// © 2016 and later: Unicode, Inc. and others.

// License & terms of use: http://www.unicode.org/copyright.html

/*

 **********************************************************************

 *   Copyright (C) 2005-2013, International Business Machines

 *   Corporation and others.  All Rights Reserved.

 **********************************************************************

 */

#include "unicode/utypes.h"

#if !UCONFIG_NO_CONVERSION

#include "csrucode.h"

#include "csmatch.h"

U_NAMESPACE_BEGIN

CharsetRecog_Unicode::~CharsetRecog_Unicode()

{

    // nothing to do

}

CharsetRecog_UTF_16_BE::~CharsetRecog_UTF_16_BE()

{

    // nothing to do

}

const char *CharsetRecog_UTF_16_BE::getName() const

{

    return "UTF-16BE";

}

// UTF-16 confidence calculation. Very simple minded, but better than nothing.

//   Any 8 bit non-control characters bump the confidence up. These have a zero high byte,

//     and are very likely to be UTF-16, although they could also be part of a UTF-32 code.

//   NULs are a contra-indication, they will appear commonly if the actual encoding is UTF-32.

//   NULs should be rare in actual text. 

static int32_t adjustConfidence(char16_t codeUnit, int32_t confidence) {

    if (codeUnit == 0) {

        confidence -= 10;

    } else if ((codeUnit >= 0x20 && codeUnit <= 0xff) || codeUnit == 0x0a) {

        confidence += 10;

    }

    if (confidence < 0) {

        confidence = 0;

    } else if (confidence > 100) {

        confidence = 100;

    }

    return confidence;

}

UBool CharsetRecog_UTF_16_BE::match(InputText* textIn, CharsetMatch *results) const

{

    const uint8_t *input = textIn->fRawInput;

    int32_t confidence = 10;

    int32_t length = textIn->fRawLength;

    int32_t bytesToCheck = (length > 30) ? 30 : length;

    for (int32_t charIndex=0; charIndex<bytesToCheck-1; charIndex+=2) {

        char16_t codeUnit = (input[charIndex] << 8) | input[charIndex + 1];

        if (charIndex == 0 && codeUnit == 0xFEFF) {

            confidence = 100;

            break;

        }

        confidence = adjustConfidence(codeUnit, confidence);

        if (confidence == 0 || confidence == 100) {

            break;

        }

    }

    if (bytesToCheck < 4 && confidence < 100) {

        confidence = 0;

    }

    results->set(textIn, this, confidence);

    return (confidence > 0);

}

CharsetRecog_UTF_16_LE::~CharsetRecog_UTF_16_LE()

{

    // nothing to do

}

const char *CharsetRecog_UTF_16_LE::getName() const

{

    return "UTF-16LE";

}

UBool CharsetRecog_UTF_16_LE::match(InputText* textIn, CharsetMatch *results) const

{

    const uint8_t *input = textIn->fRawInput;

    int32_t confidence = 10;

    int32_t length = textIn->fRawLength;

    int32_t bytesToCheck = (length > 30) ? 30 : length;

    for (int32_t charIndex=0; charIndex<bytesToCheck-1; charIndex+=2) {

        char16_t codeUnit = input[charIndex] | (input[charIndex + 1] << 8);

        if (charIndex == 0 && codeUnit == 0xFEFF) {

            confidence = 100;     // UTF-16 BOM

            if (length >= 4 && input[2] == 0 && input[3] == 0) {

                confidence = 0;   // UTF-32 BOM

            }

            break;

        }

        confidence = adjustConfidence(codeUnit, confidence);

        if (confidence == 0 || confidence == 100) {

            break;

        }

    }

    if (bytesToCheck < 4 && confidence < 100) {

        confidence = 0;

    }

    results->set(textIn, this, confidence);

    return (confidence > 0);

}

CharsetRecog_UTF_32::~CharsetRecog_UTF_32()

{

    // nothing to do

}

UBool CharsetRecog_UTF_32::match(InputText* textIn, CharsetMatch *results) const

{

    const uint8_t *input = textIn->fRawInput;

    int32_t limit = (textIn->fRawLength / 4) * 4;

    int32_t numValid = 0;

    int32_t numInvalid = 0;

    bool hasBOM = false;

    int32_t confidence = 0;

    if (limit > 0 && getChar(input, 0) == 0x0000FEFFUL) {

        hasBOM = true;

    }

    for(int32_t i = 0; i < limit; i += 4) {

        int32_t ch = getChar(input, i);

        if (ch < 0 || ch >= 0x10FFFF || (ch >= 0xD800 && ch <= 0xDFFF)) {

            numInvalid += 1;

        } else {

            numValid += 1;

        }

    }

    // Cook up some sort of confidence score, based on presence of a BOM

    //    and the existence of valid and/or invalid multi-byte sequences.

    if (hasBOM && numInvalid==0) {

        confidence = 100;

    } else if (hasBOM && numValid > numInvalid*10) {

        confidence = 80;

    } else if (numValid > 3 && numInvalid == 0) {

        confidence = 100;            

    } else if (numValid > 0 && numInvalid == 0) {

        confidence = 80;

    } else if (numValid > numInvalid*10) {

        // Probably corrupt UTF-32BE data.  Valid sequences aren't likely by chance.

        confidence = 25;

    }

    results->set(textIn, this, confidence);

    return (confidence > 0);

}

CharsetRecog_UTF_32_BE::~CharsetRecog_UTF_32_BE()

{

    // nothing to do

}

const char *CharsetRecog_UTF_32_BE::getName() const

{

    return "UTF-32BE";

}

int32_t CharsetRecog_UTF_32_BE::getChar(const uint8_t *input, int32_t index) const

{

    return input[index + 0] << 24 | input[index + 1] << 16 |

           input[index + 2] <<  8 | input[index + 3];

} 

CharsetRecog_UTF_32_LE::~CharsetRecog_UTF_32_LE()

{

    // nothing to do

}

const char *CharsetRecog_UTF_32_LE::getName() const

{

    return "UTF-32LE";

}

int32_t CharsetRecog_UTF_32_LE::getChar(const uint8_t *input, int32_t index) const

{

    return input[index + 3] << 24 | input[index + 2] << 16 |

           input[index + 1] <<  8 | input[index + 0];

}

U_NAMESPACE_END

#endif