/*
 * nwc, a NanoWasm compiler
 * Copyright (C) 2025 Xavier Del Campo Romero
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Adapted from:
 *
 * 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/.
 *
 * Which, in turn, was adapted from the wac project:
 * https://github.com/kanaka/wac
 *
 * Copyright (C) Joel Martin <github@martintribe.org>
 * The wac project is licensed under the MPL 2.0 (Mozilla Public License
 * 2.0). The text of the MPL 2.0 license is included below and can be
 * found at https://www.mozilla.org/MPL/2.0/
 */

#include "types.h"
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>

static int read_leb128(FILE *const f, const unsigned maxbits, const bool sign,
    unsigned long long *const out)
{
    uint8_t byte;
    unsigned long long result = 0;
    unsigned shift = 0, bcnt = 0;

    for (;;)
    {
        if (!fread(&byte, sizeof byte, 1, f))
        {
            if (ferror(f))
                fprintf(stderr, "%s: ferror\n", __func__);

            return -1;
        }

        result |= (unsigned long long)(byte & 0x7f) << shift;
        shift += 7;

        if (!(byte & 0x80))
            break;
        else if (++bcnt > (maxbits + 7u - 1u) / 7u)
        {
            fprintf(stderr, "%s: overflow\n", __func__);
            return -1;
        }
    }

    if (sign && (shift < maxbits) && (byte & 0x40))
        result |= -1ll << shift;

    *out = result;
    return 0;
}

int read_varint1(FILE *const f, varint1 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 1, true, &res))
        return -1;

    *out = res;
    return 0;
}

int read_varint7(FILE *const f, varint7 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 7, true, &res))
        return -1;

    *out = res;
    return 0;
}

int read_value_type(FILE *const f, value_type *const out)
{
    return read_varint7(f, out);
}

int read_varint32(FILE *const f, varint32 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 32, true, &res))
        return -1;

    *out = res;
    return 0;
}

int read_varint64(FILE *const f, varint64 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 64, true, &res))
        return -1;

    *out = res;
    return 0;
}

int read_varuint1(FILE *const f, varuint1 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 1, false, &res))
        return -1;

    *out = res;
    return 0;
}

int read_varuint7(FILE *const f, varuint7 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 7, false, &res))
        return -1;

    *out = res;
    return 0;
}

int read_varuint32(FILE *const f, varuint32 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 32, false, &res))
        return -1;

    *out = res;
    return 0;
}

int read_varuint64(FILE *const f, varuint64 *const out)
{
    unsigned long long res;

    if (read_leb128(f, 64, false, &res))
        return -1;

    *out = res;
    return 0;
}