/*
 * 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/log.h>
#include <nw/routines.h>

static void (*const fn[])(struct nw_mod *) =
{
    nwp_section_custom,
    nwp_section_type,
    nwp_section_import,
    nwp_section_function,
    nwp_section_table,
    nwp_section_memory,
    nwp_section_global,
    nwp_section_export,
    nwp_section_start,
    nwp_section_element,
    nwp_section_code,
    nwp_section_data,
    nwp_section_data_count
};

static enum nw_state get_offset(struct nw_mod *const m)
{
    struct nw_mod_section *const s = &m->section;
    const struct nw_io_cfg *const cfg = &m->cfg.io;
    const enum nw_state n = cfg->tell(&s->offset, cfg->user);
    long *const offset = &m->sections[s->section];

    if (n)
        return n;
    /* Custom section can appear more than once. */
    else if (s->section != NW_SECTION_CUSTOM && *offset)
    {
#ifdef NW_LOG
        nwp_log("ignoring duplicate section %u\n", (unsigned)s->section);
#endif
        nwp_section_skip(m);
    }
    else
    {
        *offset = s->offset;
        fn[s->section](m);
    }

    return NW_AGAIN;
}

static enum nw_state get_length(struct nw_mod *const m)
{
    struct nw_mod_section *const s = &m->section;
    struct nw_sm_leb128 *const l = &s->leb128;
    const struct nw_io_cfg *const cfg = &m->cfg.io;
    const enum nw_state n = nwp_varuint32(cfg, l, &s->len, cfg->user);

    if (n)
        return n;

    m->next = get_offset;
    return NW_AGAIN;
}

static enum nw_state get_section(struct nw_mod *const m)
{
    const struct nw_io_cfg *const cfg = &m->cfg.io;
    struct nw_mod_section *const s = &m->section;
    struct nw_sm_leb128 *const l = &s->leb128;
    const enum nw_state n = nwp_varuint7(cfg, l, &s->section, cfg->user);

    if (n)
    {
        if (cfg->eof(cfg->user))
            return NW_OK;

        return n;
    }
    else if (s->section >= sizeof fn / sizeof *fn)
    {
#ifdef NW_LOG
        nwp_log("invalid section %u\n", (unsigned)s->section);
#endif
        return NW_FATAL;
    }

    m->next = get_length;
    return NW_AGAIN;
}

void nwp_section(struct nw_mod *const m)
{
    const struct nw_mod_section s = {0};

    m->section = s;
    m->next = get_section;
}