// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0

/*!
  \class QmlJS::PersistentTrie::Trie

  \brief The Trie class implements a trie that is
  persistent (not on disk but in memory).

  This means that several versions can coexist, as adding an element
  is non-destructive, and as much as possible is shared.

  The trie is only \e partially ordered. It preserves the order
  of the inserted elements as much as possible.
  This makes some operations a bit slower, but is considered
  a feature.
  This means the order in which you insert the elements matters.

  An important use case for this is completions, and several
  strategies are available.
  Results order can be improved by using the matching strength.

  All const operations are threadsafe, and copy is cheap (only a
  QSharedPointer copy).

  Assigning a shared pointer is not threadsafe, so updating the
  head is not threadsafe, and should be done only on a local
  instance (shared pointer used only from a single thread), or
  protected with locks.

  This is a two-level implementation, based on a fully functional
  implementation (PersistentTrie::Trie), which could be private
  but was left public because deemed useful.

  Would gain from some memory optimization, or direct string implementation.
 */

#include "persistenttrie.h"

#include <QDebug>
#include <QMap>
#include <QString>
#include <QStringList>

#include <algorithm>
#include <utility>

namespace QmlJS {
namespace PersistentTrie {

TrieNode::TrieNode(const QString &pre, QList<TrieNode::Ptr> post) :
    prefix(pre), postfixes(post) {}

TrieNode::TrieNode(const TrieNode &o) : prefix(o.prefix),
    postfixes(o.postfixes) {}

TrieNode::Ptr TrieNode::create(const QString &pre, QList<TrieNode::Ptr> post)
{
    return TrieNode::Ptr(new TrieNode(pre,post));
}

void TrieNode::complete(QStringList &res, const TrieNode::Ptr &trie,
    const QString &value, const QString &base, LookupFlags flags)
{
    // one could also modify this and make it return a TrieNode, instead of a QStringList
    if (trie.isNull())
        return;
    QString::const_iterator i = trie->prefix.constBegin(), iEnd = trie->prefix.constEnd();
    QString::const_iterator j = value.constBegin(), jEnd = value.constEnd();
    while (i != iEnd && j != jEnd) {
        if (i->isSpace()) {
            if (! j->isSpace() && (flags & SkipSpaces) == 0)
                return;
            while (j != jEnd && j->isSpace()) {
                ++j;
            } ;
            do {
                ++i;
            } while (i != iEnd && i->isSpace());
        } else {
            if (*i != *j && ((flags & CaseInsensitive) == 0 || i->toLower() != j->toLower())) {
                if ((flags & SkipChars) != 0)
                    --j;
                else
                    return;
            }
            ++i;
            ++j;
        }
    }
    QString base2 = base + trie->prefix;
    if (j == jEnd) {
        if (trie->postfixes.isEmpty())
            res.append(base2);
        if (trie->postfixes.size() == 1) {
            complete(res, trie->postfixes[0],QString(), base2, flags);
            return;
        }
        for (TrieNode::Ptr t : std::as_const(trie->postfixes)) {
            if ((flags & Partial) != 0)
                res.append(base2 + t->prefix);
            else
                complete(res, t, QString(), base2, flags);
        }
        return;
    }
    for (const TrieNode::Ptr &v : std::as_const(trie->postfixes)) {
        QString::const_iterator vi = v->prefix.constBegin(), vEnd = v->prefix.constEnd();
        if (vi != vEnd && (*vi == *j || ((flags & CaseInsensitive) != 0
            && vi->toLower() == j->toLower()) || ((flags & SkipChars) != 0)))
            complete(res, v, value.right(jEnd-j), base2, flags);
    }
}

