#include "./tagvalue.h"
#include "./tag.h"

#include "./id3/id3genres.h"

#include <c++utilities/conversion/binaryconversion.h>
#include <c++utilities/conversion/conversionexception.h>
#include <c++utilities/conversion/stringbuilder.h>
#include <c++utilities/conversion/stringconversion.h>

#include <algorithm>
#include <cstring>
#include <utility>

using namespace std;
using namespace ConversionUtilities;
using namespace ChronoUtilities;

namespace TagParser {

/*!
 * \brief Returns the string representation of the specified \a dataType.
 */
const char *tagDataTypeString(TagDataType dataType)
{
    switch (dataType) {
    case TagDataType::Text:
        return "text";
    case TagDataType::Integer:
        return "integer";
    case TagDataType::PositionInSet:
        return "position in set";
    case TagDataType::StandardGenreIndex:
        return "genre index";
    case TagDataType::TimeSpan:
        return "time span";
    case TagDataType::DateTime:
        return "date time";
    case TagDataType::Picture:
        return "picture";
    case TagDataType::Binary:
        return "binary";
    default:
        return "undefined";
    }
}

/*!
 * \class TagParser::TagValue
 * \brief The TagValue class wraps values of different types. It is meant to be assigned to a tag field.
 *
 * For a list of supported types see TagParser::TagDataType.
 */

/*!
 * \brief Constructs a new TagValue holding a copy of the given TagValue instance.
 * \param other Specifies another TagValue instance.
 */
TagValue::TagValue(const TagValue &other)
    : m_size(other.m_size)
    , m_desc(other.m_desc)
    , m_mimeType(other.m_mimeType)
    , m_language(other.m_language)
    , m_type(other.m_type)
    , m_encoding(other.m_encoding)
    , m_descEncoding(other.m_descEncoding)
    , m_labeledAsReadonly(other.m_labeledAsReadonly)
{
    if (!other.isEmpty()) {
        m_ptr = make_unique<char[]>(m_size);
        std::copy(other.m_ptr.get(), other.m_ptr.get() + other.m_size, m_ptr.get());
    }
}

/*!
 * \brief Assigns the value of another TagValue to the current instance.
 */
TagValue &TagValue::operator=(const TagValue &other)
{
    if (this == &other) {
        return *this;
    }
    m_size = other.m_size;
    m_type = other.m_type;
    m_desc = other.m_desc;
    m_mimeType = other.m_mimeType;
    m_language = other.m_language;
    m_labeledAsReadonly = other.m_labeledAsReadonly;
    m_encoding = other.m_encoding;
    m_descEncoding = other.m_descEncoding;
    if (other.isEmpty()) {
        m_ptr.reset();
    } else {
        m_ptr = make_unique<char[]>(m_size);
        std::copy(other.m_ptr.get(), other.m_ptr.get() + other.m_size, m_ptr.get());
    }
    return *this;
}

/*!
 * \brief Returns whether both instances are equal.
 *
 * If the data types are not equal, two instances are still considered equal if the string representation
 * is identical. The encoding and meta data must be equal as well if relevant for the data type.
 *
 * \sa TagValueTests::testEqualityOperator()
 */
bool TagValue::operator==(const TagValue &other) const
{
    // check whether meta-data is equal
    if (m_desc != other.m_desc || (!m_desc.empty() && m_descEncoding != other.m_descEncoding) || m_mimeType != other.m_mimeType
        || m_language != other.m_language || m_labeledAsReadonly != other.m_labeledAsReadonly) {
        return false;
    }

