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#include "simtexth.h"

#include "translator.h"

#include <QtCore/QByteArray>

#include <QtCore/QString>

#include <QtCore/QList>

QT_BEGIN_NAMESPACE

typedef QList<TranslatorMessage> TML;

/*

  How similar are two texts?  The approach used here relies on co-occurrence

  matrices and is very efficient.

  Let's see with an example: how similar are "here" and "hither"?  The

  co-occurrence matrix M for "here" is M[h,e] = 1, M[e,r] = 1, M[r,e] = 1, and 0

  elsewhere; the matrix N for "hither" is N[h,i] = 1, N[i,t] = 1, ...,

  N[h,e] = 1, N[e,r] = 1, and 0 elsewhere.  The union U of both matrices is the

  matrix U[i,j] = max { M[i,j], N[i,j] }, and the intersection V is

  V[i,j] = min { M[i,j], N[i,j] }.  The score for a pair of texts is

      score = (sum of V[i,j] over all i, j) / (sum of U[i,j] over all i, j),

  a formula suggested by Arnt Gulbrandsen.  Here we have

      score = 2 / 6,

  or one third.

  The implementation differs from this in a few details.  Most importantly,

  repetitions are ignored; for input "xxx", M[x,x] equals 1, not 2.

*/

/*

  Every character is assigned to one of 20 buckets so that the co-occurrence

  matrix requires only 20 * 20 = 400 bits, not 256 * 256 = 65536 bits or even

  more if we want the whole Unicode.  Which character falls in which bucket is

  arbitrary.

  The second half of the table is a replica of the first half, because of

  laziness.

*/

static const int indexOf[256] = {

    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,

    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,

//      !   "   #   $   %   &   '   (   )   *   +   ,   -   .   /

    0,  2,  6,  7,  10, 12, 15, 19, 2,  6,  7,  10, 12, 15, 19, 0,

//  0   1   2   3   4   5   6   7   8   9   :   ;   <   =   >   ?

    1,  3,  4,  5,  8,  9,  11, 13, 14, 16, 2,  6,  7,  10, 12, 15,

//  @   A   B   C   D   E   F   G   H   I   J   K   L   M   N   O

    0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  6,  10, 11, 12, 13, 14,

//  P   Q   R   S   T   U   V   W   X   Y   Z   [   \   ]   ^   _

    15, 12, 16, 17, 18, 19, 2,  10, 15, 7,  19, 2,  6,  7,  10, 0,

//  `   a   b   c   d   e   f   g   h   i   j   k   l   m   n   o

    0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  6,  10, 11, 12, 13, 14,

//  p   q   r   s   t   u   v   w   x   y   z   {   |   }   ~

    15, 12, 16, 17, 18, 19, 2,  10, 15, 7,  19, 2,  6,  7,  10, 0,

    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,

    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,

    0,  2,  6,  7,  10, 12, 15, 19, 2,  6,  7,  10, 12, 15, 19, 0,

    1,  3,  4,  5,  8,  9,  11, 13, 14, 16, 2,  6,  7,  10, 12, 15,

    0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  6,  10, 11, 12, 13, 14,

    15, 12, 16, 17, 18, 19, 2,  10, 15, 7,  19, 2,  6,  7,  10, 0,

    0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  6,  10, 11, 12, 13, 14,

    15, 12, 16, 17, 18, 19, 2,  10, 15, 7,  19, 2,  6,  7,  10, 0

};

/*

  The entry bitCount[i] (for i between 0 and 255) is the number of bits used to

  represent i in binary.

*/

static const int bitCount[256] = {

    0,  1,  1,  2,  1,  2,  2,  3,  1,  2,  2,  3,  2,  3,  3,  4,

    1,  2,  2,  3,  2,  3,  3,  4,  2,  3,  3,  4,  3,  4,  4,  5,

    1,  2,  2,  3,  2,  3,  3,  4,  2,  3,  3,  4,  3,  4,  4,  5,

    2,  3,  3,  4,  3,  4,  4,  5,  3,  4,  4,  5,  4,  5,  5,  6,

    1,  2,  2,  3,  2,  3,  3,  4,  2,  3,  3,  4,  3,  4,  4,  5,

    2,  3,  3,  4,  3,  4,  4,  5,  3,  4,  4,  5,  4,  5,  5,  6,

    2,  3,  3,  4,  3,  4,  4,  5,  3,  4,  4,  5,  4,  5,  5,  6,

    3,  4,  4,  5,  4,  5,  5,  6,  4,  5,  5,  6,  5,  6,  6,  7,

    1,  2,  2,  3,  2,  3,  3,  4,  2,  3,  3,  4,  3,  4,  4,  5,

    2,  3,  3,  4,  3,  4,  4,  5,  3,  4,  4,  5,  4,  5,  5,  6,

    2,  3,  3,  4,  3,  4,  4,  5,  3,  4,  4,  5,  4,  5,  5,  6,

    3,  4,  4,  5,  4,  5,  5,  6,  4,  5,  5,  6,  5,  6,  6,  7,

    2,  3,  3,  4,  3,  4,  4,  5,  3,  4,  4,  5,  4,  5,  5,  6,

    3,  4,  4,  5,  4,  5,  5,  6,  4,  5,  5,  6,  5,  6,  6,  7,

    3,  4,  4,  5,  4,  5,  5,  6,  4,  5,  5,  6,  5,  6,  6,  7,

    4,  5,  5,  6,  5,  6,  6,  7,  5,  6,  6,  7,  6,  7,  7,  8

};

