#include <WiFi.h>
#include "ThingSpeak.h"
#include <TinyGPS++.h>

#define RXD2 16
#define TXD2 17
#define GPS_BAUDRATE 9600

TinyGPSPlus gps;

char ssid[] = "Wokwi-GUEST"; 
char pass[] = "";

WiFiClient client;

unsigned long myChannelNumber = 3266633;
const char * myWriteAPIKey = "ZX4MY8NFRUASQG5N";

unsigned long previousMillis = 0;
const long interval = 20000;

String lat_data = "";
String lng_data = "";

void setup() {

  Serial.begin(9600);
  Serial2.begin(GPS_BAUDRATE, SERIAL_8N1, RXD2, TXD2);

  Serial.println("ESP32 GPS Tracker");

  WiFi.begin(ssid, pass);
  Serial.print("Connecting WiFi");

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println();
  Serial.println("WiFi Connected");

  ThingSpeak.begin(client);
}

void loop() {

  while (Serial2.available() > 0) {
    gps.encode(Serial2.read());
  }

  if (gps.location.isValid()) {

    lat_data = String(gps.location.lat(), 6);
    lng_data = String(gps.location.lng(), 6);

    Serial.print("Latitude : ");
    Serial.println(lat_data);

    Serial.print("Longitude: ");
    Serial.println(lng_data);
  }
  else {
    Serial.println("Waiting GPS signal...");
  }

  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {

    previousMillis = currentMillis;

    ThingSpeak.setField(1, lat_data);
    ThingSpeak.setField(2, lng_data);

    int x = ThingSpeak.writeFields(myChannelNumber, myWriteAPIKey);

    if (x == 200) {
      Serial.println("Data sent to ThingSpeak");
    } else {
      Serial.println("ThingSpeak error code: " + String(x));
    }
  }

  delay(1000);
}