//
// Created by cfif on 24.04.23.
//
#include "string.h"
#include "inttypes.h"

int b64invs[] = {62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58,
                 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 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, -1, -1, -1, -1, -1, -1, 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};


int b64_isvalidchar(char c) {
    if (c >= '0' && c <= '9')
        return 1;
    if (c >= 'A' && c <= 'Z')
        return 1;
    if (c >= 'a' && c <= 'z')
        return 1;
    if (c == '+' || c == '/' || c == '=')
        return 1;
    return 0;
}

size_t b64_decoded_size(const char *in) {
    size_t len;
    size_t ret;
    size_t i;

    if (in == NULL)
        return 0;

    len = strlen(in);
    ret = len / 4 * 3;

    for (i = len; i-- > 0;) {
        if (in[i] == '=') {
            ret--;
        } else {
            break;
        }
    }

    return ret;
}


int b64_decode(const char *in, unsigned char *out, size_t outlen) {
    size_t len;
    size_t i;
    size_t j;
    int v;

    if (in == NULL || out == NULL)
        return 0;

    len = strlen(in);
    if (outlen < b64_decoded_size(in) || len % 4 != 0)
        return 0;

    for (i = 0; i < len; i++) {
        if (!b64_isvalidchar(in[i])) {
            return 0;
        }
    }

    for (i = 0, j = 0; i < len; i += 4, j += 3) {
        v = b64invs[in[i] - 43];
        v = (v << 6) | b64invs[in[i + 1] - 43];
        v = in[i + 2] == '=' ? v << 6 : (v << 6) | b64invs[in[i + 2] - 43];
        v = in[i + 3] == '=' ? v << 6 : (v << 6) | b64invs[in[i + 3] - 43];

        out[j] = (v >> 16) & 0xFF;
        if (in[i + 2] != '=')
            out[j + 1] = (v >> 8) & 0xFF;
        if (in[i + 3] != '=')
            out[j + 2] = v & 0xFF;
    }

    return 1;
}

static const char base64_table[] = {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
        'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p',
        'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '+', '/'
};


size_t base64_encode(char *target, size_t target_len, const char *source, size_t source_len) {
    size_t i;
    int8_t j;
    size_t target_idx = 0;
    size_t longer = (source_len % 3) ? (3 - (source_len % 3)) : 0;
    size_t source_len_b64 = source_len + longer;
    size_t len = (((source_len_b64) * 4) / 3);
    int8_t x = 5;
    int8_t current = 0;
//    LWIP_UNUSED_ARG(target_len);

//    LWIP_ASSERT("target_len is too short", target_len >= len);

    for (i = 0; i < source_len_b64; i++) {
        int8_t b = (i < source_len ? (int8_t) source[i] : 0);
        for (j = 7; j >= 0; j--, x--) {
            if ((b & (1 << j)) != 0) {
                current = (int8_t) (current | (1U << x));
            }
            if (x == 0) {
                target[target_idx++] = base64_table[current];
                x = 6;
                current = 0;
            }
        }
    }
    for (i = len - longer; i < len; i++) {
        target[i] = '=';
    }
    return len;
}