//https://randomnerdtutorials.com/guide-for-oled-display-with-arduino/

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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

#define BUZZER_PIN 8 // 🛎️ connect buzzer here!

float speed = 0.0;
float fineSpeed = 0.0;
bool accelerating = true;
bool blinkState = false;
unsigned long lastBlinkTime = 0;
const int blinkInterval = 100; // 100ms blinking

void setup() {
  Serial.begin(9600);
  randomSeed(analogRead(A0));

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  display.clearDisplay();

  pinMode(BUZZER_PIN, OUTPUT); // Setup buzzer pin
  digitalWrite(BUZZER_PIN, LOW); // Make sure it's OFF at start
}

void loop() {
  // Update speed
  if (accelerating) {
    speed += random(23, 38) * 0.01;
    if (speed >= 35.0) {
      accelerating = false;
    }
  } else {
    speed -= random(15, 115) * 0.1;
    if (speed <= 0.0) {
      speed = 0.0;
      accelerating = true;
    }
  }

  fineSpeed = speed * 100;

  // Blinking and Buzzer Logic
  if (speed >= 33.0) {
    unsigned long currentMillis = millis();
    if (currentMillis - lastBlinkTime >= blinkInterval) {
      blinkState = !blinkState;
      display.invertDisplay(blinkState);
      lastBlinkTime = currentMillis;

      // Beep when blinking ON
      if (blinkState) {
        digitalWrite(BUZZER_PIN, HIGH); // BEEP
      } else {
        digitalWrite(BUZZER_PIN, LOW); // silent
      }
    }
  } else {
    display.invertDisplay(false);
    digitalWrite(BUZZER_PIN, LOW); // make sure buzzer is off
    blinkState = false;
  }

  // Draw Speedometer
  display.clearDisplay();

  display.fillCircle(64, 32, 60, WHITE);
  display.fillCircle(64, 32, 57, BLACK);
  display.fillCircle(64, 32, 55, WHITE);
  display.fillCircle(64, 32, 50, BLACK);

  // Fine Speed
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(85, 38);

  int fineSpeedDisplay = ((int)fineSpeed) % 100;
  if (fineSpeedDisplay < 10) {
    display.print("0");
  }
  display.println(fineSpeedDisplay);

  // Main Speed
  display.setTextSize(5);
  display.setCursor(26, 16);

  int displaySpeed = (int)speed;
  if (displaySpeed < 10) {
    display.print("0");
  }
  display.println(displaySpeed);

  display.display();

  delay(30);
}