void setup() {
  Serial.begin(115200);
  Serial.println("hi Mom!");
}

void loop()
{
  logicFSM();   // crank it along

// for now only a .. z make sense (no filter or tolower or...)

  char theChar;
  if (Serial.available()) {
    theChar = Serial.read();
    if ('a' <= theChar && theChar <= 'z') {
//      Serial.println(theChar);
      logicFSM(theChar);
    }
  }

  logicFSM(0);  // move it along.

  delay(777);  // sue me. this is a work in progress
}

enum logic {IDLE, AWAIT, ERROR, FINI};
enum display {OFF, GOOD, BAD, SUCCESS, WOW};

const char *logicTags[] = {"Idle", "Await", "Error", "Fini"};

void logicFSM(char theChar)
{
//  byte state = IDLE;
  static byte state = IDLE;
  static unsigned long timer;  // general use timer
  static char previous;
  static char undisposedChar;

  if (!theChar && undisposedChar) {
    theChar = undisposedChar;
    undisposedChar = 0;
  }

  if (theChar) {
    Serial.print("= ");
    Serial.println(theChar);
  }

{
  static byte lastPrinted = -1;
  if (lastPrinted != state) {
    Serial.print("logic: ");
    Serial.println(logicTags[state]);

    lastPrinted = state;
  }
}

  switch (state) {
  case IDLE :
//    Serial.print("                    IDLE char "); Serial.println(theChar ? theChar : '.');
    if (theChar)
      if (theChar != 'a') {
        undisposedChar = theChar;   // kludge
        previous = theChar;         // kludge
        state = AWAIT;                              // make this fall through
      }
      else state = FINI;

    break;

  case AWAIT :
    if (theChar)
      if (theChar == previous) {
        Serial.println("              !");
        if (theChar == 'a')
          state = FINI;
        else
          previous--;
      }
      else {
        Serial.println("              X");
        state = ERROR;
      }

    break;

// harsh punishment for now
  case ERROR :
    state = IDLE;
  
    break;

  case FINI :
    Serial.println("ding ding!");
    state = IDLE;

    break;

  default :
    Serial.println("Rotten Denmark!");
    for (; ; );
  }
}

// service or just call logicFSM(0)
void logicFSM()
{
  logicFSM(0);
}








/*

void logicFSM(int x)
{
  if (x > 0)
    Serial.println(x);
}


void logicFSM()
{
  static int counter;
  if (++counter >= 10) {
    logicFSM(100);
    counter = 0;
  }
}
*/