#pragma once

#include <stdint.h>
#include <stddef.h>

static inline int base64_decode_value(unsigned char c) {
  if (c >= 'A' && c <= 'Z') return c - 'A';
  if (c >= 'a' && c <= 'z') return c - 'a' + 26;
  if (c >= '0' && c <= '9') return c - '0' + 52;
  if (c == '+') return 62;
  if (c == '/') return 63;
  if (c == '=') return -2;
  return -1;
}

static inline int decode_base64(const unsigned char *in, size_t in_len, unsigned char *out) {
  size_t out_len = 0;
  int buf = 0;
  int bits = 0;

  for (size_t i = 0; i < in_len; ++i) {
    int v = base64_decode_value(in[i]);
    if (v == -1) {
      continue;
    }
    if (v == -2) {
      break;
    }

    buf = (buf << 6) | v;
    bits += 6;
    while (bits >= 8) {
      bits -= 8;
      out[out_len++] = (unsigned char)((buf >> bits) & 0xFF);
    }
  }

  return (int)out_len;
}