TrieNode::Ptr TrieNode::insertF(const TrieNode::Ptr &trie,
    const QString &value)
{
    if (trie.isNull()) {
        if (value.isEmpty())
            return trie;
        return TrieNode::create(value);
    }
    typedef TrieNode T;
    QString::const_iterator i = trie->prefix.constBegin(), iEnd = trie->prefix.constEnd();
    QString::const_iterator j = value.constBegin(), jEnd = value.constEnd();
    while (i != iEnd && j != jEnd) {
        if (i->isSpace()) {
            if (! j->isSpace())
                break;
            do {
                ++j;
            } while (j != jEnd && j->isSpace());
            do {
                ++i;
            } while (i != iEnd && i->isSpace());
        } else {
            if (*i != *j)
                break;
            ++i;
            ++j;
        }
    }
    if (i == iEnd) {
        if (j == jEnd)
            return trie;
        int tSize = trie->postfixes.size();
        for (int i=0; i < tSize; ++i) {
            const T::Ptr &v=trie->postfixes[i];
            QString::const_iterator vi = v->prefix.constBegin(), vEnd = v->prefix.constEnd();
            if (vi != vEnd && *vi == *j) {
                T::Ptr res = insertF(v, value.right(jEnd-j));
                if (res != v) {
                    QList<T::Ptr> post = trie->postfixes;
                    post.replace(i, res);
                    return T::create(trie->prefix,post);
                } else {
                    return trie;
                }
            }
        }
        QList<T::Ptr> post = trie->postfixes;
        if (post.isEmpty())
            post.append(T::create());
        post.append(T::create(value.right(jEnd - j)));
        return T::create(trie->prefix, post);
    } else {
        T::Ptr newTrie1 = T::create(trie->prefix.right(iEnd - i), trie->postfixes);
        T::Ptr newTrie2 = T::create(value.right(jEnd - j));
        return T::create(trie->prefix.left(i - trie->prefix.constBegin()),
                            QList<T::Ptr>() << newTrie1 << newTrie2);
    }
}

bool TrieNode::contains(const TrieNode::Ptr &trie,
    const QString &value, LookupFlags flags)
{
    if (trie.isNull())
        return false;
    QString::const_iterator i = trie->prefix.constBegin(), iEnd = trie->prefix.constEnd();
    QString::const_iterator j = value.constBegin(), jEnd = value.constEnd();
    while (i != iEnd && j != jEnd) {
        if (i->isSpace()) {
            if (! j->isSpace())
                return false;
            do {
                ++j;
            } while (j != jEnd && j->isSpace());
            do {
                ++i;
            } while (i != iEnd && i->isSpace());
        } else {
            if (*i != *j && ((flags & CaseInsensitive) == 0 || i->toLower() != j->toLower()))
                return false;
            ++i;
            ++j;
        }
    }
    if (j == jEnd) {
        if ((flags & Partial) != 0)
            return true;
        if (i == iEnd) {
            for (const TrieNode::Ptr &t : std::as_const(trie->postfixes))
                if (t->prefix.isEmpty())
                    return true;
            return trie->postfixes.isEmpty();
        }
        return false;
    }
    if (i != iEnd)
        return false;
    bool res = false;
    for (const TrieNode::Ptr &v : std::as_const(trie->postfixes)) {
        QString::const_iterator vi = v->prefix.constBegin(), vEnd = v->prefix.constEnd();
        if (vi != vEnd && (*vi == *j || ((flags & CaseInsensitive) != 0
            && vi->toLower() == j->toLower())))
            res = res || contains(v, value.right(jEnd-j), flags);
    }
    return res;
}

namespace {
class Appender {
public:
    Appender() {}
    QStringList res;
    void operator()(const QString &s) {
        res.append(s);
    }
};
}

QStringList TrieNode::stringList(const TrieNode::Ptr &trie)
{
    Appender a;
    enumerateTrieNode<Appender>(trie, a, QString());
    return a.res;
}

bool TrieNode::isSame(const TrieNode::Ptr &trie1, const TrieNode::Ptr &trie2)
{
    if (trie1.data() == trie2.data())
        return true;
    if (trie1.isNull() || trie2.isNull())
        return false; // assume never to generate non null empty tries
    if (trie1->prefix != trie2->prefix)
        return false; // assume no excess splitting
    QList<TrieNode::Ptr> t1 = trie1->postfixes, t2 =trie2->postfixes;
    int nEl = t1.size();
    if (nEl != t2.size()) return false;
    // different order = different trie
    for (int i = 0; i < nEl; ++i) {
        if (!isSame(t1.value(i), t2.value(i)))
            return false;
    }
    return true;
}

namespace {
class ReplaceInTrie
{
public:
    TrieNode::Ptr trie;
    QHash<QString, QString> replacements;
    ReplaceInTrie() { }
    void operator()(QString s)
    {
        QString res = s;
        for (auto i = replacements.cbegin(), end = replacements.cend(); i != end; ++i)
            res.replace(i.key(), i.value());
        trie = TrieNode::insertF(trie,res);
    }
};
}

