/*******************************************************************************
 * Copyright IBM Corp. and others 2000
 *
 * This program and the accompanying materials are made available under
 * the terms of the Eclipse Public License 2.0 which accompanies this
 * distribution and is available at https://www.eclipse.org/legal/epl-2.0/
 * or the Apache License, Version 2.0 which accompanies this distribution
 * and is available at https://www.apache.org/licenses/LICENSE-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License, v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception [1] and GNU General Public
 * License, version 2 with the OpenJDK Assembly Exception [2].
 *
 * [1] https://www.gnu.org/software/classpath/license.html
 * [2] https://openjdk.org/legal/assembly-exception.html
 *
 * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0 OR GPL-2.0-only WITH OpenJDK-assembly-exception-1.0
 *******************************************************************************/

#ifndef HEDGETREE_INCL
#define HEDGETREE_INCL

#include <stdint.h>
#include <string.h>
#include "env/FrontEnd.hpp" // TR_FrontEnd (ptr only)
#include "compile/Compilation.hpp"
#include "env/IO.hpp"
#include "env/TRMemory.hpp"
#include "infra/Assert.hpp"

// Implementation of Symmetric Binary B-Trees
//    (also called "hedge trees")
//
// Hedge trees have the properties:
//    - every node has at most 2 pointers, each either to a sibling or a child
//    - there are never two consecutive sibling pointers on any search path
//    - all leaf nodes (ones with zero or one child) are at the same height
//
// Search paths are at most 2 * height.
// Tree balancing is needed less frequently than with AVL trees.

template<class T> class TR_HedgeNode {
public:
    TR_ALLOC(TR_Memory::HedgeTree)

    TR_HedgeNode(int32_t key) { initialize(key); }

    void initialize(int32_t key)
    {
        _key = key;
        _left = NULL;
        _right = NULL;
        _parent = NULL;
        _leftSibling = false;
        _rightSibling = false;
    }

    int32_t getKey() { return _key; }

    T *left() { return _left; }

    T *right() { return _right; }

    T *&leftReference() { return _left; }

    T *&rightReference() { return _right; }

    void setLeft(T *node)
    {
        _left = node;
        if (node)
            node->setParent((T *)this);
    }

    void setRight(T *node)
    {
        _right = node;
        if (node)
            node->setParent((T *)this);
    }

    bool isLeftSibling() { return _leftSibling; }

    bool isRightSibling() { return _rightSibling; }

    void setRightSibling(bool b) { _rightSibling = b; }

    void setLeftSibling(bool b) { _leftSibling = b; }

    T *getParent() { return _parent; }

    void setParent(T *node) { _parent = node; }

    bool verify(T *parent)
    {
        if (isLeftSibling() && (_left->isLeftSibling() || _left->isRightSibling())) {
            TR_ASSERT(0, "Double sibling chain for key %d", getKey());
            return false;
        }
        if (isRightSibling() && (_right->isLeftSibling() || _right->isRightSibling())) {
            TR_ASSERT(0, "Double sibling chain for key %d", getKey());
            return false;
        }
        if (_parent != parent) {
            TR_ASSERT(0, "Bad parent for key %d", getKey());
            return false;
        }
        if (!_left && isLeftSibling()) {
            TR_ASSERT(0, "Null left sibling for key %d", getKey());
            return false;
        }
        if (!_right && isRightSibling()) {
            TR_ASSERT(0, "Null right sibling for key %d", getKey());
            return false;
        }
        if (!_left) {
            if (_right) {
                if (!isRightSibling()) {
                    TR_ASSERT(0, "Non-leaf is missing child for key %d", getKey());
                    return false;
                }
                return _right->verify((T *)this);
            }
            return true;
        }
        if (!_right) {
            if (!isLeftSibling()) {
                TR_ASSERT(0, "Non-leaf is missing child for key %d", getKey());
                return false;
            }
            return _left->verify((T *)this);
        }
        int32_t lh = _left->height();
        int32_t rh = _right->height();
        if (!isLeftSibling())
            lh++;
        if (!isRightSibling())
            rh++;
        if (lh != rh)
            TR_ASSERT(0, "Lhs and rhs different heights for key %d", getKey());
        return lh == rh;
    }

    int32_t height()
    {
        int32_t h;
        if (_left) {
            h = _left->height();
            if (!isLeftSibling())
                h++;
        } else if (_right) {
            h = _right->height();
            if (!isRightSibling())
                h++;
        } else
            h = 1;
        return h;
    }

