TreeNode.h

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// ================================================================ //
//                                                                  //
//   File      : TreeNode.h                                         //
//   Purpose   :                                                    //
//                                                                  //
//   Coded by Ralf Westram (coder@reallysoft.de) in December 2013   //
//   Institute of Microbiology (Technical University Munich)        //
//   http://www.arb-home.de/                                        //
//                                                                  //
// ================================================================ //

#ifndef TREENODE_H
#define TREENODE_H

#ifndef ARBDBT_H
#include "arbdbt.h"
#endif
#ifndef _GLIBCXX_ALGORITHM
#include <algorithm>
#endif

#define rt_assert(cond) arb_assert(cond)

#if defined(DEBUG) || defined(UNIT_TESTS) // UT_DIFF
# define PROVIDE_TREE_STRUCTURE_TESTS
#endif
#if defined(DEVEL_RALF) && defined(PROVIDE_TREE_STRUCTURE_TESTS)
# define AUTO_CHECK_TREE_STRUCTURE // Note: dramatically slows down most tree operations
#endif

class TreeRoot;
class TreeNode;
class ARB_edge;

enum TreeOrder { // contains bit values!
    ORDER_BIG_DOWN      = 1, // bit 0 set -> big branches down
    ORDER_BIG_TO_EDGE   = 2, // bit 1 set -> big branches to edge
    ORDER_BIG_TO_CENTER = 4, // bit 2 set -> big branches to center
    ORDER_ALTERNATING   = 8, // bit 3 set -> alternate bit 0

    // user visible orders:
    BIG_BRANCHES_TO_TOP      = 0,
    BIG_BRANCHES_TO_BOTTOM   = ORDER_BIG_DOWN,
    BIG_BRANCHES_TO_EDGE     = ORDER_BIG_TO_EDGE,
    BIG_BRANCHES_TO_CENTER   = ORDER_BIG_TO_CENTER,
    BIG_BRANCHES_ALTERNATING = ORDER_BIG_TO_CENTER|ORDER_ALTERNATING,
};

#define DEFINE_READ_ACCESSORS(TYPE, ACCESS, MEMBER)     \
    TYPE ACCESS() { return MEMBER; }                    \
    const TYPE ACCESS() const { return MEMBER; }

class TreeRoot : virtual Noncopyable {
    TreeNode *rootNode;            // root node of the tree
    bool      deleteWithNodes;
    bool      seenBootstrapDuringLoad;

protected:
    void predelete() {
        // should be called from dtor of derived class defining makeNode/destroyNode
        if (rootNode) {
            destroyNode(rootNode);
            rt_assert(!rootNode);
        }
    }
public:
    explicit TreeRoot(bool deleteWithNodes_) :
        rootNode(NULp),
        deleteWithNodes(deleteWithNodes_),
        seenBootstrapDuringLoad(false)
    {
    }
    virtual ~TreeRoot();
    virtual void change_root(TreeNode *old, TreeNode *newroot);

    void delete_by_node() {
        if (deleteWithNodes) {
            rt_assert(!rootNode);
            delete this;
        }
    }

    bool has_bootstrap() const {
        return seenBootstrapDuringLoad;
    }
    void set_bootstrap_seen(bool seen) {
        seenBootstrapDuringLoad = seen;
    }

    virtual TreeNode *makeNode() const             = 0;
    virtual void destroyNode(TreeNode *node) const = 0;

    DEFINE_READ_ACCESSORS(TreeNode*, get_root_node, rootNode);

    ARB_edge find_innermost_edge();
};
MARK_NONFINAL_METHOD(TreeRoot,change_root,(TreeNode*,TreeNode*));

inline GBT_RemarkType parse_remark(const char *remark, double& bootstrap) {
    if (!remark) return REMARK_NONE;

    const char *end = NULp;
    bootstrap       = strtod(remark, (char**)&end);

    bool is_bootstrap = end[0] == '%' && end[1] == 0;
    return is_bootstrap ? REMARK_BOOTSTRAP : REMARK_OTHER;
}
inline bool parse_treelabel(const char*& label, double& bootstrap) {
    const char *end = NULp;
    bootstrap       = strtod(label, (char**)&end);

