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// Burton Computer Corporation
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package org.javimmutable.collections;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

/**
 * Immutable implementation of both Map.Entry and JImmutableMap.Entry that uses the same equals() and hashCode() implementations as
 * documented in javadoc for Map.Entry.
 */
@Immutable
public class MapEntry
    implements JImmutableMap.Entry,
               Map.Entry
{
    protected final K key;
    protected final V value;

    public MapEntry(Map.Entry entry)
    {
        this(entry.getKey(), entry.getValue());
    }

    public MapEntry(JImmutableMap.Entry entry)
    {
        this(entry.getKey(), entry.getValue());
    }

    public MapEntry(K key,
                    V value)
    {
        this.key = key;
        this.value = value;
    }

    @Nonnull
    public static  MapEntry of(Map.Entry entry)
    {
        return new MapEntry(entry);
    }

    @Nonnull
    public static  MapEntry of(JImmutableMap.Entry entry)
    {
        return new MapEntry(entry);
    }

    @Nonnull
    public static  MapEntry of(K key,
                                           V value)
    {
        return new MapEntry(key, value);
    }

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

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

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

    @Override
    public int hashCode()
    {
        return ((key == null) ? 0 : key.hashCode()) ^
               ((value == null) ? 0 : value.hashCode());
    }

    @Override
    public boolean equals(Object o)
    {
        if (o instanceof JImmutableMap.Entry) {
            JImmutableMap.Entry jentry = (JImmutableMap.Entry)o;
            //noinspection ConstantConditions
            return ((key == null) ? (jentry.getKey() == null) : key.equals(jentry.getKey())) &&
                   ((value == null) ? (jentry.getValue() == null) : value.equals(jentry.getValue()));
        }

        if (!(o instanceof Map.Entry)) {
            return false;
        }

        Map.Entry entry2 = (Map.Entry)o;
        return ((key == null) ? (entry2.getKey() == null) : key.equals(entry2.getKey())) &&
               ((value == null) ? (entry2.getValue() == null) : value.equals(entry2.getValue()));
    }

    @Override
    public String toString()
    {
        return makeToString(this);
    }

    private static void addToString(StringBuilder sb,
                                    Object obj)
    {
        if (obj == null) {
            sb.append("null");
        } else {
            sb.append(obj);
        }
    }

    public static String makeToString(JImmutableMap.Entry entry)
    {
        StringBuilder sb = new StringBuilder();
        addToString(sb, entry);
        return sb.toString();
    }

    public static void addToString(StringBuilder sb,
                                   JImmutableMap.Entry entry)
    {
        addToString(sb, entry.getKey());
        sb.append("=");
        addToString(sb, entry.getValue());
    }

    public static  List> toMutableEntries(@Nonnull Collection> source)
    {
        return source.stream().map(e -> MapEntry.of(e)).collect(Collectors.toList());
    }

    public static  List> toImmutableEntries(@Nonnull Collection> source)
    {
        return source.stream().map(e -> MapEntry.of(e)).collect(Collectors.toList());
    }
}