struct CoMatrix

{

    /*

      The matrix has 20 * 20 = 400 entries.  This requires 50 bytes, or 13

      words.  Some operations are performed on words for more efficiency.

    */

    union {

        quint8 b[52];

        quint32 w[13];

    };

    CoMatrix() { memset( b, 0, 52 ); }

    CoMatrix(const QString &str)

    {

        QByteArray ba = str.toUtf8();

        const char *text = ba.constData();

        char c = '\0', d;

        memset( b, 0, 52 );

        /*

          The Knuth books are not in the office only for show; they help make

          loops 30% faster and 20% as readable.

        */

        while ( (d = *text) != '\0' ) {

            setCoOccurence( c, d );

            if ( (c = *++text) != '\0' ) {

                setCoOccurence( d, c );

                text++;

            }

        }

    }

    void setCoOccurence( char c, char d ) {

        int k = indexOf[(uchar) c] + 20 * indexOf[(uchar) d];

        b[k >> 3] |= (1 << (k & 0x7));

    }

    int worth() const {

        int w = 0;

        for ( int i = 0; i < 50; i++ )

            w += bitCount[b[i]];

        return w;

    }

};

static inline CoMatrix reunion(const CoMatrix &m, const CoMatrix &n)

{

    CoMatrix p;

    for (int i = 0; i < 13; ++i)

        p.w[i] = m.w[i] | n.w[i];

    return p;

}

static inline CoMatrix intersection(const CoMatrix &m, const CoMatrix &n)

{

    CoMatrix p;

    for (int i = 0; i < 13; ++i)

        p.w[i] = m.w[i] & n.w[i];

    return p;

}

StringSimilarityMatcher::StringSimilarityMatcher(const QString &stringToMatch)

{

    m_cm = new CoMatrix(stringToMatch);

    m_length = stringToMatch.length();

}

int StringSimilarityMatcher::getSimilarityScore(const QString &strCandidate)

{

    CoMatrix cmTarget(strCandidate);

    int delta = qAbs(m_length - strCandidate.size());

    int score = ( (intersection(*m_cm, cmTarget).worth() + 1) << 10 ) /

        ( reunion(*m_cm, cmTarget).worth() + (delta << 1) + 1 );

    return score;

}

StringSimilarityMatcher::~StringSimilarityMatcher()

{

    delete m_cm;

}

/**

 * Checks how similar two strings are.

 * The return value is the score, and a higher score is more similar

 * than one with a low score.

 * Linguist considers a score over 190 to be a good match.

 * \sa StringSimilarityMatcher

 */

int getSimilarityScore(const QString &str1, const QString &str2)

{

    CoMatrix cmTarget(str2);

    CoMatrix cm(str1);

    int delta = qAbs(str1.size() - str2.size());

    int score = ( (intersection(cm, cmTarget).worth() + 1) << 10 )

        / ( reunion(cm, cmTarget).worth() + (delta << 1) + 1 );

    return score;

}

CandidateList similarTextHeuristicCandidates(const Translator *tor,

    const QString &text, int maxCandidates)

{

    QList<int> scores;

    CandidateList candidates;

    TML all = tor->translatedMessages();

    foreach (const TranslatorMessage &mtm, all) {

        if (mtm.type() == TranslatorMessage::Unfinished

            || mtm.translation().isEmpty())

            continue;

        QString s = mtm.sourceText();

        int score = getSimilarityScore(s, text);

        if (candidates.size() == maxCandidates && score > scores[maxCandidates - 1] )

            candidates.removeLast();

        if (candidates.size() < maxCandidates && score >= textSimilarityThreshold) {

            Candidate cand( s, mtm.translation() );

            int i;

            for (i = 0; i < candidates.size(); i++) {

                if (score >= scores.at(i)) {

                    if (score == scores.at(i)) {

                        if (candidates.at(i) == cand)

                            goto continue_outer_loop;

                    } else {

                        break;

                    }

                }

            }

            scores.insert(i, score);

            candidates.insert(i, cand);

        }

        continue_outer_loop:

        ;

    }

    return candidates;

}

QT_END_NAMESPACE