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Library providing immutable/persistent collection classes for Java. While collections are immutable they provide methods for adding and removing values by creating new modified copies of themselves. Each copy shares almost all of its structure with other copies to minimize memory consumption.
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//
// Burton Computer Corporation
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//
// Copyright (c) 2021, Burton Computer Corporation
// All rights reserved.
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package org.javimmutable.collections.hash.map;

import org.javimmutable.collections.Func1;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.MapEntry;
import org.javimmutable.collections.Proc2;
import org.javimmutable.collections.Proc2Throws;
import org.javimmutable.collections.common.CollisionMap;
import org.javimmutable.collections.iterators.GenericIterator;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

@Immutable
public class ArraySingleValueMapNode
    implements ArrayMapNode
{
    private final K key;
    private final V value;

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

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

    @Override
    public int size(@Nonnull CollisionMap collisionMap)
    {
        return 1;
    }

    @Override
    public V getValueOr(@Nonnull CollisionMap collisionMap,
                        @Nonnull K key,
                        V defaultValue)
    {
        return key.equals(this.key) ? value : defaultValue;
    }

    @Nonnull
    @Override
    public Holder find(@Nonnull CollisionMap collisionMap,
                          @Nonnull K key)
    {
        return key.equals(this.key) ? Holders.of(value) : Holders.of();
    }

    @Nonnull
    @Override
    public ArrayMapNode assign(@Nonnull CollisionMap collisionMap,
                                     @Nonnull K key,
                                     V value)
    {
        final K thisKey = this.key;
        final V thisValue = this.value;
        if (!key.equals(thisKey)) {
            return new ArrayMultiValueMapNode<>(collisionMap.dual(thisKey, thisValue, key, value));
        } else if (value == thisValue) {
            return this;
        } else {
            return new ArraySingleValueMapNode<>(thisKey, value);
        }
    }

    @Nonnull
    @Override
    public ArrayMapNode update(@Nonnull CollisionMap collisionMap,
                                     @Nonnull K key,
                                     @Nonnull Func1, V> generator)
    {
        final K thisKey = this.key;
        final V thisValue = this.value;
        if (!key.equals(thisKey)) {
            final V value = generator.apply(Holders.of());
            return new ArrayMultiValueMapNode<>(collisionMap.dual(thisKey, thisValue, key, value));
        } else {
            final V value = generator.apply(Holders.of(thisValue));
            if (value == thisValue) {
                return this;
            } else {
                return new ArraySingleValueMapNode<>(thisKey, value);
            }
        }
    }

    @Nullable
    @Override
    public ArrayMapNode delete(@Nonnull CollisionMap collisionMap,
                                     @Nonnull K key)
    {
        return key.equals(this.key) ? null : this;
    }

    @Nonnull
    @Override
    public GenericIterator.Iterable keys(@Nonnull CollisionMap collisionMap)
    {
        return GenericIterator.singleValueIterable(key);
    }

    @Nonnull
    @Override
    public GenericIterator.Iterable values(@Nonnull CollisionMap collisionMap)
    {
        return GenericIterator.singleValueIterable(value);
    }

    @Nonnull
    @Override
    public GenericIterator.Iterable> entries(@Nonnull CollisionMap collisionMap)
    {
        return GenericIterator.singleValueIterable(MapEntry.entry(key, value));
    }

    @Override
    public void forEach(@Nonnull CollisionMap collisionMap,
                        @Nonnull Proc2 proc)
    {
        proc.apply(key, value);
    }

    @Override
    public  void forEachThrows(@Nonnull CollisionMap collisionMap,
                                                    @Nonnull Proc2Throws proc)
        throws E
    {
        proc.apply(key, value);
    }
}