/* This file is part of KDevelop
   Copyright 2014 Sven Brauch <svenbrauch@gmail.com>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this library; see the file COPYING.LIB.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
 */

#include "abbreviations.h"

#include <QStringList>
#include <util/path.h>

namespace KDevelop {
// Taken and adapted for kdevelop from katecompletionmodel.cpp
static bool matchesAbbreviationHelper(const QStringRef& word, const QString& typed,
                                      const QVarLengthArray<int, 32>& offsets,
                                      int& depth, int atWord = -1, int i = 0)
{
    int atLetter = 1;
    for (; i < typed.size(); i++) {
        const QChar c = typed.at(i).toLower();
        bool haveNextWord = offsets.size() > atWord + 1;
        bool canCompare = atWord != -1 && word.size() > offsets.at(atWord) + atLetter;
        if (canCompare && c == word.at(offsets.at(atWord) + atLetter).toLower()) {
            // the typed letter matches a letter after the current word beginning
            if (!haveNextWord || c != word.at(offsets.at(atWord + 1)).toLower()) {
                // good, simple case, no conflict
                atLetter += 1;
                continue;
            }
            // For maliciously crafted data, the code used here theoretically can have very high
            // complexity. Thus ensure we don't run into this case, by limiting the amount of branches
            // we walk through to 128.
            depth++;
            if (depth > 128) {
                return false;
            }
            // the letter matches both the next word beginning and the next character in the word
            if (haveNextWord && matchesAbbreviationHelper(word, typed, offsets, depth, atWord + 1, i + 1)) {
                // resolving the conflict by taking the next word's first character worked, fine
                return true;
            }
            // otherwise, continue by taking the next letter in the current word.
            atLetter += 1;
            continue;
        } else if (haveNextWord && c == word.at(offsets.at(atWord + 1)).toLower()) {
            // the typed letter matches the next word beginning
            atWord++;
            atLetter = 1;
            continue;
        }
        // no match
        return false;
    }

    // all characters of the typed word were matched
    return true;
}

bool matchesAbbreviation(const QStringRef& word, const QString& typed)
{
    // A mismatch is very likely for random even for the first letter,
    // thus this optimization makes sense.
    if (word.at(0).toLower() != typed.at(0).toLower()) {
        return false;
    }

    // First, check if all letters are contained in the word in the right order.
    int atLetter = 0;
    for (const QChar c : typed) {
        while (c.toLower() != word.at(atLetter).toLower()) {
            atLetter += 1;
            if (atLetter >= word.size()) {
                return false;
            }
        }
    }

    bool haveUnderscore = true;
    QVarLengthArray<int, 32> offsets;
    // We want to make "KComplM" match "KateCompletionModel"; this means we need
    // to allow parts of the typed text to be not part of the actual abbreviation,
    // which consists only of the uppercased / underscored letters (so "KCM" in this case).
    // However it might be ambiguous whether a letter is part of such a word or part of
    // the following abbreviation, so we need to find all possible word offsets first,
    // then compare.
    for (int i = 0; i < word.size(); i++) {
        const QChar c = word.at(i);
        if (c == QLatin1Char('_') || c == QLatin1Char('-')) {
            haveUnderscore = true;
        } else if (haveUnderscore || c.isUpper()) {
            offsets.append(i);
            haveUnderscore = false;
        }
    }

    int depth = 0;
    return matchesAbbreviationHelper(word, typed, offsets, depth);
}

bool matchesPath(const QString& path, const QString& typed)
{
    int consumed = 0;
    int pos = 0;
    // try to find all the characters in typed in the right order in the path;
    // jumps are allowed everywhere
    while (consumed < typed.size() && pos < path.size()) {
        if (typed.at(consumed).toLower() == path.at(pos).toLower()) {
            consumed++;
        }
        pos++;
    }
    return consumed == typed.size();
}

