// For later
const int W_H = 1;
const int W_L = 0;
const int M_O = 1;
const int M_I = 0;
// MAX PINS
const int MAX_PINS = 12;
// Hold pin info
struct {
  int m;
  int w;
  int number;
} pins[12];
// Characters for pin commands
char pin_number = 'x';
char pin_action = 'x';
char pin_chars[MAX_PINS] = {'2','3','4','5','6','7','8','9','A','B','C','D'};

void setup() {
  // Initialize pins and struct
  for (int pc=0; pc < MAX_PINS; pc++) {
    int temp_pin = pc + 2;
    pinMode(temp_pin, INPUT);
    pins[pc].m = M_I;
    pins[pc].w = W_L;
    pins[pc].number = temp_pin;
  }
  
  // Start serial
  Serial.begin(9600);
  while(!Serial) { ; }
}

void loop() {
  // Check for incoming bits that are looking for the controller
  if (Serial.available() > 0) {
    char c = Serial.read();
    if (pin_number == 'x') {
      pin_number = c;
    }
    else if (pin_action == 'x') {
      pin_action = c;
    }
  }
  // If you have enough, go
  if (pin_number != 'x' && pin_action != 'x') {
    goCommand();
  }
  // Pause
  delay(100);
}

int findPin(int pin) {
  for(int cnt=0; cnt < MAX_PINS; cnt++) {
    if (pin == pins[cnt].number) {
      return cnt;
    }
  }
  return 99;
}

int findPinFromChar() {
  for (int cnt = 0; cnt < MAX_PINS; cnt++) {
    if (pin_chars[cnt] == pin_number) {
      return cnt;
    }
  }
  return 99;
}

void switchMode(int pin) {
  int c = findPin(pin);
  if (c >= MAX_PINS) { return; }
  if (pins[c].m == M_O) {
    pinMode(pins[c].number, INPUT);
    pins[c].m = M_I;
  } else {
    pinMode(pins[c].number, OUTPUT);
    pins[c].m = M_O;
  }
}

void switchWrite(int pin) {
  int c = findPin(pin);
  if (c >= MAX_PINS) { return; }
  if (pins[c].m == M_I) { return; }
  if (pins[c].w == W_H) {
    digitalWrite(pins[c].number, LOW);
    pins[c].w = W_L;
  } else {
    digitalWrite(pins[c].number, HIGH);
    pins[c].w = W_H;
  }
}

void feedBack() {
  int p = findPinFromChar();
  if (p == 99) return;
  int pmw = pins[p].m + (pins[p].w * 2);
  Serial.print(pin_chars[p]);
  Serial.print(pmw, DEC);
}

void resetChars() {
  pin_number = 'x';
  pin_action = 'x';
}

void goCommand() {
  if (pin_action != 'M' && pin_action != 'W') { resetChars(); return; }
  int p = findPinFromChar();
  if (p >= MAX_PINS) { resetChars(); return; }
  if (pin_action == 'M') {
    switchMode(pins[p].number);
  }
  if (pin_action == 'W') {
    switchWrite(pins[p].number);
  }
  feedBack();
  resetChars();
}