// sprit-forth: A portable subroutine-threaded Forth.
// Copyright (C) 2024  Clyne Sullivan <clyne@bitgloo.com>
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Library General Public License as published by
// the Free Software Foundation; either version 2 of the License, or (at your
// option) any later version.
//
// This library is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE.  See the GNU Library General Public License for
// more details.
//
// You should have received a copy of the GNU Library General Public License
// along with this library; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.

#include "core.hpp"
#include "executor.hpp"
#include "state.hpp"
#include "types.hpp"

#include <cctype>
#include <cstdlib>

__attribute__((weak))
int findword(const char *, int)
{
    return -1;
}

[[nodiscard]]
static Error parseword(const char *start, const char *end)
{
    auto result = Error::none;

    if (start != end) {
        if (auto word = Forth.find(start, end - start); word) {
            if (!word->immediate() && Forth.state) {
                comma((Cell)word->list);
            } else {
                result = Exec.execute1(word);
            }
        } else if (isdigit(*start) || (*start == '-' && isdigit(*(start + 1)))) {
            Forth.push(std::atoi(start));

            if (Forth.state)
                compileliteral();
        } else if (findword(start, end - start)) {
            return Error::noword;
        }
    }

    return result;
}

[[nodiscard]]
static Error parseSource()
{
    auto result = Error::none;
    char *start = (char *)Forth.source;
    char *end = start;
    auto& i = *((char *)&Forth.sourcei);

    while (result == Error::none && i < Forth.sourceu) {
        if (isspace(*end) || *end == '\0') {
            if (end - start < 1) {
                start = ++end;
                ++i;
            } else {
                ++i; // discard the space
                result = parseword(start, end);
                start = (char *)Forth.source + i;
                end = start;
            }
        } else {
            ++end;
            ++i;
        }
    }

    return result;
}

[[nodiscard]]
Error parse()
{
    // Reset source buffer and try to fill it with getinput().
    Forth.source = (Cell)&Forth.sourcei + 1;
    Forth.sourceu = 0;
    Forth.sourcei = 0;
    getinput();
    addkey('\0');

    return parseSource();
}