/*
 * nanowasm, a tiny WebAssembly/Wasm interpreter
 * Copyright (C) 2023-2024  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/log.h>
#include <nw/sections.h>
#include <nanowasm/nw.h>
#include <nw/types.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

static int check_table_type(FILE *const f)
{
    enum {ANYFUNC = 0x70};
    varint7 elem_type;

    if (varint7_read(f, &elem_type))
    {
        LOG("%s: varint7_read failed\n", __func__);
        return -1;
    }
    else if (elem_type != ANYFUNC)
    {
        LOG("%s: expected %x, got %x", __func__, ANYFUNC,
            (int)elem_type);
        return -1;
    }

    /* TODO: what to do with this? */
    struct resizable_limits r;

    return check_resizable_limits(f, &r);
}

static int check(FILE *const f, const unsigned long len)
{
    const long start = ftell(f);

    if (start < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    varuint32 count;

    if (varuint32_read(f, &count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }

    for (varuint32 i = 0; i < count; i++)
        if (check_table_type(f))
        {
            LOG("%s: check_table_type failed\n", __func__);
            return -1;
        }

    const long end = ftell(f);

    if (end < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    const unsigned long size = end - start;

    if (size != len)
    {
        LOG("%s: size exceeded (%lu expected, got %lu)\n",
                __func__, len, size);
        return -1;
    }

    return 0;
}

int section_table_check(const struct section *const s, struct nw_mod *const m,
    const unsigned long len)
{
    FILE *const f = s->f;

    if (m->sections.table)
    {
        LOG("%s: ignoring duplicate section\n", __func__);
        return fseek(f, len, SEEK_CUR);
    }

    const long offset = ftell(f);

    if (offset < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (check(f, len))
    {
        LOG("%s: check failed\n", __func__);
        return -1;
    }

    m->sections.table = offset;
    return 0;
}