#include <HardwareSerial.h> // Using HardwareSerial2 for better performance

// --- SIM7080G Pin Definitions ---
// Make sure these match your board's actual connections.
// If using the Waveshare example's pins 10,11 this would need SoftwareSerial.
// We are using HardwareSerial2 here (pins 16, 17) for efficiency if available.
#define LTE_RX_PIN 16 // ESP32 GPIO16 connected to SIM7080G TX
#define LTE_TX_PIN 17 // ESP32 GPIO17 connected to SIM7080G RX
#define PWRKEY_PIN 4  // ESP32 GPIO4 connected to SIM7080G PWRKEY (as before)

// --- Function Prototypes ---
// REVISED: powerUp function based on Waveshare example timing
void powerUp(); 
// REVISED: sendCommandAndPrintAllResponse - will simply print all modem output
String sendCommandAndPrintAllResponse(String command, unsigned long timeoutMs = 3000); 

void setup() {
  Serial.begin(115200); // For debugging output to PC
  while (!Serial) {
    delay(10); // Wait for Serial Monitor to connect
  }
  Serial.println("--- Starting SIM7080G Basic Communication Test ---");
  Serial.println("Configuring Serial2 for LTE module at 115200 baud.");

  // Initialize Serial2 for communication with the SIM7080G
  Serial2.begin(115200, SERIAL_8N1, LTE_RX_PIN, LTE_TX_PIN);

  // Set PWRKEY pin mode and ensure it's LOW initially as per Waveshare setup.
  pinMode(PWRKEY_PIN, OUTPUT);
  digitalWrite(PWRKEY_PIN, LOW); // Important to ensure a known initial state
  delay(1000); // Small delay to stabilize

  Serial.println("Attempting Modem Power Up sequence...");
  powerUp(); // Call the revised powerUp sequence

  Serial.println("Power Up sequence initiated. Waiting for modem to become responsive (up to 120 seconds)...");
  unsigned long modemReadyStartTime = millis();
  const unsigned long MODEM_READY_TIMEOUT = 120 * 1000; // Total 120 seconds timeout

  // Loop to repeatedly send "AT" and check for any response
  Serial.println("Repeatedly sending 'AT' to check for responsiveness...");
  while (millis() - modemReadyStartTime < MODEM_READY_TIMEOUT) {
    String response = sendCommandAndPrintAllResponse("AT", 1500); // Send AT, wait 1.5s for any response
    if (response.indexOf("OK") != -1) {
      Serial.println("Modem is responsive! Continuing initial checks.");
      break;
    }
    Serial.print("Modem not yet responsive (");
    Serial.print((millis() - modemReadyStartTime) / 1000);
    Serial.println("s elapsed). Retrying...");
    delay(2000); // Wait 2 seconds before retrying AT command
  }

  if (millis() - modemReadyStartTime >= MODEM_READY_TIMEOUT) {
    Serial.println("Modem did not become responsive within timeout. Check wiring, module power, and PWRKEY sequence.");
    while(true); // Halt if modem fails to become responsive
  }

  Serial.println("\n--- Basic AT Command Tests ---");
  delay(1000); // Small delay before next command
  sendCommandAndPrintAllResponse("ATI", 3000); // Get product ID
  delay(1000);
  sendCommandAndPrintAllResponse("AT+CMEE=1", 1000); // Enable verbose errors
  delay(1000);
  sendCommandAndPrintAllResponse("AT+CPIN?", 3000); // Check SIM status
  delay(1000);

  Serial.println("\n--- Setup complete. Monitor loop output for continuous checks. ---");
}


void loop() {
  // Continuously check basic modem status to see if it remains responsive
  Serial.println("\n--- Loop: Continuous Basic Checks ---");
  sendCommandAndPrintAllResponse("AT", 1000);
  delay(5000); // Check every 5 seconds
}


// REVISED: powerUp function based on Waveshare example timing
void powerUp(){
  Serial.println("Applying power pulse to PWRKEY_PIN (GPIO4)...");
  digitalWrite(PWRKEY_PIN, HIGH); // Ensure HIGH first (idle state)
  delay(100); // Small stabilization delay

  digitalWrite(PWRKEY_PIN, LOW); // Pull PWRKEY low
  delay(2000); // Hold low for 2 seconds (as per Waveshare example)
  digitalWrite(PWRKEY_PIN, HIGH); // Release PWRKEY (set HIGH)
  // The long boot delay is handled in setup() to monitor responsiveness
  Serial.println("PWRKEY pulse complete. Module should now be booting.");
}


// REVISED: sendCommandAndPrintAllResponse function for raw modem output debugging
String sendCommandAndPrintAllResponse(String command, unsigned long timeoutMs) {
  Serial.print("Sending: ");
  Serial.println(command);

  // Clear Serial2 receive buffer before sending command
  while (Serial2.available()) {
    Serial2.read();
  }

  Serial2.println(command); // Send command to the modem

  String rawResponse = "";
  unsigned long startTime = millis();
  
  while (millis() - startTime < timeoutMs) { 
    if (Serial2.available()) {
      char c = (char)Serial2.read();
      rawResponse += c;
      startTime = millis(); // Reset timeout as long as data is being received
    }
    delay(1); // Small delay to prevent busy-waiting
  }

  Serial.println("--- Raw Modem Response Received ---");
  Serial.println(rawResponse); // Print everything received (raw, untrimmed)
  Serial.println("-----------------------------------");
  
  return rawResponse; // Return the raw response for checking in setup/loop
}