#if DEBUG
    void printTree(TR::FILE *outFile, int32_t indent, char *prefix, bool isLeftChild, bool isSibling)
    {
        int32_t prefixPos = isSibling ? indent : indent - 3;
        if (prefixPos > 0) {
            if (isLeftChild)
                prefix[prefixPos] = '|';
            else
                prefix[prefixPos] = ' ';
        }
        if (_right) {
            if (isRightSibling())
                _right->printTree(outFile, indent, prefix, false, true);
            else
                _right->printTree(outFile, indent + 5, prefix, false, false);
        } else
            trfprintf(outFile, "%.*s\n", prefixPos + 1, prefix);
        if (isSibling)
            trfprintf(outFile, "%.*s%d\n", prefixPos, prefix, getKey());
        else
            trfprintf(outFile, "%.*s-->%d\n", prefixPos, prefix, getKey());
        if (prefixPos > 0) {
            if (!isLeftChild)
                prefix[prefixPos] = '|';
            else
                prefix[prefixPos] = ' ';
        }
        if (_left) {
            if (isLeftSibling())
                _left->printTree(outFile, indent, prefix, true, true);
            else
                _left->printTree(outFile, indent + 5, prefix, true, false);
        } else
            trfprintf(outFile, "%.*s\n", prefixPos + 1, prefix);
        prefix[prefixPos] = ' ';
    }
#else
    void printTree(TR::FILE *outFile, int32_t indent, char *prefix, bool isLeftChild, bool isSibling) {}
#endif

private:
    T *_left;
    T *_right;
    T *_parent;
    int32_t _key;
    bool _leftSibling;
    bool _rightSibling;
};

template<class T> class TR_HedgeTree {
public:
    TR_ALLOC(TR_Memory::HedgeTree)

    TR_HedgeTree()
        : _root(NULL)
    {}

    T *getRoot() { return _root; }

    void setRoot(T *node)
    {
        _root = node;
        if (node)
            node->setParent(NULL);
    }

    T *&rootReference() { return _root; }

    bool isEmpty() { return _root == NULL; }

    bool verify() { return _root ? _root->verify(NULL) : true; }

    T *find(int32_t key)
    {
        // Search the tree for the node with the given key.
        //
        for (T *node = _root; node;) {
            if (key < node->getKey())
                node = node->left();
            else if (key > node->getKey())
                node = node->right();
            else
                return node;
        }
        return NULL;
    }

#if DEBUG
    void print(TR::FILE *outFile)
    {
        if (outFile == NULL)
            return;
        if (!_root) {
            trfprintf(outFile, "     empty\n");
            return;
        }
        char prefix[80];
        memset(prefix, ' ', 80);
        _root->printTree(outFile, 3, prefix, false, false);
        trfflush(outFile);
    }
#else
    void print(TR::FILE *outFile) {}
#endif

private:
    T *_root;
};

template<class T> class TR_HedgeTreeIterator {
public:
    TR_ALLOC(TR_Memory::HedgeTree)

    TR_HedgeTreeIterator()
        : _tree(NULL)
        , _next(NULL)
    {}

    TR_HedgeTreeIterator(TR_HedgeTree<T> &tree) { reset(tree); }

    TR_HedgeTree<T> *getBase() { return _tree; }

    void reset(TR_HedgeTree<T> &tree)
    {
        _tree = &tree;
        _next = getLeftmost(tree.getRoot());
    }

    T *getFirst()
    {
        T *node = getLeftmost(_tree->getRoot());
        _next = getNextHigher(node);
        return node;
    }

