/*
 * 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/interp.h>
#include <nw/io.h>
#include <nw/log.h>
#include <nw/routines.h>
#include <nw/types.h>
#include <limits.h>
#include <string.h>

static enum nw_state get_content_type(struct nw_mod *);

static int push(const void *const src, const size_t n, void *const user)
{
    struct nw_mod *const m = user;
    struct nw_sm_gl *const gl = &m->sm.global;

    if (n > sizeof gl->value)
    {
#ifdef NW_LOG
        nwp_log("stack overflow\n");
#endif
        return -1;
    }

    memcpy(&gl->value, src, n);
    return n;
}

static enum nw_state loop(struct nw_mod *const m)
{
    struct nw_sm_gl *const gl = &m->sm.global;
    const enum nw_state n = nwp_interp_run(&gl->interp);

    if (n)
        return n;

    m->next = ++gl->entry_i >= m->global_count ?
        nwp_section_exit : get_content_type;
    return NW_AGAIN;
}

static enum nw_state get_global(struct nw_mod *const m)
{
    struct nw_sm_gl *const gl = &m->sm.global;
    struct nw_interp_cfg cfg = {0};

    cfg.m = m;
    cfg.io = m->cfg.io;
    cfg.user = m;
    cfg.stack.push = push;

    if (nwp_interp_start(&gl->interp, &cfg, &nwp_interp_initexpr_set))
    {
#ifdef NW_LOG
        nwp_log("nw_interp_start failed\n");
#endif
        return NW_FATAL;
    }

    m->next = loop;
    return NW_AGAIN;
}

static enum nw_state get_mutability(struct nw_mod *const m)
{
    nw_varuint1 mutability;
    const struct nw_io_cfg *const cfg = &m->cfg.io;
    struct nw_sm_gl *const gl = &m->sm.global;
    struct nw_sm_leb128 *const l = &gl->leb128;
    const enum nw_state n = nwp_varuint1(cfg, l, &mutability, cfg->user);

    if (n)
        return n;

    m->next = get_global;
    return NW_AGAIN;
}

static enum nw_state get_content_type(struct nw_mod *const m)
{
    nw_varint7 content_type;
    const struct nw_io_cfg *const cfg = &m->cfg.io;
    struct nw_sm_gl *const gl = &m->sm.global;
    struct nw_sm_leb128 *const l = &gl->leb128;
    const enum nw_state n = nwp_varint7(cfg, l, &content_type, cfg->user);
    enum nw_type type;

    /* TODO: do not ignore type */
    if (n)
        return n;
    else if (nwp_get_type(content_type, &type))
    {
#ifdef NW_LOG
        nwp_log("nwp_get_type failed\n");
#endif
        return NW_FATAL;
    }

    m->next = get_mutability;
    return NW_AGAIN;
}

static enum nw_state get_count(struct nw_mod *const m)
{
    const struct nw_io_cfg *const cfg = &m->cfg.io;
    struct nw_sm_gl *const gl = &m->sm.global;
    struct nw_sm_leb128 *const l = &gl->leb128;
    enum nw_state n;

    if (!m->sections[NW_SECTION_IMPORT])
    {
#ifdef NW_LOG
        nwp_log("global section found before import section\n");
#endif
        return NW_FATAL;
    }
    else if ((n = nwp_varuint32(cfg, l, &m->global_count, cfg->user)))
        return n;
    else if (m->global_count > ULONG_MAX / sizeof (struct nw_global))
    {
#ifdef NW_LOG
        nwp_log("global_count too large: %lu\n",
            (unsigned long)m->global_count);
#endif
        return NW_FATAL;
    }

    m->out.global = m->global_count * sizeof (struct nw_global);
    m->next = m->global_count ? get_content_type : nwp_section_exit;
    return NW_AGAIN;
}

void nwp_section_global(struct nw_mod *const m)
{
    const struct nw_sm_gl g = {0};

    m->sm.global = g;
    m->next = get_count;
}