    // check for equality if both types are identical
    if (m_type == other.m_type) {
        switch (m_type) {
        case TagDataType::Text:
            if (m_size != other.m_size && m_encoding != other.m_encoding) {
                // don't consider differently encoded text values equal
                return false;
            }
            return strncmp(m_ptr.get(), other.m_ptr.get(), m_size) == 0;
        case TagDataType::PositionInSet:
            return toPositionInSet() == other.toPositionInSet();
        case TagDataType::Integer:
            return toInteger() == other.toInteger();
        case TagDataType::StandardGenreIndex:
            return toStandardGenreIndex() == other.toStandardGenreIndex();
        case TagDataType::TimeSpan:
            return toTimeSpan() == other.toTimeSpan();
        case TagDataType::DateTime:
            return toDateTime() == other.toDateTime();
        case TagDataType::Picture:
        case TagDataType::Binary:
        case TagDataType::Undefined:
            if (m_size != other.m_size) {
                return false;
            }
            return strncmp(m_ptr.get(), other.m_ptr.get(), m_size) == 0;
        }
        return false;
    }

    // check for equality if types are different by comparing the string representation
    try {
        return toString() == other.toString(m_encoding);
    } catch (const ConversionException &) {
        return false;
    }
}

/*!
 * \brief Wipes assigned meta data.
 *  - Clears description, mime type and language.
 *  - Resets the read-only flag to false.
 *  - Resets the encoding to TagTextEncoding::Latin1.
 *  - Resets the data type to TagDataType::Undefined.
 */
void TagValue::clearMetadata()
{
    m_desc.clear();
    m_mimeType.clear();
    m_language.clear();
    m_labeledAsReadonly = false;
    m_encoding = TagTextEncoding::Latin1;
    m_descEncoding = TagTextEncoding::Latin1;
    m_type = TagDataType::Undefined;
}

/*!
 * \brief Converts the value of the current TagValue object to its equivalent
 *        integer representation.
 * \throws Throws ConversionException on failure.
 */
int32 TagValue::toInteger() const
{
    if (isEmpty()) {
        return 0;
    }
    switch (m_type) {
    case TagDataType::Text:
        switch (m_encoding) {
        case TagTextEncoding::Unspecified:
        case TagTextEncoding::Latin1:
        case TagTextEncoding::Utf8:
            return ConversionUtilities::bufferToNumber<int32>(m_ptr.get(), m_size);
        case TagTextEncoding::Utf16LittleEndian:
        case TagTextEncoding::Utf16BigEndian:
            u16string u16str(reinterpret_cast<char16_t *>(m_ptr.get()), m_size / 2);
            ensureHostByteOrder(u16str, m_encoding);
            return ConversionUtilities::stringToNumber<int32>(u16str);
        }
    case TagDataType::Integer:
    case TagDataType::PositionInSet:
    case TagDataType::StandardGenreIndex:
        if (m_size == sizeof(int32)) {
            return *reinterpret_cast<int32 *>(m_ptr.get());
        }
        throw ConversionException("Can not convert assigned data to integer because the data size is not appropriate.");
    default:
        throw ConversionException(argsToString("Can not convert ", tagDataTypeString(m_type), " to integer."));
    }
}

/*!
 * \brief Converts the value of the current TagValue object to its equivalent
 *        standard genre index.
 * \throws Throws ConversionException on failure.
 */
int TagValue::toStandardGenreIndex() const
{
    if (isEmpty()) {
        return Id3Genres::emptyGenreIndex();
    }
    int index = 0;
    switch (m_type) {
    case TagDataType::Text: {
        try {
            index = toInteger();
        } catch (const ConversionException &) {
            TagTextEncoding encoding = TagTextEncoding::Utf8;
            if (m_encoding == TagTextEncoding::Latin1) {
                // no need to convert Latin-1 to UTF-8 (makes no difference in case of genre strings)
                encoding = TagTextEncoding::Unspecified;
            }
            index = Id3Genres::indexFromString(toString(encoding));
        }
        break;
    }
    case TagDataType::StandardGenreIndex:
    case TagDataType::Integer:
        if (m_size != sizeof(int32)) {
            throw ConversionException("The assigned index/integer is of unappropriate size.");
        }
        index = static_cast<int>(*reinterpret_cast<int32 *>(m_ptr.get()));
        break;
    default:
        throw ConversionException(argsToString("Can not convert ", tagDataTypeString(m_type), " to genre index."));
    }
    if (!Id3Genres::isEmptyGenre(index) && !Id3Genres::isIndexSupported(index)) {
        throw ConversionException("The assigned number is not a valid standard genre index.");
    }
    return index;
}

