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package org.mapfish.print.parser;

import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.Collections2;
import com.google.common.collect.Sets;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Collection;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * Utility method for getting and setting parameters on Processor Input and Output objects.
 *
 * @author Jesse on 3/30/14.
 */
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 = new Predicate() {
        @Override
        public boolean apply(@Nullable final Field input) {
            return 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 = new Predicate() {
        @Override
        public boolean apply(@Nullable final Field input) {
            return 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 = new Predicate() {
        @Override
        public boolean apply(@Nullable final Field input) {
            return 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 = new Predicate() {
        @Override
        public boolean apply(@Nullable final Field input) {
            return input != null && Modifier.isFinal(input.getModifiers());
        }
    };

    private static final Function FIELD_TO_NAME = new Function() {
        @Nullable
        @Override
        public String apply(final Field input) {
            return input.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 = Sets.newHashSet();
        getAllAttributes(classToInspect, allFields, Functions.identity(), Predicates.alwaysTrue());
        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 = Sets.newHashSet();
        getAllAttributes(classToInspect, allFields, Functions.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 filteredResults = Collections2.filter(Arrays.asList(classToInspect.getFields()), filter);
            Collection resultsForClass = Collections2.transform(filteredResults, map);
            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 = Sets.newHashSet();
        getAllAttributes(classToInspect, allFields, FIELD_TO_NAME, Predicates.alwaysTrue());
        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 = Sets.newHashSet();
        getAllAttributes(classToInspect, allFields, FIELD_TO_NAME, filter);
        return allFields;
    }
}