#include <Arduino.h>
#include "DHT.h"
#include <WiFi.h>
#include <PubSubClient.h>
#include <esp_task_wdt.h>  // Watchdog timer

// ── WiFi Credentials ───────────────────────────────────────────
#define WIFI_SSID       "Wokwi-GUEST"         // WiFi network name
#define WIFI_PASSWORD   ""                     // WiFi password (empty for Wokwi)

// ── Mosquitto MQTT Broker Config ───────────────────────────────
#define MQTT_BROKER     "test.mosquitto.org"   // Public Mosquitto test broker
#define MQTT_PORT       1883                   // Default MQTT port

// ── MQTT Topics ────────────────────────────────────────────────
#define TOPIC_TEMP        "home/sensor/temperature"  // Topic for temperature
#define TOPIC_HUMIDITY    "home/sensor/humidity"     // Topic for humidity
#define TOPIC_HUMIDIFIER  "home/sensor/humidifier"   // Topic for humidifier state

// ── Pin Definitions ────────────────────────────────────────────
#define DHTPIN         4      // GPIO pin connected to DHT22 data line
#define DHTTYPE        DHT22  // Sensor type: DHT22
#define HUMIDIFIER_PIN 21     // GPIO pin connected to humidifier relay

// ── Timing & Thresholds ────────────────────────────────────────
#define BAUD_RATE          115200  // Serial Monitor baud rate
#define READ_INTERVAL      2000    // Delay between sensor readings (ms)
#define HUMIDITY_LOW       70.0    // Humidity % below which humidifier may trigger
#define HUMIDITY_HIGH      90.0    // Humidity % at which humidifier turns off
#define TRIGGER_DELAY      10000   // Humidity must stay below 70% for 10s to trigger
#define RECONNECT_COOLDOWN 5000    // Min time between WiFi/MQTT reconnect attempts (ms)
#define WIFI_TIMEOUT       15000   // Max time to wait for WiFi at startup (ms)
#define MQTT_TIMEOUT       15000   // Max time to wait for MQTT at startup (ms)

DHT dht(DHTPIN, DHTTYPE);      // DHT22 sensor object
WiFiClient espClient;           // WiFi client for MQTT
PubSubClient mqtt(espClient);   // MQTT client using WiFi

// ── State Variables ────────────────────────────────────────────
bool humidifierOn = false;               // Tracks humidifier state (always FALSE on boot)
unsigned long lowHumidityStartTime = 0;  // Timestamp when humidity first dropped below 70%
bool lowHumidityTimerActive = false;     // Tracks if 10s countdown is active
unsigned long lastReadTime = 0;          // Timestamp of last sensor read
unsigned long lastReconnectAttempt = 0;  // Timestamp of last WiFi/MQTT reconnect attempt

// ── Generate Unique MQTT Client ID from MAC Address ────────────
String getMQTTClientId() {
  // Uses ESP32's unique MAC address to avoid client ID conflicts on broker
  return "ESP32_Humidifier_" + String((uint32_t)ESP.getEfuseMac(), HEX);
}

// ── Non-blocking WiFi + MQTT Reconnection with Cooldown ────────
void maintainConnections() {
  // Respect cooldown — don't spam reconnect attempts
  if (millis() - lastReconnectAttempt < RECONNECT_COOLDOWN) return;
  lastReconnectAttempt = millis();

  // If WiFi dropped or never connected, attempt reconnect without blocking
  if (WiFi.status() != WL_CONNECTED) {
    Serial.println("WiFi not connected — attempting reconnect...");
    WiFi.disconnect();
    WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
    // Returns immediately — humidifier logic continues uninterrupted
    return;
  }

  // If MQTT dropped (but WiFi is fine), attempt single reconnect without blocking
  if (!mqtt.connected()) {
    Serial.print("MQTT not connected — attempting reconnect...");
    String clientId = getMQTTClientId();
    if (mqtt.connect(clientId.c_str())) {
      Serial.println(" Reconnected!");
    } else {
      Serial.print(" Failed. RC=");
      Serial.println(mqtt.state());
      // Returns immediately — will retry after cooldown
    }
  }
}

// ── Publish All Sensor Data to MQTT ────────────────────────────
void publishData(float tempC, float humidity, bool humidifierState) {
  char buffer[16]; // Buffer to hold converted values as strings

  // Publish temperature
  snprintf(buffer, sizeof(buffer), "%.2f", tempC);
  mqtt.publish(TOPIC_TEMP, buffer);

  // Publish humidity
  snprintf(buffer, sizeof(buffer), "%.2f", humidity);
  mqtt.publish(TOPIC_HUMIDITY, buffer);

  // Publish humidifier state as "ON" or "OFF"
  mqtt.publish(TOPIC_HUMIDIFIER, humidifierState ? "ON" : "OFF");

  Serial.println(">> Data published to MQTT");
}

// ── Humidifier Control Logic (always runs, network-independent) ─
void controlHumidifier(float humidity) {

  if (!humidifierOn) {
    // Humidifier OFF — watch for humidity dropping below 70%
    if (humidity < HUMIDITY_LOW) {
      if (!lowHumidityTimerActive) {
        // Humidity just dropped below 70% — start 10s countdown
        lowHumidityStartTime = millis();
        lowHumidityTimerActive = true;
        Serial.println(">> Humidity below 70% — starting 10s timer...");
      } else {
        // Timer already running — check if 10 seconds have passed
        unsigned long elapsed = millis() - lowHumidityStartTime;
        if (elapsed >= TRIGGER_DELAY) {
          // 10s confirmed low humidity — turn humidifier ON
          humidifierOn = true;
          digitalWrite(HUMIDIFIER_PIN, HIGH);
          lowHumidityTimerActive = false; // Reset timer flag
          Serial.println(">> 10s elapsed — HUMIDIFIER TURNED ON");
        } else {
          // Still within 10s window — show countdown
          Serial.print(">> Timer running: ");
          Serial.print(elapsed / 1000);
          Serial.println("s / 10s");
        }
      }
    } else {
      // Humidity back above 70% before 10s elapsed — cancel timer
      if (lowHumidityTimerActive) {
        lowHumidityTimerActive = false;
        Serial.println(">> Humidity recovered — 10s timer reset");
      }
    }

