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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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.
 */
package org.apache.sshd.common.util;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.NavigableMap;
import java.util.Objects;
import java.util.TreeMap;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Collectors;

/**
 * Represents an un-modifiable pair of values
 *
 * @author Apache MINA SSHD Project
 */
public final class MapEntryUtils {
    @SuppressWarnings({ "rawtypes", "unchecked" })
    private static final Comparator> BY_KEY_COMPARATOR = (o1, o2) -> {
        Comparable k1 = o1.getKey();
        Comparable k2 = o2.getKey();
        return k1.compareTo(k2);
    };

    @SuppressWarnings("rawtypes")
    private static final Supplier CASE_INSENSITIVE_MAP_FACTORY = () -> new TreeMap<>(String.CASE_INSENSITIVE_ORDER);

    private MapEntryUtils() {
        throw new UnsupportedOperationException("No instance");
    }

    /**
     * @param   The {@link Comparable} key type
     * @param   The associated entry value
     * @return     A {@link Comparator} for {@link java.util.Map.Entry}-ies that compares the key values
     */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static , V> Comparator> byKeyEntryComparator() {
        return (Comparator) BY_KEY_COMPARATOR;
    }

    public static class GenericMapPopulator> implements Supplier {
        private final M map;

        public GenericMapPopulator(M map) {
            this.map = Objects.requireNonNull(map, "No map provided");
        }

        public GenericMapPopulator put(K k, V v) {
            map.put(k, v);
            return this;
        }

        public GenericMapPopulator remove(K k) {
            map.remove(k);
            return this;
        }

        public GenericMapPopulator putAll(Map other) {
            map.putAll(other);
            return this;
        }

        public GenericMapPopulator clear() {
            map.clear();
            return this;
        }

        @Override
        public M get() {
            return map;
        }
    }

    public static class MapBuilder extends GenericMapPopulator> {
        public MapBuilder() {
            super(new LinkedHashMap<>());
        }

        @Override
        public MapBuilder put(K k, V v) {
            super.put(k, v);
            return this;
        }

        @Override
        public MapBuilder remove(K k) {
            super.remove(k);
            return this;
        }

        @Override
        public MapBuilder putAll(Map other) {
            super.putAll(other);
            return this;
        }

        @Override
        public MapBuilder clear() {
            super.clear();
            return this;
        }

        public Map build() {
            return get();
        }

        public Map immutable() {
            return Collections.unmodifiableMap(build());
        }

        public static  MapBuilder builder() {
            return new MapBuilder<>();
        }

    }

    public static class NavigableMapBuilder extends GenericMapPopulator> {
        public NavigableMapBuilder(Comparator comparator) {
            super(new TreeMap<>(Objects.requireNonNull(comparator, "No comparator provided")));
        }

        @Override
        public NavigableMapBuilder put(K k, V v) {
            super.put(k, v);
            return this;
        }

        @Override
        public NavigableMapBuilder remove(K k) {
            super.remove(k);
            return this;
        }

        @Override
        public NavigableMapBuilder putAll(Map other) {
            super.putAll(other);
            return this;
        }

        @Override
        public NavigableMapBuilder clear() {
            super.clear();
            return this;
        }

        public NavigableMap build() {
            return get();
        }

        public NavigableMap immutable() {
            return Collections.unmodifiableNavigableMap(build());
        }

        public static , V> NavigableMapBuilder builder() {
            return builder(Comparator.naturalOrder());
        }

        public static  NavigableMapBuilder builder(Comparator comparator) {
            return new NavigableMapBuilder<>(comparator);
        }
    }

    public static class EnumMapBuilder, V> extends GenericMapPopulator> {
        public EnumMapBuilder(Class keyType) {
            super(new EnumMap<>(Objects.requireNonNull(keyType, "No enum class specified")));
        }

        @Override
        public EnumMapBuilder put(K k, V v) {
            super.put(k, v);
            return this;
        }

