// Copyright (C) 2021 The Qt Company Ltd.
// Copyright (C) 2016 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#include "qipaddress_p.h"
#include "private/qlocale_tools_p.h"
#include "private/qtools_p.h"
#include "qvarlengtharray.h"

QT_BEGIN_NAMESPACE

using namespace Qt::StringLiterals;

namespace QIPAddressUtils {

static QString number(quint8 val)
{
    QString zero = QStringLiteral("0");
    return val ? qulltoa(val, 10, zero) : zero;
}

typedef QVarLengthArray<char, 64> Buffer;
static const QChar *checkedToAscii(Buffer &buffer, const QChar *begin, const QChar *end)
{
    const auto *const ubegin = reinterpret_cast<const char16_t *>(begin);
    const auto *const uend = reinterpret_cast<const char16_t *>(end);
    auto *src = ubegin;

    buffer.resize(uend - ubegin + 1);
    char *dst = buffer.data();

    while (src != uend) {
        if (*src >= 0x7f)
            return reinterpret_cast<const QChar *>(src);
        *dst++ = *src++;
    }
    *dst = '\0';
    return nullptr;
}

static bool parseIp4Internal(IPv4Address &address, const char *ptr, bool acceptLeadingZero);
bool parseIp4(IPv4Address &address, const QChar *begin, const QChar *end)
{
    Q_ASSERT(begin != end);
    Buffer buffer;
    if (checkedToAscii(buffer, begin, end))
        return false;

    const char *ptr = buffer.data();
    return parseIp4Internal(address, ptr, true);
}

static bool parseIp4Internal(IPv4Address &address, const char *ptr, bool acceptLeadingZero)
{
    address = 0;
    int dotCount = 0;
    const char *const stop = ptr + qstrlen(ptr);
    while (dotCount < 4) {
        if (!acceptLeadingZero && *ptr == '0' &&
                ptr[1] != '.' && ptr[1] != '\0')
            return false;

        auto [ll, used] = qstrntoull(ptr, stop - ptr, 0);
        const quint32 x = quint32(ll);
        if (used <= 0 || ll != x)
            return false;

        if (ptr[used] == '.' || dotCount == 3) {
            if (x & ~0xff)
                return false;
            address <<= 8;
        } else if (dotCount == 2) {
            if (x & ~0xffff)
                return false;
            address <<= 16;
        } else if (dotCount == 1) {
            if (x & ~0xffffff)
                return false;
            address <<= 24;
        }
        address |= x;

        if (dotCount == 3 || ptr[used] == '\0')
            return ptr[used] == '\0';
        if (ptr[used] != '.')
            return false;

        ++dotCount;
        ptr += used + 1;
    }
    return false;
}

void toString(QString &appendTo, IPv4Address address)
{
    // reconstructing is easy
    // use the fast operator% that pre-calculates the size
    appendTo += number(address >> 24) % u'.'
                % number(address >> 16) % u'.'
                % number(address >> 8) % u'.'
                % number(address);
}

/*!
    \internal
    \since 5.0

    Parses one IPv6 address from \a begin to \a end and stores the
    representation in \a address. Returns null if everything was parsed
    correctly, or the pointer to the first bad character where parsing failed.
    If the parsing failed for a reason not related to a particular character,
    returns \a end.
*/
const QChar *parseIp6(IPv6Address &address, const QChar *begin, const QChar *end)
{
    Q_ASSERT(begin != end);
    Buffer buffer;
    const QChar *ret = checkedToAscii(buffer, begin, end);
    if (ret)
        return ret;

    const char *ptr = buffer.data();
    const char *const stop = ptr + buffer.size();

    // count the colons
    int colonCount = 0;
    int dotCount = 0;
    while (*ptr) {
        if (*ptr == ':')
            ++colonCount;
        if (*ptr == '.')
            ++dotCount;
        ++ptr;
    }
    // IPv4-in-IPv6 addresses are stricter in what they accept
    if (dotCount != 0 && dotCount != 3)
        return end;

    memset(address, 0, sizeof address);
    if (colonCount == 2 && end - begin == 2) // "::"
        return nullptr;

    // if there's a double colon ("::"), this is how many zeroes it means
    int zeroWordsToFill;
    ptr = buffer.data();

    // there are two cases where 8 colons are allowed: at the ends
    // so test that before the colon-count test
    if ((ptr[0] == ':' && ptr[1] == ':') ||
            (ptr[end - begin - 2] == ':' && ptr[end - begin - 1] == ':')) {
        zeroWordsToFill = 9 - colonCount;
    } else if (colonCount < 2 || colonCount > 7) {
        return end;
    } else {
        zeroWordsToFill = 8 - colonCount;
    }
    if (dotCount)
        --zeroWordsToFill;

    int pos = 0;
    while (pos < 15) {
        if (*ptr == ':') {
            // empty field, we hope it's "::"
            if (zeroWordsToFill < 1)
                return begin + (ptr - buffer.data());
            if (pos == 0 || pos == colonCount * 2) {
                if (ptr[0] == '\0' || ptr[1] != ':')
                    return begin + (ptr - buffer.data());
                ++ptr;
            }
            pos += zeroWordsToFill * 2;
            zeroWordsToFill = 0;
            ++ptr;
            continue;
        }

        auto [ll, used] = qstrntoull(ptr, stop - ptr, 16);
        quint16 x = ll;

