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/*
 *  Copyright 2013 Samppa Saarela
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.javersion.util;

import static com.google.common.collect.Iterables.transform;
import static java.util.Arrays.asList;
import static java.util.Spliterators.emptySpliterator;
import static org.javersion.util.AbstractRedBlackTree.Color.RED;

import java.util.*;
import java.util.stream.Collectors;

import javax.annotation.concurrent.Immutable;

import org.javersion.util.PersistentTreeSet.Node;

import com.google.common.base.Function;
import com.google.common.collect.Iterators;

@Immutable
public class PersistentTreeSet extends AbstractRedBlackTree, PersistentTreeSet> implements PersistentSet {

    @SuppressWarnings("rawtypes")
    private static final PersistentTreeSet EMPTY = new PersistentTreeSet();

    @SuppressWarnings("rawtypes")
    private static final Function GET_ELEMENT = input -> input != null ? ((Node)input).getKey() : null;

    @SuppressWarnings("unchecked")
    public static  PersistentTreeSet empty() {
        return EMPTY;
    }

    public static  PersistentTreeSet empty(Comparator comparator) {
        return new PersistentTreeSet<>(comparator);
    }

    public static > PersistentTreeSet of(E... elements) {
        return new PersistentTreeSet().conjAll(asList(elements));
    }

    public static  PersistentTreeSet of(Comparator comparator, E... elements) {
        return new PersistentTreeSet<>(comparator).conjAll(asList(elements));
    }


    private final Node root;

    private final int size;

    private PersistentTreeSet() {
        super();
        root = null;
        size = 0;
    }

    private PersistentTreeSet(Comparator comparator) {
        super(comparator);
        root = null;
        size = 0;
    }

    private PersistentTreeSet(Comparator comparator, Node root, int size) {
        super(comparator);
        this.root = root;
        this.size = size;
    }

    public int size() {
        return size;
    }

    @Override
    public boolean contains(Object key) {
        return find(root, key) != null;
    }

    Node root() {
        return root;
    }

    @Override
    public Set asSet() {
        return new ImmutableSet<>(this);
    }

    @Override
    public PersistentTreeSet conj(E value) {
        UpdateContext> context = new UpdateContext<>(1);
        return doAdd(context, root, new Node<>(context, value, RED));
    }

    @Override
    public PersistentTreeSet conjAll(Collection coll) {
        final UpdateContext> context = new UpdateContext<>(32);
        return doAddAll(context, root, transform(coll, new EntryToNode<>(context)));
    }

    @Override
    public PersistentTreeSet disj(Object keyObj) {
        return doRemove(new UpdateContext<>(1), root, keyObj);
    }

    @Override
    public MutableSet toMutableSet() {
        // TODO
        return null;
    }

    @SuppressWarnings("unchecked")
    public Iterator iterator() {
        return Iterators.transform(doIterator(root, true), GET_ELEMENT);
    }

    @Override
    public Spliterator spliterator() {
        if (root != null) {
            return new ElementSpliterator(root, size, comparator);
        } else {
            return emptySpliterator();
        }
    }

    @SuppressWarnings("unchecked")
    @Override
    protected PersistentTreeSet doReturn(Comparator comparator, Node newRoot, int newSize) {
        if (newRoot == root) {
            return this;
        } else if (newRoot == null) {
            return EMPTY;
        }
        return new PersistentTreeSet<>(comparator, newRoot, newSize);
    }

    public String toString() {
        return stream().map(Objects::toString).collect(Collectors.joining(", ", "[", "]"));
    }

    private static final class EntryToNode implements Function> {
        private final UpdateContext> context;

        private EntryToNode(UpdateContext> context) {
            this.context = context;
        }

        @Override
        public Node apply(E input) {
            return new Node(context, input, RED);
        }
    }

    static class Node extends AbstractRedBlackTree.Node> {

        public Node(UpdateContext> context, E key, Color color) {
            this(context, key, color, null, null);
        }

        public Node(UpdateContext> context, E key, Color color, Node left, Node right) {
            super(context, key, color, left, right);
        }

        public E getKey() {
            return key;
        }

        @Override
        public Node self() {
            return this;
        }

        @Override
        protected Node cloneWith(UpdateContext> currentContext) {
            return new Node(currentContext, key, color, left, right);
        }

        @Override
        protected Node replaceWith(UpdateContext> currentContext, Node node) {
            return this;
        }
    }

    static class ElementSpliterator extends RBSpliterator> {

        private final Comparator comparator;

        public ElementSpliterator(Node root, int size, Comparator comparator) {
            super(root, size, SORTED | DISTINCT | IMMUTABLE);
            this.comparator = comparator;
        }

        protected ElementSpliterator(int sizeEstimate, Comparator comparator) {
            super(sizeEstimate, SORTED | DISTINCT | IMMUTABLE);
            this.comparator = comparator;
        }

        @Override
        protected RBSpliterator> newSpliterator(int sizeEstimate) {
            return new ElementSpliterator(sizeEstimate, comparator);
        }

        @Override
        protected E apply(Node node) {
            return node.key;
        }

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

    }
}