TrieNode::Ptr TrieNode::replaceF(const TrieNode::Ptr &trie, const QHash<QString, QString> &replacements)
{
    // inefficient...
    ReplaceInTrie rep;
    rep.replacements = replacements;
    enumerateTrieNode<ReplaceInTrie>(trie, rep, QString());
    return rep.trie;
}

std::pair<TrieNode::Ptr,int> TrieNode::intersectF(
    const TrieNode::Ptr &v1, const TrieNode::Ptr &v2, int index1)
{
    typedef TrieNode::Ptr P;
    typedef QMap<QString,int>::const_iterator MapIterator;
    if (v1.isNull() || v2.isNull())
        return std::make_pair(P(nullptr), ((v1.isNull()) ? 1 : 0) | ((v2.isNull()) ? 2 : 0));
    QString::const_iterator i = v1->prefix.constBegin()+index1, iEnd = v1->prefix.constEnd();
    QString::const_iterator j = v2->prefix.constBegin(), jEnd = v2->prefix.constEnd();
    while (i != iEnd && j != jEnd) {
        if (i->isSpace()) {
            if (! j->isSpace())
                break;
            do {
                ++j;
            } while (j != jEnd && j->isSpace());
            do {
                ++i;
            } while (i != iEnd && i->isSpace());
        } else {
            if (*i != *j)
                break;
            ++i;
            ++j;
        }
    }
    if (i == iEnd) {
        if (j == jEnd) {
            if (v1->postfixes.isEmpty() || v2->postfixes.isEmpty()) {
                if (v1->postfixes.isEmpty() && v2->postfixes.isEmpty())
                    return std::make_pair(v1, 3);
                for (P t1 : std::as_const(v1->postfixes))
                    if (t1->prefix.isEmpty()) {
                        if (index1 == 0)
                            return std::make_pair(v2, 2);
                        else
                            return std::make_pair(TrieNode::create(
                                v1->prefix.left(index1).append(v2->prefix), v2->postfixes),0);
                    }
                for (P t2 : std::as_const(v2->postfixes))
                    if (t2->prefix.isEmpty())
                        return std::make_pair(v1,1);
                return std::make_pair(P(nullptr), 0);
            }
            QMap<QString,int> p1, p2;
            QList<P> p3;
            int ii = 0;
            for (P t1 : std::as_const(v1->postfixes))
                p1[t1->prefix] = ii++;
            ii = 0;
            for (P t2 : std::as_const(v2->postfixes))
                p2[t2->prefix] = ii++;
            MapIterator p1Ptr = p1.constBegin(), p2Ptr = p2.constBegin(),
                p1End = p1.constEnd(), p2End = p2.constEnd();
            int sameV1V2 = 3;
            while (p1Ptr != p1End && p2Ptr != p2End) {
                if (p1Ptr.key().isEmpty()) {
                    if (p2Ptr.key().isEmpty()) {
                        if (sameV1V2 == 0)
                            p3.append(v1->postfixes.at(p1Ptr.value()));
                        ++p1Ptr;
                        ++p2Ptr;
                    } else {
                        if (sameV1V2 == 1)
                            for (MapIterator p1I = p1.constBegin();p1I != p1Ptr; ++p1I)
                                p3.append(v1->postfixes.at(p1I.value()));
                        ++p1Ptr;
                        sameV1V2 &= 2;
                    }
                } else if (p2Ptr.key().isEmpty()) {
                    if (sameV1V2 == 2)
                        for (MapIterator p2I = p2.constBegin(); p2I != p2Ptr; ++p2I)
                                p3.append(v2->postfixes.at(p2I.value()));
                    ++p2Ptr;
                    sameV1V2 &= 1;
                } else {
                    QChar c1 = p1Ptr.key().at(0);
                    QChar c2 = p2Ptr.key().at(0);
                    if (c1 < c2) {
                        if (sameV1V2 == 1)
                            for (MapIterator p1I = p1.constBegin(); p1I != p1Ptr; ++p1I)
                                p3.append(v1->postfixes.at(p1I.value()));
                        ++p1Ptr;
                        sameV1V2 &= 2;
                    } else if (c1 > c2) {
                        if (sameV1V2 == 2)
                            for (MapIterator  p2I = p2.constBegin(); p2I != p2Ptr; ++p2I)
                                    p3.append(v2->postfixes.at(p2I. value()));
                        ++p2Ptr;
                        sameV1V2 &= 1;
                    } else {
                        std::pair<P,int> res = intersectF(v1->postfixes.at(p1Ptr.value()),
                            v2->postfixes.at(p2Ptr.value()));
                        if (sameV1V2 !=0 && (sameV1V2 & res.second) == 0) {
                            if ((sameV1V2 & 1) == 1)
                                for (MapIterator p1I = p1.constBegin(); p1I != p1Ptr; ++p1I)
                                    p3.append(v1->postfixes.at(p1I.value()));
                            if (sameV1V2 == 2)
                                for (MapIterator p2I = p2.constBegin(); p2I != p2Ptr; ++p2I)
                                    p3.append(v2->postfixes.at(p2I.value()));
                        }
                        sameV1V2 &= res.second;
                        if (sameV1V2 == 0 && !res.first.isNull())
                            p3.append(res.first);
                        ++p1Ptr;
                        ++p2Ptr;
                    }
                }
            }
            if (p1Ptr != p1End) {
                if (sameV1V2 == 1)
                    for (MapIterator p1I = p1.constBegin(); p1I != p1Ptr; ++p1I)
                        p3.append(v1->postfixes.at(p1I.value()));
                sameV1V2 &= 2;
            } else if (p2Ptr != p2End) {
                if (sameV1V2 == 2) {
                    for (MapIterator  p2I = p2.constBegin(); p2I != p2Ptr; ++p2I)
                        p3.append(v2->postfixes.at(p2I. value()));
                }
                sameV1V2 &= 1;
            }
            switch (sameV1V2) {
            case 0:
                if (p3.isEmpty())
                   return std::make_pair(P(nullptr),0);
                else
                    return std::make_pair(TrieNode::create(v1->prefix,p3),0);
            case 2:
                if (index1 == 0)
                    return std::make_pair(v2,2);
                else
                    return std::make_pair(TrieNode::create(
                            v1->prefix.left(index1).append(v2->prefix), v2->postfixes), 0);
            default:
                return std::make_pair(v1,sameV1V2);
            }
        }
       // i == iEnd && j != jEnd
        for (const P &t1 : std::as_const(v1->postfixes))
            if ((!t1->prefix.isEmpty()) && t1->prefix.at(0) == *j) {
                std::pair<P,int> res = intersectF(v2,t1,j-v2->prefix.constBegin());
                if (index1 == 0)
                    return std::make_pair(res.first, (((res.second & 1)==1) ? 2 : 0));
                else
                    return std::make_pair(TrieNode::create(
                        v1->prefix.left(index1).append(res.first->prefix),
                        res.first->postfixes), 0);
            }
        return std::make_pair(P(nullptr), 0);
    } else {
        // i != iEnd && j == jEnd
        for (P t2 : std::as_const(v2->postfixes))
            if (!t2->prefix.isEmpty() && t2->prefix.at(0) == *i) {
                std::pair<P,int> res = intersectF(v1,t2,i-v1->prefix.constBegin());
                return std::make_pair(res.first, (res.second & 1));
            }
        return std::make_pair(P(nullptr), 0);
    }
}

