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

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

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

// Pin
#define trigPin 3
#define echoPin 2
#define buzzerPin 8
#define ledPin 9
#define vrPin A0

long duration;
int distance;
int limitDistance;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  pinMode(ledPin, OUTPUT);

  Serial.begin(9600);

  // เริ่มจอ OLED
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED failed");
    while (true);
  }

  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
}

void loop() {
  // อ่าน VR (0–1023 → 5–400 cm)
  limitDistance = map(analogRead(vrPin), 0, 1023, 5, 400);

  // Ultrasonic
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH, 30000);
  distance = duration * 0.034 / 2;

  // เงื่อนไขเตือน
  if (distance > 0 && distance <= limitDistance) {
    digitalWrite(buzzerPin, HIGH);
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(buzzerPin, LOW);
    digitalWrite(ledPin, LOW);
  }

  // แสดงผล OLED
  display.clearDisplay();
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.print("Distance: ");
  display.print(distance);
  display.println(" cm");

  display.setCursor(0, 16);
  display.print("Limit: ");
  display.print(limitDistance);
  display.println(" cm");

  display.setCursor(0, 32);
  if (distance <= limitDistance) {
    display.println("STATUS: ALERT!");
  } else {
    display.println("STATUS: SAFE");
  }

  display.display();

  delay(200);
}