// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qisciicodec_p.h"
#include "qtextcodec_p.h"
#include "qlist.h"

QT_BEGIN_NAMESPACE

/*!
    \class QIsciiCodec
    \inmodule QtCore5Compat
    \brief The QIsciiCodec class provides conversion to and from the ISCII encoding.

    \internal
*/


struct Codecs {
    const char name[10];
    ushort base;
};

static const Codecs codecs [] = {
    { "iscii-dev", 0x900 },
    { "iscii-bng", 0x980 },
    { "iscii-pnj", 0xa00 },
    { "iscii-gjr", 0xa80 },
    { "iscii-ori", 0xb00 },
    { "iscii-tml", 0xb80 },
    { "iscii-tlg", 0xc00 },
    { "iscii-knd", 0xc80 },
    { "iscii-mlm", 0xd00 }
};

QTextCodec *QIsciiCodec::create(const char *name)
{
    QIsciiCodec *codec = nullptr;
    for (int i = 0; i < 9; ++i) {
        if (qTextCodecNameMatch(name, codecs[i].name)) {
            codec = new QIsciiCodec(i);
            break;
        }
    }
    return codec;
}

QIsciiCodec::~QIsciiCodec()
{
}

QByteArray QIsciiCodec::name() const
{
  return codecs[idx].name;
}

int QIsciiCodec::mibEnum() const
{
    /* There is no MIBEnum for Iscii */
    return -3000-idx;
}

static const uchar inv = 0xFF;

/* iscii range from 0xa0 - 0xff */
static const uchar iscii_to_uni_table[0x60] = {
    0x00, 0x01, 0x02, 0x03,
    0x05, 0x06, 0x07, 0x08,
    0x09, 0x0a, 0x0b, 0x0e,
    0x0f, 0x20, 0x0d, 0x12,

    0x13, 0x14, 0x11, 0x15,
    0x16, 0x17, 0x18, 0x19,
    0x1a, 0x1b, 0x1c, 0x1d,
    0x1e, 0x1f, 0x20, 0x21,

    0x22, 0x23, 0x24, 0x25,
    0x26, 0x27, 0x28, 0x29,
    0x2a, 0x2b, 0x2c, 0x2d,
    0x2e, 0x2f, 0x5f, 0x30,

    0x31, 0x32, 0x33, 0x34,
    0x35, 0x36, 0x37, 0x38,
    0x39,  inv, 0x3e, 0x3f,
    0x40, 0x41, 0x42, 0x43,

    0x46, 0x47, 0x48, 0x45,
    0x4a, 0x4b, 0x4c, 0x49,
    0x4d, 0x3c, 0x64, 0x00,
    0x00, 0x00, 0x00, 0x00,

    0x00, 0x66, 0x67, 0x68,
    0x69, 0x6a, 0x6b, 0x6c,
    0x6d, 0x6e, 0x6f, 0x00,
    0x00, 0x00, 0x00, 0x00
};

static const uchar uni_to_iscii_table[0x80] = {
    0x00, 0xa1, 0xa2, 0xa3,
    0x00, 0xa4, 0xa5, 0xa6,
    0xa7, 0xa8, 0xa9, 0xaa,
    0x00, 0xae, 0xab, 0xac,

    0xad, 0xb2, 0xaf, 0xb0,
    0xb1, 0xb3, 0xb4, 0xb5,
    0xb6, 0xb7, 0xb8, 0xb9,
    0xba, 0xbb, 0xbc, 0xbd,

    0xbe, 0xbf, 0xc0, 0xc1,
    0xc2, 0xc3, 0xc4, 0xc5,
    0xc6, 0xc7, 0xc8, 0xc9,
    0xca, 0xcb, 0xcc, 0xcd,

    0xcf, 0xd0, 0xd1, 0xd2,
    0xd3, 0xd4, 0xd5, 0xd6,
    0xd7, 0xd8, 0x00, 0x00,
    0xe9, 0x00, 0xda, 0xdb,

    0xdc, 0xdd, 0xde, 0xdf,
    0x00, 0xe3, 0xe0, 0xe1,
    0xe2, 0xe7, 0xe4, 0xe5,
    0xe6, 0xe8, 0x00, 0x00,

    0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
    0x01, 0x02, 0x03, 0x04, // decomposable into the uc codes listed here + nukta
    0x05, 0x06, 0x07, 0xce,

