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Library for generating PDFs and images from online webmapping services
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package org.mapfish.print.parser;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import javax.annotation.Nullable;

/**
 * Utility method for getting and setting parameters on Processor Input and Output objects.
 */
public final class ParserUtils {
    /**
     * A filter (for the get attribute methods) that selects only the attributes that are required and
     * excludes all of those with defaults, and therefore are considered optional.
     */
    public static final Predicate FILTER_ONLY_REQUIRED_ATTRIBUTES =
            input -> input != null && input.getAnnotation(HasDefaultValue.class) == null &&
                    !Modifier.isFinal(input.getModifiers());
    /**
     * A filter (for the get attribute methods) that selects only the attributes that are NOT required and
     * excludes all of those that are considered required.
     */
    public static final Predicate FILTER_HAS_DEFAULT_ATTRIBUTES =
            input -> input != null && input.getAnnotation(HasDefaultValue.class) != null;
    /**
     * A filter (for the get attribute methods) that selects only the attributes that are non final. (Can be
     * modified)
     */
    public static final Predicate FILTER_NON_FINAL_FIELDS =
            input -> input != null && !Modifier.isFinal(input.getModifiers());
    /**
     * A filter (for the get attribute methods) that selects only the attributes that are final. (Can NOT be
     * modified)
     */
    public static final Predicate FILTER_FINAL_FIELDS =
            (@Nullable final Field input) -> input != null && Modifier.isFinal(input.getModifiers());

    private static final Function FIELD_TO_NAME = Field::getName;

    private ParserUtils() {
        // intentionally empty.
    }

    /**
     * Inspects the object and all superclasses for public, non-final, accessible methods and returns a
     * collection containing all the attributes found.
     *
     * @param classToInspect the class under inspection.
     */
    public static Collection getAllAttributes(final Class classToInspect) {
        Set allFields = new HashSet<>();
        getAllAttributes(classToInspect, allFields, Function.identity(), field -> true);
        return allFields;
    }

    /**
     * Get a subset of the attributes of the provided class.  An attribute is each public field in the class
     * or super class.
     *
     * @param classToInspect the class to inspect
     * @param filter a predicate that returns true when a attribute should be kept in resulting
     *         collection.
     */
    public static Collection getAttributes(
            final Class classToInspect, final Predicate filter) {
        Set allFields = new HashSet<>();
        getAllAttributes(classToInspect, allFields, Function.identity(), filter);
        return allFields;
    }

    private static  void getAllAttributes(
            final Class classToInspect, final Set results,
            final Function map, final Predicate filter) {

        if (classToInspect != null && classToInspect != Void.class) {
            Collection resultsForClass = Arrays.stream(classToInspect.getFields())
                    .filter(filter)
                    .map(map)
                    .collect(Collectors.toList());
            results.addAll(resultsForClass);
            if (classToInspect.getSuperclass() != null) {
                getAllAttributes(classToInspect.getSuperclass(), results, map, filter);
            }
        }
    }

    /**
     * Converts all non-final properties in {@link #getAllAttributes(Class)} to a set of the attribute names.
     *
     * @param classToInspect the class to inspect
     */
    public static Set getAllAttributeNames(final Class classToInspect) {
        Set allFields = new HashSet<>();
        getAllAttributes(classToInspect, allFields, FIELD_TO_NAME, field -> true);
        return allFields;
    }

    /**
     * Converts all properties in {@link #getAllAttributes(Class)} to a set of the attribute names.
     *
     * @param classToInspect the class to inspect
     * @param filter a predicate that returns true when a attribute should be kept in resulting
     *         collection.
     */
    public static Set getAttributeNames(
            final Class classToInspect, final Predicate filter) {
        Set allFields = new HashSet<>();
        getAllAttributes(classToInspect, allFields, FIELD_TO_NAME, filter);
        return allFields;
    }
}