#include <WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>
#include <ArduinoJson.h>

// WiFi
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// MQTT
const char* mqtt_server = "broker.hivemq.com";

WiFiClient espClient;
PubSubClient client(espClient);

// LCD
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Keypad
const byte ROWS = 4;
const byte COLS = 4;

char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte rowPins[ROWS] = {13, 12, 14, 27};
byte colPins[COLS] = {26, 25, 33, 32};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// STATES
int step = 0;
String type = "";
String number = "";
String cvv = "";
String pin = "";

void callback(char* topic, byte* payload, unsigned int length) {
  String msg = "";
  for (int i = 0; i < length; i++) msg += (char)payload[i];

  lcd.clear();
  if (msg.indexOf("success") != -1) {
    lcd.print("PAYMENT OK");
  } else {
    lcd.print("FAILED");
  }

  delay(3000);
  resetFlow();
}

void reconnect() {
  while (!client.connected()) {
    if (client.connect("ClientESP32")) {
      client.subscribe("payment/response");
    }
  }
}

void showMenu() {
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("1.Debit 2.Crd");
  lcd.setCursor(0,1);
  lcd.print("3.UPI");
}

void resetFlow() {
  step = 0;
  type = "";
  number = "";
  cvv = "";
  pin = "";
  showMenu();
}

void setup() {
  lcd.init();
  lcd.backlight();

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED);

  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);

  showMenu();
}

void loop() {
  if (!client.connected()) reconnect();
  client.loop();

  char key = keypad.getKey();
  if (!key) return;

  // STEP 0 → SELECT TYPE
  if (step == 0) {
    if (key == '1') { type = "debit"; step = 1; }
    else if (key == '2') { type = "credit"; step = 1; }
    else if (key == '3') { type = "upi"; step = 1; }

    lcd.clear();
    lcd.print("Enter Number:");
    return;
  }

  // STEP 1 → ENTER NUMBER / UPI
  if (step == 1) {
    if (key == '#') {
      step = (type == "upi") ? 3 : 2;

      lcd.clear();
      if (type == "upi") {
        lcd.print("Enter PIN:");
      } else {
        lcd.print("Enter CVV:");
      }
    } else {
      number += key;
      lcd.setCursor(0,1);
      lcd.print(number);
    }
    return;
  }

  // STEP 2 → ENTER CVV
  if (step == 2) {
    if (key == '#') {
      step = 3;
      lcd.clear();
      lcd.print("Enter PIN:");
    } else {
      cvv += key;
      lcd.setCursor(0,1);
      lcd.print("***");
    }
    return;
  }

  // STEP 3 → ENTER PIN
  if (step == 3) {
    if (key == '#') {
      sendData();
    } else {
      pin += key;
      lcd.setCursor(0,1);
      lcd.print("****");
    }
    return;
  }
}

void sendData() {
  StaticJsonDocument<256> doc;

  doc["type"] = type;
  doc["number"] = number;
  doc["cvv"] = cvv;
  doc["pin"] = pin;

  char buffer[256];
  serializeJson(doc, buffer);

  client.publish("payment/request", buffer);

  lcd.clear();
  lcd.print("Processing...");
}