/*
 * 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_value_type(FILE *const f, enum value_type *const vtype)
{
    varint7 value_type;

    if (varint7_read(f, &value_type))
    {
        LOG("%s: varint7_read failed\n", __func__);
        return -1;
    }
    else if (vtype && get_value_type(value_type, vtype))
    {
        LOG("%s: get_value_type failed\n", __func__);
        return -1;
    }

    return 0;
}

static int check_func_type(FILE *const f, struct retval *const r)
{
    varint7 form;
    varuint32 param_count;

    if (varint7_read(f, &form))
    {
        LOG("%s: varint7_read failed\n", __func__);
        return -1;
    }
    else if (varuint32_read(f, &param_count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }

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

    varuint1 return_count;
    enum value_type vtype;

    if (varuint1_read(f, &return_count))
    {
        LOG("%s: varuint1_read failed\n", __func__);
        return -1;
    }
    else if (return_count && check_value_type(f, &vtype))
    {
        LOG("%s: check_value_type 2 failed\n", __func__);
        return -1;
    }

    *r = (const struct retval)
    {
        .returns = return_count,
        .type = vtype
    };

    return 0;
}

static int run(FILE *const f, const unsigned long len, const varuint32 idx,
    struct retval *const out)
{
    const long start = ftell(f);
    varuint32 count;

    if (start < 0)
    {
        LOG("%s: ftell(3): %s\n", __func__, strerror(errno));
        return -1;
    }
    else if (varuint32_read(f, &count))
    {
        LOG("%s: varuint32_read failed\n", __func__);
        return -1;
    }

    for (varuint32 i = 0; i < count; i++)
    {
        struct retval r;

        if (check_func_type(f, &r))
        {
            LOG("%s: check_func_type failed\n", __func__);
            return -1;
        }
        else if (out && i == idx)
        {
            *out = r;
            return 0;
        }
    }

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

    if (m->sections.type)
    {
        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 (run(f, len, 0, NULL))
    {
        LOG("%s: check failed\n", __func__);
        return -1;
    }

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

int section_type_push(FILE *const f, const struct nw_mod *const m,
    const varuint32 idx, struct retval *const out)
{
#if 0
    const long offset = m->sections.type;

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

    return run(f, 0, idx, out);
#endif
    return -1;
}