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

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.common.AbstractJImmutableMap;
import org.javimmutable.collections.common.Conditions;
import org.javimmutable.collections.common.MutableDelta;
import org.javimmutable.collections.common.StreamConstants;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

@Immutable
public class JImmutableTreeMap
    extends AbstractJImmutableMap
{
    @SuppressWarnings("unchecked")
    private static final JImmutableTreeMap EMPTY = new JImmutableTreeMap(new ComparableComparator());

    private final Comparator comparator;
    private final TreeNode root;
    private final int size;

    /**
     * Constructs an empty map using the specified Comparator.  Note that the Comparator MUST BE IMMUTABLE.
     * The Comparator will be retained and used throughout the life of the map and its offspring and will
     * be aggressively shared so it is imperative that the Comparator be completely immutable.
     */
    private JImmutableTreeMap(Comparator comparator)
    {
        this(comparator, EmptyNode.of(), 0);
    }

    @SuppressWarnings("unchecked")
    public static , V> JImmutableTreeMap of()
    {
        return (JImmutableTreeMap)EMPTY;
    }

    /**
     * Constructs an empty map using the specified Comparator.  Note that the Comparator MUST BE IMMUTABLE.
     * The Comparator will be retained and used throughout the life of the map and its offspring and will
     * be aggressively shared so it is imperative that the Comparator be completely immutable.
     */
    public static  JImmutableTreeMap of(Comparator comparator)
    {
        return new JImmutableTreeMap<>(comparator);
    }

    /**
     * Constructs a new map containing the same key/value pairs as map using a ComparableComparator
     * to compare the keys.
     */
    public static , V> JImmutableTreeMap of(Map map)
    {
        JImmutableTreeMap answer = of();
        for (Map.Entry entry : map.entrySet()) {
            answer = answer.assign(entry.getKey(), entry.getValue());
        }
        return answer;
    }

    private JImmutableTreeMap(Comparator comparator,
                              TreeNode root,
                              int size)
    {
        this.comparator = comparator;
        this.root = root;
        this.size = size;
    }

    @Override
    public V getValueOr(K key,
                        V defaultValue)
    {
        if (key == null) {
            throw new NullPointerException();
        }
        return root.getValueOr(comparator, key, defaultValue);
    }

    @Nonnull
    @Override
    public Holder find(@Nonnull K key)
    {
        Conditions.stopNull(key);
        return root.find(comparator, key);
    }

    @Nonnull
    @Override
    public Holder> findEntry(@Nonnull K key)
    {
        Conditions.stopNull(key);
        return root.findEntry(comparator, key);
    }

    @Nonnull
    @Override
    public JImmutableTreeMap assign(@Nonnull K key,
                                          V value)
    {
        Conditions.stopNull(key);
        MutableDelta sizeDelta = new MutableDelta();
        TreeNode newRoot = root.assign(comparator, key, value, sizeDelta);
        if (newRoot == root) {
            return this;
        } else {
            return create(newRoot, sizeDelta.getValue());
        }
    }

    @Nonnull
    @Override
    public JImmutableTreeMap delete(@Nonnull K key)
    {
        Conditions.stopNull(key);
        MutableDelta sizeDelta = new MutableDelta();
        TreeNode newRoot = root.delete(comparator, key, sizeDelta);
        if (newRoot == root) {
            return this;
        } else {
            return create(newRoot, sizeDelta.getValue());
        }
    }

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

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

    @Override
    @Nonnull
    public Cursor> cursor()
    {
        return root.cursor();
    }

    @Nonnull
    @Override
    public SplitableIterator> iterator()
    {
        return root.iterator();
    }

    @Override
    public int getSpliteratorCharacteristics()
    {
        return StreamConstants.SPLITERATOR_ORDERED;
    }

    public List getKeysList()
    {
        List keys = new LinkedList<>();
        for (Entry entry : this) {
            keys.add(entry.getKey());
        }
        return Collections.unmodifiableList(keys);
    }

    public void verifyDepthsMatch()
    {
        root.verifyDepthsMatch();
    }

    @Override
    public void checkInvariants()
    {
        verifyDepthsMatch();
        //TODO: add more than verifyDepthsMatch?
    }

    public Comparator getComparator()
    {
        return comparator;
    }

    private JImmutableTreeMap create(TreeNode root,
                                           int sizeDelta)
    {
        return new JImmutableTreeMap<>(comparator, root, size + sizeDelta);
    }
}