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

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

/*

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

 *   Copyright (C) 2005-2014, International Business Machines

 *   Corporation and others.  All Rights Reserved.

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

 */

#include "unicode/utypes.h"

#if !UCONFIG_NO_CONVERSION

#include "csrutf8.h"

#include "csmatch.h"

U_NAMESPACE_BEGIN

CharsetRecog_UTF8::~CharsetRecog_UTF8()

{

    // nothing to do

}

const char *CharsetRecog_UTF8::getName() const

{

    return "UTF-8";

}

UBool CharsetRecog_UTF8::match(InputText* input, CharsetMatch *results) const {

    bool hasBOM = FALSE;

    int32_t numValid = 0;

    int32_t numInvalid = 0;

    const uint8_t *inputBytes = input->fRawInput;

    int32_t i;

    int32_t trailBytes = 0;

    int32_t confidence;

    if (input->fRawLength >= 3 && 

        inputBytes[0] == 0xEF && inputBytes[1] == 0xBB && inputBytes[2] == 0xBF) {

            hasBOM = TRUE;

    }

    // Scan for multi-byte sequences

    for (i=0; i < input->fRawLength; i += 1) {

        int32_t b = inputBytes[i];

        if ((b & 0x80) == 0) {

            continue;   // ASCII

        }

        // Hi bit on char found.  Figure out how long the sequence should be

        if ((b & 0x0E0) == 0x0C0) {

            trailBytes = 1;

        } else if ((b & 0x0F0) == 0x0E0) {

            trailBytes = 2;

        } else if ((b & 0x0F8) == 0xF0) {

            trailBytes = 3;

        } else {

            numInvalid += 1;

            continue;

        }

        // Verify that we've got the right number of trail bytes in the sequence

        for (;;) {

            i += 1;

            if (i >= input->fRawLength) {

                break;

            }

            b = inputBytes[i];

            if ((b & 0xC0) != 0x080) {

                numInvalid += 1;

                break;

            }

            if (--trailBytes == 0) {

                numValid += 1;

                break;

            }

        }

    }

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

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

    confidence = 0;

    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 == 0 && numInvalid == 0) {

        // Plain ASCII. Confidence must be > 10, it's more likely than UTF-16, which

        //              accepts ASCII with confidence = 10.

        confidence = 15;

    } else if (numValid > numInvalid*10) {

        // Probably corruput utf-8 data.  Valid sequences aren't likely by chance.

        confidence = 25;

    }

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

    return (confidence > 0);

}

U_NAMESPACE_END

#endif