/*
 * 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 <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>

static int run(FILE *const f, const varuint32 idx,
    struct section_function *const out)
{
    varuint32 count;

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

    for (varuint32 i = 0; i < count; i++)
    {
        varuint32 type;

        if (varuint32_read(f, &type))
        {
            LOG("%s: varuint32_read type failed\n", __func__);
            return -1;
        }
        else if (out && i == idx)
        {
            out->type = type;
            out->nreturn = count;
            return 0;
        }
    }

    if (out)
    {
        LOG("%s: could not find function index %ju\n", __func__,
            (uintmax_t)idx);
        return -1;
    }

    return 0;
}

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

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

    const long start = ftell(f);

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

    m->sections.function = start;
    return 0;
}

int section_function(const struct section *const s,
    const struct nw_mod *const m, const varuint32 idx,
    struct section_function *const f)
{
    const long offset = m->sections.function;

    if (offset <= 0)
    {
        LOG("%s: function section not found", __func__);
        return -1;
    }
    else if (fseek(s->f, offset, SEEK_SET))
    {
        LOG("%s: fseek(3): %s\n", __func__, strerror(errno));
        return -1;
    }

    return run(s->f, idx, f);
}