extern "C" int lwip_hook_ip6_input(void *p) { return 0; }
#include <TinyGPS++.h>
#include <WiFi.h>
#include <HTTPClient.h>
#include <time.h>

// ---------------- WiFi Configuration ----------------
const char* ssid = "Wokwi-GUEST";  // For Wokwi simulation
const char* password = "";

// ---------------- ThingSpeak Configuration ----------------
String writeAPIKey = "6WOBZ5TINVQKCQGK"; // Replace with your ThingSpeak write API key
const char* server = "http://api.thingspeak.com/update";

// ---------------- GPS Config ----------------
#define GPS_BAUDRATE 9600
TinyGPSPlus gps;

// Simulated XBee on Serial1
#define XBEE_BAUDRATE 9600

String DEVICE_ID = "ESP32_4A:7F:2C:9D:1B:6E"; // Unique ID

bool onTollRoad = false;
bool xbee = false;

float startLat = 12.971600;
float startLon = 77.594600;
float totalDistance = 0.0;

// Simulated movement
float latStep = 0.00045;
float lonStep = 0.00045;
float curLat = startLat;
float curLon = startLon;

// ---------------- Helper Functions ----------------

// Haversine formula to calculate distance in meters
float haversine(float lat1, float lon1, float lat2, float lon2) {
  const float R = 6371000; // Earth radius in meters
  float dLat = (lat2 - lat1) * PI / 180.0;
  float dLon = (lon2 - lon1) * PI / 180.0;
  float a = sin(dLat/2)*sin(dLat/2) + cos(lat1*PI/180.0)*cos(lat2*PI/180.0)*sin(dLon/2)*sin(dLon/2);
  float c = 2*atan2(sqrt(a), sqrt(1-a));
  return R * c;
}

// Get current date & time
String getDateTime() {
  time_t now;
  struct tm timeinfo;
  time(&now);
  localtime_r(&now, &timeinfo);

  char buffer[32];
  sprintf(buffer, "%02d:%02d:%02d|%02d:%02d:%02d",
          timeinfo.tm_year % 100,
          timeinfo.tm_mon + 1,
          timeinfo.tm_mday,
          timeinfo.tm_hour,
          timeinfo.tm_min,
          timeinfo.tm_sec);
  return String(buffer);
}

// ---------------- Setup ----------------
void setup() {
  Serial.begin(115200);
  Serial2.begin(GPS_BAUDRATE, SERIAL_8N1, 16, 17);
  Serial1.begin(XBEE_BAUDRATE);

  Serial.println(F("--------------------------------------"));
  Serial.println(F("ESP32 GPS + XBee Simulation"));
  Serial.println(F("--------------------------------------"));

  // Initialize WiFi
  WiFi.begin(ssid, password);
  Serial.print("Connecting to WiFi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\n✅ WiFi Connected!");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  // Initialize NTP time (GMT+5:30)
  configTime(5 * 3600 + 1800, 0, "pool.ntp.org", "time.nist.gov");
  delay(1000);
  Serial.println("--------------------------------------\n");
}

// ---------------- Loop ----------------
void loop() {
  // Simulate GPS data reading
  while (Serial2.available() > 0) {
    gps.encode(Serial2.read());
  }

  // Simulated handshake commands via Serial monitor
  while (Serial.available() > 0) {
    String xbeeMsg = Serial.readStringUntil('\n');
    xbeeMsg.trim();

    if (xbeeMsg == "TOLL_ENTRY") {
      onTollRoad = true;
      totalDistance = 0.0;
      curLat = startLat;
      curLon = startLon;
      Serial.println("Toll entry detected!");
    }
    if (xbeeMsg == "Digi_Handshake") {
      xbee = true;
      Serial.println("Transmission...");
      delay(1000);
    }
    if (xbeeMsg == "TOLL_EXIT") {
      onTollRoad = false;
      Serial.println("Toll Road Exited!");
    }
  }

  // Simulate linear GPS movement
  curLat += latStep;
  curLon += lonStep;

  // Calculate distance if on toll road
  if (onTollRoad) {
    static float prevLat = startLat;
    static float prevLon = startLon;
    totalDistance += haversine(prevLat, prevLon, curLat, curLon);
    prevLat = curLat;
    prevLon = curLon;
  }

  // When handshake occurs → transmit + send to ThingSpeak
  if (xbee) {
    float distanceKm = totalDistance / 1000.0;
    String timestamp = getDateTime();

    String payload = DEVICE_ID + "|" + String(distanceKm, 3) + "km|" +
                     String(curLat, 6) + "|" + String(curLon, 6) + "|" + timestamp;

    Serial.println("\n--------------------------------------");
    Serial.println("ESP32 GPS + XBee Simulation");
    Serial.println("--------------------------------------");
    Serial.println("Toll entry detected!");
    Serial.println("Transmission...");
    delay(800);
    Serial.println("Payload sent:");
    Serial.println(payload);
    Serial.println("Transmitted!");
    Serial.println("Toll Road Exited!");
    Serial.println("--------------------------------------\n");

    // Send via XBee (simulated)
    Serial1.println(payload);

    // ---------------- Send to ThingSpeak ----------------
    if (WiFi.status() == WL_CONNECTED) {
      HTTPClient http;
      String url = String(server) + "?api_key=" + writeAPIKey +
                   "&field1=" + String(distanceKm, 3) +
                   "&field2=" + String(curLat, 6) +
                   "&field3=" + String(curLon, 6) +
                   "&field4=" + timestamp +
                   "&field5=" + DEVICE_ID;

      Serial.println("[ThingSpeak] Sending data...");
      http.begin(url);
      int httpResponseCode = http.GET();

      if (httpResponseCode > 0) {
        Serial.println("✅ ThingSpeak Response Code: " + String(httpResponseCode));
      } else {
        Serial.println("❌ Error sending data: " + String(httpResponseCode));
      }
      http.end();
    } else {
      Serial.println("⚠️ WiFi not connected, skipping ThingSpeak upload!");
    }

    // Reset for next transmission
    totalDistance = 0.0;
    startLat = curLat;
    startLon = curLon;
    xbee = false;
    delay(3000);
  }

  delay(500);
}