/****************************************************************************************************************************
  cencode.c - c source to a base64 encoding algorithm implementation

  This is part of the libb64 project, and has been placed in the public domain.
  For details, see http://sourceforge.net/projects/libb64

  For W5500 LwIP Ethernet in ESP32 (ESP32 + W5500)

  AsyncWebServer_ESP32_W5500 is a library for the LwIP Ethernet W5500 in ESP32 to run AsyncWebServer

  Based on and modified from ESPAsyncWebServer (https://github.com/me-no-dev/ESPAsyncWebServer)
  Built by Khoi Hoang https://github.com/khoih-prog/AsyncWebServer_ESP32_W5500
  Licensed under GPLv3 license
 *****************************************************************************************************************************/

#include "cencode.h"

const int CHARS_PER_LINE = 72;

/////////////////////////////////////////////////

void base64_init_encodestate(base64_encodestate* state_in)
{
  state_in->step = step_A;
  state_in->result = 0;
  state_in->stepcount = 0;
}

/////////////////////////////////////////////////

char base64_encode_value(char value_in)
{
  static const char* encoding = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

  if (value_in > 63)
    return '=';

  return encoding[(unsigned int)value_in];
}

/////////////////////////////////////////////////

int base64_encode_block(const char* plaintext_in, int length_in, char* code_out, base64_encodestate* state_in)
{
  const char* plainchar = plaintext_in;
  const char* const plaintextend = plaintext_in + length_in;
  char* codechar = code_out;
  char result;
  char fragment;

  result = state_in->result;

  switch (state_in->step)
  {
      while (1)
      {
      case step_A:
        if (plainchar == plaintextend)
        {
          state_in->result = result;
          state_in->step = step_A;
          return codechar - code_out;
        }

        fragment = *plainchar++;
        result = (fragment & 0x0fc) >> 2;
        *codechar++ = base64_encode_value(result);
        result = (fragment & 0x003) << 4;

      // fall through

      case step_B:
        if (plainchar == plaintextend)
        {
          state_in->result = result;
          state_in->step = step_B;
          return codechar - code_out;
        }

        fragment = *plainchar++;
        result |= (fragment & 0x0f0) >> 4;
        *codechar++ = base64_encode_value(result);
        result = (fragment & 0x00f) << 2;

      // fall through

      case step_C:
        if (plainchar == plaintextend)
        {
          state_in->result = result;
          state_in->step = step_C;
          return codechar - code_out;
        }

        fragment = *plainchar++;
        result |= (fragment & 0x0c0) >> 6;
        *codechar++ = base64_encode_value(result);
        result  = (fragment & 0x03f) >> 0;
        *codechar++ = base64_encode_value(result);

        ++(state_in->stepcount);

        if (state_in->stepcount == CHARS_PER_LINE / 4)
        {
          *codechar++ = '\n';
          state_in->stepcount = 0;
        }

        // fall through
      }
  }

  /* control should not reach here */
  return codechar - code_out;
}

/////////////////////////////////////////////////

int base64_encode_blockend(char* code_out, base64_encodestate* state_in)
{
  char* codechar = code_out;

  switch (state_in->step)
  {
    case step_B:
      *codechar++ = base64_encode_value(state_in->result);
      *codechar++ = '=';
      *codechar++ = '=';
      break;

    case step_C:
      *codechar++ = base64_encode_value(state_in->result);
      *codechar++ = '=';
      break;

    case step_A:
      break;
  }

  *codechar = 0x00;

  return codechar - code_out;
}

/////////////////////////////////////////////////

int base64_encode_chars(const char* plaintext_in, int length_in, char* code_out)
{
  base64_encodestate _state;
  base64_init_encodestate(&_state);
  int len = base64_encode_block(plaintext_in, length_in, code_out, &_state);

  return len + base64_encode_blockend((code_out + len), &_state);
}