/*
 * nanowasm, a tiny WebAssembly/Wasm interpreter
 * Copyright (C) 2023-2025  Xavier Del Campo Romero
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#include <nanowasm/nw.h>
#include <nw/io.h>
#include <nw/interp.h>
#include <nw/log.h>
#include <nw/routines.h>
#include <nw/stack.h>
#include <nw/types.h>

static enum nw_state push(struct nw_interp *const i)
{
    struct nw_i_sm_arithm *const s = &i->sm.arithm;
    const enum nw_state n = nwp_stack_push(i, &s->io);

    if (n)
        return n;

    i->push_type = s->type;
    nwp_interp_resume(i);
    return NW_AGAIN;
}

static int init_io(struct nw_interp *const i)
{
    struct nw_i_sm_arithm *const s = &i->sm.arithm;
    size_t sz;

    if (nwp_type_sz(s->type, &sz))
    {
        static const char *const exc = "invalid operand type";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s: %#x\n", exc, (unsigned)s->type);
#endif
        return -1;
    }
    else
    {
        struct nw_sm_io io = {0};

        io.buf = &s->value;
        io.n = sz;
        s->io = io;
    }

    return 0;
}

static enum nw_state pop_left(struct nw_interp *const i)
{
    struct nw_i_sm_arithm *const s = &i->sm.arithm;
    const enum nw_state n = nwp_stack_pop(i, &s->io);

    if (n)
        return n;

    s->out.left = s->value;

    if (s->op(&s->out, &s->value))
    {
        static const char *const exc = "arithmetic operation failed";

        i->exception = exc;
#ifdef NW_LOG
        nwp_log("%s\n", exc);
#endif
        return NW_FATAL;
    }
    else if (init_io(i))
        return NW_FATAL;

    i->next = push;
    return NW_AGAIN;
}

static enum nw_state pop_right(struct nw_interp *const i)
{
    struct nw_i_sm_arithm *const s = &i->sm.arithm;
    const enum nw_state n = nwp_stack_pop(i, &s->io);

    if (n)
        return n;
    else if (init_io(i))
        return NW_FATAL;

    s->out.right = s->value;
    i->next = pop_left;
    return NW_AGAIN;
}

static enum nw_state prepare_right(struct nw_interp *const i)
{
    if (init_io(i))
        return NW_FATAL;

    i->next = pop_right;
    return NW_AGAIN;
}

void nwp_arithm(struct nw_interp *const i, const enum nw_type t,
    int (*const op)(const struct nw_i_sm_arithm_out *, union nw_value *))
{
    const struct nw_i_sm_arithm s = {0};
    struct nw_i_sm_arithm *const ps = &i->sm.arithm;

    *ps = s;
    ps->type = t;
    ps->op = op;
    i->next = prepare_right;
}