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

#define WIFI_SSID     "Wokwi-GUEST"
#define WIFI_PASSWORD ""
#define FIREBASE_HOST "libritrack-55c60-default-rtdb.firebaseio.com"
#define FIREBASE_AUTH "1FCMsdskRdw58NhGgnmfC2QfRtqvVh0XAHZM7BQ9"

#define TRIG_PIN  5
#define ECHO_PIN  18
#define LED_RED   2
#define LED_GREEN 15

#define OCCUPIED_THRESHOLD_CM 30

long readDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  long duration = pulseIn(ECHO_PIN, HIGH, 30000);
  return duration * 0.034 / 2;
}

void sendToFirebase(bool occupied, int distance) {
  HTTPClient http;
  String url = "https://" + String(FIREBASE_HOST) + "/seats/1.json?auth=" + FIREBASE_AUTH;

  String payload = "{\"occupied\":" + String(occupied ? "true" : "false") +
                   ",\"distance_cm\":" + String(distance) + "}";

  http.begin(url);
  http.addHeader("Content-Type", "application/json");
  int responseCode = http.PATCH(payload);

  Serial.printf("Firebase response: %d\n", responseCode);
  http.end();
}

void setup() {
  Serial.begin(115200);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_RED, OUTPUT);
  pinMode(LED_GREEN, OUTPUT);

  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to WiFi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500); Serial.print(".");
  }
  Serial.println(" connected!");
}

void loop() {
  long dist = readDistance();
  bool occupied = (dist > 0 && dist < OCCUPIED_THRESHOLD_CM);

  digitalWrite(LED_RED,   occupied ? HIGH : LOW);
  digitalWrite(LED_GREEN, occupied ? LOW  : HIGH);

  Serial.printf("Distance: %ldcm → %s\n", dist, occupied ? "OCCUPIED" : "FREE");

  sendToFirebase(occupied, (int)dist);

  delay(2000);
}