#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <SPI.h>
#include <MFRC522.h>
#include <HTTPSRedirect.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

#define SS_PIN   2  // D4
#define RST_PIN  0  // D3
#define BUZZER   4  // D2
#define PUSH_BUTTON D7  // Button to remove last item

LiquidCrystal_I2C lcd(0x27, 16, 2);
MFRC522 mfrc522(SS_PIN, RST_PIN);
MFRC522::MIFARE_Key key;  
MFRC522::StatusCode status;

// WiFi credentials
const char* ssid = "Your_SSID";
const char* password = "Your_PASSWORD";

// Google Apps Script Deployment ID
const char *GScriptId = "Your_Google_Script_ID";

// Google Sheets API settings
const char* host = "script.google.com";
const int httpsPort = 443;
String url = String("/macros/s/") + GScriptId + "/exec";
HTTPSRedirect* client = nullptr;

// Store RFID tag data and item prices
struct Item {
  String id;
  String name;
  float price;
};

// List of items and their prices
Item items[] = {
  {"A1B2C3D4", "Apple", 1.50},
  {"E5F6G7H8", "Milk", 2.00},
  {"I9J1K2L3", "Bread", 1.20},
  {"M4N5O6P7", "Eggs", 3.50}
};

float total_bill = 0.0;

void setup() {
  pinMode(BUZZER, OUTPUT);
  pinMode(PUSH_BUTTON, INPUT_PULLUP);
  
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  
  lcd.init();
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Connecting WiFi...");

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }

  Serial.println("\nWiFi Connected!");
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("WiFi Connected");
  delay(2000);

  client = new HTTPSRedirect(httpsPort);
  client->setInsecure();
  client->setPrintResponseBody(true);
  client->setContentTypeHeader("application/json");

  for (int i = 0; i < 5; i++) {
    if (client->connect(host, httpsPort)) {
      Serial.println("Connected to Google Sheets!");
      break;
    }
    Serial.println("Connection failed, retrying...");
    delay(2000);
  }

  delete client;
  client = nullptr;
}

void loop() {
  if (digitalRead(PUSH_BUTTON) == LOW) {
    erasePreviousData();
    delay(500);
  }

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Scan Item...");

  if (!mfrc522.PICC_IsNewCardPresent() || !mfrc522.PICC_ReadCardSerial()) {
    return;
  }

  String scannedID = "";
  for (byte i = 0; i < mfrc522.uid.size; i++) {
    scannedID += String(mfrc522.uid.uidByte[i], HEX);
  }
  scannedID.toUpperCase();
  Serial.println("Scanned ID: " + scannedID);

  bool itemFound = false;
  String itemName;
  float itemPrice = 0.0;

  for (int i = 0; i < sizeof(items) / sizeof(items[0]); i++) {
    if (scannedID.equals(items[i].id)) {
      itemFound = true;
      itemName = items[i].name;
      itemPrice = items[i].price;
      total_bill += itemPrice;
      break;
    }
  }

  if (itemFound) {
    Serial.println("Item: " + itemName + " Price: $" + String(itemPrice));
    
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Added: " + itemName);
    lcd.setCursor(0, 1);
    lcd.print("Total: $" + String(total_bill));
    
    digitalWrite(BUZZER, HIGH);
    delay(500);
    digitalWrite(BUZZER, LOW);
    
    String payload = "{\"command\": \"insert_row\", \"values\": \"" + itemName + "," + String(itemPrice) + "," + String(total_bill) + "\"}";
    sendDataToGoogle(payload);
  } else {
    Serial.println("Unknown Item!");
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Unknown Item!");
    delay(2000);
  }

  delay(3000);
}

void sendDataToGoogle(String payload) {
  client = new HTTPSRedirect(httpsPort);
  client->setInsecure();

  if (client->POST(url, host, payload)) {
    Serial.println("Data sent to Google Sheets");
  } else {
    Serial.println("Error sending data.");
  }

  delete client;
  client = nullptr;
  delay(5000);
}

void erasePreviousData() {
  Serial.println("Removing last item...");
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Removing item...");

  String erase_payload = "{\"command\": \"delete_last_row\"}";
  client = new HTTPSRedirect(httpsPort);
  client->setInsecure();

  if (client->POST(url, host, erase_payload)) {
    Serial.println("Last item removed.");
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Item Removed!");
  } else {
    Serial.println("Erase failed.");
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Erase Failed!");
  }

  delete client;
  client = nullptr;
  delay(2000);
}