#include "base64.h"

static const char b64chars[] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const uint8_t b64decode_table[256] = {
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63,
     52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,  0,255,255,
    255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
     15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255,
    255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
     41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
    255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
};

std::string base64Encode(const uint8_t* p, size_t len) {
    std::string out;
    out.reserve(((len + 2) / 3) * 4);

    size_t i = 0;
    while (i + 2 < len) {
        uint32_t v = (p[i] << 16) | (p[i+1] << 8) | p[i+2];
        out.push_back(b64chars[(v >> 18) & 0x3F]);
        out.push_back(b64chars[(v >> 12) & 0x3F]);
        out.push_back(b64chars[(v >>  6) & 0x3F]);
        out.push_back(b64chars[(v      ) & 0x3F]);
        i += 3;
    }
    if (i + 1 == len) {
        uint32_t v = p[i] << 16;
        out.push_back(b64chars[(v >> 18) & 0x3F]);
        out.push_back(b64chars[(v >> 12) & 0x3F]);
        out.push_back('=');
        out.push_back('=');
    } else if (i + 2 == len) {
        uint32_t v = (p[i] << 16) | (p[i+1] << 8);
        out.push_back(b64chars[(v >> 18) & 0x3F]);
        out.push_back(b64chars[(v >> 12) & 0x3F]);
        out.push_back(b64chars[(v >>  6) & 0x3F]);
        out.push_back('=');
    }
    return out;
}

std::string base64Encode(const std::string& data) {
    return base64Encode(reinterpret_cast<const uint8_t*>(data.data()),
                        data.size());
}

std::string base64Decode(const std::string& data) {
    std::string out;
    out.reserve(data.size() * 3 / 4);

    uint32_t buf = 0;
    int bits = 0;
    for (char c : data) {
        if (c == '=' || c == '\n' || c == '\r') continue;
        uint8_t val = b64decode_table[static_cast<uint8_t>(c)];
        if (val == 255) continue;
        buf = (buf << 6) | val;
        bits += 6;
        if (bits >= 8) {
            bits -= 8;
            out.push_back(static_cast<char>((buf >> bits) & 0xFF));
        }
    }
    return out;
}