    bool is_bootstrap = end != label;
    if (is_bootstrap) {
        if (end[0] == '%') {
            ++end;
            bootstrap = bootstrap/100.0; // percent -> [0..1]
        }
        is_bootstrap = end[0] == ':' || !end[0]; // followed by ':' or at EOS

        switch (end[0]) {
            case ':': label        = end+1; break;
            case 0:   label        = NULp;  break;
            default:  is_bootstrap = false; break;
        }
    }

    return is_bootstrap;
}

#define KEELED_INDICATOR '!' // prefixed to names of "keeled groups" (not meant to be changed)

struct TreeNode : virtual Noncopyable {
    TreeNode *father, *leftson, *rightson;
    GBT_LEN   leftlen, rightlen;
    GBDATA   *gb_node;
    char     *name;

private:
    bool leaf;
    bool keeledOver;  // node has group info and tree-root was moved "inside" that group -> group changed meaning (see #735)
    bool inverseLeft; // (only if keeledOver) true -> left son contains "inverse" of original group; false -> right son dito

    SmartCharPtr remark_branch; // remark_branch normally contains some bootstrap value in format 'xx%'
                                // if you store other info there, please make sure that this info does not start with digits!!
                                // Otherwise the tree export routines will not work correctly!

    GBT_LEN& length_ref() { return is_leftson() ? father->leftlen : father->rightlen; }
    const GBT_LEN& length_ref() const { return const_cast<TreeNode*>(this)->length_ref(); }

    void keelOver(TreeNode *prev, TreeNode *next, double len);

protected:
    TreeNode*& self_ref() {
        return is_leftson() ? father->leftson : father->rightson;
    }
    void unlink_from_father() {
        if (father) {
            self_ref() = NULp;
            father     = NULp;
        }
    }

    inline void swap_node_info(TreeNode *other, bool ofKeeledGroups);
    void fixKeeledOrientation() {
        if (father->keeledOver) {
            father->inverseLeft = is_leftson();
            rt_assert(is_keeled_group());
        }
    }

public:

    bool is_leaf() const { return leaf; }
    void markAsLeaf() {
        rt_assert(!is_leaf());
        rt_assert(!leftson && !rightson); // only allowed during setup!
        leaf = true;
    }

    DEFINE_READ_ACCESSORS(TreeNode*, get_father,   father);
    DEFINE_READ_ACCESSORS(TreeNode*, get_leftson,  leftson);
    DEFINE_READ_ACCESSORS(TreeNode*, get_rightson, rightson);

    // Note: unittests for these attributes are in ../NTREE/ad_trees.cxx@TEST_TreeNode_attributes

    bool is_son_of(const TreeNode *Father) const {
        return father == Father &&
            (father->leftson == this || father->rightson == this);
    }
    bool is_leftson() const {
        // left when root is at bottom; see also ../SL/ARB_TREE/ARB_Tree.hxx@is_upper_son
        gb_assert(is_son_of(get_father())); // do only call with sons!
        return father->leftson == this;
    }
    bool is_rightson() const {
        gb_assert(is_son_of(get_father())); // do only call with sons!
        return father->rightson == this;
    }

    bool is_inside(const TreeNode *subtree) const {
        return this == subtree || (father && get_father()->is_inside(subtree));
    }
    bool is_ancestor_of(const TreeNode *descendant) const {
        return !is_leaf() && descendant != this && descendant->is_inside(this);
    }
    bool in_same_branch_as(const TreeNode *other) const {
        // returns true if 'this' and 'other' are in ONE branch
        return this == other || is_ancestor_of(other) || other->is_ancestor_of(this);
    }
    bool in_other_branch_than(const TreeNode *other) const {
        // returns true if 'this' and 'other' are NOT in one branch
        return !in_same_branch_as(other);
    }
    const TreeNode *ancestor_common_with(const TreeNode *other) const;
    TreeNode *ancestor_common_with(TreeNode *other) { return const_cast<TreeNode*>(ancestor_common_with(const_cast<const TreeNode*>(other))); }

    bool is_son_of_root() const {
        return father && !father->father && father->is_root_node();
    }