namespace {
class InplaceTrie{
public:
    TrieNode::Ptr trie;

    void operator()(QString s){
        trie = TrieNode::insertF(trie,s);
    }
};
}

std::pair<TrieNode::Ptr,int> TrieNode::mergeF(
    const TrieNode::Ptr &v1, const TrieNode::Ptr &v2)
{
    //could be much more efficient if implemented directly on the trie like intersectF
    InplaceTrie t;
    t.trie = v1;
    enumerateTrieNode<InplaceTrie>(v2, t, QString());
    return std::make_pair(t.trie, ((t.trie == v1) ? 1 : 0));
}

QDebug &TrieNode::printStrings(QDebug &dbg, const TrieNode::Ptr &trie)
{
    if (trie.isNull())
        return dbg << "Trie{*NULL*}";
    dbg<<"Trie{ contents:[";
    bool first = true;
    const QStringList list = stringList(trie);
    for (const QString &s : list) {
        if (!first)
            dbg << ",";
        else
            first = false;
        dbg << s;
    }
    dbg << "]}";
    return dbg;
}

QDebug &TrieNode::describe(QDebug &dbg, const TrieNode::Ptr &trie,
    int indent = 0)
{
    dbg.space();
    dbg.nospace();
    if (trie.isNull()) {
        dbg << "NULL";
        return dbg;
    }
    dbg << trie->prefix;
    int newIndent = indent + trie->prefix.size() + 3;
    bool newLine = false;
    for (TrieNode::Ptr sub : std::as_const(trie->postfixes)) {
        if (newLine) {
            dbg << "\n";
            for (int i=0; i < newIndent; ++i)
                dbg << " ";
        } else {
            newLine = true;
        }
        describe(dbg, sub, newIndent);
    }
    return dbg;
}

QDebug operator<<(QDebug dbg, const TrieNode::Ptr &trie)
{
    dbg.nospace()<<"Trie{\n";
    TrieNode::describe(dbg,trie,0);
    dbg << "}";
    return dbg.space();
}
QDebug operator<<(QDebug dbg, const Trie &trie)
{
    dbg.nospace()<<"Trie{\n";
    TrieNode::describe(dbg,trie.trie,0);
    dbg << "}";
    return dbg.space();
}
Trie::Trie() {}
Trie::Trie(const TrieNode::Ptr &trie) : trie(trie) {}

