#include <WiFi.h>
#include <PubSubClient.h>
#include <PID_v1.h>
#include <DHT.h>

// --- Ubidots & Network Settings ---
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// Ubidots MQTT Configuration
const char* mqtt_server = "industrial.api.ubidots.com"; 
#define UBIDOTS_TOKEN "BBFF-3sCuW2gt5Ghq17c50h4Mqsgp8L4OPI"  // Put your BBFF-xxx token here
//#define DEVICE_LABEL  "private"            // The Device Label in Ubidots
#define VAR_SETPOINT  "target-temp"   // The Variable Label for your slider

// --- Hardware Settings ---
#define DHTPIN 4         // Connect DHT11 Data pin to GPIO 4
#define DHTTYPE DHT22
#define FAN_PIN 16       // Connect MOSFET Gate to GPIO 16

// --- Objects ---
WiFiClient espClient;
PubSubClient client(espClient);
DHT dht(DHTPIN, DHTTYPE);

// --- PID Variables ---
double Setpoint, Input, Output;
// PID Tuning (Aggressive P for fan, Slow I for steady state)
double Kp = 20.0, Ki = 5.0, Kd = 1.0;

// REVERSE mode: Fan speeds UP when Temp goes UP
PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, REVERSE);

// --- Timing Variables ---
unsigned long lastPIDTime = 0;
const long pidInterval = 2000; // 2 seconds (matches DHT11 speed)

unsigned long lastReconnectAttempt = 0;
const long reconnectInterval = 5000; // Try to reconnect every 5 seconds

/* ================= Subscribe Topics ================= */
const char* SUB_TOPIC1 = "/v1.6/devices/private/target-temp/lv";

// --- MQTT Callback (Received Message Handler) ---
// This runs when Ubidots sends a new value for the "target-temp"
void callback(char* topic, byte* payload, unsigned int length) {
  // 1. Create a buffer for the message
  char message[length + 1];
  for (int i = 0; i < length; i++) {
    message[i] = (char)payload[i];
  }
  message[length] = '\0'; // Null-terminate string

  // 2. Check which topic triggered the callback
  // Topic format: /v1.6/devices/{device_label}/{variable_label}/lv
  String topicStr = String(topic);
  
  if (topicStr.indexOf(VAR_SETPOINT) > 0) {
    Setpoint = atof(message); // Convert string to float
    Serial.print("Updated Setpoint from Ubidots: ");
    Serial.println(Setpoint);
  }
}

boolean attemptReconnect() {
    Serial.println("Connecting to Ubidots MQTT...");
    if (client.connect("ESP32_Client", UBIDOTS_TOKEN, "")) {
      Serial.println("Connected to Ubidots");
      client.subscribe(SUB_TOPIC1, 1);
      return true;
    } else {
      Serial.print("Failed, rc=");
      Serial.print(client.state());
      return false;
    }
}

void setup() {
  Serial.begin(115200);
  dht.begin();
  
  // Setup WiFi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWiFi connected");

  // Setup MQTT
  client.setBufferSize(512);
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);

  // Setup PID
  Setpoint = 25.0; // Default target
  myPID.SetMode(AUTOMATIC);
  myPID.SetSampleTime(pidInterval); 
  myPID.SetOutputLimits(0, 255); // Standard PWM limits
}

void loop() {

  // 1. Run Control Loop (Non-blocking Timer)
  unsigned long now = millis();
  if (now - lastPIDTime >= pidInterval) {
    lastPIDTime = now;

    // A. Read Sensor
    float t = dht.readTemperature();
    if (isnan(t)) {
      Serial.println("DHT Read Failed!");
      return; 
    }

    // B. Compute PID
    Input = t;
    myPID.Compute();

    // C. Control Fan
    // Note: analogWrite works on ESP32 Core 3.0+. Use ledcWrite for older versions.
    analogWrite(FAN_PIN, (int)Output); 

    // D. Publish Status to Ubidots
    // Ubidots expects JSON: {"variable": value, "variable2": value}
    // Topic: /v1.6/devices/{device_label}
    
      String topic = String("/v1.6/devices/private");
    
    // Format JSON string
    String payload = String("{\"temperature\":") + t + "," + String("\"fan-speed\":") + Output + "," + String("\"current-setpoint\":") + Setpoint + "}";
    
    client.publish(topic.c_str(), payload.c_str());
    Serial.println("Published: " + payload);

  }

  // A. Check WiFi
  if (WiFi.status() != WL_CONNECTED) {
     // You could add logic here to blink an LED indicating "No WiFi"
     // But we do NOTHING blocking here.
  }
  // B. Check MQTT
  else {
    if (!client.connected()) {
      // Only try to reconnect once every 5 seconds
      if (now - lastReconnectAttempt > reconnectInterval) {
        lastReconnectAttempt = now;
        // Attempt to connect. If it fails, we just continue looping PID.
        if (attemptReconnect()){
          lastReconnectAttempt = 0; // Reset timer on success
        }
      }
    } else {
      // C. Maintain Connection
      client.loop();
    }
  }
}