  } else {
    // Humidifier ON — turn off only when humidity reaches or exceeds 90%
    if (humidity >= HUMIDITY_HIGH) {
      humidifierOn = false;
      digitalWrite(HUMIDIFIER_PIN, LOW);
      Serial.println(">> Humidity reached 90% — HUMIDIFIER TURNED OFF");
    }
  }
}

void setup() {
  Serial.begin(BAUD_RATE);
  delay(1000);

  // ── Watchdog Timer Setup ──────────────────────────────────────
  // Arduino core already initializes the WDT — just register our task with it
  // Do NOT call esp_task_wdt_init() — that causes "TWDT already initialized" error
  esp_task_wdt_add(NULL);
  Serial.println("Watchdog timer registered");

  // ── Humidifier Pin Setup ──────────────────────────────────────
  // On every boot (including post power-cut), humidifier always starts OFF
  // ESP32 waits for humidity to drop below 70% fresh — no assumed state
  pinMode(HUMIDIFIER_PIN, OUTPUT);
  digitalWrite(HUMIDIFIER_PIN, LOW);
  Serial.println("Humidifier set to OFF on boot — waiting for sensor readings");

  dht.begin(); // Initialize DHT22 sensor

  // ── WiFi Connection with 15s Timeout ─────────────────────────
  // If WiFi fails (wrong password, no signal), setup() moves on after 15s
  // Humidifier will still run — maintainConnections() retries WiFi in background
  Serial.print("Connecting to WiFi: ");
  Serial.println(WIFI_SSID);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

  unsigned long wifiStart = millis();
  while (WiFi.status() != WL_CONNECTED) {
    esp_task_wdt_reset();                    // Keep watchdog happy while waiting
    if (millis() - wifiStart > WIFI_TIMEOUT) {
      Serial.println("\nWiFi timeout — continuing without WiFi.");
      Serial.println("Humidifier will still run. Retrying WiFi in background.");
      break;                                 // Exit — don't block forever
    }
    delay(500);
    Serial.print(".");
  }
  if (WiFi.status() == WL_CONNECTED) {
    Serial.println("\nWiFi Connected! IP: " + WiFi.localIP().toString());
  }

  // ── MQTT Connection with 15s Timeout ─────────────────────────
  // Only attempt if WiFi is connected
  // If MQTT fails or is slow, setup() moves on after 15s
  if (WiFi.status() == WL_CONNECTED) {
    mqtt.setServer(MQTT_BROKER, MQTT_PORT);
    String clientId = getMQTTClientId();
    Serial.print("Connecting to MQTT as: ");
    Serial.println(clientId);

    unsigned long mqttStart = millis();
    while (!mqtt.connected()) {
      esp_task_wdt_reset();                      // Keep watchdog happy while waiting
      if (millis() - mqttStart > MQTT_TIMEOUT) {
        Serial.println("MQTT timeout — continuing without MQTT.");
        Serial.println("Humidifier will still run. Retrying MQTT in background.");
        break;                                   // Exit — don't block forever
      }
      mqtt.connect(clientId.c_str());
      delay(1000);
      Serial.print(".");
    }
    if (mqtt.connected()) Serial.println("\nMQTT Connected!");
  }

  Serial.println("--------------------------------------------------");
  Serial.println("System Ready — DHT22 + Humidifier + MQTT");
  Serial.println("Boot behavior: Humidifier OFF, sensor decides state");
  Serial.println("--------------------------------------------------");
}

void loop() {
  // Reset watchdog — confirms loop is still running healthy
  esp_task_wdt_reset();

  // Keep WiFi and MQTT alive — non-blocking, won't pause humidifier
  maintainConnections();
  if (mqtt.connected()) mqtt.loop();

  // Only read sensor every READ_INTERVAL ms (non-blocking)
  if (millis() - lastReadTime < READ_INTERVAL) return;
  lastReadTime = millis();

  float humidity = dht.readHumidity();    // Read humidity (%)
  float tempC    = dht.readTemperature(); // Read temperature (°C)

  // Check if sensor reading failed
  if (isnan(humidity) || isnan(tempC)) {
    Serial.println("ERROR: Failed to read from DHT22! Check wiring.");
    return;
  }

  // Print sensor data and humidifier state to Serial Monitor
  Serial.print("Temp: ");
  Serial.print(tempC);
  Serial.print(" °C  |  Humidity: ");
  Serial.print(humidity);
  Serial.print(" %  |  Humidifier: ");
  Serial.println(humidifierOn ? "ON" : "OFF");

  // Run humidifier logic (always executes regardless of network state)
  controlHumidifier(humidity);

  // Publish to MQTT only if connected — skips silently if offline
  if (mqtt.connected()) {
    publishData(tempC, humidity, humidifierOn);
  } else {
    Serial.println(">> MQTT offline — skipping publish, humidifier still running");
  }
}