/*!
 * \brief Converts the value of the current TagValue object to its equivalent
 *        PositionInSet representation.
 * \throws Throws ConversionException on failure.
 */
PositionInSet TagValue::toPositionInSet() const
{
    if (isEmpty()) {
        return PositionInSet();
    }
    switch (m_type) {
    case TagDataType::Text:
        switch (m_encoding) {
        case TagTextEncoding::Unspecified:
        case TagTextEncoding::Latin1:
        case TagTextEncoding::Utf8:
            return PositionInSet(string(m_ptr.get(), m_size));
        case TagTextEncoding::Utf16LittleEndian:
        case TagTextEncoding::Utf16BigEndian:
            u16string u16str(reinterpret_cast<char16_t *>(m_ptr.get()), m_size / 2);
            ensureHostByteOrder(u16str, m_encoding);
            return PositionInSet(u16str);
        }
    case TagDataType::Integer:
    case TagDataType::PositionInSet:
        switch (m_size) {
        case sizeof(int32):
            return PositionInSet(*(reinterpret_cast<int32 *>(m_ptr.get())));
        case 2 * sizeof(int32):
            return PositionInSet(*(reinterpret_cast<int32 *>(m_ptr.get())), *(reinterpret_cast<int32 *>(m_ptr.get() + sizeof(int32))));
        default:
            throw ConversionException("The size of the assigned data is not appropriate.");
        }
    default:
        throw ConversionException(argsToString("Can not convert ", tagDataTypeString(m_type), " to position in set."));
    }
}

/*!
 * \brief Converts the value of the current TagValue object to its equivalent
 *        TimeSpan representation.
 * \throws Throws ConversionException on failure.
 */
TimeSpan TagValue::toTimeSpan() const
{
    if (isEmpty()) {
        return TimeSpan();
    }
    switch (m_type) {
    case TagDataType::Text:
        return TimeSpan::fromString(toString(m_encoding == TagTextEncoding::Utf8 ? TagTextEncoding::Utf8 : TagTextEncoding::Latin1));
    case TagDataType::Integer:
    case TagDataType::TimeSpan:
        switch (m_size) {
        case sizeof(int32):
            return TimeSpan(*(reinterpret_cast<int32 *>(m_ptr.get())));
        case sizeof(int64):
            return TimeSpan(*(reinterpret_cast<int64 *>(m_ptr.get())));
        default:
            throw ConversionException("The size of the assigned integer is not appropriate for conversion to time span.");
        }
    default:
        throw ConversionException(argsToString("Can not convert ", tagDataTypeString(m_type), " to time span."));
    }
}

/*!
 * \brief Converts the value of the current TagValue object to its equivalent
 *        DateTime representation.
 * \throws Throws ConversionException on failure.
 */
DateTime TagValue::toDateTime() const
{
    if (isEmpty()) {
        return DateTime();
    }
    switch (m_type) {
    case TagDataType::Text:
        return DateTime::fromString(toString(m_encoding == TagTextEncoding::Utf8 ? TagTextEncoding::Utf8 : TagTextEncoding::Latin1));
    case TagDataType::Integer:
    case TagDataType::DateTime:
        if (m_size == sizeof(int32)) {
            return DateTime(*(reinterpret_cast<uint32 *>(m_ptr.get())));
        } else if (m_size == sizeof(int64)) {
            return DateTime(*(reinterpret_cast<uint64 *>(m_ptr.get())));
        } else {
            throw ConversionException("The size of the assigned integer is not appropriate for conversion to date time.");
        }
    default:
        throw ConversionException(argsToString("Can not convert ", tagDataTypeString(m_type), " to date time."));
    }
}