    T *getNext()
    {
        if (!_next)
            return NULL;
        T *node = _next;
        _next = getNextHigher(node);
        return node;
    }

private:
    T *getLeftmost(T *root)
    {
        if (root)
            while (root->left())
                root = root->left();
        return root;
    }

    T *getNextHigher(T *node)
    {
        if (!node)
            return NULL;
        if (node->right())
            return getLeftmost(node->right());
        int32_t key = node->getKey();
        for (node = node->getParent(); node && node->getKey() <= key; node = node->getParent()) {
        }
        return node;
    }

    TR_HedgeTree<T> *_tree;
    T *_next;
};

template<class T> class TR_HedgeTreeHandler {
public:
    TR_ALLOC(TR_Memory::HedgeTree)

    T *find(int32_t key, TR_HedgeTree<T> &tree) { return tree.find(key); }

    T *findOrCreate(int32_t key, TR_HedgeTree<T> &tree)
    {
        int32_t rebalance;
        T *result;
        if (debug("traceHedge"))
            diagnostic("\nCall findOrCreate with key %d\n", key);
        if (tree.getRoot()) {
            _nodeToBeInserted = NULL;
            _treeChanged = false;
            result = findOrCreate(key, tree.rootReference(), rebalance);
        } else {
            result = allocate(key);
            tree.setRoot(result);
            _treeChanged = true;
        }
        if (_treeChanged && debug("traceHedge")) {
            diagnostic("Tree after insertion of key %d:\n", key);
            tree.print(comp()->getOutFile());
            tree.verify();
        }
        return result;
    }

    T *insert(T *newNode, TR_HedgeTree<T> &tree)
    {
        int32_t rebalance;
        T *result;
        newNode->setLeft(NULL);
        newNode->setRight(NULL);
        newNode->setLeftSibling(false);
        newNode->setRightSibling(false);
        if (debug("traceHedge"))
            diagnostic("\nCall insert with key %d\n", newNode->getKey());
        if (tree.getRoot()) {
            _nodeToBeInserted = newNode;
            _treeChanged = false;
            result = findOrCreate(newNode->getKey(), tree.rootReference(), rebalance);
        } else {
            result = newNode;
            tree.setRoot(newNode);
            _treeChanged = true;
        }
        if (_treeChanged && debug("traceHedge")) {
            diagnostic("Tree after insertion of key %d:\n", newNode->getKey());
            tree.print(comp()->getOutFile());
            tree.verify();
        }
        return result;
    }

    T *remove(int32_t key, TR_HedgeTree<T> &tree)
    {
        int32_t rebalance;
        _treeChanged = false;
        if (debug("traceHedge"))
            diagnostic("\nCall remove with key %d\n", key);
        T *result = remove(key, tree.rootReference(), rebalance);
        if (_treeChanged && debug("traceHedge")) {
            diagnostic("Tree after removal of key %d:\n", key);
            tree.print(comp()->getOutFile());
            tree.verify();
        }
        return result;
    }

    T *copyAll(TR_HedgeTree<T> &tree) { return copySubtree(tree.getRoot()); }

    T *copySubtree(T *node)
    {
        if (!node)
            return NULL;
        T *newNode = copy(node);
        newNode->setLeft(copySubtree(node->left()));
        newNode->setRight(copySubtree(node->right()));
        newNode->setLeftSibling(node->isLeftSibling());
        newNode->setRightSibling(node->isRightSibling());
        return newNode;
    }

    void empty(TR_HedgeTree<T> &tree) { emptySubtree(tree.rootReference()); }

    T *getRoot(TR_HedgeTree<T> &tree) { return tree.getRoot(); }

    void setRoot(TR_HedgeTree<T> &tree, T *node) { tree.setRoot(node); }

    virtual TR::Compilation *comp() = 0;

protected:
    virtual T *allocate(int32_t key) = 0;
    virtual void free(T *node) = 0;
    virtual T *copy(T *node) = 0;

private:
    inline T *findOrCreate(int32_t key, T *&node, int32_t &rebalance);
    inline T *remove(int32_t key, T *&node, int32_t &rebalance);
    inline void swapRightmost(T *&node, T *&swap);

    void emptySubtree(T *&node)
    {
        if (node) {
            emptySubtree(node->leftReference());
            emptySubtree(node->rightReference());
            free(node);
            node = NULL;
        }
    }