QStringList Trie::complete(const QString &root, const QString &base,
    LookupFlags flags) const
{
    QStringList res;
    TrieNode::complete(res, trie, root, base, flags);
    return res;
}

bool Trie::contains(const QString &value, LookupFlags flags) const
{
    return TrieNode::contains(trie, value, flags);
}

QStringList Trie::stringList() const
{
    return TrieNode::stringList(trie);
}

/*!
    Inserts into the current trie.

    Non threadsafe. Only use this function on an instance that is used only
    in a single thread, or that is protected by locks.
 */
void Trie::insert(const QString &value)
{
    trie = TrieNode::insertF(trie, value);
}

/*!
    Intersects into the current trie.

    Non threadsafe. Only use this function on an instance that is used only
    in a single thread, or that is protected by locks.
 */
void Trie::intersect(const Trie &v)
{
    trie = TrieNode::intersectF(trie, v.trie).first;
}

/*!
    Merges the given trie into the current one.

    Non threadsafe. Only use this function on an instance that is used only
    in a single thread, or that is protected by locks.
 */
void Trie::merge(const Trie &v)
{
    trie = TrieNode::mergeF(trie, v.trie).first;
}

void Trie::replace(const QHash<QString, QString> &replacements)
{
    trie = TrieNode::replaceF(trie, replacements);
}

bool Trie::isEmpty() const
{
    return trie.isNull(); // assuming to never generate an empty non null trie
}

bool Trie::operator==(const Trie &o) const
{
    return TrieNode::isSame(trie,o.trie);
}

bool Trie::operator!=(const Trie &o) const
{
    return !TrieNode::isSame(trie,o.trie);
}

Trie Trie::insertF(const QString &value) const
{
    return Trie(TrieNode::insertF(trie, value));
}

Trie Trie::intersectF(const Trie &v) const
{
    return Trie(TrieNode::intersectF(trie, v.trie).first);
}

Trie Trie::mergeF(const Trie &v) const
{
    return Trie(TrieNode::mergeF(trie, v.trie).first);
}

Trie Trie::replaceF(const QHash<QString, QString> &replacements) const
{
    return Trie(TrieNode::replaceF(trie, replacements));
}

/*!

  Returns a number defining how well \a searchStr matches \a str.

  Quite simplistic, looks only at the first match, and prefers contiguous
  matches, or matches to capitalized or separated words.
  Match to the last character is also preferred.
*/
int matchStrength(const QString &searchStr, const QString &str)
{
    QString::const_iterator i = searchStr.constBegin(), iEnd = searchStr.constEnd(),
        j = str.constBegin(), jEnd = str.constEnd();
    bool lastWasNotUpper=true, lastWasSpacer=true, lastWasMatch = false, didJump = false;
    int res = 0;
    while (i != iEnd && j != jEnd) {
        bool thisIsUpper = (*j).isUpper();
        bool thisIsLetterOrNumber = (*j).isLetterOrNumber();
        if ((*i).toLower() == (*j).toLower()) {
            if (lastWasMatch || (lastWasNotUpper && thisIsUpper)
                || (thisIsUpper && (*i).isUpper())
                || (lastWasSpacer && thisIsLetterOrNumber))
                ++res;
            lastWasMatch = true;
            ++i;
        } else {
            didJump = true;
            lastWasMatch = false;
        }
        ++j;
        lastWasNotUpper = !thisIsUpper;
        lastWasSpacer = !thisIsLetterOrNumber;
    }
    if (i != iEnd)
        return i - iEnd;
    if (j == jEnd)
        ++res;
    if (!didJump)
        res+=2;
    return res;
}

namespace {
class CompareMatchStrength{
    QString searchStr;
public:
    CompareMatchStrength(const QString& searchStr) : searchStr(searchStr) { }
    bool operator()(const QString &v1, const QString &v2) {
        return matchStrength(searchStr,v1) > matchStrength(searchStr,v2);
    }
};
}

/*!
    Returns a number defining the matching strength of \a res to \a searchStr.
*/
QStringList matchStrengthSort(const QString &searchStr, QStringList &res)
{
    CompareMatchStrength compare(searchStr);
    std::stable_sort(res.begin(), res.end(), compare);
    return res;
}

} // end namespace PersistentTrie
} // end namespace QmlJS