    0x00, 0x00, 0x00, 0x00,
    0xea, 0x08, 0xf1, 0xf2,
    0xf3, 0xf4, 0xf5, 0xf6,
    0xf7, 0xf8, 0xf9, 0xfa,

    0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00
};

static const uchar uni_to_iscii_pairs[] = {
    0x00, 0x00,
    0x15, 0x3c, // 0x958
    0x16, 0x3c, // 0x959
    0x17, 0x3c, // 0x95a
    0x1c, 0x3c, // 0x95b
    0x21, 0x3c, // 0x95c
    0x22, 0x3c, // 0x95d
    0x2b, 0x3c, // 0x95e
    0x64, 0x64  // 0x965
};


QByteArray QIsciiCodec::convertFromUnicode(const QChar *uc, int len, ConverterState *state) const
{
    char replacement = '?';
    bool halant = false;
    if (state) {
        if (state->flags & ConvertInvalidToNull)
            replacement = 0;
        halant = state->state_data[0];
    }
    int invalid = 0;

    QByteArray result(2 * len, QT_PREPEND_NAMESPACE(Qt::Uninitialized)); // worst case

    uchar *ch = reinterpret_cast<uchar *>(result.data());

    const int base = codecs[idx].base;

    for (int i =0; i < len; ++i) {
        const ushort codePoint = uc[i].unicode();

        /* The low 7 bits of ISCII is plain ASCII. However, we go all the
         * way up to 0xA0 such that we can roundtrip with convertToUnicode()'s
         * behavior. */
        if(codePoint < 0xA0) {
            *ch++ = static_cast<uchar>(codePoint);
            continue;
        }

        const int pos = codePoint - base;
        if (pos > 0 && pos < 0x80) {
            uchar iscii = uni_to_iscii_table[pos];
            if (iscii > 0x80) {
                *ch++ = iscii;
            } else if (iscii) {
                Q_ASSERT((2 * iscii) < (sizeof(uni_to_iscii_pairs) / sizeof(uni_to_iscii_pairs[0])));
                const uchar *pair = uni_to_iscii_pairs + 2*iscii;
                *ch++ = *pair++;
                *ch++ = *pair++;
            } else {
                *ch++ = replacement;
                ++invalid;
            }
        } else {
            if (uc[i].unicode() == 0x200c) { // ZWNJ
                if (halant)
                    // Consonant Halant ZWNJ -> Consonant Halant Halant
                    *ch++ = 0xe8;
            } else if (uc[i].unicode() == 0x200d) { // ZWJ
                if (halant)
                    // Consonant Halant ZWJ -> Consonant Halant Nukta
                    *ch++ = 0xe9;
            } else {
                *ch++ = replacement;
                ++invalid;
            }
        }
        halant = (pos == 0x4d);
    }
    result.truncate(ch - (uchar *)result.data());

    if (state) {
        state->invalidChars += invalid;
        state->state_data[0] = halant;
    }
    return result;
}

QString QIsciiCodec::convertToUnicode(const char* chars, int len, ConverterState *state) const
{
    bool halant = false;
    if (state) {
        halant = state->state_data[0];
    }

    QString result(len, QT_PREPEND_NAMESPACE(Qt::Uninitialized));
    QChar *uc = result.data();

    const int base = codecs[idx].base;

    for (int i = 0; i < len; ++i) {
        char16_t ch = (uchar) chars[i];
        if (ch < 0xa0)
            *uc++ = ch;
        else {
            ushort c = iscii_to_uni_table[ch - 0xa0];
            if (halant && (ch == inv || ch == 0xe9)) {
                // Consonant Halant inv -> Consonant Halant ZWJ
                // Consonant Halant Nukta -> Consonant Halant ZWJ
                *uc++ = QChar(0x200d);
            } else if (halant && ch == 0xe8) {
                // Consonant Halant Halant -> Consonant Halant ZWNJ
                *uc++ = QChar(0x200c);
            } else {
                *uc++ = QChar(c+base);
            }
        }
        halant = ((uchar)chars[i] == 0xe8);
    }
    result.resize(uc - result.unicode());

    if (state) {
        state->state_data[0] = halant;
    }
    return result;
}

QT_END_NAMESPACE
