#define BLYNK_PRINT Serial

#define BLYNK_TEMPLATE_ID "TMPL3f8NjF3lP"
#define BLYNK_TEMPLATE_NAME "Real time Inventory Tracking System"
#define BLYNK_AUTH_TOKEN "v0x8Z3Cfu5sqACD8aYgkFGJbnlmWhiXP"

#include <WiFi.h>
#include <BlynkSimpleEsp32.h>
#include "HX711.h"
/* WiFi credentials */
char ssid[] = "Wokwi-GUEST";
char pass[] = "";

/* HX711 pins (match Wokwi) */
#define DT_PIN  4
#define SCK_PIN 5

HX711 scale;
/* Inventory settings */
const int TOTAL_BOOKS = 20;
const float WEIGHT_PER_BOOK = 0.50;   // kg (change if needed)

float shelfWeight = 0;
int booksRemaining = 0;

/* Timer */
BlynkTimer timer;
/* -------- TARE BUTTON (V3) -------- */
BLYNK_WRITE(V3) {
  int tareCmd = param.asInt();
  if (tareCmd == 1) {
    scale.tare();
    Serial.println("Shelf tared");
  }
}

/* -------- READ LOAD CELL -------- */
void readLoadCell() {

  if (!scale.is_ready()) {
    Serial.println("HX711 not ready");
    return;
  }

  shelfWeight = scale.get_units(10);
  if (shelfWeight < 0) shelfWeight = 0;

  booksRemaining = shelfWeight / WEIGHT_PER_BOOK;
  if (booksRemaining > TOTAL_BOOKS) booksRemaining = TOTAL_BOOKS;
  if (booksRemaining < 0) booksRemaining = 0;

  /* Shelf status logic */
  String status;
  if (booksRemaining == 0) {
    status = "EMPTY";
  } else if (booksRemaining <= 5) {
    status = "LOW STOCK";
  } else {
    status = "OK";
  }

  /* Send to Blynk */
  Blynk.virtualWrite(V0, shelfWeight);        // Shelf Weight (kg)
  Blynk.virtualWrite(V1, booksRemaining);    // Books Remaining
  Blynk.virtualWrite(V2, status);             // Shelf Status

  /* Serial monitor */
  Serial.print("Weight (kg): ");
  Serial.print(shelfWeight);
  Serial.print(" | Books: ");
  Serial.print(booksRemaining);
  Serial.print(" | Status: ");
  Serial.println(status);
}

void setup() {
  Serial.begin(9600);
  /* HX711 init */
  scale.begin(DT_PIN, SCK_PIN);
  scale.set_scale(420.0);   // ⚠️ Adjust after calibration
  scale.tare();

  /* Blynk connection */
  Blynk.begin(BLYNK_AUTH_TOKEN, ssid, pass);
  /* Read sensor every 2 seconds */
  timer.setInterval(2000L, readLoadCell);
}
void loop() {
  Blynk.run();
  timer.run();
}