/*
 * 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 <nw/interp.h>
#include <nw/io.h>
#include <nw/log.h>
#include <nw/opcodes.h>
#include <nw/ops.h>
#include <nw/stack.h>
#include <nw/types.h>

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

    if (n)
        return n;

    nwp_interp_resume(i);
    return NW_AGAIN;
}

static enum nw_state pop_left(struct nw_interp *const i)
{
    struct nw_i_sm_select *const s = &i->sm.select;
    const enum nw_state n = nwp_stack_pop(i, &s->io);
    struct nw_sm_io io = {0};

    if (n)
        return n;

    io.buf = s->condition ? &s->left : &s->right;
    io.n = s->sz;
    s->io = io;
    i->next = push;
    return NW_AGAIN;
}

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

    if (n)
        return n;
    else
    {
        struct nw_sm_io io = {0};

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

    i->next = pop_left;
    return NW_AGAIN;
}

static enum nw_state pop_condition(struct nw_interp *const i)
{
    struct nw_i_sm_select *const s = &i->sm.select;
    const enum nw_state n = nwp_stack_pop(i, &s->io);

    if (n)
        return n;
    else
    {
        struct nw_sm_io io = {0};

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

    i->next = pop_right;
    return NW_AGAIN;
}

static enum nw_state check(struct nw_interp *const i)
{
    struct nw_i_sm_select *const s = &i->sm.select;

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

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

        io.buf = &s->condition;
        io.n = sizeof s->condition;
        s->io = io;
    }

    i->next = pop_condition;
    return NW_AGAIN;
}

void nwp_op_select(struct nw_interp *const i)
{
    const struct nw_i_sm_select s = {0};

    i->sm.select = s;
    i->next = check;
}