const int button1 = A0;
const int button2 = A1;
const int button3 = A2;
const int button4 = A3;
int countTens = 0;
int countOnes = 0;
int blinks = 0;
bool state1 = false;
bool state2 = false;
bool state3 = false;
bool state4 = false;

long interval = 100;
unsigned long prevTime = 0;

//The line below is the array containing all the binary numbers for the digits on a SSD from 0 to 9
const int number[11] = {0b0111111,
0b0000110, 0b1011011, 0b1001111,
0b1100110, 0b1101101, 0b1111101,
0b0000111, 0b1111111, 0b1101111,
0b0000000};

void setup(){
  for (int i = 0; i <= 13; i++)
    pinMode(i, OUTPUT); //Set all pins from 0 to 13 as OUTPUT
  pinMode(button1, INPUT_PULLUP);
  pinMode(button2, INPUT_PULLUP);
  pinMode(button3, INPUT_PULLUP);
  pinMode(button4, INPUT_PULLUP);
  for(int i = 0,z = 0;i < 7;i++, z++){ // defaults displays to 00
    digitalWrite(i, bitRead(number[0],z));
  }
  for(int j = 7,c = 0;j <= 13;j++, c++){
    digitalWrite(j, bitRead(number[0],c));
  }
}

void loop(){
  unsigned long currentTime = millis();
  if(digitalRead(button1) == LOW){
    state1 = true;
    state2 = false;
    state3 = false;
    state4 = false;
    countOnes = 9;
    countTens = 9;
  }
  else if(digitalRead(button2) == LOW){
    state1 = false;
    state2 = true;
    state3 = false;
    state4 = false;
    countOnes = 0;
    countTens = 0;
  }
  else if(digitalRead(button3) == LOW){
    state1 = false;
    state2 = false;
    state3 = true;
    state4 = false;
    countOnes = 0;
    countTens = 9;
  }
  else if(digitalRead(button4) == LOW){
    state1 = false;
    state2 = false;
    state3 = false;
    state4 = true;
    blinks = 0;
  }
  if(state1){
    if((currentTime - prevTime)>interval){
      resetDisplay();
      display_ones(countOnes);
      incDecTens(countTens);
      countOnes--;
      if(countOnes < 0){
        countOnes = 9;
        countTens--;
        if(countTens < 0)
          countTens = 9;
      }
      prevTime = currentTime;
    }
  }
  else if(state2){
    if((currentTime - prevTime)>interval){
      resetDisplay();
      display_ones(countOnes);
      incDecTens(countTens);
      countOnes++;
      if(countOnes > 9){
        countOnes = 0;
        countTens++;
        if(countTens > 9)
          countTens = 0;
      }
      prevTime = currentTime;
    }
  }
  else if(state3){
    if((currentTime - prevTime)>interval){
      resetDisplay();
      display_ones(countOnes);
      incDecTens(countTens);
      countOnes++;
      if(countOnes > 9)
        countOnes = 0;
      countTens--;
      if(countTens < 0)
        countTens = 9;
      prevTime = currentTime;
    }
  }
  else if(state4){
    if(blinks < 10){
      if((currentTime - prevTime)>interval)
        turnOff();
      if((currentTime - prevTime)>interval*2){
        resetDisplay();
        prevTime = currentTime;
        blinks++;
      }
    }
  }
}

void display_ones(const int x){
  int pin2, b;
  for (pin2 = 7, b = 0; pin2 <= 13; pin2++, b++) {
    digitalWrite(pin2, bitRead(number[x], b));
  }
}
  
void incDecTens(const int t){
  int pin1, a;
  for (pin1 = 0, a = 0; pin1 < 7; pin1++, a++){
    digitalWrite(pin1, bitRead(number[t],a));
  }
}

void resetDisplay(){
  int pins, l;
  for(pins = 0, l = 0;pins < 7;pins++, l++){
    digitalWrite(pins, bitRead(number[0],l));
  }
  for(pins = 7, l = 0;pins <= 13;pins++, l++){
    digitalWrite(pins, bitRead(number[0],l));
  }
}

void turnOff(){
  int pins, l;
  for(pins = 0, l = 0;pins < 7;pins++, l++){
    digitalWrite(pins, bitRead(number[11],l));
  }
  for(pins = 7, l = 0;pins <= 13;pins++, l++){
    digitalWrite(pins, bitRead(number[11],l));
  }
}