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

// Pin Definitions
#define TRIGGER_PIN 14
#define ECHO_PIN 27
#define RELAY_PIN 26
#define BUZZER_PIN 25

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

// Timing variables
unsigned long previousMillisUltrasonic = 0;
unsigned long previousMillisRelay = 0;
unsigned long previousMillisDisplay = 0;
unsigned long relayTimer = 0;

const long ultrasonicInterval = 500; // 500 ms for ultrasonic sensor
const long relayTimeout = 5000;      // 5 seconds timeout to close door
const long displayInterval = 200;    // 200 ms for OLED update

bool relayState = false; // Relay state (open/close door)
float distance = 0;

void setup() {
  pinMode(TRIGGER_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(RELAY_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  
  digitalWrite(RELAY_PIN, LOW); // Initial state: door closed
  digitalWrite(BUZZER_PIN, LOW);

  // OLED initialization
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("Initializing...");
  display.display();

  Serial.begin(115200);
}

void loop() {
  unsigned long currentMillis = millis();
  
  // Ultrasonic sensor check
  if (currentMillis - previousMillisUltrasonic >= ultrasonicInterval) {
    previousMillisUltrasonic = currentMillis;
    distance = getDistance();  // Function to calculate distance
    
    if (distance > 0 && distance <= 5) {
      // If object is too close, sound the buzzer
      digitalWrite(BUZZER_PIN, HIGH);
    } else {
      digitalWrite(BUZZER_PIN, LOW);
    }

    // Control relay based on distance
    if (distance > 0 && distance < 10) {
      digitalWrite(RELAY_PIN, HIGH); // Open door
      relayState = true;
      relayTimer = currentMillis; // Reset the timer for relay
    }
  }

  // Relay control: close after 5 seconds if no object
  if (relayState && currentMillis - relayTimer >= relayTimeout) {
    digitalWrite(RELAY_PIN, LOW); // Close door
    relayState = false;
  }

  // OLED update
  if (currentMillis - previousMillisDisplay >= displayInterval) {
    previousMillisDisplay = currentMillis;
    display.clearDisplay();
    
    if (distance > 0) {
      display.setCursor(0, 0);
      display.print("Distance: ");
      display.print(distance);
      display.println(" cm");
    } else {
      display.setCursor(0, 0);
      display.println("Waiting...");
    }

    if (relayState) {
      display.setCursor(0, 20);
      display.println("Pintu Terbuka");
    } else {
      display.setCursor(0, 20);
      display.println("Pintu Tertutup");
    }

    display.display();
  }
}

// Function to calculate distance from ultrasonic sensor
float getDistance() {
  // Send a 10us pulse to the trigger pin
  digitalWrite(TRIGGER_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIGGER_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN, LOW);

  // Read the echo pin and calculate distance
  long duration = pulseIn(ECHO_PIN, HIGH);
  float distance = (duration * 0.034) / 2; // Speed of sound 343 m/s -> 0.034 cm/us

  if (distance >= 400 || distance <= 0) {
    return -1; // Invalid distance
  } else {
    return distance;
  }
}