#include <WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <DHT.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <Adafruit_BMP085.h>

#define DHTPIN         4       // Digital GPIO4 (DHT22)
#define DHTTYPE        DHT22
#define ONE_WIRE_BUS   18      // DS18B20 Soil Temperature
#define SOIL_MOIST_PIN 35      // Potentiometer simulating Soil Moisture
#define MQ2_PIN        34      // MQ-2 Gas Sensor Analog Pin
#define RELAY_PUMP_PIN 26      // Water Pump Relay Output

// Calibration values for Soil Moisture mapping
#define DRY_SOIL_RAW   3200
#define WET_SOIL_RAW   1400

// Wi-Fi & MQTT Credentials
const char* ssid = "Wokwi-GUEST";
const char* password = "";
const char* mqtt_server = "broker.hivemq.com";
const int mqtt_port = 1883;

// MQTT Topics
const char* topic_telemetry = "wokwi/agri/telemetry";
const char* topic_control   = "wokwi/agri/control";

DHT dht(DHTPIN, DHTTYPE);
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature ds18b20(&oneWire);
Adafruit_BMP085 bmp;
LiquidCrystal_I2C lcd(0x27, 20, 4);

WiFiClient espClient;
PubSubClient client(espClient);

// Global State Variables
bool manualPumpOverride = false;
bool pumpState = false;
float airTemp = 0.0, airHum = 0.0, soilTemp = 0.0, pressure = 0.0;
int soilMoist = 0, gasRaw = 0;

unsigned long lastSensorReadTime = 0;
unsigned long lastFastSensorReadTime = 0;
unsigned long lastLCDUpdateTime = 0;

const unsigned long SENSOR_INTERVAL      = 1000; // Read environment sensors (DHT22/BMP) every 1s
const unsigned long FAST_SENSOR_INTERVAL = 50;   // Read Potentiometer & Gas ADC every 50ms for instant response
const unsigned long LCD_INTERVAL         = 100;  // Refresh LCD 10 times per second (100ms) for real-time display

void updateLCD(); // Forward declaration for instant trigger

void mqttCallback(char* topic, byte* payload, unsigned int length) {
  String message = "";
  for (unsigned int i = 0; i < length; i++) {
    message += (char)payload[i];
  }
  
  Serial.print("MQTT Received [");
  Serial.print(topic);
  Serial.print("]: ");
  Serial.println(message);

  if (message == "PUMP_ON") {
    manualPumpOverride = true;
    pumpState = true;
    digitalWrite(RELAY_PUMP_PIN, HIGH);
    Serial.println("Pump manually forced ON");
  } else if (message == "PUMP_OFF") {
    manualPumpOverride = true;
    pumpState = false;
    digitalWrite(RELAY_PUMP_PIN, LOW);
    Serial.println("Pump manually forced OFF");
  } else if (message == "PUMP_AUTO") {
    manualPumpOverride = false;
    Serial.println("Pump returned to AUTO Mode");
  }

  // INSTANT LCD UPDATE on MQTT command reception (0ms delay)
  updateLCD();
}

void reconnectMQTT() {
  while (!client.connected()) {
    Serial.print("Connecting to HiveMQ Broker...");
    String clientId = "ESP32AgriHub-" + String(random(0, 0xffff), HEX);
    if (client.connect(clientId.c_str())) {
      Serial.println(" Connected!");
      client.subscribe(topic_control);
      client.publish(topic_telemetry, "{\"status\":\"ONLINE\"}");
    } else {
      Serial.print(" Failed (rc=");
      Serial.print(client.state());
      Serial.println("). Retrying in 2 seconds...");
      vTaskDelay(2000 / portTICK_PERIOD_MS);
    }
  }
}

// Ultra-fast reading for interactive analog sensors (potentiometer & gas)
void readFastSensors() {
  // Read Soil Moisture
  int rawSoil = analogRead(SOIL_MOIST_PIN);
  soilMoist = map(rawSoil, DRY_SOIL_RAW, WET_SOIL_RAW, 0, 100);
  soilMoist = constrain(soilMoist, 0, 100);

  // Read MQ-2 Gas
  gasRaw = analogRead(MQ2_PIN);

  // Auto Irrigation Logic
  if (!manualPumpOverride) {
    if (soilMoist < 30) {
      digitalWrite(RELAY_PUMP_PIN, HIGH);
      pumpState = true;
    } else {
      digitalWrite(RELAY_PUMP_PIN, LOW);
      pumpState = false;
    }
  }
}