/*!
 * \brief Returns the encoding parameter (name of the character set and bytes per character) for the specified \a tagTextEncoding.
 */
pair<const char *, float> encodingParameter(TagTextEncoding tagTextEncoding)
{
    switch (tagTextEncoding) {
    case TagTextEncoding::Latin1:
        return make_pair("ISO-8859-1", 1.0f);
    case TagTextEncoding::Utf8:
        return make_pair("UTF-8", 1.0f);
    case TagTextEncoding::Utf16LittleEndian:
        return make_pair("UTF-16LE", 2.0f);
    case TagTextEncoding::Utf16BigEndian:
        return make_pair("UTF-16BE", 2.0f);
    default:
        return make_pair(nullptr, 0.0f);
    }
}

/*!
 * \brief Converts the currently assigned text value to the specified \a encoding.
 * \throws Throws ConversionUtilities::ConversionException() if the conversion fails.
 * \remarks
 * - Does nothing if dataEncoding() equals \a encoding.
 * - Sets dataEncoding() to the specified \a encoding if the conversion succeeds.
 * - Does not do any conversion if the current type() is not TagDataType::Text.
 * \sa convertDataEncodingForTag()
 */
void TagValue::convertDataEncoding(TagTextEncoding encoding)
{
    if (m_encoding == encoding) {
        return;
    }
    if (type() == TagDataType::Text) {
        StringData encodedData;
        switch (encoding) {
        case TagTextEncoding::Utf8:
            // use pre-defined methods when encoding to UTF-8
            switch (dataEncoding()) {
            case TagTextEncoding::Latin1:
                encodedData = convertLatin1ToUtf8(m_ptr.get(), m_size);
                break;
            case TagTextEncoding::Utf16LittleEndian:
                encodedData = convertUtf16LEToUtf8(m_ptr.get(), m_size);
                break;
            case TagTextEncoding::Utf16BigEndian:
                encodedData = convertUtf16BEToUtf8(m_ptr.get(), m_size);
                break;
            default:;
            }
            break;
        default: {
            // otherwise, determine input and output parameter to use general covertString method
            const auto inputParameter = encodingParameter(dataEncoding());
            const auto outputParameter = encodingParameter(encoding);
            encodedData
                = convertString(inputParameter.first, outputParameter.first, m_ptr.get(), m_size, outputParameter.second / inputParameter.second);
        }
        }
        // can't just move the encoded data because it needs to be deleted with free
        m_ptr = make_unique<char[]>(m_size = encodedData.second);
        copy(encodedData.first.get(), encodedData.first.get() + encodedData.second, m_ptr.get());
    }
    m_encoding = encoding;
}

/*!
 * \brief Ensures the encoding of the currently assigned text value is supported by the specified \a tag.
 * \sa This is a convenience method for convertDataEncoding().
 */
void TagValue::convertDataEncodingForTag(const Tag *tag)
{
    if (type() == TagDataType::Text && !tag->canEncodingBeUsed(dataEncoding())) {
        convertDataEncoding(tag->proposedTextEncoding());
    }
}

/*!
 * \brief Converts the value of the current TagValue object to its equivalent
 *        std::string representation.
 * \param result Specifies the string to store the result.
 * \param encoding Specifies the encoding to to be used; set to TagTextEncoding::Unspecified to use the
 *        present encoding without any character set conversion.
 * \remarks If UTF-16 is the desired output \a encoding, it makes sense to use the toWString() method instead.
 * \throws Throws ConversionException on failure.
 */
void TagValue::toString(string &result, TagTextEncoding encoding) const
{
    if (isEmpty()) {
        result.clear();
        return;
    }

