/*-
 * ============LICENSE_START=======================================================
 *  Copyright (C) 2019-2021 Nordix Foundation.
 *  Modifications Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
 * ================================================================================
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 * ============LICENSE_END=========================================================
 */

package org.onap.policy.models.base;

import java.lang.reflect.InvocationTargetException;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.function.Function;
import java.util.stream.Collectors;
import javax.ws.rs.core.Response;
import org.apache.commons.collections4.CollectionUtils;
import org.apache.commons.collections4.MapUtils;

/**
 * Utility class for Policy Framework concept utilities.
 *
 * @author Liam Fallon (liam.fallon@est.tech)
 */
public final class PfUtils {
    private PfUtils() {
        // Cannot be subclassed
    }

    /**
     * Compare two objects using their equals methods, nulls are allowed.
     *
     * @param leftObject the first object
     * @param rightObject the second object
     * @return a measure of the comparison
     */
    public static int compareObjects(final Object leftObject, final Object rightObject) {
        if (leftObject == null && rightObject == null) {
            return 0;
        }

        if (leftObject == null) {
            return 1;
        }

        if (rightObject == null) {
            return -1;
        }

        if (!leftObject.equals(rightObject)) {
            return leftObject.hashCode() - rightObject.hashCode();
        }

        return 0;
    }

    /**
     * Compare two collections of the same type, nulls are allowed.
     *
     * @param leftCollection the first collection
     * @param rightCollection the second collection
     * @return a measure of the comparison
     */
    public static <T> int compareCollections(final Collection<T> leftCollection, final Collection<T> rightCollection) {
        if (CollectionUtils.isEmpty(leftCollection) && CollectionUtils.isEmpty(rightCollection)) {
            return 0;
        }

        return compareObjects(leftCollection, rightCollection);
    }


    /**
     * Compare two maps of the same type, nulls are allowed.
     *
     * @param leftMap the first map
     * @param rightMap the second map
     * @return a measure of the comparison
     */
    public static <K, V> int compareMaps(final Map<K, V> leftMap, final Map<K, V> rightMap) {
        if (MapUtils.isEmpty(leftMap) && MapUtils.isEmpty(rightMap)) {
            return 0;
        }

        return compareObjects(leftMap, rightMap);
    }

    /**
     * Convenience method to apply a mapping function to all of the elements of a list, generating a new list.
     *
     * @param source list whose elements are to be mapped, or {@code null}
     * @param mapFunc mapping function
     * @param defaultValue value to be returned if source is {@code null}
     * @return a new list, containing mappings of all of the items in the original list
     */
    public static <T, R> List<R> mapList(List<T> source, Function<T, R> mapFunc, List<R> defaultValue) {
        if (source == null) {
            return defaultValue;
        }

        return source.stream().map(mapFunc).collect(Collectors.toList());
    }

    /**
     * Convenience method to apply a mapping function to all of the elements of a list, generating a new list.
     *
     * @param source list whose elements are to be mapped, or {@code null}
     * @param mapFunc mapping function
     * @return a new list, containing mappings of all of the items in the original list, or {@code null} if the source
     *         is {@code null}
     */
    public static <T, R> List<R> mapList(List<T> source, Function<T, R> mapFunc) {
        return mapList(source, mapFunc, null);
    }

    /**
     * Convenience method to apply a mapping function to all of the values of a map, generating a new map.
     *
     * @param source map whose values are to be mapped, or {@code null}
     * @param mapFunc mapping function
     * @param defaultValue value to be returned if source is {@code null}
     * @return a new map, containing mappings of all of the items in the original map
     */
    public static <K, T, R> Map<K, R> mapMap(Map<K, T> source, Function<T, R> mapFunc,
            Map<K, R> defaultValue) {
        if (source == null) {
            return defaultValue;
        }

        Map<K, R> map = new LinkedHashMap<>();
        for (Entry<K, T> ent : source.entrySet()) {
            map.put(ent.getKey(), mapFunc.apply(ent.getValue()));
        }

        return map;
    }

    /**
     * Convenience method to apply a mapping function to all of the values of a map, generating a new map.
     *
     * @param source map whose values are to be mapped, or {@code null}
     * @param mapFunc mapping function
     * @return a new map, containing mappings of all of the items in the original map, or {@code null} if the source is
     *         {@code null}
     */
    public static <K, T, R> Map<K, R> mapMap(Map<K, T> source, Function<T, R> mapFunc) {
        return mapMap(source, mapFunc, null);
    }

    /**
     * Makes a copy of an object using the copy constructor from the object's class.
     *
     * @param source object to be copied
     * @return a copy of the source, or {@code null} if the source is {@code null}
     * @throws PfModelRuntimeException if the object cannot be copied
     */
    public static <T> T makeCopy(T source) {
        if (source == null) {
            return null;
        }

        try {
            @SuppressWarnings("unchecked")
            Class<? extends T> clazz = (Class<? extends T>) source.getClass();

            return clazz.getConstructor(clazz).newInstance(source);

        } catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException
                | RuntimeException e) {
            throw new PfModelRuntimeException(Response.Status.INTERNAL_SERVER_ERROR,
                    "error copying concept key class: " + source.getClass().getName(), e);
        }
    }
}