#include "common.h"

static const char base64_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const uint8_t base64_index[256] = { 
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 62, 63, 62, 62, 63,
 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,  0,  0,  0,  0,  0,  0,
  0,  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, 0,  0,  0,  0, 63,
  0, 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 };


void ecdaa_rand(void *buffer, size_t buflen) {
    getrandom(buffer, buflen, 0);
}

char bin2hex(uint8_t byte) {
    uint8_t word = byte & 0x0f;
    char hex = 0;
    if (word >= 0 && word <= 9) hex = word + '0';
    else if (word >= 10 && word <= 15) hex = word - 10 + 'A';
    return hex;
}

uint8_t hex2bin(char hex) {
    uint8_t byte = 0;
    if (hex >= '0' && hex <= '9') byte = hex - '0';
    else if (hex >= 'a' && hex <= 'f') byte = hex - 'a' + 10;
    else if (hex >= 'A' && hex <= 'F') byte = hex - 'A' + 10;
    return byte;
}

void ecdaa_hextobin(const char *in_hex, uint8_t *out_bin, size_t outlen) {
    for (size_t i = 0, j = 0; i < outlen; i++, j+=2) {
        uint8_t val = hex2bin(in_hex[j]);
        val += hex2bin(in_hex[j+1]) * 16;
        out_bin[i] = (char) val;
    }
}

void ecdaa_bintohex(const uint8_t *in_bin, char *out_hex, size_t inlen) {
    for (size_t i = 0, j = 0; i < inlen; i++, j+=2) {
        out_hex[j] = bin2hex(in_bin[i]);
        out_hex[j+1] = bin2hex(in_bin[i] >> 4);
    }
}

void ecdaa_encode(const uint8_t *in_dec, char *out_enc, size_t inlen) {
    int outlen = 4 * ((inlen + 2) / 3);
    int i = 0;
    int j = 0;

    while(i < inlen) {
        uint32_t octet_a = i < inlen ? in_dec[i++] : 0;
        uint32_t octet_b = i < inlen ? in_dec[i++] : 0;
        uint32_t octet_c = i < inlen ? in_dec[i++] : 0;

        uint32_t triple = (octet_a << 16) + (octet_b << 8) + octet_c;

        out_enc[j++] = base64_table[(triple >> 18) & 0x3F];
        out_enc[j++] = base64_table[(triple >> 12) & 0x3F];
        out_enc[j++] = base64_table[(triple >> 6) & 0x3F];
        out_enc[j++] = base64_table[(triple) & 0x3F];
    }
    switch (inlen % 3) {
    case 1:
        out_enc[j-2] = '=';
    case 2:    
        out_enc[j-1] = '=';
    default:
        break;
    }
}

void ecdaa_decode(const uint8_t *in_enc, char *out_dec, size_t outlen) {
    int inlen = 4 * ((outlen + 2) / 3); 
    int i = 0;
    int j = 0;
    
    while (i < inlen) {
        uint32_t sextet_a = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];
        uint32_t sextet_b = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];
        uint32_t sextet_c = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];
        uint32_t sextet_d = in_enc[i] == '=' ? 0 & i++ : base64_index[in_enc[i++]];

        uint32_t triple = (sextet_a << 18) + (sextet_b << 12) + (sextet_c << 6) + sextet_d;

        if (j < outlen) out_dec[j++] = (triple >> 16) & 0xFF;
        if (j < outlen) out_dec[j++] = (triple >> 8) & 0xFF;
        if (j < outlen) out_dec[j++] = triple & 0xFF;
    }
}