SeparatorPrefixTree.h

#pragma once
#include <QString>
#include <QMap>
#include <QStringList>

template <char Tseparator>
class SeparatorPrefixTree
{
public:
    SeparatorPrefixTree(QStringList paths)
    {
        insert(paths);
    }

    SeparatorPrefixTree(bool contained = false)
    {
        m_contained = contained;
    }

    void insert(QStringList paths)
    {
        for(auto &path: paths)
        {
            insert(path);
        }
    }

    /// insert an exact path into the tree
    SeparatorPrefixTree & insert(QString path)
    {
        auto sepIndex = path.indexOf(Tseparator);
        if(sepIndex == -1)
        {
            children[path] = SeparatorPrefixTree(true);
            return children[path];
        }
        else
        {
            auto prefix = path.left(sepIndex);
            if(!children.contains(prefix))
            {
                children[prefix] = SeparatorPrefixTree(false);
            }
            return children[prefix].insert(path.mid(sepIndex + 1));
        }
    }

    /// is the path fully contained in the tree?
    bool contains(QString path) const
    {
        auto node = find(path);
        return node != nullptr;
    }

    /// does the tree cover a path? That means the prefix of the path is contained in the tree
    bool covers(QString path) const
    {
        // if we found some valid node, it's good enough. the tree covers the path
        if(m_contained)
        {
            return true;
        }
        auto sepIndex = path.indexOf(Tseparator);
        if(sepIndex == -1)
        {
            auto found = children.find(path);
            if(found == children.end())
            {
                return false;
            }
            return (*found).covers(QString());
        }
        else
        {
            auto prefix = path.left(sepIndex);
            auto found = children.find(prefix);
            if(found == children.end())
            {
                return false;
            }
            return (*found).covers(path.mid(sepIndex + 1));
        }
    }

    /// return the contained path that covers the path specified
    QString cover(QString path) const
    {
        // if we found some valid node, it's good enough. the tree covers the path
        if(m_contained)
        {
            return QString("");
        }
        auto sepIndex = path.indexOf(Tseparator);
        if(sepIndex == -1)
        {
            auto found = children.find(path);
            if(found == children.end())
            {
                return QString();
            }
            auto nested = (*found).cover(QString());
            if(nested.isNull())
            {
                return nested;
            }
            if(nested.isEmpty())
                return path;
            return path + Tseparator + nested;
        }
        else
        {
            auto prefix = path.left(sepIndex);
            auto found = children.find(prefix);
            if(found == children.end())
            {
                return QString();
            }
            auto nested = (*found).cover(path.mid(sepIndex + 1));
            if(nested.isNull())
            {
                return nested;
            }
            if(nested.isEmpty())
                return prefix;
            return prefix + Tseparator + nested;
        }
    }

    /// Does the path-specified node exist in the tree? It does not have to be contained.
    bool exists(QString path) const
    {
        auto sepIndex = path.indexOf(Tseparator);
        if(sepIndex == -1)
        {
            auto found = children.find(path);
            if(found == children.end())
            {
                return false;
            }
            return true;
        }
        else
        {
            auto prefix = path.left(sepIndex);
            auto found = children.find(prefix);
            if(found == children.end())
            {
                return false;
            }
            return (*found).exists(path.mid(sepIndex + 1));
        }
    }

    /// find a node in the tree by name
    const SeparatorPrefixTree * find(QString path) const
    {
        auto sepIndex = path.indexOf(Tseparator);
        if(sepIndex == -1)
        {
            auto found = children.find(path);
            if(found == children.end())
            {
                return nullptr;
            }
            return &(*found);
        }
        else
        {
            auto prefix = path.left(sepIndex);
            auto found = children.find(prefix);
            if(found == children.end())
            {
                return nullptr;
            }
            return (*found).find(path.mid(sepIndex + 1));
        }
    }

    /// is this a leaf node?
    bool leaf() const
    {
        return children.isEmpty();
    }

    /// is this node actually contained in the tree, or is it purely structural?
    bool contained() const
    {
        return m_contained;
    }

    /// Remove a path from the tree
    bool remove(QString path)
    {
        return removeInternal(path) != Failed;
    }

    /// Clear all children of this node tree node
    void clear()
    {
        children.clear();
    }

    QStringList toStringList() const
    {
        QStringList collected;
        // collecting these is more expensive.
        auto iter = children.begin();
        while(iter != children.end())
        {
            QStringList list = iter.value().toStringList();
            for(int i = 0; i < list.size(); i++)
            {
                list[i] = iter.key() + Tseparator + list[i];
            }
            collected.append(list);
            if((*iter).m_contained)
            {
                collected.append(iter.key());
            }
            iter++;
        }
        return collected;
    }
private:
    enum Removal
    {
        Failed,
        Succeeded,
        HasChildren
    };
    Removal removeInternal(QString path = QString())
    {
        if(path.isEmpty())
        {
            if(!m_contained)
            {
                // remove all children - we are removing a prefix
                clear();
                return Succeeded;
            }
            m_contained = false;
            if(children.size())
            {
                return HasChildren;
            }
            return Succeeded;
        }
        Removal remStatus = Failed;
        QString childToRemove;
        auto sepIndex = path.indexOf(Tseparator);
        if(sepIndex == -1)
        {
            childToRemove = path;
            auto found = children.find(childToRemove);
            if(found == children.end())
            {
                return Failed;
            }
            remStatus = (*found).removeInternal();
        }
        else
        {
            childToRemove = path.left(sepIndex);
            auto found = children.find(childToRemove);
            if(found == children.end())
            {
                return Failed;
            }
            remStatus = (*found).removeInternal(path.mid(sepIndex + 1));
        }
        switch (remStatus)
        {
            case Failed:
            case HasChildren:
            {
                return remStatus;
            }
            case Succeeded:
            {
                children.remove(childToRemove);
                if(m_contained)
                {
                    return HasChildren;
                }
                if(children.size())
                {
                    return HasChildren;
                }
                return Succeeded;
            }
        }
        return Failed;
    }

private:
    QMap<QString,SeparatorPrefixTree<Tseparator>> children;
    bool m_contained = false;
};