// slang-mangled-lexer.cpp
#include "slang-mangled-lexer.h"

#include <assert.h>

namespace Slang {

UInt MangledLexer::readCount()
{
    int c = peekChar();
    if (!CharUtil::isDigit((char)c))
    {
        SLANG_UNEXPECTED("bad name mangling");
        UNREACHABLE_RETURN(0);
    }
    nextChar();

    if (c == '0')
        return 0;

    UInt count = 0;
    for (;;)
    {
        count = count * 10 + c - '0';
        c = peekChar();
        if (!CharUtil::isDigit((char)c))
            return count;

        nextChar();
    }
}

void MangledLexer::readGenericParam()
{
    switch (peekChar())
    {
    case 'T':
    case 'C':
        nextChar();
        break;

    case 'v':
        nextChar();
        readType();
        break;

    default:
        SLANG_UNEXPECTED("bad name mangling");
        break;
    }
}

void MangledLexer::readGenericParams()
{
    _expect("g");
    UInt paramCount = readCount();
    for (UInt pp = 0; pp < paramCount; pp++)
    {
        readGenericParam();
    }
}

void MangledLexer::readType()
{
    int c = peekChar();
    switch (c)
    {
    case 'V':
    case 'b':
    case 'i':
    case 'u':
    case 'U':
    case 'h':
    case 'f':
    case 'd':
        nextChar();
        break;

    case 'v':
        nextChar();
        readSimpleIntVal();
        readType();
        break;

    default:
        readNamedType();
        break;
    }
}

void MangledLexer::readVal()
{
    switch (peekChar())
    {
    case 'k':
        nextChar();
        readCount();
        break;

    case 'K':
        nextChar();
        readRawStringSegment();
        break;

    default:
        readType();
        break;
    }

}

void MangledLexer::readGenericArgs()
{
    _expect("G");
    UInt argCount = readCount();
    for (UInt aa = 0; aa < argCount; aa++)
    {
        readGenericArg();
    }
}

UnownedStringSlice MangledLexer::readSimpleName()
{
    UnownedStringSlice result;
    for (;;)
    {
        int c = peekChar();

        if (c == 'g')
        {
            readGenericParams();
            continue;
        }
        else if (c == 'G')
        {
            readGenericArgs();
            continue;
        }
        else if (c == 'X')
        {
            readExtensionSpec();
            continue;
        }

        if (!CharUtil::isDigit((char)c))
            return result;

        // Read the length part
        UInt count = readCount();
        if (count > UInt(m_end - m_cursor))
        {
            SLANG_UNEXPECTED("bad name mangling");
            UNREACHABLE_RETURN(result);
        }

        result = UnownedStringSlice(m_cursor, m_cursor + count);
        m_cursor += count;
    }
}

String MangledLexer::readRawStringSegment()
{
    bool escapeMode = false;
    if (peekChar() == 'R')
    {
        escapeMode = true;
        nextChar();
    }
    // Read the length part
    UInt count = readCount();
    if (count > UInt(m_end - m_cursor))
    {
        SLANG_UNEXPECTED("bad name mangling");
        UNREACHABLE_RETURN(UnownedStringSlice());
    }

    auto result = UnownedStringSlice(m_cursor, m_cursor + count);
    m_cursor += count;
    if (escapeMode)
        return unescapeString(result);
    return result;
}

String MangledLexer::unescapeString(UnownedStringSlice str)
{
    StringBuilder sb;
    Index cursor = 0;
    while (cursor < str.getLength())
    {
        auto ch = str[cursor];
        auto nextCh = 0;
        if (cursor + 1 < str.getLength())
        {
            nextCh = str[cursor + 1];
        }
        if (ch == '_' && nextCh == 'u')
        {
            sb.appendChar('_');
            cursor += 2;
        }
        else if (ch == '_')
        {
            cursor++;
            Int charValue = 0;
            while (cursor < str.getLength())
            {
                auto current = str[cursor];
                if (current == 'x')
                    break;
                charValue = charValue * 16 + CharUtil::getHexDigitValue(current);
                cursor++;
            }
            sb.appendChar((char)charValue);
            cursor++;
        }
        else
        {
            sb.appendChar(ch);
            cursor++;
        }
    }
    return sb.produceString();
}

UInt MangledLexer::readParamCount()
{
    _expect("p");
    UInt count = readCount();
    _expect("p");
    return count;
}

/* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! MangledNameParser !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! */

/* static */SlangResult MangledNameParser::parseModuleName(const UnownedStringSlice& in, String& outModuleName)
{
    MangledLexer lexer(in);
    {
        switch (lexer.peekChar())
        {
        case 'T':
        case 'G':
        case 'V':
        {
            lexer.nextChar();
            break;
        }
        default: break;
        }
    }

    auto name = lexer.readRawStringSegment();
    if (name.getLength() == 0)
    {
        return SLANG_FAIL;
    }

    outModuleName = name;
    return SLANG_OK;
}

} // namespace Slang