    GBT_LEN get_branchlength() const { return length_ref(); }
    void set_branchlength(GBT_LEN newlen) {
        gb_assert(!is_nan_or_inf(newlen));
        length_ref() = newlen;
    }

    GBT_LEN get_branchlength_unrooted() const {
        if (father->is_root_node()) {
            return father->leftlen+father->rightlen;
        }
        return get_branchlength();
    }
    void set_branchlength_unrooted(GBT_LEN newlen) {
        if (father->is_root_node()) {
            father->leftlen  = newlen/2;
            father->rightlen = newlen-father->leftlen; // make sure sum equals newlen
        }
        else {
            set_branchlength(newlen);
        }
    }

    GBT_LEN sum_child_lengths() const;
    GBT_LEN root_distance() const {
        return father ? get_branchlength()+father->root_distance() : 0.0;
    }
    GBT_LEN intree_distance_to(const TreeNode *other) const {
        const TreeNode *ancestor = ancestor_common_with(other);
        return root_distance() + other->root_distance() - 2*ancestor->root_distance();
    }

    void remove_bootstrap();                        // remove bootstrap values from subtree
    GB_ERROR apply_aci_to_remarks(const char *aci, const GBL_call_env& callEnv);

    void reset_branchlengths();                     // reset branchlengths of subtree to tree_defaults::LENGTH
    void scale_branchlengths(double factor);

    void bootstrap2branchlen();                     // copy bootstraps to branchlengths
    void branchlen2bootstrap();                     // copy branchlengths to bootstraps

    GBT_RemarkType parse_bootstrap(double& bootstrap) const {
        rt_assert(!is_leaf()); // only inner nodes may have bootstraps
        return parse_remark(remark_branch.content(), bootstrap);
    }

    const char *get_remark() const {
        rt_assert(!is_leaf()); // only inner nodes may have bootstraps
        return remark_branch.content();
    }
    const SmartCharPtr& get_remark_ptr() const {
        rt_assert(!is_leaf()); // only inner nodes may have bootstraps
        return remark_branch;
    }
    bool is_inner_node_with_remark() const { return !is_leaf() && get_remark_ptr().isSet(); }
    void use_as_remark(const SmartCharPtr& newRemark) {
        rt_assert(!is_leaf()); // only inner nodes may have bootstraps
        remark_branch = newRemark;
    }
    void set_remark(const char *newRemark) {
        use_as_remark(strdup(newRemark));
    }
    void set_bootstrap(double bootstrap) {
        use_as_remark(GBS_global_string_copy("%i%%", int(bootstrap+0.5)));
    }
    void remove_remark() {
        SmartCharPtr norem;
        use_as_remark(norem);
    }
#if defined(ASSERTION_USED) || defined(PROVIDE_TREE_STRUCTURE_TESTS)
    bool has_no_remark() const { return remark_branch.isNull(); }
    bool has_valid_root_remarks() const;
#endif

private:

    friend void TreeRoot::change_root(TreeNode *old, TreeNode *newroot);

    TreeRoot *tree_root;

    // ------------------
    //      functions

    void reorder_subtree(TreeOrder mode);

protected:
    void set_tree_root(TreeRoot *new_root);

    bool at_root() const {
        return !father || !father->father;
    }
    virtual ~TreeNode() {
        if (tree_root) {
            rt_assert(tree_root->get_root_node() == this); // you may only free the root-node or unlinked nodes (i.e. nodes where tree_root is NULp)

