//Constants don't change
const int returnButton = 13; //Orange button to return coins
const int selectButton = 12; //Putple button to select options
const int scrollButton = 11; //Pink button to scroll through options

//The selection number, varies 0 - 5 (6 choices)
int selection = 0;
// used for dollar / cent selection
bool dollCentSelection = false; // false= dollars

int lastScrollState = 1;  // < with INPUT_PULLUP the pin starts HIGH
int lastSelectState = 1;  // < with INPUT_PULLUP the pin starts HIGH
int lastReturnState = 1;  // < with INPUT_PULLUP the pin starts HIGH

int credit = 0; //The amount of money the user put into the machine

void selectSelect()  {

  int btnState = digitalRead(selectButton);  // read the button pin
  if (btnState != lastSelectState)  {       // see if it changed
    lastSelectState = btnState;             // remember where it is
    if (btnState == LOW)  {             // if LOW it is pressed
      Serial.println("Select pressed");
      Serial.print("You have chosen ");
      Serial.println(selection? "dollars" : "cents");
    } else  {   // else it's HIGH, it was released
      Serial.println("Select released");
    }
    delay(20);  // for debounce
  }
}

void returnSelect()  {

  int btnState = digitalRead(returnButton);  // read the button pin
  if (btnState != lastReturnState)  {       // see if it changed
    lastReturnState = btnState;             // remember where it is
    if (btnState == LOW)  {             // if LOW it is pressed
      Serial.println("Return pressed");
      if (credit == 0)  {
        Serial.println("Nothing to return");
      } else {
        Serial.print("We owe you ");
        Serial.println(credit);
      }
    } else  {   // else it's HIGH, it was released
      Serial.println("Return released");
    }
    delay(20);  // for debounce
  }
}

//scrolls through the options of paying with coins or bills
void dollCentSelect() {  // < "int" here means "this function returns an integer"
  // read the pushbutton input pin
  int scrollState = digitalRead(scrollButton);  // < EDIT
  // compare the buttonState to its previous state
  if (scrollState != lastScrollState) {
    // save the new state right when it's detected
    // save the current state as the last state, for
    // the next time through the loop
    lastScrollState = scrollState;
    // if the state has changed, increment the counter
    if (scrollState == LOW) { // went from off to on
      selection = ! selection;
      Serial.println("Doll / Cent pressed");
      Serial.println(selection? "Dollars" : "Cents");
      //Serial.println(selection);
      //selection = selection + 1;  // print the selection before you increment it
      //if (selection > 1) selection = 0;
    } else {  // went from on to off
      Serial.println("Doll / Cent released");
    }
    // delay a little bit to avoid debouncing
    delay(20); // Wait for 5 millisecond(s)
  }
}

void setup() {
  Serial.begin(9600);
  // use the constants defined for each pin
  pinMode(returnButton, INPUT_PULLUP);
  pinMode(selectButton, INPUT_PULLUP);
  pinMode(scrollButton, INPUT_PULLUP);
}

void loop() {
  if (digitalRead(returnButton) == LOW) {
    returnSelect();
  } else if (digitalRead(selectButton) == LOW) {
    selectSelect();
  } else if (digitalRead(scrollButton) == LOW) {
    dollCentSelect();
  }
}