    T *_nodeToBeInserted;
    bool _treeChanged;
};

template<class T> T *TR_HedgeTreeHandler<T>::findOrCreate(int32_t key, T *&node, int32_t &rebalance)
{
    // Search the tree for the node with the given key. Insertion may cause the
    // slot containing the node pointer to be updated.
    // "rebalance" is a returned value with the following meaning:
    //    rebalance = 0: no change in structure of this subtree
    //    rebalance = 1: this node has acquired a sibling
    //    rebalance = 2: this subtree has increased in height
    //
    // If the search failed, create a new node and insert it
    //
    T *result;
    T *p1, *p2;

    if (key < node->getKey()) {
        // Search the left subtree. Rebalance if necessary
        //
        if (!node->left()) {
            if (_nodeToBeInserted)
                result = _nodeToBeInserted;
            else
                result = allocate(key);
            node->setLeft(result);
            _treeChanged = true;
            rebalance = 2;
        } else
            result = findOrCreate(key, node->leftReference(), rebalance);
        if (rebalance) {
            if (node->isLeftSibling()) {
                // If the subtree acquired a sibling this level now has 3 nodes in
                // the search path, so we must split the level.
                // Thus the height of this subtree will always have increased.
                //
                rebalance = 2;
                p1 = node->left();
                node->setLeftSibling(false);
                if (p1->isLeftSibling()) {
                    // Left subtree is lifted to a new level above this node
                    //
                    node->setLeft(p1->right());
                    p1->setLeftSibling(false);
                    p1->setParent(node->getParent());
                    p1->setRight(node);
                    node = p1;
                } else if (p1->isRightSibling()) {
                    // Left subtree's right subtree is lifted to a new level above
                    // this node
                    //
                    p2 = p1->right();
                    p1->setRight(p2->left());
                    p1->setRightSibling(false);
                    node->setLeft(p2->right());
                    node->setLeftSibling(false);
                    p2->setLeft(p1);
                    p2->setParent(node->getParent());
                    p2->setRight(node);
                    node = p2;
                }
            } else {
                // Left subtree is a child. If its height has increased, raise it
                // to become a sibling. Otherwise rebalancing is complete.
                //
                if (--rebalance)
                    node->setLeftSibling(true);
            }
        }
    }

    else if (key > node->getKey()) {
        // Search the right subtree. Rebalance if necessary
        //
        if (!node->right()) {
            if (_nodeToBeInserted)
                result = _nodeToBeInserted;
            else
                result = allocate(key);
            node->setRight(result);
            _treeChanged = true;
            rebalance = 2;
        } else
            result = findOrCreate(key, node->rightReference(), rebalance);
        if (rebalance) {
            if (node->isRightSibling()) {
                // If the subtree acquired a sibling this level now has 3 nodes in
                // the search path, so we must split the level.
                // Thus the height of this subtree will always have increased.
                //
                rebalance = 2;
                p1 = node->right();
                node->setRightSibling(false);
                if (p1->isRightSibling()) {
                    // Right subtree is lifted to a new level above this node
                    //
                    node->setRight(p1->left());
                    p1->setRightSibling(false);
                    p1->setParent(node->getParent());
                    p1->setLeft(node);
                    node = p1;
                } else if (p1->isLeftSibling()) {
                    // Right subtree's left subtree is lifted to a new level above
                    // this node
                    //
                    p2 = p1->left();
                    p1->setLeft(p2->right());
                    p1->setLeftSibling(false);
                    node->setRight(p2->left());
                    node->setRightSibling(false);
                    p2->setRight(p1);
                    p2->setParent(node->getParent());
                    p2->setLeft(node);
                    node = p2;
                }
            } else {
                // Right subtree is a child. If its height has increased, raise it
                // to become a sibling. Otherwise rebalancing is complete.
                //
                if (--rebalance)
                    node->setRightSibling(true);
            }
        }
    }