    switch (m_type) {
    case TagDataType::Text:
        if (encoding == TagTextEncoding::Unspecified || dataEncoding() == TagTextEncoding::Unspecified || encoding == dataEncoding()) {
            result.assign(m_ptr.get(), m_size);
        } else {
            StringData encodedData;
            switch (encoding) {
            case TagTextEncoding::Utf8:
                // use pre-defined methods when encoding to UTF-8
                switch (dataEncoding()) {
                case TagTextEncoding::Latin1:
                    encodedData = convertLatin1ToUtf8(m_ptr.get(), m_size);
                    break;
                case TagTextEncoding::Utf16LittleEndian:
                    encodedData = convertUtf16LEToUtf8(m_ptr.get(), m_size);
                    break;
                case TagTextEncoding::Utf16BigEndian:
                    encodedData = convertUtf16BEToUtf8(m_ptr.get(), m_size);
                    break;
                default:;
                }
                break;
            default: {
                // otherwise, determine input and output parameter to use general covertString method
                const auto inputParameter = encodingParameter(dataEncoding());
                const auto outputParameter = encodingParameter(encoding);
                encodedData
                    = convertString(inputParameter.first, outputParameter.first, m_ptr.get(), m_size, outputParameter.second / inputParameter.second);
            }
            }
            result.assign(encodedData.first.get(), encodedData.second);
        }
        return;
    case TagDataType::Integer:
        result = ConversionUtilities::numberToString(toInteger());
        break;
    case TagDataType::PositionInSet:
        result = toPositionInSet().toString();
        break;
    case TagDataType::StandardGenreIndex: {
        const auto genreIndex = toInteger();
        if (Id3Genres::isEmptyGenre(genreIndex)) {
            result.clear();
        } else if (const char *genreName = Id3Genres::stringFromIndex(genreIndex)) {
            result.assign(genreName);
        } else {
            throw ConversionException("No string representation for the assigned standard genre index available.");
        }
        break;
    }
    case TagDataType::TimeSpan:
        result = toTimeSpan().toString();
        break;
    case TagDataType::DateTime:
        result = toDateTime().toString();
        break;
    default:
        throw ConversionException(argsToString("Can not convert ", tagDataTypeString(m_type), " to string."));
    }
    if (encoding == TagTextEncoding::Utf16LittleEndian || encoding == TagTextEncoding::Utf16BigEndian) {
        auto encodedData = encoding == TagTextEncoding::Utf16LittleEndian ? convertUtf8ToUtf16LE(result.data(), result.size())
                                                                          : convertUtf8ToUtf16BE(result.data(), result.size());
        result.assign(encodedData.first.get(), encodedData.second);
    }
}

/*!
 * \brief Converts the value of the current TagValue object to its equivalent
 *        std::u16string representation.
 * \throws Throws ConversionException on failure.
 * \remarks Use this only, if \a encoding is an UTF-16 encoding.
 * \sa toString()
 */
void TagValue::toWString(std::u16string &result, TagTextEncoding encoding) const
{
    if (isEmpty()) {
        result.clear();
        return;
    }

