#include <WiFi.h>
#include <HTTPClient.h>

#define TRIG_PIN 5
#define ECHO_PIN 18
#define LED_PIN 23

// Replace with your WiFi credentials
const char* ssid ="Wokwi-GUEST";
const char* password = "";

// ThingSpeak details
const char* server = "http://api.thingspeak.com/update";
const char* apiKey = "mwa0000038550648";
const char* channelID = "3057597";  // Store channel ID separately (string)

// Optional: print channel ID at startup
void printChannelInfo() {
  Serial.print("ThingSpeak Channel ID:3057597 ");
  Serial.println(channelID);
  Serial.print("ThingSpeak Write API Key:mwa0000038550648 ");
  Serial.println(apiKey);
}

void setup() {
  Serial.begin(115200);
  
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);

  // Connect to WiFi
  WiFi.begin(ssid, password);
  Serial.print("Connecting to WiFi");

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

  printChannelInfo();
}

void loop() {
  // Trigger ultrasonic sensor
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read echo duration
  long duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate distance in cm
  float distance = duration * 0.034 / 2;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  int occupancy = 0;

  // Determine occupancy
  int ledState = 0;
  if (distance > 0 && distance < 400) {
    occupancy = 1;              // Occupied
    digitalWrite(LED_PIN, HIGH);
  } else {
    occupancy = 0;              // Free
    digitalWrite(LED_PIN, LOW);
  }

  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;

    // Build URL with occupancy data (channel ID NOT included in URL)
     String url = String(server) + "?api_key=" + apiKey + "&field1=" + occupancy + "&field2=" + ledState;
    http.begin(url);
    int httpResponseCode = http.GET();

    if (httpResponseCode > 0) {
      String response = http.getString();
      Serial.print("ThingSpeak response: ");
      Serial.println(response);
    } else {
      Serial.print("Error sending to ThingSpeak. HTTP code: ");
      Serial.println(httpResponseCode);
    }
    http.end();
  } else {
    Serial.println("WiFi Disconnected");
  }

  delay(15000);  // Wait 15 seconds per ThingSpeak API limits
}