    else {
        rebalance = 0;
        result = node;
    }

    return result;
}

template<class T> T *TR_HedgeTreeHandler<T>::remove(int32_t key, T *&node, int32_t &rebalance)
{
    // Find the node with the given key and delete it from the tree
    // Deletion may cause the slot containing the node pointer to be updated.
    // "rebalance" is a returned value with the following meaning:
    //    rebalance = 0: no change in structure of this subtree
    //    rebalance = 1: this subtree has decreased in height
    //
    if (node == NULL) {
        // Node not found
        //
        rebalance = 0;
        return NULL;
    }

    T *result;
    T *p1, *p2, *p3;
    bool takeLeftBranch = false;

    if (key == node->getKey()) {
        // This is the node to be deleted. If it is a leaf node just remove it
        // from the tree. Otherwise swap it with the rightmost leaf node of the
        // left subtree and continue down the left subtree. This way we end up
        // always deleting a leaf node.
        //
        result = node;
        _treeChanged = true;
        if (node->right() == NULL) {
            rebalance = node->isLeftSibling() ? 0 : 1;
            if (node->left())
                node->left()->setParent(node->getParent());
            node = node->left();
            return result;
        }
        if (node->left() == NULL) {
            rebalance = node->isRightSibling() ? 0 : 1;
            node->right()->setParent(node->getParent());
            node = node->right();
            return result;
        }
        swapRightmost(node->leftReference(), node);
        takeLeftBranch = true;
    }

    if (takeLeftBranch || key < node->getKey()) {
        // Look in the left subtree
        //
        result = remove(key, node->leftReference(), rebalance);
        if (rebalance) {
            // The height of the subtree has changed. We must rebalance this node.
            // In the diagrams that follow, B is this node and A is the subtree
            // that has become shorter.
            //
            if (node->isLeftSibling()) {
                // Left subtree is a sibling. Make it a child to bring the height
                // back up to its original value.
                //
                //         |                 |
                //         |                 |
                //      A--B       ==>       B
                //          \               / \
            //           C             A   C
                //
                node->setLeftSibling(false);
                rebalance = 0;
            } else {
                p1 = node->right();
                p2 = p1->left();
                if ((node->isRightSibling() && p2->isRightSibling())
                    || (!node->isRightSibling() && p1->isLeftSibling())) {
                    // Right subtree's left subtree is lifted to a new level above
                    // this node. The original height is then restored.
                    //
                    //         |                |
                    //         |                |
                    //         B----C    ==>    D----C
                    //        /    / \         /    / \
               //       A    D-G E       B    G   E
                    //           /           / \
               //          F           A   F
                    //
                    //
                    //         |                |
                    //         |                |
                    //         B----C    ==>    D----C
                    //        /    / \         /    / \
               //       A  F-D-G E       B-F  G   E
                    //                       /
                    //                      A
                    //
                    //
                    //         |                |
                    //         |                |
                    //         B         ==>    D
                    //        / \              / \
               //       A D-C-E          B   C--E
                    //        / \            /\  /
                    //       F   G          A  F G
                    //
                    //
                    //         |                |
                    //         |                |
                    //         B         ==>    D