bool matchesAbbreviationMulti(const QString& word, const QStringList& typedFragments)
{
    if (word.size() == 0) {
        return true;
    }
    int lastSpace = 0;
    int matchedFragments = 0;
    for (int i = 0; i < word.size(); i++) {
        const QChar& c = word.at(i);
        bool isDoubleColon = false;
        // if it's not a separation char, walk over it.
        if (c != QLatin1Char(' ') && c != QLatin1Char('/') && i != word.size() - 1) {
            if (c != QLatin1Char(':') && i < word.size() - 1 && word.at(i + 1) != QLatin1Char(':')) {
                continue;
            }
            isDoubleColon = true;
            i++;
        }
        // if it's '/', ' ' or '::', split the word here and check the next sub-word.
        const QStringRef wordFragment = word.midRef(lastSpace, i - lastSpace);
        const QString& typedFragment = typedFragments.at(matchedFragments);
        Q_ASSERT(!typedFragment.isEmpty());
        if (!wordFragment.isEmpty() && matchesAbbreviation(wordFragment, typedFragment)) {
            matchedFragments += 1;
            if (matchedFragments == typedFragments.size()) {
                break;
            }
        }
        lastSpace = isDoubleColon ? i : i + 1;
    }

    return matchedFragments == typedFragments.size();
}

int matchPathFilter(const Path& toFilter, const QStringList& text, const Path& prefixPath)
{
    enum PathFilterMatchQuality {
        NoMatch = -1,
        ExactMatch = 0,
        StartMatch = 1,
        OtherMatch = 2 // and anything higher than that
    };
    const QVector<QString>& segments = toFilter.segments();

    if (text.count() > segments.count()) {
        // number of segments mismatches, thus item cannot match
        return NoMatch;
    }

    bool allMatched = true;
    int searchIndex = text.size() - 1;
    int pathIndex = segments.size() - 1;
    int lastMatchIndex = -1;
    // stop early if more search fragments remain than available after path index
    while (pathIndex >= 0 && searchIndex >= 0
           && (pathIndex + text.size() - searchIndex - 1) < segments.size()) {
        const QString& segment = segments.at(pathIndex);
        const QString& typedSegment = text.at(searchIndex);
        const int matchIndex = segment.indexOf(typedSegment, 0, Qt::CaseInsensitive);
        const bool isLastPathSegment = pathIndex == segments.size() - 1;
        const bool isLastSearchSegment = searchIndex == text.size() - 1;

        // check for exact matches
        allMatched &= matchIndex == 0 && segment.size() == typedSegment.size();

        // check for fuzzy matches
        bool isMatch = matchIndex != -1;
        // do fuzzy path matching on the last segment
        if (!isMatch && isLastPathSegment && isLastSearchSegment) {
            isMatch = matchesPath(segment, typedSegment);
        } else if (!isMatch) { // check other segments for abbreviations
            isMatch = matchesAbbreviation(segment.midRef(0), typedSegment);
        }

        if (!isMatch) {
            // no match, try with next path segment
            --pathIndex;
            continue;
        }
        // else we matched
        if (isLastPathSegment) {
            lastMatchIndex = matchIndex;
        }
        --searchIndex;
        --pathIndex;
    }

    if (searchIndex != -1) {
        return NoMatch;
    }

    const int segmentMatchDistance = segments.size() - (pathIndex + 1);
    const bool inPrefixPath = segmentMatchDistance > (segments.size() - prefixPath.segments().size())
                              && prefixPath.isParentOf(toFilter);
    // penalize matches that fall into the shared suffix
    const int penalty = (inPrefixPath) ? 1024 : 0;

    if (allMatched && !inPrefixPath) {
        return ExactMatch + penalty;
    } else if (lastMatchIndex == 0) {
        // prefer matches whose last element starts with the filter
        return StartMatch + penalty;
    } else {
        // prefer matches closer to the end of the path
        return OtherMatch + segmentMatchDistance + penalty;
    }
}
} // namespace KDevelop
