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package org.javimmutable.collections.inorder;

import org.javimmutable.collections.GenericCollector;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.JImmutableMultiset;
import org.javimmutable.collections.JImmutableSet;
import org.javimmutable.collections.common.AbstractJImmutableMultiset;
import org.javimmutable.collections.serialization.JImmutableInsertOrderMultisetProxy;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.io.Serializable;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.stream.Collector;

/**
 * JImmutableMultisetImplementation built on top of a JImmutableInsertOrderMap. During iteration,
 * elements are returned in the same order they were inserted into the set. Performance is slower
 * than hash or tree sets, but should be sufficient for most algorithms where insert order matters.
 */
@Immutable
public class JImmutableInsertOrderMultiset
    extends AbstractJImmutableMultiset
    implements Serializable
{
    @SuppressWarnings("unchecked")
    private static final JImmutableInsertOrderMultiset EMPTY = new JImmutableInsertOrderMultiset(JImmutableInsertOrderMap.of(), 0);
    private static final long serialVersionUID = -121805;

    private JImmutableInsertOrderMultiset(JImmutableMap map,
                                          int occurrences)
    {
        super(map, occurrences);
    }

    @SuppressWarnings("unchecked")
    public static  JImmutableInsertOrderMultiset of()
    {
        return (JImmutableInsertOrderMultiset)EMPTY;
    }

    @Nonnull
    @Override
    public JImmutableInsertOrderMultiset deleteAll()
    {
        return of();
    }

    @Nonnull
    @Override
    public Collector> setCollector()
    {
        return GenericCollector.ordered(this, deleteAll(), a -> a.isEmpty(), (a, v) -> a.insert(v), (a, b) -> a.insertAll(b));
    }

    @Nonnull
    @Override
    public Collector> multisetCollector()
    {
        return GenericCollector.ordered(this, deleteAll(), a -> a.isEmpty(), (a, v) -> a.insert(v), (a, b) -> a.insertAll(b));
    }

    @Override
    protected JImmutableInsertOrderMultiset create(JImmutableMap map,
                                                      int occurrences)
    {
        return new JImmutableInsertOrderMultiset<>(map, occurrences);
    }

    @Override
    protected Map emptyMutableMap()
    {
        return new LinkedHashMap<>();
    }

    private Object writeReplace()
    {
        return new JImmutableInsertOrderMultisetProxy(this);
    }
}