                    //        / \              / \
               //       A D-C            B   C
                    //        / \ \          / \  /\
               //       F   G E        A   F G E
                    //
                    //
                    p1->setLeft(p2->right());
                    p1->setLeftSibling(false);
                    p2->setRight(p1);
                    node->setRight(p2->left());
                    node->setRightSibling(p2->isLeftSibling());
                    p2->setParent(node->getParent());
                    p2->setLeft(node);
                    p2->setLeftSibling(false);
                    node = p2;
                    rebalance = 0;
                } else if (node->isRightSibling() && p2->isLeftSibling()) {
                    // Right subtree's left subtree's left subtree is lifted to a
                    // new level above this node. The original height is then restored.
                    //
                    //         |                |
                    //         |                |
                    //         B-----C   ==>    F-----C
                    //        /     / \        /     / \
               //       A  F--D   E      B     D   E
                    //         / \  \        / \   / \
               //        H   I  G      A   H I   G
                    //
                    p3 = p2->left();
                    p2->setLeft(p3->right());
                    p2->setLeftSibling(false);
                    node->setRight(p3->left());
                    node->setRightSibling(false);
                    p3->setRight(p1);
                    p3->setRightSibling(true);
                    p3->setParent(node->getParent());
                    p3->setLeft(node);
                    node = p3;
                    rebalance = 0;
                } else if (node->isRightSibling()) {
                    // Right subtree is lifted to a new level above this node. The
                    // original height is then restored.
                    //
                    //         |                   |
                    //         |                   |
                    //         B-----C   ==>       C
                    //        /     / \           / \
               //       A     D   E      B--D   E
                    //            / \        / \  \
               //           F   G      A   F  G
                    //
                    node->setRight(p2->left());
                    node->setRightSibling(false);
                    p1->setParent(node->getParent());
                    p2->setLeft(node);
                    p2->setLeftSibling(true);
                    node = p1;
                    rebalance = 0;
                } else if (p1->isRightSibling()) {
                    // Right subtree is lifted to a new level above this node. The
                    // original height is not restored.
                    //
                    //         |                   |
                    //         |                   |
                    //         B         ==>    B--C--E
                    //        / \              / \
               //       A   C--E         A   D
                    //          /
                    //         D
                    //
                    node->setRight(p1->left());
                    p1->setParent(node->getParent());
                    p1->setLeft(node);
                    p1->setLeftSibling(true);
                    node = p1;
                } else {
                    // Raise the right subtree to be a sibling. The resulting tree
                    // is still shorter so the parent will have to rebalance.
                    // If this is a sibling of the parent, the parent will make it a
                    // child to restore the height, so no double-sibling chain will
                    // result.
                    //
                    //         |                |
                    //         |                |
                    //         B         ==>    B--C
                    //        / \              /  / \
               //       A   C            A  D   E
                    //          / \
               //         D   E
                    //
                    node->setRightSibling(true);
                }
            }
        }
    }

