/*  -*- C++ -*-

    SPDX-FileCopyrightText: 1998 Netscape Communications Corporation <developer@mozilla.org>

    SPDX-License-Identifier: MIT

*/

#include "nsLatin1Prober.h"

#include <format>

#include <numeric>

#define UDF 0 // undefined

#define OTH 1 // other

#define ASC 2 // ascii capital letter

#define ASS 3 // ascii small letter

#define ACV 4 // accent capital vowel

#define ACO 5 // accent capital other

#define ASV 6 // accent small vowel

#define ASO 7 // accent small other

#define CLASS_NUM 8 // total classes

namespace kencodingprober

{

static const unsigned char Latin1_CharToClass[] = {

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 00 - 07

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 08 - 0F

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 10 - 17

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 18 - 1F

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 20 - 27

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 28 - 2F

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 30 - 37

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 38 - 3F

    OTH, ASC, ASC, ASC, ASC, ASC, ASC, ASC, // 40 - 47

    ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC, // 48 - 4F

    ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC, // 50 - 57

    ASC, ASC, ASC, OTH, OTH, OTH, OTH, OTH, // 58 - 5F

    OTH, ASS, ASS, ASS, ASS, ASS, ASS, ASS, // 60 - 67

    ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS, // 68 - 6F

    ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS, // 70 - 77

    ASS, ASS, ASS, OTH, OTH, OTH, OTH, OTH, // 78 - 7F

    OTH, UDF, OTH, ASO, OTH, OTH, OTH, OTH, // 80 - 87

    OTH, OTH, ACO, OTH, ACO, UDF, ACO, UDF, // 88 - 8F

    UDF, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // 90 - 97

    OTH, OTH, ASO, OTH, ASO, UDF, ASO, ACO, // 98 - 9F

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // A0 - A7

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // A8 - AF

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // B0 - B7

    OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, // B8 - BF

    ACV, ACV, ACV, ACV, ACV, ACV, ACO, ACO, // C0 - C7

    ACV, ACV, ACV, ACV, ACV, ACV, ACV, ACV, // C8 - CF

    ACO, ACO, ACV, ACV, ACV, ACV, ACV, OTH, // D0 - D7

    ACV, ACV, ACV, ACV, ACV, ACO, ACO, ACO, // D8 - DF

    ASV, ASV, ASV, ASV, ASV, ASV, ASO, ASO, // E0 - E7

    ASV, ASV, ASV, ASV, ASV, ASV, ASV, ASV, // E8 - EF

    ASO, ASO, ASV, ASV, ASV, ASV, ASV, OTH, // F0 - F7

    ASV, ASV, ASV, ASV, ASV, ASO, ASO, ASO, // F8 - FF

};

/* 0 : illegal

   1 : very unlikely

   2 : normal

   3 : very likely

*/

static const unsigned char Latin1ClassModel[] = {

    /*      UDF OTH ASC ASS ACV ACO ASV ASO  */

    /*UDF*/ 0, 0, 0, 0, 0, 0, 0, 0,

    /*OTH*/ 0, 3, 3, 3, 3, 3, 3, 3,

    /*ASC*/ 0, 3, 3, 3, 3, 3, 3, 3,

    /*ASS*/ 0, 3, 3, 3, 1, 1, 3, 3,

    /*ACV*/ 0, 3, 3, 3, 1, 2, 1, 2,

    /*ACO*/ 0, 3, 3, 3, 3, 3, 3, 3,

    /*ASV*/ 0, 3, 1, 3, 1, 1, 1, 3,

    /*ASO*/ 0, 3, 1, 3, 1, 1, 3, 3,

};

nsLatin1Prober::nsLatin1Prober()

    : mLastCharClass(OTH)

{

}

nsProbingState nsLatin1Prober::HandleData(const char *aBuf, unsigned int aLen)

{

    char *newBuf1 = nullptr;

    unsigned int newLen1 = 0;

    if (!FilterWithEnglishLetters(aBuf, aLen, &newBuf1, newLen1)) {

        newBuf1 = (char *)aBuf;

        newLen1 = aLen;

    }

    for (unsigned int i = 0; i < newLen1; i++) {

        const unsigned char charClass = Latin1_CharToClass[(unsigned char)newBuf1[i]];

        const unsigned char freq = Latin1ClassModel[mLastCharClass * CLASS_NUM + charClass];

        if (freq == 0) {

            mState = eNotMe;

            break;

        }

        mFreqCounter[freq]++;

        mLastCharClass = charClass;

    }

    if (newBuf1 != aBuf) {

        free(newBuf1);

    }

    return mState;

}

float nsLatin1Prober::GetConfidence(void)

{

    if (mState == eNotMe) {

        return 0.01f;

    }

    float confidence;

    const auto total = std::accumulate(mFreqCounter.begin(), mFreqCounter.end(), 0ul);

    if (!total) {

        confidence = 0.0f;

    } else {

        confidence = mFreqCounter[3] * 1.0f / total;

        confidence -= mFreqCounter[1] * 20.0f / total;

    }

    if (confidence < 0.0f) {

        confidence = 0.0f;

    }

    // lower the confidence of latin1 so that other more accurate detector

    // can take priority.

    confidence *= 0.50f;

    return confidence;

}

std::string nsLatin1Prober::StatusOutput(uint8_t /* indent */)

{

    return std::format( //

        "{:1.3f} [{}] [{} {} {} {}]",

        GetConfidence(),

        GetCharSetName(),

        mFreqCounter[0],

        mFreqCounter[1],

        mFreqCounter[2],

        mFreqCounter[3]);

}

}