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

// Include the Custom Font for a professional UI
#include <Fonts/FreeSans9pt7b.h>

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

// DS18B20 Setup
#define ONE_WIRE_BUS 2 
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
DeviceAddress tempDeviceAddress; 

void setup() {
  Serial.begin(9600);

  // Initialize OLED
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { 
    for(;;); // Don't proceed, loop forever if display fails
  }

  sensors.begin();
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setRotation(2);
}

void loop() {
  display.clearDisplay();
  
  // 1. Header with Custom Font
  display.setFont(&FreeSans9pt7b);
  display.setCursor(0, 15); // Custom fonts use baseline (y) coordinates
  display.println("Sensor ID:");
  
  // Draw a decorative line
  display.drawLine(0, 18, 120, 18, SSD1306_WHITE);

  // 2. Search for the sensor serial number
  oneWire.reset_search();
  if (oneWire.search(tempDeviceAddress)) {
    
    // Switch back to standard font for the long serial string (better fit)
    display.setFont(); 
    display.setCursor(0, 28);
    display.print("HEX: ");
    
    // Print the 8-byte Serial Number
    for (uint8_t i = 0; i < 8; i++) {
      if (tempDeviceAddress[i] < 16) display.print("0");
      display.print(tempDeviceAddress[i], HEX);
      if (i < 7) display.print(":");
    }

    // 3. Display Temperature for verification
    sensors.requestTemperatures();
    float tempC = sensors.getTempC(tempDeviceAddress);
    
    display.setFont(&FreeSans9pt7b);
    display.setCursor(0, 63);
    display.print("Temp: ");
    display.print(tempC, 1);
    display.print(" C");

  } else {
    // Error state if no sensor is plugged in
    display.setFont();
    display.setCursor(0, 35);
    display.println("NO SENSOR DETECTED");
    display.println("Check Pin D2 & 4.7k");
  }

  display.display(); // Push buffer to hardware
  delay(1500);       // Refresh rate
}