    else {
        // Look in the right subtree
        //
        result = remove(key, node->rightReference(), rebalance);
        if (rebalance) {
            // The height of the subtree has changed. We must rebalance this node.
            // In the diagrams that follow, B is this node and A is the subtree
            // that has become shorter.
            //
            if (node->isRightSibling()) {
                // Right subtree is a sibling. Make it a child to bring the height
                // back up to its original value.
                //
                //         |                 |
                //         |                 |
                //         B--A    ==>       B
                //        /                 / \
            //       C                 C   A
                //
                node->setRightSibling(false);
                rebalance = 0;
            } else {
                p1 = node->left();
                p2 = p1->right();
                if ((node->isLeftSibling() && p2->isLeftSibling())
                    || (!node->isLeftSibling() && p1->isRightSibling())) {
                    // Left subtree's right subtree is lifted to a new level above
                    // this node. The original height is then restored.
                    //
                    //              |                |
                    //              |                |
                    //         C----B    ==>    C----D
                    //        / \    \         / \    \
               //       E G-D    A       E   G    B
                    //            \                   / \
               //             F                 F   A
                    //
                    //
                    //              |                |
                    //              |                |
                    //         C----B    ==>    C----D
                    //        / \    \         / \    \
               //       E G-D-F  A       E   G  F-B
                    //                                  \
               //                                   A
                    //
                    //
                    //         |                |
                    //         |                |
                    //         B         ==>    D
                    //        / \              / \
               //     E-C-D A         E--C   B
                    //        / \              \ / \
               //       G   F             G F  A
                    //
                    //
                    //         |                |
                    //         |                |
                    //         B         ==>    D
                    //        / \              / \
               //       C-D A            C   B
                    //      / / \            /\  / \
               //     E G   F          E  G F  A
                    //
                    //
                    p1->setRight(p2->left());
                    p1->setRightSibling(false);
                    p2->setLeft(p1);
                    node->setLeft(p2->right());
                    node->setLeftSibling(p2->isRightSibling());
                    p2->setParent(node->getParent());
                    p2->setRight(node);
                    p2->setRightSibling(false);
                    node = p2;
                    rebalance = 0;
                } else if (node->isLeftSibling() && p2->isRightSibling()) {
                    // Left subtree's right subtree's right subtree is lifted to a
                    // new level above this node. The original height is then restored.
                    //
                    //               |                |
                    //               |                |
                    //         C-----B   ==>    C-----F
                    //        / \     \        / \     \
               //       E   D--F  A      E   D     B
                    //          /  / \           / \   / \
               //         G  I   H         G   I H   A
                    //
                    p3 = p2->right();
                    p2->setRight(p3->left());
                    p2->setRightSibling(false);
                    node->setLeft(p3->right());
                    node->setLeftSibling(false);
                    p3->setLeft(p1);
                    p3->setLeftSibling(true);
                    p3->setParent(node->getParent());
                    p3->setRight(node);
                    node = p3;
                    rebalance = 0;
                } else if (node->isLeftSibling()) {
                    // Left subtree is lifted to a new level above this node. The
                    // original height is then restored.
                    //
                    //               |             |
                    //               |             |
                    //         C-----B   ==>       C
                    //        / \     \           / \
               //       E   D     A         E   D--B
                    //          / \                 /  / \
               //         G   F               G  F   A
                    //
                    node->setLeft(p2->right());
                    node->setLeftSibling(false);
                    p1->setParent(node->getParent());
                    p2->setRight(node);
                    p2->setRightSibling(true);
                    node = p1;
                    rebalance = 0;
                } else if (p1->isLeftSibling()) {
                    // Left subtree is lifted to a new level above this node. The
                    // original height is not restored.
                    //
                    //         |                   |
                    //         |                   |
                    //         B         ==>    E--C--B
                    //        / \                    / \
               //    E--C   A                  D   A
                    //        \
               //         D
                    //
                    node->setLeft(p1->right());
                    p1->setParent(node->getParent());
                    p1->setRight(node);
                    p1->setRightSibling(true);
                    node = p1;
                } else {
                    // Raise the left subtree to be a sibling. The resulting tree
                    // is still shorter so the parent will have to rebalance.
                    // If this is a sibling of the parent, the parent will make it a
                    // child to restore the height, so no double-sibling chain will
                    // result.
                    //
                    //         |                   |
                    //         |                   |
                    //         B         ==>    C--B
                    //        / \              / \  \
               //       C   A            E   D  A
                    //      / \
               //     E   D
                    //
                    node->setLeftSibling(true);
                }
            }
        }
    }

    return result;
}

template<class T> void TR_HedgeTreeHandler<T>::swapRightmost(T *&node, T *&swap)
{
    // Find the rightmost node in this subtree and swap it with the given node
    //
    if (node->right()) {
        swapRightmost(node->rightReference(), swap);
    } else {
        // This is it
        //
        bool b;
        b = node->isLeftSibling();
        node->setLeftSibling(swap->isLeftSibling());
        swap->setLeftSibling(b);
        b = node->isRightSibling();
        node->setRightSibling(swap->isRightSibling());
        swap->setRightSibling(b);

        T *t = swap->right();
        swap->setRight(node->right());
        node->setRight(t);
        T *t1 = swap->getParent();
        if (node == swap->left()) {
            // Special case if this is the immediate child
            //
            t = node;
            swap->setLeft(t->left());
            t->setLeft(swap);
            t->setParent(t1);
            swap = t;
        } else {
            t = swap->left();
            swap->setLeft(node->left());
            node->setLeft(t);
            t = node;
            swap->setParent(node->getParent());
            node = swap;
            t->setParent(t1);
            swap = t;
        }
    }
}

#endif
