// Smart Onion Storage Controller - ESP32 (Arduino IDE)
// - DHT22 temp/humidity
// - MQ analog gas sensor
// - I2C LCD 16x2
// - 2 relays: fan and mist sprayer
// - SMS alert via SIM800 (Serial1)
// Maintains temperature between 0 - 5 C and humidity 65 - 70% with hysteresis

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include "DHT.h"

// ---------------- USER CONFIG - EDIT IF NEEDED ----------------
#define PHONE_NUMBER "+918302308101"   // SMS alerts go to this number (your requested)
const int GAS_THRESHOLD = 800;        // tune this after measuring baseline (0-4095)
const unsigned long ALERT_COOLDOWN_MS = 10UL * 60UL * 1000UL; // 10 min between SMS alerts
// ---------------- END USER CONFIG --------------------------------

// Pins
#define DHTPIN 4
#define DHTTYPE DHT22
#define MQ_PIN 34          // analog input (ADC)
#define RELAY_FAN 26       // controls fan
#define RELAY_MIST 27      // controls mist sprayer

// GSM Serial (Serial1 on ESP32)
#define GSM_SERIAL Serial1
#define GSM_TX_PIN 17  // ESP32 Tx -> GSM Rx
#define GSM_RX_PIN 16  // ESP32 Rx <- GSM Tx
#define GSM_BAUD 9600

// I2C LCD (common address 0x27). Adjust if your backpack uses 0x3F.
LiquidCrystal_I2C lcd(0x27, 16, 2);
DHT dht(DHTPIN, DHTTYPE);

// Function prototypes (so we can call from setup)
String sendGSMCommand(String cmd, unsigned long timeout = 2000);
void sendAlertSMS(float tempC, float hum, int gasRaw);

// Control setpoints and hysteresis
const float TEMP_TARGET_LOW = 0.0;    // lower bound (°C)
const float TEMP_TARGET_HIGH = 5.0;   // upper bound (°C)
// We'll use hysteresis band of 0.8°C (adjust if necessary)
const float TEMP_HYST = 0.8;

// Humidity target range (65% - 70%)
const float HUM_LOW = 65.0;
const float HUM_HIGH = 70.0;
const float HUM_HYST = 3.0; // hysteresis to prevent frequent toggles

// State variables
bool fanState = false;
bool mistState = false;
bool alertSent = false;
unsigned long lastAlertMs = 0;
unsigned long lastReadMs = 0;
const unsigned long READ_INTERVAL_MS = 3000; // read sensors every 3 seconds

void setup() {
  Serial.begin(115200);
  delay(100);

  // Initialize GSM serial
  GSM_SERIAL.begin(GSM_BAUD, SERIAL_8N1, GSM_RX_PIN, GSM_TX_PIN);

  // Pins for relays
  pinMode(RELAY_FAN, OUTPUT);
  pinMode(RELAY_MIST, OUTPUT);

  // Assuming relay module is active HIGH to turn on. If your module is active LOW invert the logic.
  digitalWrite(RELAY_FAN, LOW);  // OFF
  digitalWrite(RELAY_MIST, LOW); // OFF

  // LCD and sensor init
  lcd.init();
  lcd.backlight();
  dht.begin();

  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Onion Storage");
  lcd.setCursor(0,1);
  lcd.print("Booting...");
  delay(1200);
  lcd.clear();

  // Basic GSM init commands
  sendGSMCommand("AT", 1000);
  delay(200);
  sendGSMCommand("ATE0", 500);      // disable echo
  delay(200);
  sendGSMCommand("AT+CMGF=1", 1000); // SMS text mode
  delay(200);
}

void loop() {
  unsigned long now = millis();
  if (now - lastReadMs >= READ_INTERVAL_MS) {
    lastReadMs = now;
    readSensorsAndControl();
  }
}

// Read sensors, display on LCD, control relays, and handle gas alert
void readSensorsAndControl() {
  // Read DHT
  float hum = dht.readHumidity();
  float tempC = dht.readTemperature();

  // If DHT failed, keep previous or show error
  bool dhtOk = !(isnan(hum) || isnan(tempC));

  // Read gas (MQ) analog value (0 - 4095)
  int gasRaw = analogRead(MQ_PIN);

  // Display on Serial
  if (dhtOk) {
    Serial.printf("Temp: %.2f C, Hum: %.2f %% | GasRaw: %d\n", tempC, hum, gasRaw);
  } else {
    Serial.printf("DHT read failed | GasRaw: %d\n", gasRaw);
  }

