#include <Arduino.h>
#include "HX711.h"
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// ---------------- Pin map ----------------
#define HX711_DOUT_PIN 32
#define HX711_SCK_PIN  33

#define RED_LED_PIN    21
#define BTN_PIN        26

#define I2C_SDA_PIN    4
#define I2C_SCL_PIN    15
#define LCD_I2C_ADDR   0x27  // Common I2C address (try 0x3F if no display)

// ---------------- Objects ----------------
HX711 scale;
LiquidCrystal_I2C lcd(LCD_I2C_ADDR, 16, 2);

// ---------------- Inventory params ----------------
float calibration_factor = -7050.0f;   // adjust during calibration
const float item_unit_weight_kg = 25.0f;   // weight per bag
const int   low_stock_threshold_bags = 2;  // threshold
unsigned long lastWeightMillis = 0;

// LED blink control
bool lowStockState = false;
unsigned long lastBlinkMillis = 0;
const unsigned long blinkInterval = 500; // ms
bool ledOn = false;

// Button debounce
unsigned long lastBtnMillis = 0;
const unsigned long btnDebounce = 250;
bool lastBtnState = HIGH;

void setup() {
  Serial.begin(115200);
  delay(200);

  // LCD init
  Wire.begin(I2C_SDA_PIN, I2C_SCL_PIN);
  lcd.init();
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Inventory System");
  lcd.setCursor(0,1);
  lcd.print("Initializing...");
  delay(1500);
  lcd.clear();

  // HX711 init
  scale.begin(HX711_DOUT_PIN, HX711_SCK_PIN);
  scale.set_scale(calibration_factor);
  scale.tare();
  Serial.println("HX711 initialized and tared.");

  // LED + button
  pinMode(RED_LED_PIN, OUTPUT);
  digitalWrite(RED_LED_PIN, LOW);
  pinMode(BTN_PIN, INPUT_PULLUP);

  Serial.println("Setup complete.");
}

float readFilteredWeightKg(int samples = 5) {
  if (!scale.is_ready()) return 0.0;
  float w = scale.get_units(samples);
  if (fabs(w) < 0.01) w = 0.0;
  return w;
}

int getBagsFromWeight(float weightKg) {
  int bags = (int) round(weightKg / item_unit_weight_kg);
  return (bags < 0 ? 0 : bags);
}

void updateLCD(float weightKg, int bags) {
  lcd.setCursor(0,0);
  char line1[17];
  snprintf(line1, 17, "Wt:%6.1f kg", weightKg);
  lcd.print(line1);

  lcd.setCursor(0,1);
  if (bags <= low_stock_threshold_bags) {
    lcd.print("Status: LOW STOCK ");
  } else {
    char line2[17];
    snprintf(line2, 17, "Stock:%2d bag(s) ", bags);
    lcd.print(line2);
  }
}

void handleLowStockLed(bool low) {
  if (low) {
    unsigned long now = millis();
    if (now - lastBlinkMillis >= blinkInterval) {
      lastBlinkMillis = now;
      ledOn = !ledOn;
      digitalWrite(RED_LED_PIN, ledOn ? HIGH : LOW);
    }
  } else {
    digitalWrite(RED_LED_PIN, LOW);
    ledOn = false;
  }
}

void loop() {
  // Pushbutton simulates RFID scan
  bool btnState = digitalRead(BTN_PIN);
  if (btnState == LOW && lastBtnState == HIGH && (millis() - lastBtnMillis) > btnDebounce) {
    lastBtnMillis = millis();
    Serial.println("=== Simulated RFID SCAN ===");
    Serial.println("ItemID: RICE_25KG_001");
    Serial.print("Timestamp: ");
    Serial.println(millis()/1000);
    Serial.println("===========================");
  }
  lastBtnState = btnState;

  // Weight reading every 1s
  if (millis() - lastWeightMillis > 1000) {
    lastWeightMillis = millis();
    float weightKg = readFilteredWeightKg(5);
    int bags = getBagsFromWeight(weightKg);

    updateLCD(weightKg, bags);

    Serial.print("Weight: ");
    Serial.print(weightKg, 2);
    Serial.print(" kg  ~ ");
    Serial.print(bags);
    Serial.println(" bag(s)");

    lowStockState = (bags <= low_stock_threshold_bags);
  }

  handleLowStockLed(lowStockState);
}