }
            b.append(Double.valueOf(values[i]) * arg0.doubleValue());
        }

        return b.toString();
    }
}