            TreeRoot *root = tree_root;
            root->TreeRoot::change_root(this, NULp);
            root->delete_by_node();
        }
        delete leftson;  gb_assert(!leftson); // cannot use destroy here
        delete rightson; gb_assert(!rightson);

        unlink_from_father();

        free(name);
    }
    void destroy()  {
        rt_assert(knownNonNull(this));
        TreeRoot *myRoot = get_tree_root();
        rt_assert(myRoot); // if this fails, you need to use destroy(TreeRoot*), i.e. destroy(TreeNode*, TreeRoot*)
        myRoot->destroyNode(this);
    }
    void destroy(TreeRoot *viaRoot) {
        rt_assert(knownNonNull(this));
#if defined(ASSERTION_USED)
        TreeRoot *myRoot = get_tree_root();
        rt_assert(!myRoot || myRoot == viaRoot);
#endif
        viaRoot->destroyNode(this);
    }

public:
    TreeNode(TreeRoot *root) :
        father(NULp), leftson(NULp), rightson(NULp),
        leftlen(0.0), rightlen(0.0),
        gb_node(NULp),
        name(NULp),
        leaf(false),
        keeledOver(false),
        inverseLeft(false),
        tree_root(root)
    {}
    static void destroy(TreeNode *that)  { // replacement for destructor
        if (that) that->destroy();
    }
    static void destroy(TreeNode *that, TreeRoot *root) {
        if (that) that->destroy(root);
    }

    TreeNode *fixDeletedSon(); // @@@ review (design)

    void unlink_from_DB();

    void announce_tree_constructed() { // @@@ use this function or just call change_root instead?
        // (has to be) called after tree has been constructed
        gb_assert(!father); // has to be called with root-node!
        get_tree_root()->change_root(NULp, this);
    }

    virtual unsigned get_leaf_count() const = 0;
    virtual void compute_tree()             = 0;

    void forget_origin() { set_tree_root(NULp); }
    void forget_relatives() {
        leftson  = NULp;
        rightson = NULp;
        father   = NULp;
    }

    TreeRoot *get_tree_root() const { return tree_root; }

    const TreeNode *get_root_node() const {
        if (!tree_root) return NULp; // nodes removed from tree have no root-node

        const TreeNode *root = tree_root->get_root_node();
        rt_assert(is_inside(root)); // this is not in tree - behavior of get_root_node() changed!
        return root;
    }
    TreeNode *get_root_node() { return const_cast<TreeNode*>(const_cast<const TreeNode*>(this)->get_root_node()); }

    bool is_root_node() const { return !father && get_root_node() == this; }
    virtual void set_root();

    TreeNode *get_brother() {
        rt_assert(!is_root_node()); // root node has no brother
        rt_assert(father);          // this is a removed node (not root, but no father)
        return is_leftson() ? get_father()->get_rightson() : get_father()->get_leftson();
    }
    const TreeNode *get_brother() const {
        return const_cast<const TreeNode*>(const_cast<TreeNode*>(this)->get_brother());
    }

    bool has_group_info() const {
        rt_assert(!is_leaf()); // a leaf never has group info (useless call)
        return gb_node && name;
    }
    TreeNode *keelTarget() {
        return (has_group_info() && keeledOver) ? (inverseLeft ? get_leftson() : get_rightson()) : NULp;
    }
    const TreeNode *keelTarget() const {
        return const_cast<TreeNode*>(this)->keelTarget();
    }
    bool keelsDownGroup(const TreeNode *toSon) const {
        // returns true if node has a group keeled down 'toSon'
        return keelTarget() == toSon;
    }
    void unkeelGroup() {
        rt_assert(keelTarget());
        keeledOver = false;
    }
    int keeledStateInfo() const { // keeled-state as stored in database
        return keeledOver ? (inverseLeft ? 1 : 2) : 0;
    }
    void setKeeledState(int keeledState) {
        keeledOver  = keeledState;
        inverseLeft = keeledState == 1;
    }

    bool is_normal_group() const {
        // returns true when node shall show a "normal" group
        rt_assert(!is_leaf()); // useless call (a normal group never may occur at leaf)
        return has_group_info() && !keeledOver;
    }
    bool is_keeled_group() const {
        // returns true when node shall show a "keeled" group.
        // (i.e. when father has a keeled group oriented towards 'this')
        return father && father->keelsDownGroup(this);
    }
    bool is_clade() const {
        // return true, if a clickable group shall be displayed in tree
        // (Note: keeled groups may appear at leafs)
        return (!is_leaf() && is_normal_group()) || is_keeled_group();
    }

    const char *get_group_name() const {
        return
            !is_leaf() && is_normal_group()
            ? name
            : (is_keeled_group() ? father->name : NULp);
    }

    const TreeNode *find_parent_with_groupInfo(bool skipKeeledBrothers = false) const {
        const TreeNode *child  = this;
        const TreeNode *parent = get_father();

        while (parent) {
            if (parent->has_group_info()) {
                if (!skipKeeledBrothers) break; // report any group

                const TreeNode *keeled = parent->keelTarget();
                if (!keeled || keeled == child) break;