// Periodic reading for environment sensors & MQTT publishing
void readSlowSensors() {
  // Read DHT22
  float t = dht.readTemperature();
  float h = dht.readHumidity();
  if (!isnan(t)) airTemp = t;
  if (!isnan(h)) airHum = h;

  // Read DS18B20 Soil Temp (Non-blocking)
  soilTemp = ds18b20.getTempCByIndex(0);
  ds18b20.requestTemperatures(); // Trigger next conversion asynchronously

  // Read Barometric Pressure
  pressure = bmp.readPressure() / 100.0F; // Pa to hPa

  // Publish JSON Payload to MQTT
  String payload = "{";
  payload += "\"airTemp\":" + String(airTemp, 1) + ",";
  payload += "\"airHum\":" + String(airHum, 1) + ",";
  payload += "\"soilTemp\":" + String(soilTemp, 1) + ",";
  payload += "\"soilMoist\":" + String(soilMoist) + ",";
  payload += "\"pressure\":" + String(pressure, 1) + ",";
  payload += "\"gasRaw\":" + String(gasRaw) + ",";
  payload += "\"pump\":" + String(pumpState ? "true" : "false") + ",";
  payload += "\"mode\":\"" + String(manualPumpOverride ? "MANUAL" : "AUTO") + "\"";
  payload += "}";

  client.publish(topic_telemetry, payload.c_str());
}

void updateLCD() {
  lcd.setCursor(0, 0);
  lcd.print("Air: ");
  lcd.print(airTemp, 1);
  lcd.print((char)223);
  lcd.print("C  Hum:");
  lcd.print((int)airHum);
  lcd.print("%  ");

  lcd.setCursor(0, 1);
  lcd.print("Soil:");
  lcd.print(soilTemp, 1);
  lcd.print((char)223);
  lcd.print("C Moist:");
  lcd.print(soilMoist);
  lcd.print("%   ");

  lcd.setCursor(0, 2);
  lcd.print("Pres:");
  lcd.print((int)pressure);
  lcd.print("hPa Gas:");
  lcd.print(gasRaw);
  lcd.print("    ");

  lcd.setCursor(0, 3);
  lcd.print("Pump:");
  lcd.print(pumpState ? "ON " : "OFF");
  lcd.print(" Mode:");
  lcd.print(manualPumpOverride ? "MANUAL " : "AUTO   ");
}

void setup() {
  Serial.begin(115200);

  pinMode(RELAY_PUMP_PIN, OUTPUT);
  digitalWrite(RELAY_PUMP_PIN, LOW);

  // Initialize LCD
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("AGRI TECH HUB V2.0");
  lcd.setCursor(0, 1);
  lcd.print("Connecting WiFi...");

  // Initialize Sensors
  dht.begin();
  ds18b20.begin();
  
  // CRITICAL FIX: Disable blocking delay on DS18B20 reads!
  ds18b20.setWaitForConversion(false); 
  ds18b20.requestTemperatures(); // Start initial conversion

  if (!bmp.begin()) {
    Serial.println("BMP180 Sensor Error!");
  }

  // Connect Wi-Fi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    vTaskDelay(250 / portTICK_PERIOD_MS);
    Serial.print(".");
  }
  Serial.println("\nWiFi Connected!");

  lcd.setCursor(0, 2);
  lcd.print("WiFi Connected!");
  lcd.setCursor(0, 3);
  lcd.print("Connecting MQTT...");

  client.setServer(mqtt_server, mqtt_port);
  client.setCallback(mqttCallback);

  reconnectMQTT();
  lcd.clear();
}

void loop() {
  if (!client.connected()) {
    reconnectMQTT();
  }
  client.loop();

  unsigned long currentMillis = millis();

  // 1. Instant 50ms read for potentiometer & gas slider interactions
  if (currentMillis - lastFastSensorReadTime >= FAST_SENSOR_INTERVAL) {
    lastFastSensorReadTime = currentMillis;
    readFastSensors();
  }

  // 2. 1000ms read for environment sensors & MQTT publishing
  if (currentMillis - lastSensorReadTime >= SENSOR_INTERVAL) {
    lastSensorReadTime = currentMillis;
    readSlowSensors();
  }

  // 3. Super-fast 100ms LCD refresh rate (10 FPS)
  if (currentMillis - lastLCDUpdateTime >= LCD_INTERVAL) {
    lastLCDUpdateTime = currentMillis;
    updateLCD();
  }

  // Yield time back to Wokwi WebAssembly Engine
  vTaskDelay(5 / portTICK_PERIOD_MS);
}