        @Override
        public EnumMapBuilder remove(K k) {
            super.remove(k);
            return this;
        }

        @Override
        public EnumMapBuilder putAll(Map other) {
            super.putAll(other);
            return this;
        }

        @Override
        public EnumMapBuilder clear() {
            super.clear();
            return this;
        }

        public Map build() {
            return get();
        }

        public Map immutable() {
            return Collections.unmodifiableMap(build());
        }

        public static , V> EnumMapBuilder builder(Class keyType) {
            return new EnumMapBuilder<>(keyType);
        }
    }

    public static int size(Map m) {
        return (m == null) ? 0 : m.size();
    }

    public static boolean isEmpty(Map m) {
        return size(m) <= 0;
    }

    public static boolean isNotEmpty(Map m) {
        return !isEmpty(m);
    }

    /**
     * @param   Type of mapped value
     * @return     A {@link Supplier} that returns a new {@link NavigableMap} whenever its {@code get()} method
     *             is invoked
     */
    @SuppressWarnings("unchecked")
    public static  Supplier> caseInsensitiveMap() {
        return CASE_INSENSITIVE_MAP_FACTORY;
    }

    /**
     * Flips between keys and values of an input map
     *
     * @param                        Original map key type
     * @param                        Original map value type
     * @param                        Flipped map type
     * @param  map                      The original map to flip
     * @param  mapCreator               The creator of the target map
     * @param  allowDuplicates          Whether to ignore duplicates on flip
     * @return                          The flipped map result
     * @throws IllegalArgumentException if allowDuplicates is {@code false} and a duplicate value found in the
     *                                  original map.
     */
    public static > M flipMap(
            Map map, Supplier mapCreator, boolean allowDuplicates) {
        M result = Objects.requireNonNull(mapCreator.get(), "No map created");
        map.forEach((key, value) -> {
            K prev = result.put(value, key);
            if ((prev != null) && (!allowDuplicates)) {
                ValidateUtils.throwIllegalArgumentException("Multiple values for key=%s: current=%s, previous=%s", value, key,
                        prev);
            }
        });

        return result;
    }

    @SafeVarargs
    public static > M mapValues(
            Function keyMapper, Supplier mapCreator, V... values) {
        return mapValues(keyMapper, mapCreator, GenericUtils.isEmpty(values) ? Collections.emptyList() : Arrays.asList(values));
    }

    /**
     * Creates a map out of a group of values
     *
     * @param          The key type
     * @param          The value type
     * @param          The result {@link Map} type
     * @param  keyMapper  The {@link Function} that generates a key for a given value. If the returned key is
     *                    {@code null} then the value is not mapped
     * @param  mapCreator The {@link Supplier} used to create/retrieve the result map - provided non-empty group of
     *                    values
     * @param  values     The values to be mapped
     * @return            The resulting {@link Map} - Note: no validation is made to ensure that 2 (or more)
     *                    values are not mapped to the same key
     */
    public static > M mapValues(
            Function keyMapper,
            Supplier mapCreator,
            Collection values) {
        M map = mapCreator.get();
        for (V v : values) {
            K k = keyMapper.apply(v);
            if (k == null) {
                continue; // debug breakpoint
            }
            map.put(k, v);
        }

        return map;
    }

    public static  NavigableMap toSortedMap(
            Iterable values, Function keyMapper,
            Function valueMapper, Comparator comparator) {
        return GenericUtils.stream(values).collect(toSortedMap(keyMapper, valueMapper, comparator));
    }

    public static  Collector> toSortedMap(
            Function keyMapper,
            Function valueMapper,
            Comparator comparator) {
        return Collectors.toMap(keyMapper, valueMapper, throwingMerger(), () -> new TreeMap<>(comparator));
    }

    public static  BinaryOperator throwingMerger() {
        return (u, v) -> {
            throw new IllegalStateException(String.format("Duplicate key %s", u));
        };
    }
}




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