  // Update LCD (two lines)
  char line1[17], line2[17];
  if (dhtOk) {
    // Example: "T:  3.2C H:67.4%"
    snprintf(line1, sizeof(line1), "T:%5.1fC H:%4.1f%%", tempC, hum);
  } else {
    snprintf(line1, sizeof(line1), "T: --.-C H: --.-");
  }
  // Gas as raw number and percent (approx)
  float gasPct = (gasRaw / 4095.0) * 100.0;
  snprintf(line2, sizeof(line2), "Gas:%4d %3.0f%%", gasRaw, gasPct);

  lcd.setCursor(0,0);
  lcd.print(line1);
  // clear remainder of line if needed
  for (int i = strlen(line1); i < 16; ++i) lcd.print(' ');
  lcd.setCursor(0,1);
  lcd.print(line2);
  for (int i = strlen(line2); i < 16; ++i) lcd.print(' ');

  // CONTROL LOGIC:
  // Temperature control using hysteresis:
  if (dhtOk) {
    // Fan control (we assume fan reduces temperature / increases ventilation)
    if (!fanState) {
      // currently OFF -> check if should turn ON
      if (tempC > (TEMP_TARGET_HIGH + TEMP_HYST/2.0)) {
        setFan(true);
      }
    } else {
      // currently ON -> check if should turn OFF
      if (tempC <= (TEMP_TARGET_HIGH - TEMP_HYST/2.0)) {
        setFan(false);
      }
    }

    // Mist control for humidity: Mist increases RH
    if (!mistState) {
      if (hum < (HUM_LOW - HUM_HYST/2.0)) {
        setMist(true);
      }
    } else {
      if (hum >= (HUM_HIGH + HUM_HYST/2.0)) {
        setMist(false);
      }
    }
  }

  // GAS ALERT: if gas crosses threshold, send SMS (with cooldown)
  if (gasRaw >= GAS_THRESHOLD) {
    if (!alertSent || (millis() - lastAlertMs) >= ALERT_COOLDOWN_MS) {
      sendAlertSMS(tempC, hum, gasRaw);
      alertSent = true;
      lastAlertMs = millis();
    }
  } else {
    // Optionally reset alertSent if gas returns sufficiently low to allow future alerts
    if (alertSent && (millis() - lastAlertMs) >= ALERT_COOLDOWN_MS) {
      alertSent = false; // allow future alerts after cooldown
    }
  }
}

// Turn fan ON/OFF (update both relay and state)
void setFan(bool on) {
  fanState = on;
  // If your relay is active HIGH to turn on:
  digitalWrite(RELAY_FAN, on ? HIGH : LOW);
  Serial.printf("Fan turned %s\n", on ? "ON" : "OFF");
}

// Turn mist sprayer ON/OFF
void setMist(bool on) {
  mistState = on;
  digitalWrite(RELAY_MIST, on ? HIGH : LOW);
  Serial.printf("Mist turned %s\n", on ? "ON" : "OFF");
}

// ---------------- GSM helper functions ----------------
// Send an AT command to GSM and return collected response (non-blocking collection for 'timeout' ms)
String sendGSMCommand(String cmd, unsigned long timeout) {
  while (GSM_SERIAL.available()) GSM_SERIAL.read(); // flush
  Serial.print("GSM -> "); Serial.println(cmd);
  GSM_SERIAL.println(cmd);

  unsigned long tStart = millis();
  String response = "";
  while (millis() - tStart < timeout) {
    while (GSM_SERIAL.available()) {
      char c = (char)GSM_SERIAL.read();
      response += c;
    }
  }
  Serial.print("GSM <- "); Serial.println(response);
  return response;
}

// Compose and send SMS alert
void sendAlertSMS(float tempC, float hum, int gasRaw) {
  // Compose text
  char buf[200];
  if (isnan(tempC) || isnan(hum)) {
    snprintf(buf, sizeof(buf), "ONION ALERT! Gas:%d", gasRaw);
  } else {
    snprintf(buf, sizeof(buf), "ONION ALERT!\nT:%.1fC H:%.1f%%\nGas:%d", tempC, hum, gasRaw);
  }
  String msg = String(buf);

  // Ensure SMS mode, then issue send
  sendGSMCommand("AT+CMGF=1", 1000);
  delay(200);
  String cmd = String("AT+CMGS=\"") + PHONE_NUMBER + String("\"");
  sendGSMCommand(cmd, 1000);
  delay(200);
  // send message body
  GSM_SERIAL.print(msg);
  delay(200);
  GSM_SERIAL.write(0x1A); // Ctrl+Z to send
  Serial.println("SMS send command issued.");
  // Wait a bit and optionally read response
  delay(5000);
  String res = "";
  while (GSM_SERIAL.available()) {
    res += (char)GSM_SERIAL.read();
  }
  Serial.print("SMS response: "); Serial.println(res);
}