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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) 2005-2008, 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.feature.visitor;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.factory.CommonFactoryFinder;
import org.geotools.filter.IllegalFilterException;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;
import org.opengis.filter.FilterFactory;
import org.opengis.filter.expression.Expression;

/**
 * Calculates the maximum value of an attribute.
 *
 * @author Cory Horner, Refractions Research Inc.
 * @since 2.2.M2
 */
public class MaxVisitor implements FeatureCalc, FeatureAttributeVisitor {
    private Expression expr;
    Comparable maxvalue;
    Comparable curvalue;
    boolean visited = false;
    int countNull = 0;
    int countNaN = 0;

    public MaxVisitor(String attributeTypeName) {
        FilterFactory factory = CommonFactoryFinder.getFilterFactory(null);
        expr = factory.property(attributeTypeName);
    }

    public MaxVisitor(int attributeTypeIndex, SimpleFeatureType type)
            throws IllegalFilterException {
        FilterFactory factory = CommonFactoryFinder.getFilterFactory(null);
        expr = factory.property(type.getDescriptor(attributeTypeIndex).getLocalName());
    }

    public MaxVisitor(String attrName, SimpleFeatureType type) throws IllegalFilterException {
        FilterFactory factory = CommonFactoryFinder.getFilterFactory(null);
        expr = factory.property(type.getDescriptor(attrName).getLocalName());
    }

    public MaxVisitor(Expression expr) throws IllegalFilterException {
        this.expr = expr;
    }

    public void init(SimpleFeatureCollection collection) {
        // do nothing
    }

    @Override
    public List getExpressions() {
        return Arrays.asList(expr);
    }

    @Override
    public Optional> getResultType(List inputTypes) {
        return CalcUtil.reflectInputTypes(1, inputTypes);
    }

    /**
     * Visitor function, which looks at each feature and finds the maximum.
     *
     * @param feature the feature to be visited
     */
    public void visit(SimpleFeature feature) {
        visit((org.opengis.feature.Feature) feature);
    }

    public void visit(org.opengis.feature.Feature feature) {
        Object attribValue = expr.evaluate(feature);

        if (attribValue == null) {
            countNull++; // increment the null count, but don't store its value
            return;
        }

        if (attribValue instanceof Double) {
            double doubleVal = ((Double) attribValue).doubleValue();
            if (Double.isNaN(doubleVal) || Double.isInfinite(doubleVal)) {
                countNaN++; // increment the NaN count, but don't store NaN as the max
                return;
            }
        }

        curvalue = (Comparable) attribValue;

        if ((!visited) || (curvalue.compareTo(maxvalue) > 0)) {
            maxvalue = curvalue;
            visited = true;
        }

        // throw new IllegalStateException("Expression is not comparable!");
    }

    /**
     * Get the max value.
     *
     * @return Max value
     */
    public Comparable getMax() {
        if (!visited) {
            throw new IllegalStateException("Must visit before max value is ready!");
        }

        return maxvalue;
    }

    /** @return the number of features which returned a NaN */
    public int getNaNCount() {
        return countNaN;
    }

    /** @return the number of features which returned a null */
    public int getNullCount() {
        return countNull;
    }

    public void reset() {
        /** Reset the count and current maximum */
        this.visited = false;
        this.maxvalue = Integer.valueOf(Integer.MIN_VALUE);
        this.countNaN = 0;
        this.countNull = 0;
    }

    public Expression getExpression() {
        return expr;
    }

    public CalcResult getResult() {
        if (!visited) {
            return CalcResult.NULL_RESULT;
        }

        return new MaxResult(maxvalue);
    }

    /**
     * Overwrites the result stored by the visitor. This should only be used by optimizations which
     * will tell the visitor the answer rather than visiting all features.
     *
     * For 'max', the value stored is of type 'Comparable'.
     */
    public void setValue(Object result) {
        visited = true;
        maxvalue = (Comparable) result;
    }

    public static class MaxResult extends AbstractCalcResult {
        private Comparable maxValue;

        public MaxResult(Comparable newMaxValue) {
            maxValue = newMaxValue;
        }

        public Object getValue() {
            Comparable max = (Comparable) maxValue;

            return max;
        }

        public boolean isCompatible(CalcResult targetResults) {
            // list each calculation result which can merge with this type of result
            if (targetResults instanceof MaxResult || targetResults == CalcResult.NULL_RESULT) {
                return true;
            }

            return false;
        }

        public CalcResult merge(CalcResult resultsToAdd) {
            if (!isCompatible(resultsToAdd)) {
                throw new IllegalArgumentException("Parameter is not a compatible type");
            }

            if (resultsToAdd == CalcResult.NULL_RESULT) {
                return this;
            }

            if (resultsToAdd instanceof MaxResult) {
                // take the smaller of the 2 values
                Comparable toAdd = (Comparable) resultsToAdd.getValue();
                Comparable newMax = maxValue;

                if (newMax.getClass()
                        != toAdd.getClass()) { // 2 different data types, therefore convert
                    Class bestClass = CalcUtil.bestClass(new Object[] {toAdd, newMax});
                    if (bestClass != toAdd.getClass())
                        toAdd = (Comparable) CalcUtil.convert(toAdd, bestClass);
                    if (bestClass != newMax.getClass())
                        newMax = (Comparable) CalcUtil.convert(newMax, bestClass);
                }
                if (newMax.compareTo(toAdd) < 0) {
                    newMax = toAdd;
                }

                return new MaxResult(newMax);
            } else {
                throw new IllegalArgumentException(
                        "The CalcResults claim to be compatible, but the appropriate merge method has not been implemented.");
            }
        }
    }
}