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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
// http://www.burton-computer.com
//
// Copyright (c) 2014, Burton Computer Corporation
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//
//     Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in
//     the documentation and/or other materials provided with the
//     distribution.
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//     Neither the name of the Burton Computer Corporation nor the names
//     of its contributors may be used to endorse or promote products
//     derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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package org.javimmutable.collections.common;

import org.javimmutable.collections.Func1;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.JImmutableArray;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.MapEntry;
import org.javimmutable.collections.cursors.TransformCursor;

import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

@SuppressWarnings({"unchecked", "NullableProblems"})
public class ArrayToMapAdaptor
        extends AbstractMap
{
    private final JImmutableArray map;

    public ArrayToMapAdaptor(JImmutableArray map)
    {
        this.map = map;
    }

    public static  ArrayToMapAdaptor of(JImmutableArray map)
    {
        return new ArrayToMapAdaptor(map);
    }

    @Override
    public int size()
    {
        return map.size();
    }

    @Override
    public boolean isEmpty()
    {
        return map.size() == 0;
    }

    @Override
    public boolean containsKey(Object o)
    {
        return map.find((Integer)o).isFilled();
    }

    /**
     * Uses O(n) traversal of the PersistentMap to search for a matching value.
     *
     * @param o
     * @return
     */
    @Override
    public boolean containsValue(Object o)
    {
        for (JImmutableMap.Entry entry : map) {
            T value = entry.getValue();
            if (o == null) {
                if (value == null) {
                    return true;
                }
            } else {
                if (value != null && value.equals(o)) {
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    public T get(Object o)
    {
        return map.get((Integer)o);
    }

    @Override
    public T put(Integer k,
                 T t)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public T remove(Object o)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public void putAll(Map map)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public void clear()
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public Set keySet()
    {
        return new AbstractSet()
        {
            @Override
            public boolean isEmpty()
            {
                return map.size() == 0;
            }

            @Override
            public boolean contains(Object o)
            {
                return map.find((Integer)o).isFilled();
            }

            @Override
            public Iterator iterator()
            {
                return IteratorAdaptor.of(TransformCursor.ofKeys(map.cursor()));
            }

            @Override
            public int size()
            {
                return map.size();
            }
        };
    }

    @Override
    public Collection values()
    {
        return new AbstractCollection()
        {
            @Override
            public Iterator iterator()
            {
                return IteratorAdaptor.of(TransformCursor.ofValues(map.cursor()));
            }

            @Override
            public int size()
            {
                return map.size();
            }
        };
    }

    @Override
    public Set> entrySet()
    {
        return new AbstractSet>()
        {
            @Override
            public boolean isEmpty()
            {
                return map.size() == 0;
            }

            @Override
            public boolean contains(Object o)
            {
                if (!(o instanceof Map.Entry)) {
                    return false;
                }
                Map.Entry oEntry = (Entry)o;
                Holder> eHolder = map.findEntry(oEntry.getKey());
                return eHolder.isFilled() && new MapEntry(eHolder.getValue()).equals(oEntry);
            }

            @Override
            public Iterator> iterator()
            {
                return IteratorAdaptor.of(TransformCursor.of(map.cursor(), new Func1, Entry>()
                {
                    @Override
                    public Entry apply(JImmutableMap.Entry value)
                    {
                        return new MapEntry(value);
                    }
                }));
            }

            @Override
            public int size()
            {
                return map.size();
            }
        };
    }
}