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package net.dongliu.commons.collection;

import java.io.Serializable;
import java.util.Map;

/**
 * Immutable Pair/Tuple2.
 *
 * @param  the key type
 * @param  the value type
 */
public class Pair implements Map.Entry, Serializable {

    private static final long serialVersionUID = -6468644647295390377L;
    private final K key;
    private final V value;

    private Pair(K key, V value) {
        this.key = key;
        this.value = value;
    }

    /**
     * Create a new pair
     */
    public static  Pair of(K key, V value) {
        return new Pair<>(key, value);
    }

    @Override
    public K getKey() {
        return key;
    }

    @Override
    public V getValue() {
        return value;
    }

    /**
     * Create one new pair, replace the key with newKey.
     */
    public Pair withKey(K newKey) {
        return new Pair<>(newKey, value);
    }

    /**
     * Create one new pair, replace the value with newValue.
     */
    public Pair withValue(V newValue) {
        return new Pair<>(key, newValue);
    }

    /**
     * The first value of this tuple
     */
    public K first() {
        return key;
    }

    /**
     * The second value of this tuple
     */
    public V second() {
        return value;
    }

    /**
     * Create one new pair, replace the first value with new value.
     */
    public Pair withFirst(K first) {
        return new Pair<>(first, second());
    }

    /**
     * Create one new pair, replace the second value with new value.
     */
    public Pair withSecond(V second) {
        return new Pair<>(first(), second);
    }

    /**
     * Append a new value.
     *
     * @param third the new value
     * @return Triple hold the Pair's value and new value
     */
    public  Triple append(C third) {
        return Triple.of(first(), second(), third);
    }

    /**
     * Prepend a new value.
     *
     * @param value the new value
     * @return Triple hold new value and the Pair's value
     */
    public  Triple prepend(A value) {
        return Triple.of(value, first(), second());
    }

    @Override
    public V setValue(V value) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Pair pair = (Pair) o;

        if (key != null ? !key.equals(pair.key) : pair.key != null) return false;
        return value != null ? value.equals(pair.value) : pair.value == null;
    }

    @Override
    public int hashCode() {
        int result = key != null ? key.hashCode() : 0;
        result = 31 * result + (value != null ? value.hashCode() : 0);
        return result;
    }

    @Override
    public String toString() {
        return "(" + key + ", " + value + ")";
    }
}