#include <WiFi.h>
#include <PubSubClient.h>
#include <DHT.h>

// ===============================
// Hardware Pin Configurations
// ===============================
#define DHTPIN 15
#define DHTTYPE DHT22
#define SOIL_PIN 34
#define RELAY_PIN 2

// ===============================
// Wi-Fi Credentials
// ===============================
const char* WIFI_SSID = "Wokwi-GUEST";
const char* WIFI_PASSWORD = "";

// ===============================
// MQTT Configuration
// ===============================
const char* MQTT_BROKER = "broker.hivemq.com";
const int MQTT_PORT = 1883;

// MQTT Topics
const char* TOPIC_TELEMETRY = "farm/telemetry";
const char* TOPIC_COMMAND   = "farm/irrigation/cmd";

// ===============================
// Global Objects
// ===============================
DHT dht(DHTPIN, DHTTYPE);

WiFiClient espClient;
PubSubClient mqttClient(espClient);

// ===============================
// Telemetry Timing
// ===============================
unsigned long lastTelemetryTime = 0;
const unsigned long telemetryInterval = 2000;

// ===============================
// Wi-Fi Connection Setup
// ===============================
void setupWiFi() {
  delay(10);

  Serial.println();
  Serial.print("Connecting to WiFi: ");
  Serial.println(WIFI_SSID);

  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println();
  Serial.println("WiFi Connected Successfully!");
  Serial.print("ESP32 IP Address: ");
  Serial.println(WiFi.localIP());
}

// ===============================
// MQTT Callback Function
// ===============================
void mqttCallback(char* topic, byte* payload, unsigned int length) {

  Serial.print("Message received on topic: ");
  Serial.println(topic);

  String commandMessage = "";

  for (unsigned int i = 0; i < length; i++) {
    commandMessage += (char)payload[i];
  }

  Serial.print("Command: ");
  Serial.println(commandMessage);

  // Pump Control Logic
  if (String(topic) == TOPIC_COMMAND) {

    if (commandMessage == "ON") {
      digitalWrite(RELAY_PIN, HIGH);
      Serial.println("Pump Activated");
    }

    else if (commandMessage == "OFF") {
      digitalWrite(RELAY_PIN, LOW);
      Serial.println("Pump Deactivated");
    }
  }
}

// ===============================
// MQTT Reconnection
// ===============================
void reconnectBroker() {

  while (!mqttClient.connected()) {

    Serial.print("Connecting to MQTT Broker...");

    String clientId = "ESP32-SmartFarm-";
    clientId += String(random(0xffff), HEX);

    if (mqttClient.connect(clientId.c_str())) {

      Serial.println("Connected!");

      mqttClient.subscribe(TOPIC_COMMAND);

      Serial.print("Subscribed to: ");
      Serial.println(TOPIC_COMMAND);

    } else {

      Serial.print("Failed. Error Code: ");
      Serial.print(mqttClient.state());

      Serial.println(" Retry in 5 seconds...");
      delay(5000);
    }
  }
}

// ===============================
// Setup Function
// ===============================
void setup() {

  Serial.begin(115200);

  pinMode(RELAY_PIN, OUTPUT);

  // Pump OFF initially
  digitalWrite(RELAY_PIN, LOW);

  dht.begin();

  setupWiFi();

  mqttClient.setServer(MQTT_BROKER, MQTT_PORT);

  mqttClient.setCallback(mqttCallback);
}

// ===============================
// Main Loop
// ===============================
void loop() {

  // Ensure MQTT Connection
  if (!mqttClient.connected()) {
    reconnectBroker();
  }

  mqttClient.loop();

  unsigned long currentTime = millis();

  if (currentTime - lastTelemetryTime >= telemetryInterval) {

    lastTelemetryTime = currentTime;

    // ===========================
    // Sensor Readings
    // ===========================
    float temperature = dht.readTemperature();

    float humidity = dht.readHumidity();

    int rawSoilValue = analogRead(SOIL_PIN);

    // Convert to percentage
    float soilMoisture =
      (4095 - rawSoilValue) * 100.0 / 4095.0;

    // ===========================
    // Sensor Validation
    // ===========================
    if (isnan(temperature) || isnan(humidity)) {

      Serial.println("Sensor Reading Failed!");

      return;
    }

    // ===========================
    // Current Pump State
    // ===========================
    int pumpState = digitalRead(RELAY_PIN);

    // ===========================
    // Create JSON Payload
    // ===========================
    String payload = "{";

    payload += "\"temperature\":";
    payload += String(temperature, 2);
    payload += ",";

    payload += "\"humidity\":";
    payload += String(humidity, 2);
    payload += ",";

    payload += "\"soilMoisture\":";
    payload += String(soilMoisture, 2);
    payload += ",";

    payload += "\"pumpState\":";
    payload += String(pumpState);

    payload += "}";

    // ===========================
    // Publish MQTT Message
    // ===========================
    char messageBuffer[256];

    payload.toCharArray(messageBuffer, 256);

    if (mqttClient.publish(TOPIC_TELEMETRY, messageBuffer)) {

      Serial.println("Telemetry Published:");

      Serial.println(messageBuffer);

    } else {

      Serial.println("Failed to Publish MQTT Message");
    }

    // ===========================
    // Serial Monitor Output
    // ===========================
    Serial.println("===============");
    Serial.print("Temperature: ");
    Serial.print(temperature);
    Serial.println(" °C");

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

    Serial.print("Soil Moisture: ");
    Serial.print(soilMoisture);
    Serial.println(" %");

    Serial.print("Pump State: ");

    if (pumpState == 1) {
      Serial.println("ON");
    } else {
      Serial.println("OFF");
    }

    Serial.println("===============");
  }
}