#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <DHT.h>
#include <ESP32Servo.h>

// ================= PIN CONNECTIONS =================

// Ultrasonic sensor
#define TRIG_PIN 5
#define ECHO_PIN 18

// MQ-2 gas sensor
#define MQ2_PIN 34

// DHT22
#define DHT_PIN 4
#define DHT_TYPE DHT22

// OLED SSD1306
#define OLED_SDA 21
#define OLED_SCL 22
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1

// Relay
#define RELAY_PIN 23

// Generator electricity LED
#define LED_PIN 25

// Buzzer
#define BUZZER_PIN 26

// Servo
#define SERVO_PIN 27

// ================= OBJECTS =================

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

DHT dht(DHT_PIN, DHT_TYPE);

Servo wasteServo;

// ================= SETTINGS =================

// Change these if required
#define WASTE_FULL_DISTANCE 10
#define GAS_THRESHOLD 1800

// Relay in Wokwi is normally active LOW
#define RELAY_ON LOW
#define RELAY_OFF HIGH

// ================= SETUP =================

void setup() {

  Serial.begin(115200);

  // Pins
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  pinMode(MQ2_PIN, INPUT);

  pinMode(RELAY_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  // Start outputs OFF
  digitalWrite(RELAY_PIN, RELAY_OFF);
  digitalWrite(LED_PIN, LOW);
  digitalWrite(BUZZER_PIN, LOW);

  // Servo
  wasteServo.attach(SERVO_PIN);
  wasteServo.write(0);

  // DHT
  dht.begin();

  // OLED
  Wire.begin(OLED_SDA, OLED_SCL);

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {

    Serial.println("OLED not found!");

    while (true) {
      delay(100);
    }
  }

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

  display.setTextSize(2);
  display.setCursor(10, 5);
  display.println("WASTE");

  display.setCursor(10, 30);
  display.println("ENERGY");

  display.display();

  delay(2000);
}

// ================= ULTRASONIC =================

float getDistance() {

  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);

  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 30000);

  if (duration == 0) {
    return 400;
  }

  float distance = duration * 0.0343 / 2.0;

  return distance;
}

// ================= OLED DISPLAY =================

void showDisplay(float distance, int wastePercent,
                 int gasValue, float temperature,
                 float humidity, bool generatorON) {

  display.clearDisplay();

  display.setTextSize(1);

  display.setCursor(0, 0);
  display.println("WASTE TO ENERGY");

  display.setCursor(0, 12);
  display.print("Waste : ");
  display.print(wastePercent);
  display.println("%");

  display.setCursor(0, 22);
  display.print("Gas   : ");
  display.println(gasValue);

  display.setCursor(0, 32);
  display.print("Temp  : ");
  display.print(temperature, 1);
  display.println(" C");

  display.setCursor(0, 42);
  display.print("Humid : ");
  display.print(humidity, 0);
  display.println("%");

  display.setCursor(0, 53);
  display.print("GEN: ");

  if (generatorON) {
    display.print("ON  ");
    display.print("45W");
  } else {
    display.print("OFF");
  }

  display.display();
}

// ================= LOOP =================

void loop() {

  // Read sensors
  float distance = getDistance();

  int gasValue = analogRead(MQ2_PIN);

  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();

  // If DHT reading fails
  if (isnan(temperature)) {
    temperature = 0;
  }

  if (isnan(humidity)) {
    humidity = 0;
  }

  // ================= WASTE LEVEL =================

  // Assume bin depth = 40 cm
  int wastePercent = map((int)distance, 40, 5, 0, 100);

  wastePercent = constrain(wastePercent, 0, 100);

  // ================= GAS / GENERATOR =================

  bool generatorON = false;

  if (gasValue >= GAS_THRESHOLD) {

    generatorON = true;

    // Generator ON
    digitalWrite(RELAY_PIN, RELAY_ON);

    // Electricity indicator ON
    digitalWrite(LED_PIN, HIGH);

  } else {

    generatorON = false;

    // Generator OFF
    digitalWrite(RELAY_PIN, RELAY_OFF);

    // Electricity indicator OFF
    digitalWrite(LED_PIN, LOW);
  }

  // ================= WASTE FULL ALERT =================

  if (wastePercent >= 90) {

    digitalWrite(BUZZER_PIN, HIGH);

    // Open waste-bin door
    wasteServo.write(90);

  } else {

    digitalWrite(BUZZER_PIN, LOW);

    // Close waste-bin door
    wasteServo.write(0);
  }

  // ================= OLED =================

  showDisplay(
    distance,
    wastePercent,
    gasValue,
    temperature,
    humidity,
    generatorON
  );

  // ================= SERIAL MONITOR =================

  Serial.println("--------------------------------");

  Serial.print("Waste Level : ");
  Serial.print(wastePercent);
  Serial.println("%");

  Serial.print("Distance    : ");
  Serial.print(distance);
  Serial.println(" cm");

  Serial.print("Gas Level   : ");
  Serial.println(gasValue);

  Serial.print("Temperature : ");
  Serial.print(temperature);
  Serial.println(" C");

  Serial.print("Humidity    : ");
  Serial.print(humidity);
  Serial.println("%");

  Serial.print("Generator   : ");

  if (generatorON) {
    Serial.println("ON - 45W");
  } else {
    Serial.println("OFF");
  }

  Serial.println("--------------------------------");

  delay(1000);
}