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/*
 * Copyright (C) 2019 jsonwebtoken.io
 *
 * 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.
 */
package io.jsonwebtoken.lang;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Utility class to help with the manipulation of working with Maps.
 *
 * @since 0.11.0
 */
public final class Maps {

    private Maps() {
    } //prevent instantiation

    /**
     * Creates a new map builder with a single entry.
     *  Typical usage: 
{@code
     * Map result = Maps.of("key1", value1)
     *     .and("key2", value2)
     *     // ...
     *     .build();
     * }
     *
     * @param key   the key of an map entry to be added
     * @param value the value of map entry to be added
     * @param  the maps key type
     * @param  the maps value type
     * @return a new map builder with a single entry.
     */
    public static  MapBuilder of(K key, V value) {
        return new HashMapBuilder().and(key, value);
    }

    /**
     * Utility Builder class for fluently building maps:
     *  Typical usage: 
{@code
     * Map result = Maps.of("key1", value1)
     *     .and("key2", value2)
     *     // ...
     *     .build();
     * }
     *
     * @param  the maps key type
     * @param  the maps value type
     */
    public interface MapBuilder extends Builder> {
        /**
         * Add a new entry to this map builder
         *
         * @param key   the key of an map entry to be added
         * @param value the value of map entry to be added
         * @return the current MapBuilder to allow for method chaining.
         */
        MapBuilder and(K key, V value);

        /**
         * Returns the resulting Map object from this MapBuilder.
         *
         * @return the resulting Map object from this MapBuilder.
         */
        Map build();
    }

    private static class HashMapBuilder implements MapBuilder {

        private final Map data = new HashMap<>();

        public MapBuilder and(K key, V value) {
            data.put(key, value);
            return this;
        }

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