#include <Wire.h>
#include <LiquidCrystal_I2C.h> // importing libraries related to hardware
#include <DHT.h>

#define DHTPIN 10    // Pin where the DHT22 is connected
#define DHTTYPE DHT22  // Sets the type of DHT 22 

DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 20, 4);  // Pins the LCD is connected too

int ledPin1 = 4;  // where the red LED is connected to
int ledPin2 = 5;  // where the green LED Is conneected to

void setup() {
  Serial.begin(10000);
  Serial.println("If the gas concentration exceeds 50%, the detector will send out a warning and the red LED will light up.");
  lcd.begin(20, 4); // initilizing the lcd

  pinMode(ledPin1, OUTPUT); // setting the mode of the pin the leds are connected to, they are both off at the start
  digitalWrite(ledPin1, LOW); 

  pinMode(ledPin2, OUTPUT);
  digitalWrite(ledPin2, LOW);
  dht.begin(); // initlizing the sensor
}

void loop() {                            // we are using humidity as a proxy for gas due to there being no gas sensor
  float humidity = dht.readHumidity(); // inputing the values for humidity and storing it as a float
  float temperature = dht.readTemperature(); //inputing value for temp and storing it as a float


  if (isnan(humidity) || isnan(temperature)) { //checking if humidity or temperature are not a number 
    Serial.println("There was an error in reading the data"); // if they are Nan it prints out there was an error
    return;
  }

  if (humidity > 50)  { // an if statement to check if humidity is above desired level
    Serial.println("The gas concentration is dangerously high!");
    lcd.clear(); //clear the lcd
    lcd.setCursor(0, 0); //sets cursor of lcd to correct level
    lcd.print("DANGEROUS GAS LEVEL!"); // displays warning 
    lcd.setCursor(0, 2); // sets cursor of lcd to lower level
    lcd.print("      "); 
    lcd.print(humidity); // displayes gas level on lcd
    lcd.print("%");
    digitalWrite(ledPin1, HIGH); // turns red LED on
    digitalWrite(ledPin2, LOW); // tunrs green LED off
  } 
  else {                                                // else the gas levels are within the safe level
    Serial.println("Gas concentration is within safe levels."); //prints to console that levels are safe
    digitalWrite(ledPin1, LOW); // turns off red led
    digitalWrite(ledPin2, HIGH); // turns on green led
    lcd.clear();   // clears the lcd screen
    lcd.setCursor(0, 0); // sets the cursor of lcd to the correct level
    lcd.print("Gas: "); 
    lcd.print(humidity); // displays the gas level on lcd 
    lcd.print("%");
    lcd.setCursor(0, 2); // sets the cursor to lower level
    lcd.print("Temp: ");
    lcd.print(temperature); // displays the temperature on lcd
    lcd.print("C");
  }

  Serial.print("Gas concentration:");
  Serial.print(humidity); // prints out the gas level on console
  Serial.print("% ");
  Serial.print("Temperature: "); 
  Serial.print(temperature); // prints out the temperature to the console
  Serial.println("°C");

  delay(1000); // adds a delay to the loop to make it easier to read outputted values
}