// Copyright (c) 2014-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <base58.h>

#include <hash.h>

#include <uint256.h>

#include <util/strencodings.h>

#include <util/string.h>

#include <assert.h>

#include <string.h>

#include <limits>

using util::ContainsNoNUL;

/** All alphanumeric characters except for "0", "I", "O", and "l" */

static const char* pszBase58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

static const int8_t mapBase58[256] = {

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1, 0, 1, 2, 3, 4, 5, 6,  7, 8,-1,-1,-1,-1,-1,-1,

    -1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,

    22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,

    -1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,

    47,48,49,50,51,52,53,54, 55,56,57,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

    -1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,

};

[[nodiscard]] static bool DecodeBase58(const char* psz, std::vector<unsigned char>& vch, int max_ret_len)

{

    // Skip leading spaces.

    while (*psz && IsSpace(*psz))

        psz++;

    // Skip and count leading '1's.

    int zeroes = 0;

    int length = 0;

    while (*psz == '1') {

        zeroes++;

        if (zeroes > max_ret_len) return false;

        psz++;

    }

    // Allocate enough space in big-endian base256 representation.

    int size = strlen(psz) * 733 /1000 + 1; // log(58) / log(256), rounded up.

    std::vector<unsigned char> b256(size);

    // Process the characters.

    static_assert(std::size(mapBase58) == 256, "mapBase58.size() should be 256"); // guarantee not out of range

    while (*psz && !IsSpace(*psz)) {

        // Decode base58 character

        int carry = mapBase58[(uint8_t)*psz];

        if (carry == -1)  // Invalid b58 character

            return false;

        int i = 0;

        for (std::vector<unsigned char>::reverse_iterator it = b256.rbegin(); (carry != 0 || i < length) && (it != b256.rend()); ++it, ++i) {

            carry += 58 * (*it);

            *it = carry % 256;

            carry /= 256;

        }

        assert(carry == 0);

        length = i;

        if (length + zeroes > max_ret_len) return false;

        psz++;

    }

    // Skip trailing spaces.

    while (IsSpace(*psz))

        psz++;

    if (*psz != 0)

        return false;

    // Skip leading zeroes in b256.

    std::vector<unsigned char>::iterator it = b256.begin() + (size - length);

    // Copy result into output vector.

    vch.reserve(zeroes + (b256.end() - it));

    vch.assign(zeroes, 0x00);

    while (it != b256.end())

        vch.push_back(*(it++));

    return true;

}

std::string EncodeBase58(std::span<const unsigned char> input)

{

    // Skip & count leading zeroes.

    int zeroes = 0;

    int length = 0;

    while (input.size() > 0 && input[0] == 0) {

        input = input.subspan(1);

        zeroes++;

    }

    // Allocate enough space in big-endian base58 representation.

    int size = input.size() * 138 / 100 + 1; // log(256) / log(58), rounded up.

    std::vector<unsigned char> b58(size);

    // Process the bytes.

    while (input.size() > 0) {

        int carry = input[0];

        int i = 0;

        // Apply "b58 = b58 * 256 + ch".

        for (std::vector<unsigned char>::reverse_iterator it = b58.rbegin(); (carry != 0 || i < length) && (it != b58.rend()); it++, i++) {

            carry += 256 * (*it);

            *it = carry % 58;

            carry /= 58;

        }

        assert(carry == 0);

        length = i;

        input = input.subspan(1);

    }

    // Skip leading zeroes in base58 result.

    std::vector<unsigned char>::iterator it = b58.begin() + (size - length);

    while (it != b58.end() && *it == 0)

        it++;

    // Translate the result into a string.

    std::string str;

    str.reserve(zeroes + (b58.end() - it));

    str.assign(zeroes, '1');

    while (it != b58.end())

        str += pszBase58[*(it++)];

    return str;

}

bool DecodeBase58(const std::string& str, std::vector<unsigned char>& vchRet, int max_ret_len)

{

    if (!ContainsNoNUL(str)) {

        return false;

    }

    return DecodeBase58(str.c_str(), vchRet, max_ret_len);

}

std::string EncodeBase58Check(std::span<const unsigned char> input)

{

    // add 4-byte hash check to the end

    std::vector<unsigned char> vch(input.begin(), input.end());

    uint256 hash = Hash(vch);

    vch.insert(vch.end(), hash.data(), hash.data() + 4);

    return EncodeBase58(vch);

}

[[nodiscard]] static bool DecodeBase58Check(const char* psz, std::vector<unsigned char>& vchRet, int max_ret_len)

{

    if (!DecodeBase58(psz, vchRet, max_ret_len > std::numeric_limits<int>::max() - 4 ? std::numeric_limits<int>::max() : max_ret_len + 4) ||

        (vchRet.size() < 4)) {

        vchRet.clear();

        return false;

    }

    // re-calculate the checksum, ensure it matches the included 4-byte checksum

    uint256 hash = Hash(std::span{vchRet}.first(vchRet.size() - 4));

    if (memcmp(&hash, &vchRet[vchRet.size() - 4], 4) != 0) {

        vchRet.clear();

        return false;

    }

    vchRet.resize(vchRet.size() - 4);

    return true;

}

bool DecodeBase58Check(const std::string& str, std::vector<unsigned char>& vchRet, int max_ret)

{

    if (!ContainsNoNUL(str)) {

        return false;

    }

    return DecodeBase58Check(str.c_str(), vchRet, max_ret);

}