// #include <SPI.h>
// #include <Wire.h>
// #include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define OLED_RESET -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display (SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

int potNEW = 0; // clear pot
int potOLD = potNEW; // make them equal
int line = 1;
bool button;
#define buttonPin 3 // change lines

void setup()
{
  // Serial.begin(115200);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.begin(115200);
    Serial.println(F("SSD1306 allocation failed"));
    while (1);
  } // OLED init failed. HALT.
  display.clearDisplay();

  pinMode(buttonPin, INPUT_PULLUP);

  // Print the OVERLAY that never changes in the SETUP
  display.setTextColor(SSD1306_BLACK, SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.print("     CALIBRATION     ");
  display.setTextColor(WHITE);
  display.setCursor(35, 10);
  display.print("THR 1:   0");
  display.setCursor(35, 20);
  display.print("THR 2:   0");
  display.display();
}

void loop()
{
  potNEW = analogRead(A0);
  button = digitalRead(buttonPin);
  carrot(25, 10*line);
  // delay(150);

  // only redraw potentiometer value if value has changed
  if (potNEW != potOLD) {

    // redraw old pot value in BLACK to erase old value
    display.setCursor(70, 10);
    display.setTextColor(BLACK);
    spacepad(potOLD); // for right-alignment see function
    display.print(potOLD);
    // display.display(); // do NOT update display, it will cause flicker

    // draw new pot value in WHITE
    display.setCursor(70, 10);
    display.setTextColor(WHITE);
    spacepad(potNEW); // for right-alignment see function
    display.print(potNEW);
    display.display();

    potOLD = potNEW; // update old data
  }

  if (!button) {
    // Serial.print(line);
    display.setTextColor(BLACK);
    carrot(25, 10 * line);
    line++;
    if (line > 2)
      line = 1;
    display.setTextColor(WHITE);
    carrot(25, 10 * line);
  }
}

void spacepad(int pot) {
  // spacepadding or zeropadding creates right-alignment
  if (pot < 1000) display.print(" ");
  if (pot < 100) display.print(" ");
  if (pot < 10) display.print(" ");
}

void carrot(int x, int y) { // indicate the menu choice
  display.setCursor(x, y);
  display.print(">");
  display.display();
}