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The main module contains the GeoTools public interfaces that are used by other GeoTools modules (and GeoTools applications). Where possible we make use industry standard terms as provided by OGC and ISO standards. The formal GeoTools public api consists of gt-metadata, jts and the gt-main module. The main module contains the default implementations that are available provided to other GeoTools modules using our factory system. Factories are obtained from an appropriate FactoryFinder, giving applications a chance configure the factory used using the Factory Hints facilities. FilterFactory ff = CommonFactoryFinder.getFilterFactory(); Expression expr = ff.add( expression1, expression2 ); If you find yourself using implementation specific classes chances are you doing it wrong: Expression expr = new AddImpl( expression1, expressiom2 );

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/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2019, 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.styling.visitor;

import javax.measure.Unit;
import javax.measure.UnitConverter;
import javax.measure.quantity.Length;
import org.geotools.measure.Units;
import org.geotools.util.Converters;
import org.opengis.filter.FilterFactory;
import org.opengis.filter.expression.Expression;
import org.opengis.filter.expression.Literal;
import si.uom.SI;
import systems.uom.common.USCustomary;

class UomRescaleHelper {

    private double mapScale = 1;

    private FilterFactory ff;

    public UomRescaleHelper(FilterFactory ff, double mapScale, boolean rescaleRealWorldUnits) {
        this.ff = ff;
        this.mapScale = mapScale;
    }

    /**
     * Computes a rescaling multiplier to be applied to an unscaled value.
     *
     * @param uom the unit of measure that will be used to scale.
     * @return the rescaling multiplier for the provided parameters.
     */
    protected double computeRescaleMultiplier(Unit uom) {
        // no scaling to do if UOM is PIXEL (or null, which stands for PIXEL as well)
        if (uom == null || uom.equals(Units.PIXEL)) return 1;

        if (uom == SI.METRE) {
            return mapScale;
        }

        // converts value from meters to given UOM
        UnitConverter converter = uom.getConverterTo(SI.METRE);
        return converter.convert(mapScale);
    }

    /**
     * Used to rescale the provided unscaled value.
     *
     * @param unscaled the unscaled value.
     * @param uom the unit of measure that will be used to scale.
     * @return the expression multiplied by the provided scale.
     */
    protected Expression rescale(Expression unscaled, Unit uom) {
        if (unscaled == null || unscaled.equals(Expression.NIL)) return unscaled;

        if (unscaled instanceof Literal) {
            // check if we have a uom attached at the end of the expression
            String value = unscaled.evaluate(null, String.class);
            if (value == null) {
                throw new IllegalArgumentException(
                        "Invalid empty measure '', "
                                + "was expecting a number, eventually followed by px, m or ft");
            }
            if (value.endsWith("px")) {
                // no rescale needed for this one
                value = value.substring(0, value.length() - 2);
                return ff.literal(Converters.convert(value, Double.class));
            } else {
                if (value.endsWith("ft")) {
                    value = value.substring(0, value.length() - 2);
                    uom = USCustomary.FOOT;
                } else if (value.endsWith("m")) {
                    value = value.substring(0, value.length() - 1);
                    uom = SI.METRE;
                }
                Double measure = Converters.convert(value, Double.class);
                if (measure != null) {
                    double rescaled = rescale(measure, uom);
                    return ff.literal(rescaled);
                } else {
                    throw new IllegalArgumentException(
                            "Invalid measure '"
                                    + value
                                    + "', was expecting a number, eventually followed by px, m or ft");
                }
            }
        } else {
            // otherwise, we use the rescaleToPixels function as
            double rescaleMultiplier = computeRescaleMultiplier(uom);
            return ff.multiply(unscaled, ff.literal(rescaleMultiplier));
        }
    }

    /**
     * Used to rescale the provided dash array.
     *
     * @param dashArray the unscaled dash array. If null, the method returns null.
     * @param uom the unit of measure that will be used to scale.
     * @return the rescaled dash array
     */
    protected float[] rescale(float[] dashArray, Unit uom) {
        if (dashArray == null) return null;
        if (uom == null || uom.equals(Units.PIXEL)) return dashArray;

        float[] rescaledDashArray = new float[dashArray.length];

        for (int i = 0; i < rescaledDashArray.length; i++) {
            rescaledDashArray[i] = (float) rescale((double) dashArray[i], uom);
        }
        return rescaledDashArray;
    }

    /**
     * Used to rescale the provided unscaled value.
     *
     * @param unscaled the unscaled value.
     * @param uom the unit of measure that will be used to scale.
     * @return a scaled value.
     */
    private double rescale(double unscaled, Unit uom) {
        // computes the basic rescaled value
        return unscaled * computeRescaleMultiplier(uom);
    }
}