    string regularStrRes;
    switch (m_type) {
    case TagDataType::Text:
        if (encoding == TagTextEncoding::Unspecified || encoding == dataEncoding()) {
            result.assign(reinterpret_cast<const char16_t *>(m_ptr.get()), m_size / sizeof(char16_t));
        } else {
            StringData encodedData;
            switch (encoding) {
            case TagTextEncoding::Utf8:
                // use pre-defined methods when encoding to UTF-8
                switch (dataEncoding()) {
                case TagTextEncoding::Latin1:
                    encodedData = convertLatin1ToUtf8(m_ptr.get(), m_size);
                    break;
                case TagTextEncoding::Utf16LittleEndian:
                    encodedData = convertUtf16LEToUtf8(m_ptr.get(), m_size);
                    break;
                case TagTextEncoding::Utf16BigEndian:
                    encodedData = convertUtf16BEToUtf8(m_ptr.get(), m_size);
                    break;
                default:;
                }
                break;
            default: {
                // otherwise, determine input and output parameter to use general covertString method
                const auto inputParameter = encodingParameter(dataEncoding());
                const auto outputParameter = encodingParameter(encoding);
                encodedData
                    = convertString(inputParameter.first, outputParameter.first, m_ptr.get(), m_size, outputParameter.second / inputParameter.second);
            }
            }
            result.assign(reinterpret_cast<const char16_t *>(encodedData.first.get()), encodedData.second / sizeof(char16_t));
        }
        return;
    case TagDataType::Integer:
        regularStrRes = ConversionUtilities::numberToString(toInteger());
        break;
    case TagDataType::PositionInSet:
        regularStrRes = toPositionInSet().toString();
        break;
    case TagDataType::StandardGenreIndex: {
        const auto genreIndex = toInteger();
        if (Id3Genres::isEmptyGenre(genreIndex)) {
            regularStrRes.clear();
        } else if (const char *genreName = Id3Genres::stringFromIndex(genreIndex)) {
            regularStrRes.assign(genreName);
        } else {
            throw ConversionException("No string representation for the assigned standard genre index available.");
        }
        break;
    }
    case TagDataType::TimeSpan:
        regularStrRes = toTimeSpan().toString();
        break;
    default:
        throw ConversionException(argsToString("Can not convert ", tagDataTypeString(m_type), " to string."));
    }
    if (encoding == TagTextEncoding::Utf16LittleEndian || encoding == TagTextEncoding::Utf16BigEndian) {
        auto encodedData = encoding == TagTextEncoding::Utf16LittleEndian ? convertUtf8ToUtf16LE(regularStrRes.data(), result.size())
                                                                          : convertUtf8ToUtf16BE(regularStrRes.data(), result.size());
        result.assign(reinterpret_cast<const char16_t *>(encodedData.first.get()), encodedData.second / sizeof(const char16_t));
    }
}

/*!
 * \brief Assigns a copy of the given \a text.
 * \param text Specifies the text to be assigned.
 * \param textSize Specifies the size of \a text. (The actual number of bytes, not the number of characters.)
 * \param textEncoding Specifies the encoding of the given \a text.
 * \param convertTo Specifies the encoding to convert \a text to; set to TagTextEncoding::Unspecified to
 *                  use \a textEncoding without any character set conversions.
 * \throws Throws a ConversionException if the conversion the specified character set fails.
 * \remarks Strips the BOM of the specified \a text.
 */
void TagValue::assignText(const char *text, std::size_t textSize, TagTextEncoding textEncoding, TagTextEncoding convertTo)
{
    m_type = TagDataType::Text;
    m_encoding = convertTo == TagTextEncoding::Unspecified ? textEncoding : convertTo;

    stripBom(text, textSize, textEncoding);
    if (!textSize) {
        m_size = 0;
        m_ptr.reset();
        return;
    }

    if (convertTo == TagTextEncoding::Unspecified || textEncoding == convertTo) {
        m_ptr = make_unique<char[]>(m_size = textSize);
        copy(text, text + textSize, m_ptr.get());
        return;
    }

    StringData encodedData;
    switch (textEncoding) {
    case TagTextEncoding::Utf8:
        // use pre-defined methods when encoding to UTF-8
        switch (convertTo) {
        case TagTextEncoding::Latin1:
            encodedData = convertUtf8ToLatin1(text, textSize);
            break;
        case TagTextEncoding::Utf16LittleEndian:
            encodedData = convertUtf8ToUtf16LE(text, textSize);
            break;
        case TagTextEncoding::Utf16BigEndian:
            encodedData = convertUtf8ToUtf16BE(text, textSize);
            break;
        default:;
        }
        break;
    default: {
        // otherwise, determine input and output parameter to use general covertString method
        const auto inputParameter = encodingParameter(textEncoding);
        const auto outputParameter = encodingParameter(convertTo);
        encodedData = convertString(inputParameter.first, outputParameter.first, text, textSize, outputParameter.second / inputParameter.second);
    }
    }
    // can't just move the encoded data because it needs to be deleted with free
    m_ptr = make_unique<char[]>(m_size = encodedData.second);
    copy(encodedData.first.get(), encodedData.first.get() + encodedData.second, m_ptr.get());
}

