#include <TinyGPS++.h>
#include <SD.h>
#include <SPI.h> // Required for SD card
#include <HardwareSerial.h> // For Serial2 (GPS)
#include <SoftwareSerial.h> // For GSM

// --- GPS Definitions ---
#define GPS_BAUDRATE 9600 // The default baudrate of NEO-6M is 9600
TinyGPSPlus gps;          // the TinyGPS++ object

// --- SD Card Definitions ---
// SD Card uses ESP32's Hardware SPI pins:
// MISO: GPIO12
// MOSI: GPIO13 (Commonly 23, but we're using 15 for SD MOSI here based on original diagram)
// SCK: GPIO14
// CS (Chip Select) can be any GPIO pin. We're using GPIO13.
const int SDCARD_CS_PIN = 13; // GPIO13 for SD Card Chip Select

// --- GSM Definitions ---
// GSM module uses SoftwareSerial:
// RX (GSM) to TX (ESP32) -> ESP32 GPIO4
// TX (GSM) to RX (ESP32) -> ESP32 GPIO2
#define GSM_TX_PIN 4 // Connects to GSM Module's RXD (ESP32 TX to GSM RX)
#define GSM_RX_PIN 2 // Connects to GSM Module's TXD (ESP32 RX to GSM TX)
SoftwareSerial gsmSerial(GSM_RX_PIN, GSM_TX_PIN); // RX, TX
#define GSM_BAUDRATE 9600 // Common baud rate for SIM800L

// --- Push Button Definition (Optional, for triggering SMS) ---
const int BUTTON_PIN = 18; // GPIO18 for the button

// --- Variables for Data ---
char latitudeStr[15];
char longitudeStr[15];
char altitudeStr[15];
char speedStr[10];
char dateTimeStr[30];

// --- Helper function to send SMS ---
void sendSMS(const char* phoneNumber, const char* message) {
  Serial.print(F("Sending SMS to "));
  Serial.println(phoneNumber);
  Serial.print(F("Message: "));
  Serial.println(message);

  gsmSerial.print("AT+CMGF=1\r\n"); // Set SMS to text mode
  delay(1000);
  gsmSerial.print("AT+CMGS=\""); // Start sending SMS
  gsmSerial.print(phoneNumber);
  gsmSerial.print("\"\r\n");
  delay(1000);
  gsmSerial.print(message); // Send the message content
  delay(100);
  gsmSerial.print((char)26); // End with Ctrl+Z
  delay(3000); // Wait for SMS to send

  while (gsmSerial.available()) {
    Serial.write(gsmSerial.read()); // Read any response from GSM module
  }
  Serial.println(F("\nSMS Send Attempt Complete."));
}

// --- Helper function to log data to SD Card ---
void logToSDCard(const char* data) {
  File dataFile = SD.open("/gps_log.txt", FILE_APPEND); // Open file in append mode
  if (dataFile) {
    dataFile.println(data);
    dataFile.close();
    Serial.println(F("Data logged to SD card."));
  } else {
    Serial.println(F("Error opening gps_log.txt"));
  }
}

void setup() {
  Serial.begin(115200); // Higher baud rate for Serial Monitor
  Serial.println(F("ESP32 Combined Project Init..."));

  // Initialize GPS Serial2
  Serial2.begin(GPS_BAUDRATE); // Serial2 for GPS UART
  Serial.println(F("GPS Serial2 Initialized."));

  // Initialize SD Card
  if (!SD.begin(SDCARD_CS_PIN)) {
    Serial.println(F("SD Card initialization failed!"));
    return;
  }
  Serial.println(F("SD Card initialized."));

  // Initialize GSM SoftwareSerial
  gsmSerial.begin(GSM_BAUDRATE);
  Serial.println(F("GSM SoftwareSerial Initialized."));
  delay(1000); // Give GSM module time to power up

  // Initialize button pin
  pinMode(BUTTON_PIN, INPUT_PULLUP); // Use internal pull-up resistor

  Serial.println(F("System Ready."));
}

void loop() {
  // --- GPS Data Reading ---
  while (Serial2.available() > 0) {
    if (gps.encode(Serial2.read())) {
      if (gps.location.isValid()) {
        dtostrf(gps.location.lat(), 1, 6, latitudeStr); // Convert float to string
        dtostrf(gps.location.lng(), 1, 6, longitudeStr);
        Serial.print(F("Latitude: ")); Serial.println(latitudeStr);
        Serial.print(F("Longitude: ")); Serial.println(longitudeStr);

        if (gps.altitude.isValid()) {
          dtostrf(gps.altitude.meters(), 1, 2, altitudeStr);
          Serial.print(F("Altitude: ")); Serial.println(altitudeStr);
        } else {
          strcpy(altitudeStr, "INVALID");
          Serial.println(F("Altitude: INVALID"));
        }
      } else {
        strcpy(latitudeStr, "INVALID");
        strcpy(longitudeStr, "INVALID");
        strcpy(altitudeStr, "INVALID");
        Serial.println(F("Location: INVALID"));
      }

      Serial.print(F("Speed: "));
      if (gps.speed.isValid()) {
        dtostrf(gps.speed.kmph(), 1, 2, speedStr);
        Serial.print(speedStr); Serial.println(F(" km/h"));
      } else {
        strcpy(speedStr, "INVALID");
        Serial.println(F("INVALID"));
      }

      Serial.print(F("GPS date&time: "));
      if (gps.date.isValid() && gps.time.isValid()) {
        sprintf(dateTimeStr, "%d-%02d-%02d %02d:%02d:%02d",
                gps.date.year(), gps.date.month(), gps.date.day(),
                gps.time.hour(), gps.time.minute(), gps.time.second());
        Serial.println(dateTimeStr);
      } else {
        strcpy(dateTimeStr, "INVALID");
        Serial.println(F("INVALID"));
      }
      Serial.println(); // Blank line for readability

      // Log GPS data to SD card
      char logEntry[200];
      sprintf(logEntry, "Lat: %s, Lon: %s, Alt: %s, Speed: %s km/h, Time: %s",
              latitudeStr, longitudeStr, altitudeStr, speedStr, dateTimeStr);
      logToSDCard(logEntry);
    }
  }

  // --- Check for GPS data after a delay ---
  if (millis() > 5000 && gps.charsProcessed() < 10 && gps.location.isValid() == false) {
    Serial.println(F("No GPS data received or invalid: check wiring and custom chip files."));
  }


  // --- Button Check for SMS ---
  if (digitalRead(BUTTON_PIN) == LOW) { // Button is pressed (LOW due to INPUT_PULLUP)
    Serial.println(F("Button pressed. Initiating SMS..."));
    delay(50); // Debounce
    while (digitalRead(BUTTON_PIN) == LOW); // Wait for button release

    char smsMessage[160];
    sprintf(smsMessage, "Current Location: Lat %s, Lon %s. Time: %s", latitudeStr, longitudeStr, dateTimeStr);

    // Replace "YOUR_PHONE_NUMBER" with the actual recipient number
    sendSMS("YOUR_PHONE_NUMBER", smsMessage);
  }

  delay(100); // Small delay to prevent busy-waiting
}