#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SH110X.h>
#include <DHT.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1

// SH1106 Display Setup
Adafruit_SH1106G display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// DHT Sensor Setup
#define DHTPIN 16
#define DHTTYPE DHT11 
DHT dht(DHTPIN, DHTTYPE);

// Two LED System
#define GREEN_LED 2  // Represents Normal/Low Temperature
#define RED_LED 5   // Represents High Temperature Alert

const float HIGH_LIMIT = 30;

unsigned long lastBlinkTime = 0;
const int blinkInterval = 500;
bool redLedState = LOW;

void setup() {
  Serial.begin(115200);

  pinMode(GREEN_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);

  // ESP32 Default I2C pins
  Wire.begin(21, 22);

  if(!display.begin(0x3C, true)) {
    Serial.println(F("SH1106 allocation failed"));
    for(;;);
  }

  display.clearDisplay();
  display.setTextColor(SH110X_WHITE);
  
  // Splash Screen
  display.setTextSize(1);
  display.setCursor(15, 15);
  display.println("BIANCA ANA A SILLACAY");
  display.setCursor(10, 35);
  display.println("DIGITAL THERMOMETER");
  display.display();
  delay(3000);

  dht.begin();
}

void loop() {
  float t = dht.readTemperature();

  // Handle sensor disconnection
  if (isnan(t)) {
    display.clearDisplay();
    display.setCursor(20, 30);
    display.print("Sensor Error!");
    display.display();
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(RED_LED, LOW);
    return;
  }

  const char* statusText = "";

  if (t <= HIGH_LIMIT) {

    digitalWrite(GREEN_LED, HIGH);
    digitalWrite(RED_LED, LOW);
    statusText = "STATUS: NORMAL";
  } 
  else {
   
    digitalWrite(BLUE_LED, LOW);
    
    unsigned long currentMillis = millis();
    if (currentMillis - lastBlinkTime >= blinkInterval) {
      lastBlinkTime = currentMillis;
      redLedState = !redLedState;
      digitalWrite(RED_LED, redLedState);
    }
    statusText = "STATUS: HIGH!";
  }

  updateDisplay(t, statusText);
}

void updateDisplay(float t, const char* statusText) {
  display.clearDisplay();

  // Header UI
  display.setTextSize(1);
  display.setCursor(30, 0);
  display.print("THERMOMETER");
  display.drawFastHLine(0, 10, 128, SH110X_WHITE);

  // Large Temperature Reading
  display.setTextSize(2);
  display.setCursor(15, 25);
  display.print(t, 1);
  display.setTextSize(1);
  display.print(" o");
  display.setTextSize(2);
  display.print("C");

  // Status Indicator Box
  display.drawRect(0, 50, 128, 14, SH110X_WHITE);
  display.setCursor(20, 53);
  display.setTextSize(1);
  display.print(statusText);

  display.display();
}