#include <SoftwareSerial.h>

#define RX_PIN 26
#define TX_PIN 27
#define POWER_PIN 4
#define BAUD_RATE 115200
#define LED_PIN 12

SoftwareSerial sim(RX_PIN, TX_PIN);

bool isModemPoweredOn() {
  sim.println("AT");
  delay(1000);
  if (sim.find("OK")) {
    return true;
  } else {
    return false;
  }
}

void setup() {
  Serial.begin(BAUD_RATE);
  sim.begin(BAUD_RATE);
  pinMode(POWER_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
  Serial.println("Powering off modem.");
  digitalWrite(POWER_PIN, LOW);
  digitalWrite(LED_PIN, LOW);
  delay(1000);
  Serial.println("Powering on modem.");
  digitalWrite(POWER_PIN, HIGH);
  digitalWrite(LED_PIN, HIGH);
  delay(10000);
  
  // Check if modem is powered on
  if (isModemPoweredOn()) {
    Serial.println("Modem is powered on and ready.");
  } else {
    Serial.println("Modem is not responding to AT commands. Please check power connection and pin configuration.");
  }
}

void loop() {
  // Check if modem is registered to the network
  sim.println("AT+CREG?");
  delay(1000);
  if (sim.find("+CREG: 0,1") || sim.find("+CREG: 0,5")) {
    Serial.println("Modem registered to the network.");
    
    // Set SMS mode to text mode
    sim.println("AT+CMGF=1");
    delay(1000);
    
    // Send SMS message
    sim.println("AT+CMGS=\"+4799999999\"");
    delay(1000);
    sim.println("LilyGO-T-SIM7000G booted up!");
    delay(100);
    sim.write(26);
    delay(1000);
  } else {
    Serial.println("Modem not registered to the network. Trying to connect...");
    
    // Configure APN
    sim.println("AT+CGDCONT=1,\"IP\",\"telia\"");
    delay(1000);
    
    // Set modem to automatically select the network and start the GPRS and LTE services
    sim.println("AT+COPS=0");
    delay(5000);
    
    // Check if modem is registered to the network
    sim.println("AT+CREG?");
    delay(1000);
    if (sim.find("+CREG: 0,1") || sim.find("+CREG: 0,5")) {
      Serial.println("Modem connected to the network.");
      
      // Set SMS mode to text mode
      sim.println("AT+CMGF=1");
      delay(1000);
      
      // Send SMS message
      sim.println("AT+CMGS=\"+479999999\"");
      delay(1000);
      sim.println("LilyGO-T-SIM7000G booted up!");
      delay(100);
      sim.write(26);
      delay(1000);
    } else {
      Serial.println("Modem could not connect to the network.");
    }
  }
  
  delay(1000);
}