#include <U8glib.h>

U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NONE | U8G_I2C_OPT_DEV_0);

#define buttonUpPin 12
#define buttonSelectPin 11
#define buttonDownPin 10
#define buttonBackPin 9

int y = 10;

int clicked = 0;

void setup() {
    u8g.setFont(u8g_font_unifont);

    pinMode(buttonUpPin, INPUT_PULLUP);
    pinMode(buttonSelectPin, INPUT_PULLUP);
    pinMode(buttonDownPin, INPUT_PULLUP);
    pinMode(buttonBackPin, INPUT_PULLUP);
}

void loop() {
  if (digitalRead(buttonDownPin) == LOW) {
    y = y + 12;

    if (y > 58) {
      y = 10;
    }
  }

  if (digitalRead(buttonUpPin) == LOW) {
    y = y - 12;

    if (y < 5) {
      y = 58;
    }
  }

  if ((digitalRead(buttonSelectPin) == LOW) && (y == 10)) {
    time();
  }

  if (digitalRead(buttonBackPin) == LOW) {
    menu();
    clicked = 1;
  }

  u8g.firstPage();
  do {
    menu();
  } while (u8g.nextPage());

  delay(50);
}

void menu() {
  do {
    u8g.drawStr(20, 10, "Time");
    u8g.drawStr(20, 22, "RFID / NFC");
    u8g.drawStr(20, 34, "433 mHz");
    u8g.drawStr(20, 46, "Infra Red");
    u8g.drawStr(20, 58, "Bad USB");

    u8g.drawStr(5, y, ">");
  } while (u8g.nextPage());
}

void time() {
  while (clicked == 0) {
    u8g.firstPage();
    do {
      u8g.drawStr(20, 20, "TIME");
    } while (u8g.nextPage());
  }
}