                // continue with next parent if keeled to other branch
            }
            child  = parent;
            parent = child->get_father();
        }
        return parent;
    }
    TreeNode *find_parent_with_groupInfo(bool skipKeeledBrothers = false) {
        return const_cast<TreeNode*>(const_cast<const TreeNode*>(this)->find_parent_with_groupInfo(skipKeeledBrothers));
    }

    const TreeNode *find_parent_clade() const {
        // opposed to find_parent_with_groupInfo this reports only nodes where a group is DISPLAYED
        // (i.e. in case of keeled groups at son node)

        const TreeNode *parent   = find_parent_with_groupInfo();
        const TreeNode *myBranch = this;  // me or any ancestor
        while (parent) {
            const TreeNode *keeled = parent->keelTarget();
            if (!keeled) break; // use parent

            if (parent != father && keeled->in_same_branch_as(myBranch)) {
                parent = keeled; // use keeled
                break;
            }

            // either keeled to self, to brother or to brother of some of my ancestors -> step up
            rt_assert(keeled == this || keeled == get_brother() || keeled->get_brother()->is_ancestor_of(this));

            myBranch = parent;
            parent   = parent->find_parent_with_groupInfo();
        }

        rt_assert(implicated(parent, parent->is_clade()));

        return parent;
    }
    TreeNode *find_parent_clade() {
        return const_cast<TreeNode*>(const_cast<const TreeNode*>(this)->find_parent_clade());
    }
    int calc_clade_level() const {
        int             taxLev  = is_clade();
        const TreeNode *parent  = find_parent_clade();
        if (parent) taxLev     += parent->calc_clade_level();
        return taxLev;
    }

    int count_clades() const;

    virtual void swap_sons() {
        rt_assert(!is_leaf()); // only possible for inner nodes!

        std::swap(leftson, rightson);
        std::swap(leftlen, rightlen);
        inverseLeft = !inverseLeft;
    }
    void rotate_subtree(); // flip whole subtree ( = recursive swap_sons())
    void reorder_tree(TreeOrder mode);

    TreeNode *findLeafNamed(const char *wantedName);

    GBT_LEN reset_length_and_bootstrap() {
        if (!is_leaf()) remove_remark();
        GBT_LEN len = get_branchlength_unrooted();
        set_branchlength_unrooted(0.0);
        return len;
    }

    struct multifurc_limits {
        double bootstrap;
        double branchlength;
        bool   applyAtLeafs;
        multifurc_limits(double bootstrap_, double branchlength_, bool applyAtLeafs_)
            : bootstrap(bootstrap_),
              branchlength(branchlength_),
              applyAtLeafs(applyAtLeafs_)
        {}
    };
    class LengthCollector;

    void multifurcate();
    void set_branchlength_preserving(GBT_LEN new_len);

    void multifurcate_whole_tree(const multifurc_limits& below);
private:
    void eliminate_and_collect(const multifurc_limits& below, LengthCollector& collect);
public:

#if defined(PROVIDE_TREE_STRUCTURE_TESTS)
    Validity is_valid() const;
#endif // PROVIDE_TREE_STRUCTURE_TESTS
};
MARK_NONFINAL_METHOD(TreeNode,swap_sons,());
MARK_NONFINAL_METHOD(TreeNode,set_root,());

inline void destroy(TreeNode *that) {
    TreeNode::destroy(that);
}
inline void destroy(TreeNode *that, TreeRoot *root) {
    TreeNode::destroy(that, root);
}

// ---------------------------------------------------------------------------------------
//      macros to overwrite accessors in classes derived from TreeRoot or TreeNode:

#define DEFINE_TREE_ROOT_ACCESSORS(RootType, TreeType)                                  \
    DEFINE_DOWNCAST_ACCESSORS(TreeType, get_root_node, TreeRoot::get_root_node())

#define DEFINE_TREE_RELATIVES_ACCESSORS(TreeType) \
    DEFINE_DOWNCAST_ACCESSORS(TreeType, get_father, father); \
    DEFINE_DOWNCAST_ACCESSORS(TreeType, get_leftson, leftson);  \
    DEFINE_DOWNCAST_ACCESSORS(TreeType, get_rightson, rightson); \
    DEFINE_DOWNCAST_ACCESSORS(TreeType, get_brother, TreeNode::get_brother()); \
    DEFINE_DOWNCAST_ACCESSORS(TreeType, get_root_node, TreeNode::get_root_node());                                      \
    TreeType *findLeafNamed(const char *wantedName) { return DOWNCAST(TreeType*, TreeNode::findLeafNamed(wantedName)); }

#define DEFINE_TREE_ACCESSORS(RootType, TreeType)                                     \
    DEFINE_DOWNCAST_ACCESSORS(RootType, get_tree_root, TreeNode::get_tree_root());    \
    DEFINE_TREE_RELATIVES_ACCESSORS(TreeType)


// -------------------------
//      structure tests

#if defined(PROVIDE_TREE_STRUCTURE_TESTS)
template <typename TREE>
inline Validity tree_is_valid(const TREE *tree, bool acceptNULL) {
    if (tree) return tree->is_valid();
    return Validity(acceptNULL, "NULp tree");
}
template <typename TREE>
inline bool tree_is_valid_or_dump(const TREE *tree, bool acceptNULL) {
    Validity valid = tree_is_valid(tree, acceptNULL);
    if (!valid) fprintf(stderr, "\ntree is NOT valid (Reason: %s)\n", valid.why_not());
    return valid;
}
#endif

#if defined(AUTO_CHECK_TREE_STRUCTURE)
#define ASSERT_VALID_TREE(tree)         rt_assert(tree_is_valid_or_dump(tree, false))
#define ASSERT_VALID_TREE_OR_NULL(tree) rt_assert(tree_is_valid_or_dump(tree, true))
#else
#define ASSERT_VALID_TREE(tree)
#define ASSERT_VALID_TREE_OR_NULL(tree)
#endif // AUTO_CHECK_TREE_STRUCTURE

#if defined(PROVIDE_TREE_STRUCTURE_TESTS) && defined(UNIT_TESTS)

#define TEST_EXPECT_VALID_TREE(tree)                     TEST_VALIDITY(tree_is_valid(tree, false))
#define TEST_EXPECT_VALID_TREE_OR_NULL(tree)             TEST_VALIDITY(tree_is_valid(tree, true))
#define TEST_EXPECT_VALID_TREE__BROKEN(tree,why)         TEST_VALIDITY__BROKEN(tree_is_valid(tree, false), why)
#define TEST_EXPECT_VALID_TREE_OR_NULL__BROKEN(tree,why) TEST_VALIDITY__BROKEN(tree_is_valid(tree, true), why)

#else

#define TEST_EXPECT_VALID_TREE(tree)
#define TEST_EXPECT_VALID_TREE_OR_NULL(tree)
#define TEST_EXPECT_VALID_TREE__BROKEN(tree)
#define TEST_EXPECT_VALID_TREE_OR_NULL__BROKEN(tree)

#endif

// --------------------
//      SimpleTree

struct SimpleRoot : public TreeRoot {
    inline SimpleRoot();
    inline TreeNode *makeNode() const OVERRIDE;
    inline void destroyNode(TreeNode *node) const OVERRIDE;
};

class SimpleTree FINAL_TYPE : public TreeNode {
protected:
    ~SimpleTree() OVERRIDE {}
    friend class SimpleRoot;
public:
    SimpleTree(SimpleRoot *sroot) : TreeNode(sroot) {}

    // TreeNode interface
    unsigned get_leaf_count() const OVERRIDE {
        rt_assert(0); // @@@ impl?
        return 0;
    }
    void compute_tree() OVERRIDE {}
};