/*!
 * \brief Assigns the given integer \a value.
 * \param value Specifies the integer to be assigned.
 */
void TagValue::assignInteger(int value)
{
    m_size = sizeof(value);
    m_ptr = make_unique<char[]>(m_size);
    std::copy(reinterpret_cast<const char *>(&value), reinterpret_cast<const char *>(&value) + m_size, m_ptr.get());
    m_type = TagDataType::Integer;
    m_encoding = TagTextEncoding::Latin1;
}

/*!
 * \brief Assigns a copy of the given \a data.
 * \param data Specifies the data to be assigned.
 * \param length Specifies the length of the data.
 * \param type Specifies the type of the data as TagDataType.
 * \param encoding Specifies the encoding of the data as TagTextEncoding. The
 *                 encoding will only be considered if a text is assigned.
 */
void TagValue::assignData(const char *data, size_t length, TagDataType type, TagTextEncoding encoding)
{
    if (type == TagDataType::Text) {
        stripBom(data, length, encoding);
    }
    if (length > m_size) {
        m_ptr = make_unique<char[]>(length);
    }
    if (length) {
        std::copy(data, data + length, m_ptr.get());
    } else {
        m_ptr.reset();
    }
    m_size = length;
    m_type = type;
    m_encoding = encoding;
}

/*!
 * \brief Assigns the given \a data. Takes ownership.
 *
 * The specified data is not copied. It is moved.
 *
 * \param data Specifies the data to be assigned.
 * \param length Specifies the length of the data.
 * \param type Specifies the type of the data as TagDataType.
 * \param encoding Specifies the encoding of the data as TagTextEncoding. The
 *                 encoding will only be considered if a text is assigned.
 * \remarks Does not strip the BOM so for consistency the caller must ensure there is no BOM present.
 */
void TagValue::assignData(unique_ptr<char[]> &&data, size_t length, TagDataType type, TagTextEncoding encoding)
{
    m_size = length;
    m_type = type;
    m_encoding = encoding;
    m_ptr = move(data);
}

/*!
 * \brief Strips the byte order mask from the specified \a text.
 */
void TagValue::stripBom(const char *&text, size_t &length, TagTextEncoding encoding)
{
    switch (encoding) {
    case TagTextEncoding::Utf8:
        if ((length >= 3) && (ConversionUtilities::BE::toUInt24(text) == 0x00EFBBBF)) {
            text += 3;
            length -= 3;
        }
        break;
    case TagTextEncoding::Utf16LittleEndian:
        if ((length >= 2) && (ConversionUtilities::LE::toUInt16(text) == 0xFEFF)) {
            text += 2;
            length -= 2;
        }
        break;
    case TagTextEncoding::Utf16BigEndian:
        if ((length >= 2) && (ConversionUtilities::BE::toUInt16(text) == 0xFEFF)) {
            text += 2;
            length -= 2;
        }
        break;
    default:;
    }
}

/*!
 * \brief Ensures the byte-order of the specified UTF-16 string matches the byte-order of the machine.
 * \remarks Does nothing if \a currentEncoding already matches the byte-order of the machine.
 */
void TagValue::ensureHostByteOrder(u16string &u16str, TagTextEncoding currentEncoding)
{
    if (currentEncoding !=
#if defined(CONVERSION_UTILITIES_BYTE_ORDER_LITTLE_ENDIAN)
        TagTextEncoding::Utf16LittleEndian
#elif defined(CONVERSION_UTILITIES_BYTE_ORDER_BIG_ENDIAN)
        TagTextEncoding::Utf16BigEndian
#else
#error "Host byte order not supported"
#endif
    ) {
        for (auto &c : u16str) {
            c = swapOrder(static_cast<uint16>(c));
        }
    }
}

/*!
 * \brief Returns an empty TagValue.
 */
const TagValue &TagValue::empty()
{
    static TagValue emptyTagValue;
    return emptyTagValue;
}

} // namespace TagParser