BaseParser.cpp

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#include <Ark/Compiler/AST/BaseParser.hpp>
#include <Ark/Error/Exceptions.hpp>
 
#include <utility>
#include <algorithm>
 
#include <fmt/core.h>
 
namespace Ark::internal
{
    void BaseParser::registerNewLine(std::string::iterator it, std::size_t row)
    {
        // search for an existing new line position
        if (std::ranges::find_if(m_it_to_row, [it](const auto& pair) {
                return pair.first == it;
            }) != m_it_to_row.end())
            return;
 
        // if the mapping is empty, the loop while never hit, and we'll never insert anything
        if (m_it_to_row.empty())
        {
            m_it_to_row.emplace_back(it, row);
            return;
        }
 
        for (std::size_t i = 0, end = m_it_to_row.size(); i < end; ++i)
        {
            auto current_it = m_it_to_row[i].first;
            auto next_it = i + 1 < end ? m_it_to_row[i + 1].first : m_str.end();
            if (current_it < it && it < next_it)
            {
                m_it_to_row.insert(
                    m_it_to_row.begin() + static_cast<decltype(m_it_to_row)::difference_type>(i) + 1,
                    std::make_pair(it, row));
                break;
            }
        }
    }
 
    void BaseParser::next()
    {
        m_it = m_next_it;
        if (isEOF())
        {
            m_sym = utf8_char_t();  // reset sym to EOF
            return;
        }
 
        // getting a character from the stream
        auto [it, sym] = utf8_char_t::at(m_it, m_str.end());
        m_next_it = it;
        m_sym = sym;
 
        if (*m_it == '\n')
        {
            ++m_filepos.row;
            m_filepos.col = 0;
            registerNewLine(m_it, m_filepos.row);
        }
        else if (m_sym.isPrintable())
            m_filepos.col += m_sym.size();
    }
 
    void BaseParser::initParser(const std::string& filename, const std::string& code)
    {
        m_filename = filename;
 
        // if the input string is empty, raise an error
        if (code.empty())
        {
            m_sym = utf8_char_t();
            error("Expected symbol, got empty string", m_filepos);
        }
 
        m_str = code;
        m_it = m_next_it = m_str.begin();
 
        // otherwise, get the first symbol
        next();
    }
 
    void BaseParser::backtrack(const long n)
    {
        if (std::cmp_less(n, m_str.size()))
            m_it = m_str.begin() + n;
        else
            return;
 
        auto [it, sym] = utf8_char_t::at(m_it, m_str.end());
        m_next_it = it;
        m_sym = sym;
 
        // search for the nearest it < m_it in the map to know the line number
        for (const auto& [at, line] : m_it_to_row)
        {
            if (it <= at)
            {
                m_filepos.row = line - 1;
                break;
            }
        }
        // compute the position in the line
        const auto it_pos = static_cast<std::size_t>(std::distance(m_str.begin(), m_it));
        const std::string_view view { m_str.begin(), m_it };
        const auto nearest_newline_index = view.find_last_of('\n');
        if (nearest_newline_index != std::string_view::npos)
            m_filepos.col = it_pos - nearest_newline_index;
        else
            m_filepos.col = it_pos + 1;
    }
 
    FilePosition BaseParser::getCursor() const
    {
        return m_filepos;
    }
 
    CodeErrorContext BaseParser::generateErrorContextAtCurrentPosition() const
    {
        const auto [row, col] = getCursor();
 
        return CodeErrorContext(
            m_filename,
            // for additional contexts, the end position is useless
            FileSpan { .start = FilePos { .line = row, .column = col }, .end = std::nullopt });
    }
 
    void BaseParser::error(const std::string& error, const FilePosition start_at, const std::optional<CodeErrorContext>& additional_context) const
    {
        const auto [row, col] = getCursor();
        throw CodeError(
            error,
            CodeErrorContext(
                m_filename,
                FileSpan {
                    .start = FilePos { .line = start_at.row, .column = start_at.col },
                    .end = FilePos { .line = row, .column = col } }),
            additional_context);
    }
 
    void BaseParser::errorWithNextToken(const std::string& message, const std::optional<CodeErrorContext>& additional_context)
    {
        const auto filepos = getCursor();
 
        anyUntil(IsEither(IsInlineSpace, IsEither(IsChar('('), IsChar(')'))));
        error(message, filepos, additional_context);
    }
 
    void BaseParser::expectSuffixOrError(const char suffix, const std::string& context, const std::optional<CodeErrorContext>& additional_context)
    {
        if (!accept(IsChar(suffix)))
            errorWithNextToken(fmt::format("Missing '{}' {}", suffix, context), additional_context);
    }
 
    bool BaseParser::accept(const CharPred& t, std::string* s)
    {
        if (isEOF())
            return false;
 