SimpleRoot::SimpleRoot() : TreeRoot(true) {}
inline TreeNode *SimpleRoot::makeNode() const { return new SimpleTree(const_cast<SimpleRoot*>(this)); }
inline void SimpleRoot::destroyNode(TreeNode *node) const { delete DOWNCAST(SimpleTree*,node); }

// ----------------------
//      ARB_edge_type

enum ARB_edge_type {
    EDGE_TO_ROOT, // edge points towards the root node
    EDGE_TO_LEAF, // edge points away from the root node
    ROOT_EDGE, // edge between sons of root node
};

class ARB_edge {
    // ARB_edge is a directional edge between two non-root-nodes of the same tree
    // (can act as iterator for TreeNode)

    TreeNode      *from, *to;
    ARB_edge_type  type;

    ARB_edge_type detectType() const {
        rt_assert(to != from);
        rt_assert(!from->is_root_node());                // edges cannot be at root - use edge between sons of root!
        rt_assert(!to->is_root_node());

        if (from->father == to) return EDGE_TO_ROOT;
        if (to->father == from) return EDGE_TO_LEAF;

        rt_assert(from->get_brother() == to);       // no edge exists between 'from' and 'to'
        rt_assert(to->get_father()->is_root_node());
        return ROOT_EDGE;
    }

    GBT_LEN adjacent_distance() const;
    GBT_LEN length_or_adjacent_distance() const {
        {
            GBT_LEN len = length();
            if (len>0.0) return len;
        }
        return adjacent_distance();
    }

    void virtually_add_or_distribute_length_forward(GBT_LEN len, TreeNode::LengthCollector& collect) const;
    void virtually_distribute_length_forward(GBT_LEN len, TreeNode::LengthCollector& collect) const;
public:
    void virtually_distribute_length(GBT_LEN len, TreeNode::LengthCollector& collect) const; // @@@ hm public :(
private:

#if defined(UNIT_TESTS) // UT_DIFF
    friend void TEST_edges();
#endif

public:
    ARB_edge(TreeNode *From, TreeNode *To) :
        from(From),
        to(To),
        type(detectType())
    {}
    ARB_edge(TreeNode *From, TreeNode *To, ARB_edge_type Type) :
        from(From),
        to(To),
        type(Type)
    {
        rt_assert(type == detectType());
    }
    ARB_edge(const ARB_edge& otherEdge) :
        from(otherEdge.from),
        to(otherEdge.to),
        type(otherEdge.type)
    {
        rt_assert(type == detectType());
    }

    DECLARE_ASSIGNMENT_OPERATOR(ARB_edge);

    ARB_edge_type get_type() const { return type; }
    TreeNode *source() const { return from; }
    TreeNode *dest() const { return to; }

    TreeNode *son() const  { return type == EDGE_TO_ROOT ? from : to; }
    TreeNode *other() const  { return type == EDGE_TO_ROOT ? to : from; }

    GBT_LEN length() const {
        if (type == ROOT_EDGE) return from->get_branchlength() + to->get_branchlength();
        return son()->get_branchlength();
    }
    void set_length(GBT_LEN len)  {
        if (type == ROOT_EDGE) {
            from->set_branchlength(len/2);
            to->set_branchlength(len/2);
        }
        else {
            son()->set_branchlength(len);
        }
    }
    GBT_LEN eliminate() {
        if (type == ROOT_EDGE) {
            return source()->reset_length_and_bootstrap() + dest()->reset_length_and_bootstrap();
        }
        return son()->reset_length_and_bootstrap();
    }

    ARB_edge inverse() const {
        return ARB_edge(to, from, ARB_edge_type(type == ROOT_EDGE ? ROOT_EDGE : (EDGE_TO_LEAF+EDGE_TO_ROOT)-type));
    }

    // iterator functions: endlessly iterate over all edges of tree
    // - next:        forward  (=towards dest())
    // - previous:    backward (=back before source())
    // - counter:     forward descends left  (=upper) son first
    // - non-counter: forward descends right (=lower) son first

