#include <Wire.h>                   // I2C communication library
#include <LiquidCrystal_I2C.h>      // I2C LCD library
#include <DHT.h>                    // DHT temperature/humidity sensor library
#include <ESP32Servo.h>             // Servo control for ESP32
#include <ESP32PWM.h>               // PWM allocation for ESP32 servos
#include <WiFi.h>                   // Wi-Fi connectivity
#include <PubSubClient.h>           // MQTT client library

// Wi-Fi & MQTT Configuration 

// Wi-Fi network name and password (Wokwi-GUEST is open)
const char* ssid        = "Wokwi-GUEST";
const char* password    = "";

// Public HiveMQ broker (no authentication)
const char* mqtt_server = "broker.hivemq.com";

WiFiClient    espClient;           // TCP client for MQTT
PubSubClient  client(espClient);   // MQTT client instance

//  Hardware Pin Definitions 

// I²C LCD at address 0x27, 16 cols × 2 rows
LiquidCrystal_I2C lcd(0x27, 16, 2);

// DHT22 temp/humidity sensor on GPIO 15
#define DHTPIN    15
#define DHTTYPE   DHT22
DHT dht(DHTPIN, DHTTYPE);

// Ultrasonic HC-SR04 for trash bin (Bin A)
const int trigPin    = 27;  // Trigger pin
const int echoPin    = 26;  // Echo pin

// Compost bin sensors & actuator (Bin B)
const int moistPin   = 34;  // Soil-moisture potentiometer wiper
const int gasPin     = 35;  // MQ-2 gas sensor analog output
const int servoPin   = 25;  // Servo control pin
const int buzzerPin  = 2;   // Piezo buzzer pin

Servo    aerator;            // Servo object for mixing

// RGB LED for trash status indication (common cathode)
const int redPin     = 14;
const int greenPin   = 12;
const int bluePin    = 13;   // blue channel unused (optional)

// Thresholds & State Tracking 

const int   DIST_FULL       = 10;    // cm threshold for “bin full”
const int   MOIST_LOW       = 300;   // analog < MOIST_LOW → too dry
const int   GAS_HIGH        = 1000;  // analog > GAS_HIGH → gas alert
const float TEMP_LOW        = 10.0;  // °C lower bound
const float TEMP_HIGH       = 50.0;  // °C upper bound

int okCycles            = 0;   // consecutive “healthy” compost loops
const int READY_THRESHOLD = 5; // loops of OK before “READY” state

// setup(): Runs once at boot
void setup() {
  Serial.begin(115200);            // initialize serial monitor

  //  Initialize Wi-Fi 
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");             // waiting indicator
  }
  Serial.println("\nWiFi connected");

  //  Initialize MQTT broker connection
  client.setServer(mqtt_server, 1883);

  //  Initialize LCD 
  lcd.init();                      // turn on LCD
  lcd.backlight();                 // enable backlight

  //  Initialize DHT22 sensor 
  dht.begin();

  //  Prepare servo PWM timers (ESP32-specific) 
  ESP32PWM::allocateTimer(0);
  ESP32PWM::allocateTimer(1);
  ESP32PWM::allocateTimer(2);
  ESP32PWM::allocateTimer(3);
  aerator.attach(servoPin);        // attach servo to pin

  //  Configure GPIO modes 
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
}

// loop(): Runs repeatedly 
void loop() {
  // Ensure MQTT connection 
  if (!client.connected()) {
    while (!client.connected()) {
      Serial.print("Attempting MQTT connection...");
      if (client.connect("ESP32Client")) {
        Serial.println("connected");
      } else {
        Serial.print("failed, rc=");
        Serial.print(client.state());
        delay(2000);
      }
    }
  }
  client.loop();  // keep MQTT alive

  // Bin A: Ultrasonic distance measurement 
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  long duration = pulseIn(echoPin, HIGH);
  float distance = duration * 0.034 / 2.0;  // convert to cm
  bool binFull = (distance < DIST_FULL);    // fullness flag

  //  Bin B: Read compost sensors ---
  float temp     = dht.readTemperature();         // °C
  int   moisture = analogRead(moistPin);          // 0–4095
  int   gas      = analogRead(gasPin);            // 0–4095

  // Debug print for gas
  Serial.print("Gas Value: ");
  Serial.println(gas);

  //  Determine compost status flags 
  bool tooDry   = (moisture < MOIST_LOW);
  bool gasAlert = (gas > GAS_HIGH);
  bool tooHot   = (temp > TEMP_HIGH);
  bool tooCold  = (temp < TEMP_LOW);

  //  Update LCD display 
  lcd.clear();

  // Line 1: Trash bin status
  lcd.setCursor(0, 0);
  if (binFull) {
    lcd.print("TRASH: FULL");
    setLED(255, 0, 0);     // red LED
  } else {
    lcd.print("TRASH: OK  ");
    setLED(0, 255, 0);     // green LED
  }

  // Line 2: Compost bin status with “ready” logic
  lcd.setCursor(0, 1);
  if (tooDry || gasAlert || tooHot || tooCold) {
    // Any bad condition → mix required
    lcd.print("COMP: MIX  ");
    aerator.write(90);     // rotate servo
    tone(buzzerPin, 1000); // beep
    delay(1000);
    aerator.write(0);
    noTone(buzzerPin);

    okCycles = 0;          // reset ready counter
  } else {
    // All good → increment healthy cycle count
    okCycles++;
    if (okCycles >= READY_THRESHOLD) {
      lcd.print("COMP: READY");  // compost fully matured
    } else {
      lcd.print("COMP: OK   ");  // compost healthy but not ready
    }
  }

  //  Serial JSON logging for debug or MQTT 
  Serial.printf(
    "{\"trash_cm\":%.1f,\"temp\":%.1f,\"moisture\":%d,\"gas\":%d,"
    "\"binFull\":%d,\"okCycles\":%d}\n",
    distance, temp, moisture, gas, binFull, okCycles
  );

  // Publish to MQTT topic 
  String payload = String("{\"trash_cm\":") + distance +
                   ",\"temp\":" + temp +
                   ",\"moisture\":" + moisture +
                   ",\"gas\":" + gas +
                   ",\"compost_status\":\"" +
                     (tooDry||gasAlert||tooHot||tooCold ? "MIX"
                      : (okCycles>=READY_THRESHOLD ? "READY" : "OK")) +
                   "\",\"trash_full\":" + binFull + "}";
  client.publish("smartbin/status", payload.c_str());

  delay(3000);  // wait 3 seconds before next loop
}

//  setLED(): Control RGB LED 
void setLED(int r, int g, int b) {
  analogWrite(redPin,   r);  // red intensity
  analogWrite(greenPin, g);  // green intensity
  analogWrite(bluePin,  b);  // blue intensity (unused)
}