        // return false if the predicate couldn't consume the symbol
        if (!t(m_sym.codepoint()))
            return false;
        // otherwise, add it to the string and go to the next symbol
        if (s != nullptr)
            *s += m_sym.c_str();
 
        next();
        return true;
    }
 
    bool BaseParser::expect(const CharPred& t, std::string* s)
    {
        // throw an error if the predicate couldn't consume the symbol
        if (!t(m_sym.codepoint()))
            error("Expected " + t.name, getCursor());
        // otherwise, add it to the string and go to the next symbol
        if (s != nullptr)
            *s += m_sym.c_str();
        next();
        return true;
    }
 
    std::string BaseParser::peek() const
    {
        return m_sym.c_str();
    }
 
    bool BaseParser::space(std::string* s)
    {
        if (accept(IsSpace))
        {
            if (s != nullptr)
                s->push_back(' ');
            // loop while there are still ' ' to consume
            while (accept(IsSpace))
                ;
            return true;
        }
        return false;
    }
 
    bool BaseParser::inlineSpace(std::string* s)
    {
        if (accept(IsInlineSpace))
        {
            if (s != nullptr)
                s->push_back(' ');
            // loop while there are still ' ' to consume
            while (accept(IsInlineSpace))
                ;
            return true;
        }
        return false;
    }
 
    bool BaseParser::comment(std::string* s)
    {
        if (accept(IsChar('#'), s))
        {
            while (accept(IsNot(IsChar('\n')), s))
                ;
            accept(IsChar('\n'), s);
            return true;
        }
        return false;
    }
 
    std::string BaseParser::spaceComment()
    {
        std::string s;
 
        inlineSpace();
        while (!isEOF() && comment(&s))
            inlineSpace();
 
        return s;
    }
 
    std::string BaseParser::newlineOrComment()
    {
        std::string s;
 
        space();
        while (!isEOF() && comment(&s))
            space();
 
        return s;
    }
 
    bool BaseParser::prefix(const char c)
    {
        if (!accept(IsChar(c)))
            return false;
        return true;
    }
 
    bool BaseParser::number(std::string* s)
    {
        if (accept(IsDigit, s))
        {
            // consume all the digits available,
            // stop when the symbol isn't a digit anymore
            while (accept(IsDigit, s))
                ;
            return true;
        }
        return false;
    }
 
    bool BaseParser::signedNumber(std::string* s)
    {
        accept(IsMinus, s);
        if (!number(s))
            return false;
 
        // (optional) floating part
        accept(IsChar('.'), s) && number(s);
        // (optional) scientific part
        if (accept(IsEither(IsChar('e'), IsChar('E')), s))
        {
            accept(IsEither(IsMinus, IsChar('+')), s);
            number(s);
        }
 
        return true;
    }
 
    bool BaseParser::hexNumber(unsigned int length, std::string* s)
    {
        while (length != 0)
        {
            if (!accept(IsHex, s))
                return false;
            --length;
        }
        return true;
    }
 
    bool BaseParser::name(std::string* s)
    {
        const auto alpha_symbols = IsEither(IsAlpha, IsSymbol);
        const auto alnum_symbols = IsEither(IsAlnum, IsSymbol);
 
        if (accept(alpha_symbols, s))
        {
            while (accept(alnum_symbols, s))
                ;
            return true;
        }
        return false;
    }
 
    bool BaseParser::sequence(const std::string& s)
    {
        return std::ranges::all_of(s, [this](const char c) {
            return accept(IsChar(c));
        });
    }
 
    bool BaseParser::packageName(std::string* s)
    {
        if (accept(IsAlnum, s))
        {
            while (accept(IsEither(IsAlnum, IsEither(IsChar('_'), IsChar('-'))), s))
                ;
            return true;
        }
        return false;
    }
 
    bool BaseParser::anyUntil(const CharPred& delim, std::string* s)
    {
        if (accept(IsNot(delim), s))
        {
            while (accept(IsNot(delim), s))
                ;
            return true;
        }
        return false;
    }
 
    bool BaseParser::oneOf(const std::initializer_list<std::string> words, std::string* s)
    {
        std::string buffer;
        if (!name(&buffer))
            return false;
 
        if (s)
            *s = buffer;
 
        return std::ranges::any_of(words, [&buffer](const std::string& word) {
            return word == buffer;
        });
    }
}