#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

Adafruit_SSD1306 display = Adafruit_SSD1306(128, 64, &Wire);

int potentiometer = A0;

unsigned static int pot;
static int potRange = 1000;

unsigned static int selection;
static int numSelects = 5;
unsigned static int state;
static int screenStates = 7;

int oldSelection;
int highlighted;

void setup() {
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);

  pinMode(potentiometer, INPUT);

  selection = analogRead(potentiometer);
  oldSelection = selection;
  state = 0 + 2 * (selection - 2);
  highlighted = 1;

  loadScreen();
}

void loop() {
  pot = analogRead(potentiometer);

  pot = map(pot, 0, 1023, 0, potRange);

  select(pot);
}

void loadScreen() {
  display.display();
  delay(1000);
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
}

void select(int p) {
  int range = potRange / 5;
  for (int i = 0; i < numSelects; i++) {
    if (pot > range * i && pot <= (range * i) + range) {
      selection = i;
      if (highlighted == 1 && selection > oldSelection) {
        highlighted = 2;
        state = 2 * i - 1;
        updateScreen(state);
        oldSelection = selection;
      } else if (highlighted == 1 && selection < oldSelection) {
        highlighted = 1;
        state = 2 * i;
        updateScreen(state);
        oldSelection = selection;
      } else if (highlighted == 2 && selection > oldSelection) {
        highlighted = 2;
        state = 2 * i - 1;
        updateScreen(state);
        oldSelection = selection;
      } else if (highlighted == 2 && selection < oldSelection) {
        highlighted = 1;
        state = 2 * i;
        updateScreen(state);
        oldSelection = selection;
      }
    }
  }
  
}

void updateScreen(int s) {
  if (s == 0) {
    display.clearDisplay();
    display.setCursor(5,10);
    display.setTextColor(BLACK, WHITE);
    display.print(" First ");
    display.setTextColor(WHITE);
    display.setCursor(5,30);
    display.print(" Second ");
  } else if (s == 2) {
    display.clearDisplay();
    display.setTextColor(BLACK, WHITE);
    display.setCursor(5,10);
    display.print(" Second ");
    display.setTextColor(WHITE);
    display.setCursor(5,30);
    display.print(" Third ");
  } else if (s == 4) {
    display.clearDisplay();
    display.setTextColor(BLACK, WHITE);
    display.setCursor(5,10);
    display.print(" Third ");
    display.setTextColor(WHITE);
    display.setCursor(5,30);
    display.print(" Fourth ");
  } else if (s == 6) {
    display.clearDisplay();
    display.setTextColor(BLACK, WHITE);
    display.setCursor(5,10);
    display.print(" Fourth ");
    display.setTextColor(WHITE);
    display.setCursor(5,30);
    display.print(" Fifth ");
  } else if (s == 7) {
    display.clearDisplay();
    display.setTextColor(WHITE);
    display.setCursor(5,10);
    display.print(" Fourth ");
    display.setTextColor(BLACK, WHITE);
    display.setCursor(5,30);
    display.print(" Fifth ");
  } else if (s == 5) {
    display.clearDisplay();
    display.setTextColor(WHITE);
    display.setCursor(5,10);
    display.print(" Third ");
    display.setTextColor(BLACK, WHITE);
    display.setCursor(5,30);
    display.print(" Fourth ");
  } else if (s == 3) {
    display.clearDisplay();
    display.setTextColor(WHITE);
    display.setCursor(5,10);
    display.print(" Second ");
    display.setTextColor(BLACK, WHITE);
    display.setCursor(5,30);
    display.print(" Third ");
  } else if (s == 1) {
    display.clearDisplay();
    display.setTextColor(WHITE);
    display.setCursor(5,10);
    display.print(" First ");
    display.setTextColor(BLACK, WHITE);
    display.setCursor(5,30);
    display.print(" Second ");
  }
  display.display();
}