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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.Func1;
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.StreamConstants;
import org.javimmutable.collections.serialization.JImmutableTreeMapProxy;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.io.Serializable;
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
    implements Serializable
{
    private static final Comparator EMPTY_COMPARATOR = ComparableComparator.of();
    @SuppressWarnings("unchecked")
    private static final JImmutableTreeMap EMPTY = new JImmutableTreeMap(EMPTY_COMPARATOR, EmptyNode.of(), 0);

    private static final long serialVersionUID = -121805;

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

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

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

    @Nonnull
    public static  JImmutableTreeMap of(@Nonnull Comparator comparator)
    {
        return new JImmutableTreeMap<>(comparator, EmptyNode.of(), 0);
    }

    /**
     * Constructs a new map containing the same key/value pairs as map using a ComparableComparator
     * to compare the keys.
     */
    @Nonnull
    @Deprecated
    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;
    }

    @Override
    public V getValueOr(K key,
                        V defaultValue)
    {
        Conditions.stopNull(key);
        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);
        final UpdateResult result = root.assign(comparator, key, value);
        return resultForAssign(result);
    }

    @Nonnull
    @Override
    public JImmutableTreeMap update(@Nonnull K key,
                                          @Nonnull Func1, V> generator)
    {
        Conditions.stopNull(key);
        final UpdateResult result = root.update(comparator, key, generator);
        return resultForAssign(result);
    }

    @Nonnull
    @Override
    public JImmutableTreeMap delete(@Nonnull K key)
    {
        Conditions.stopNull(key);
        final Node newRoot = root.delete(comparator, key);
        if (newRoot == root) {
            return this;
        } else if (size == 1) {
            return deleteAll();
        } else {
            return new JImmutableTreeMap<>(comparator, newRoot.compress(), size - 1);
        }
    }

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

    @Nonnull
    @Override
    public JImmutableTreeMap deleteAll()
    {
        return (comparator == EMPTY_COMPARATOR) ? EMPTY : new JImmutableTreeMap<>(comparator, EmptyNode.of(), 0);
    }

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

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

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

    @Override
    public void checkInvariants()
    {
        root.checkInvariants(comparator);
    }

    @Nonnull
    public Comparator getComparator()
    {
        return comparator;
    }

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

    @Nonnull
    private JImmutableTreeMap resultForAssign(UpdateResult result)
    {
        switch (result.type) {
            case UNCHANGED:
                return this;
            case INPLACE:
                return new JImmutableTreeMap<>(comparator, result.newNode, size + result.sizeDelta);
            case SPLIT:
                return new JImmutableTreeMap<>(comparator, new BranchNode<>(result.newNode, result.extraNode), size + result.sizeDelta);
            default:
                throw new IllegalStateException("unknown UpdateResult.Type value");
        }
    }

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