libcruft-util/cmdopt2/parser.cpp

#include "./parser.hpp"

using cruft::cmdopt2::parser;


///////////////////////////////////////////////////////////////////////////////
cruft::cmdopt2::positional&
parser::add (positional const &arg)&
{
    return m_positional.emplace_back (std::move (arg));
}


//-----------------------------------------------------------------------------
cruft::cmdopt2::keyword&
parser::add (keyword const &arg)&
{
    return m_keyword.emplace_back (std::move (arg));
}


///////////////////////////////////////////////////////////////////////////////
int
parser::parse_named (int argc, const char *const *argv) const
{
    auto cursor = argv[0];
    if (!cursor or !*cursor)
        return 0;

    if (*cursor++ != '-')
        return 0;
    if (!*cursor)
        throw std::runtime_error ("missing argument name");

    if (*cursor == '-') {
        ++cursor;
        if (!*cursor)
            throw std::runtime_error ("missing long argument name");
        return parse_long (argc, argv);
    } else {
        return parse_short (argc, argv);
    }

    unreachable ();
}


//-----------------------------------------------------------------------------
int
parser::parse_long (int argc, const char *const *argv) const
{
    CHECK (argc >= 1);
    CHECK (strlen (argv[0]) >= 2);
    CHECK (argv[0][0] == '-');
    CHECK (argv[0][1] == '-');

    auto const eq = strchr (argv[0], '=');
    std::string_view const key (argv[0] + 2, eq ?: strlen (argv[0]) + argv[0]);

    auto const pos = std::find_if (
        m_keyword.begin (),
        m_keyword.end   (),
        [&] (auto const &arg)
        {
            return arg.long_ and *arg.long_ == key;
        });
    if (pos == m_keyword.end ())
        throw std::runtime_error ("Unknown long argument");

    if (eq) {
        (*pos->acceptor1) (eq + 1);
        return 1;
    } else {
        if (pos->acceptor0) {
            CHECK (!pos->acceptor1);
            (*pos->acceptor0) ();
            return 1;
        }

        CHECK (pos->acceptor1);
        if (argc < 2)
            throw std::runtime_error ("Missing long arg value");

        if (not argv[1] or not argv[1][0] or argv[1][0] == '-')
            throw std::runtime_error ("Missing long arg value");

        (*pos->acceptor1) (argv[1]);
        return 2;
    }

    unreachable ();
}


//-----------------------------------------------------------------------------
int
parser::parse_short (int argc, const char *const *argv) const
{
    (void)argc;
    CHECK (argc >= 1);
    CHECK (strlen (argv[0]) >= 2);
    CHECK (argv[0][0] == '-');
    CHECK (argv[0][1] != '-');

    auto const len = strlen (argv[0]);
    if (len < 1)
        throw std::runtime_error ("Missing short arguments");

    // Handle single short args with a potential for an associated value
    if (len == 2) {
        auto const pos = std::find_if (
            m_keyword.begin (),
            m_keyword.end   (),
            [&] (auto const &arg)
            {
                return arg.short_ and *arg.short_ == argv[0][1];
            });

        if (pos == m_keyword.end ())
            throw std::runtime_error ("Unknown short argument");

        if (pos->acceptor0) {
            CHECK (!pos->acceptor1);
            (*pos->acceptor0) ();
            return 1;
        }

        CHECK (!pos->acceptor0);
        if (argc < 2)
            throw std::runtime_error ("Missing short argument value");
        (*pos->acceptor1) (argv[1]);
        return 2;
    }

    // Handle strings of short arguments, eg: "-vvv"
    for (std::size_t i = 1; i < len; ++i) {
        auto const pos = std::find_if (
            m_keyword.begin (),
            m_keyword.end   (),
            [&] (auto const &arg)
            {
                return arg.short_ and *arg.short_ == argv[0][1];
            });
        if (pos == m_keyword.end ())
            throw std::runtime_error ("Unknown short argument");

        if (pos->acceptor1)
            throw std::runtime_error ("Missing short argument value");

        (*pos->acceptor0) ();
    }

    return 1;
}


//-----------------------------------------------------------------------------
int
parser::parse (int const argc, const char *const *argv)
{
    if (argc <= 1)
        return argc;

    int arg_cursor = 1;
    int pos_cursor = 0;

    while (arg_cursor != argc) {
        auto const arg = argv[arg_cursor];
        if (!arg or !*arg)
            break;

        if (*arg == '-') {
            arg_cursor += parse_named (argc - arg_cursor, argv + arg_cursor);
            continue;
        }

        (*m_positional[pos_cursor].acceptor1) (argv[arg_cursor++]);
    }

    return arg_cursor;
}


///////////////////////////////////////////////////////////////////////////////
void
parser::usage (int argc, char const * const* argv, std::ostream &os) const
{
    os << "Usage:";
    if (argc > 0)
        os << ' ' << argv[0];

    static char constexpr OPTIONAL[2] { '[', ']' };
    static char constexpr REQUIRED[2] { '<', '>' };

    for (auto const &arg: m_keyword) {
        auto const &delimiters = arg.required ? REQUIRED : OPTIONAL;

        if (arg.short_)
            os << ' ' << delimiters[0] << '-'  << *arg.short_ << delimiters[1];
        if (arg.long_)
            os << ' ' << delimiters[0] << "--" << *arg.long_  << delimiters[1];
    }

    for (auto const &arg: m_positional) {
        auto const &delimiters = arg.required ? REQUIRED : OPTIONAL;
        os << ' ' << delimiters[0] << arg.name << delimiters[1];
    }

    os << '\n';
}