#include <Wire.h>
#include <RTClib.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <MPU6050.h>

RTC_DS3231 rtc;
MPU6050 accelgyro;

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

void setup() {
  Wire.begin();
  rtc.begin();
  accelgyro.initialize();

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setTextSize(2);
}

void drawLevel(float angle_x, float angle_y) {
  int x_center = SCREEN_WIDTH/2;
  int y_center = SCREEN_HEIGHT/2;
  int line_length = 20;

  display.drawLine(x_center, y_center-line_length, x_center, y_center+line_length, WHITE);
  display.drawLine(x_center-line_length, y_center, x_center+line_length, y_center, WHITE);

  int x_end = x_center + line_length*sin(angle_y*M_PI/180.0);
  int y_end = y_center + line_length*sin(angle_x*M_PI/180.0);

  display.drawLine(x_center, y_center, x_end, y_end, WHITE);
}

void loop() {
  DateTime now = rtc.now();
  int16_t ax, ay, az;
  accelgyro.getAcceleration(&ax, &ay, &az);

  float angle_x = atan2(-ay, -az) * 180.0 / M_PI;
  float angle_y = atan2(-ax, -az) * 180.0 / M_PI;

  display.clearDisplay();
  display.setCursor(0, 0);

  display.print("X: ");
  display.print(angle_x);
  display.println(" deg");
  display.print("Y: ");
  display.print(angle_y);
  display.println(" deg");

  drawLevel(angle_x, angle_y);

  display.display();

  delay(1000);
}