        // Reject malformed fields:
        // - failed to parse
        // - too many hex digits
        if (used <= 0 || used > 4)
            return begin + (ptr - buffer.data());

        if (ptr[used] == '.') {
            // this could be an IPv4 address
            // it's only valid in the last element
            if (pos != 12)
                return begin + (ptr - buffer.data());

            IPv4Address ip4;
            if (!parseIp4Internal(ip4, ptr, false))
                return begin + (ptr - buffer.data());

            address[12] = ip4 >> 24;
            address[13] = ip4 >> 16;
            address[14] = ip4 >> 8;
            address[15] = ip4;
            return nullptr;
        }

        address[pos++] = x >> 8;
        address[pos++] = x & 0xff;

        if (ptr[used] == '\0')
            break;
        if (ptr[used] != ':')
            return begin + (used + ptr - buffer.data());
        ptr += used + 1;
    }
    return pos == 16 ? nullptr : end;
}

static inline QChar toHex(uchar c)
{
    return QChar::fromLatin1(QtMiscUtils::toHexLower(c));
}

void toString(QString &appendTo, const IPv6Address address)
{
    // the longest IPv6 address possible is:
    //   "1111:2222:3333:4444:5555:6666:255.255.255.255"
    // however, this function never generates that. The longest it does
    // generate without an IPv4 address is:
    //   "1111:2222:3333:4444:5555:6666:7777:8888"
    // and the longest with an IPv4 address is:
    //   "::ffff:255.255.255.255"
    static const int Ip6AddressMaxLen = sizeof "1111:2222:3333:4444:5555:6666:7777:8888";
    static const int Ip6WithIp4AddressMaxLen = sizeof "::ffff:255.255.255.255";

    // check for the special cases
    const quint64 zeroes[] = { 0, 0 };
    bool embeddedIp4 = false;

    // we consider embedded IPv4 for:
    //  ::ffff:x.x.x.x
    //  ::x.x.x.y  except if the x are 0 too
    if (memcmp(address, zeroes, 10) == 0) {
        if (address[10] == 0xff && address[11] == 0xff) {
            embeddedIp4 = true;
        } else if (address[10] == 0 && address[11] == 0) {
            if (address[12] != 0 || address[13] != 0 || address[14] != 0) {
                embeddedIp4 = true;
            } else if (address[15] == 0) {
                appendTo.append("::"_L1);
                return;
            }
        }
    }

    // QString::reserve doesn't shrink, so it's fine to us
    appendTo.reserve(appendTo.size() +
                     (embeddedIp4 ? Ip6WithIp4AddressMaxLen : Ip6AddressMaxLen));

    // for finding where to place the "::"
    int zeroRunLength = 0; // in octets
    int zeroRunOffset = 0; // in octets
    for (int i = 0; i < 16; i += 2) {
        if (address[i] == 0 && address[i + 1] == 0) {
            // found a zero, scan forward to see how many more there are
            int j;
            for (j = i; j < 16; j += 2) {
                if (address[j] != 0 || address[j+1] != 0)
                    break;
            }

            if (j - i > zeroRunLength) {
                zeroRunLength = j - i;
                zeroRunOffset = i;
                i = j;
            }
        }
    }

    const QChar colon = u':';
    if (zeroRunLength < 4)
        zeroRunOffset = -1;
    else if (zeroRunOffset == 0)
        appendTo.append(colon);

    for (int i = 0; i < 16; i += 2) {
        if (i == zeroRunOffset) {
            appendTo.append(colon);
            i += zeroRunLength - 2;
            continue;
        }

        if (i == 12 && embeddedIp4) {
            IPv4Address ip4 = address[12] << 24 |
                              address[13] << 16 |
                              address[14] << 8 |
                              address[15];
            toString(appendTo, ip4);
            return;
        }

        if (address[i]) {
            if (address[i] >> 4) {
                appendTo.append(toHex(address[i] >> 4));
                appendTo.append(toHex(address[i] & 0xf));
                appendTo.append(toHex(address[i + 1] >> 4));
                appendTo.append(toHex(address[i + 1] & 0xf));
            } else if (address[i] & 0xf) {
                appendTo.append(toHex(address[i] & 0xf));
                appendTo.append(toHex(address[i + 1] >> 4));
                appendTo.append(toHex(address[i + 1] & 0xf));
            }
        } else if (address[i + 1] >> 4) {
            appendTo.append(toHex(address[i + 1] >> 4));
            appendTo.append(toHex(address[i + 1] & 0xf));
        } else {
            appendTo.append(toHex(address[i + 1] & 0xf));
        }

        if (i != 14)
            appendTo.append(colon);
    }
}

}
QT_END_NAMESPACE