    ARB_edge next() const { // descends rightson first (traverses leaf-edges from bottom to top)
        if (type == EDGE_TO_ROOT) {
            rt_assert(from->is_son_of(to));
            if (from->is_rightson()) return ARB_edge(to, to->get_leftson(), EDGE_TO_LEAF);
            TreeNode *father = to->get_father();
            if (father->is_root_node()) return ARB_edge(to, to->get_brother(), ROOT_EDGE);
            return ARB_edge(to, father, EDGE_TO_ROOT);
        }
        if (is_edge_to_leaf()) return inverse();
        return ARB_edge(to, to->get_rightson(), EDGE_TO_LEAF);
    }
    ARB_edge previous() const { // inverse of next(). (traverses leaf-edges from top to bottom)
        if (type == EDGE_TO_LEAF) {
            rt_assert(to->is_son_of(from));
            if (to->is_leftson()) return ARB_edge(from->get_rightson(), from, EDGE_TO_ROOT);
            TreeNode *father = from->get_father();
            if (father->is_root_node()) return ARB_edge(from->get_brother(), from, ROOT_EDGE);
            return ARB_edge(father, from, EDGE_TO_LEAF);
        }
        if (is_edge_from_leaf()) return inverse();
        return ARB_edge(from->get_leftson(), from, EDGE_TO_ROOT);
    }

    ARB_edge counter_next() const { // descends leftson first (traverses leaf-edges from top to bottom)
        if (type == EDGE_TO_ROOT) {
            rt_assert(from->is_son_of(to));
            if (from->is_leftson()) return ARB_edge(to, to->get_rightson(), EDGE_TO_LEAF);
            TreeNode *father = to->get_father();
            if (father->is_root_node()) return ARB_edge(to, to->get_brother(), ROOT_EDGE);
            return ARB_edge(to, father, EDGE_TO_ROOT);
        }
        if (is_edge_to_leaf()) return inverse();
        return ARB_edge(to, to->get_leftson(), EDGE_TO_LEAF);
    }
    ARB_edge counter_previous() const { // inverse of counter_next(). (traverses leaf-edges from bottom to top)
        if (type == EDGE_TO_LEAF) {
            rt_assert(to->is_son_of(from));
            if (to->is_rightson()) return ARB_edge(from->get_leftson(), from, EDGE_TO_ROOT);
            TreeNode *father = from->get_father();
            if (father->is_root_node()) return ARB_edge(from->get_brother(), from, ROOT_EDGE);
            return ARB_edge(father, from, EDGE_TO_LEAF);
        }
        if (is_edge_from_leaf()) return inverse();
        return ARB_edge(from->get_rightson(), from, EDGE_TO_ROOT);
    }

    static int iteration_count(int leafs_in_tree) {
        return leafs_in_tree<2 ? 0 : leafs_2_edges(leafs_in_tree, UNROOTED) * 2;
    }

    bool operator == (const ARB_edge& otherEdge) const {
        return from == otherEdge.from && to == otherEdge.to;
    }
    bool operator != (const ARB_edge& otherEdge) const {
        return !operator == (otherEdge);
    }

    bool is_edge_to_leaf() const {
        return dest()->is_leaf();
    }
    bool is_edge_from_leaf() const {
        return source()->is_leaf();
    }
    bool is_inner_edge() const {
        return !is_edge_to_leaf() && !is_edge_from_leaf();
    }

    void set_root() { son()->set_root(); }

    void multifurcate();

};

inline ARB_edge parentEdge(TreeNode *son) {
    TreeNode *father = son->get_father();
    rt_assert(father);

    if (father->is_root_node()) return ARB_edge(son, son->get_brother(), ROOT_EDGE);
    return ARB_edge(son, father, EDGE_TO_ROOT);
}
inline ARB_edge leafEdge(TreeNode *leaf) {
    rt_assert(leaf->is_leaf());
    return parentEdge(leaf).inverse();
}

inline ARB_edge rootEdge(TreeRoot *root) {
    TreeNode *root_node = root->get_root_node();
    return ARB_edge(root_node->get_leftson(), root_node->get_rightson(), ROOT_EDGE);
}

#else
#error TreeNode.h included twice
#endif // TREENODE_H