#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>
#include <DS1307RTC.h>  // Include the DS1307 RTC library
#include <TimeLib.h>     // Include the TimeLib library

const int buzzerPin = 10;  // Buzzer pin
float currentValue = 0.0;   // Store the current number
float previousValue = 0.0;  // Store the previous number
char operation = '+';       // Store the current operation
String inputAmount = "";    // Store the current input string

// Define keypad layout (4x4)
const byte ROW_NUM    = 4;    // four rows
const byte COLUMN_NUM = 4;    // four columns

char keys[ROW_NUM][COLUMN_NUM] = {
  {'1', '2', '3', '+'},
  {'4', '5', '6', '-'},
  {'7', '8', '9', '*'},
  {'C', '0', '=', '/'}
};

// Pin connections to Arduino
byte pin_rows[ROW_NUM] = {9, 8, 7, 6}; // Rows 1-4
byte pin_column[COLUMN_NUM] = {5, 4, 3, 2}; // Columns 1-4

Keypad keypad = Keypad(makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM);

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

// Idle timer
unsigned long lastActivityTime = 0;
const unsigned long idleTimeout = 10000;  // Turn off backlight after 10 seconds of inactivity

void setup() {
  lcd.begin(16, 2);  // Set up the LCD's number of columns and rows
  lcd.setBacklight(1);  // Turn on the LCD backlight
  lcd.clear();
  pinMode(buzzerPin, OUTPUT);  // Set up the buzzer

  // Initialize the RTC from DS1307
  if (!RTC.isRunning()) {
    lcd.clear();
    lcd.print("RTC not found!");
    while (1);  // Stop execution if RTC is not found
  }

  // Uncomment to set the RTC time when it's not set yet (only needed once)
  // RTC.setTime(10, 30, 0); // Set the time: 10:30:00

  // Display the initial screen
  displayHomeScreen();
}

void loop() {
  char key = keypad.getKey();

  if (key) {
    lastActivityTime = millis();  // Reset the idle timer on activity

    if (key == 'C') {
      // Clear current input and reset calculator
      currentValue = 0.0;
      previousValue = 0.0;
      operation = '+';
      inputAmount = "";
      lcd.clear();
      lcd.print("Cleared");
      delay(1000);
      displayCurrentInput();
    }
    else if (key == '=') {
      // Perform the operation and calculate the result
      performOperation();
      tone(buzzerPin, 1500, 200);  // Buzzer feedback for result
    }
    else if (key == '+' || key == '-' || key == '*' || key == '/') {
      // Save the current value and set the operation
      if (inputAmount.length() > 0) {
        currentValue = inputAmount.toFloat();
        inputAmount = "";
      }
      operation = key;
      tone(buzzerPin, 1000, 200);  // Buzzer feedback for operation
      lcd.clear();
      lcd.print("Op: ");
      lcd.print(operation);
      displayCurrentInput();
    }
    else {
      // Append the key to the input amount and display it
      if (key >= '0' && key <= '9') {
        inputAmount += key;
        displayCurrentInput();
        tone(buzzerPin, 1000, 200);  // Buzzer feedback for key press
      }
    }
  }

  // Check if idle for more than the timeout duration
  if (millis() - lastActivityTime > idleTimeout) {
    lcd.setBacklight(0);  // Turn off the LCD backlight after idle timeout
  } else {
    lcd.setBacklight(1);  // Ensure backlight is on during activity
  }

  // Display the clock and update every second
  displayClock();
}

void displayHomeScreen() {
  lcd.clear();
  lcd.setBacklight(1);
  lcd.print("ELKILEN STORE");
  delay(2000);
}

void displayCurrentInput() {
  lcd.clear();
  lcd.print("Input: Rp");
  lcd.print(inputAmount);
}

void displayClock() {
  // Get the current time using TimeLib functions
  time_t currentTime = RTC.get();  // Get the current time from the RTC

  // Use TimeLib functions to extract the hour, minute, and second
  int h = hour(currentTime);   // Get the current hour
  int m = minute(currentTime); // Get the current minute
  int s = second(currentTime); // Get the current second
  
  // Display the time on the LCD
  lcd.setCursor(0, 1);
  lcd.print(h);
  lcd.print(":");
  lcd.print(m);
  lcd.print(":");
  lcd.print(s);
}

void performOperation() {
  float result = 0.0;

  // Convert the current input to a float value
  if (inputAmount.length() > 0) {
    currentValue = inputAmount.toFloat();
    inputAmount = "";  // Clear the input string
  }

  // Perform the operation
  switch (operation) {
    case '+':
      result = previousValue + currentValue;
      break;
    case '-':
      result = previousValue - currentValue;
      break;
    case '*':
      result = previousValue * currentValue;
      break;
    case '/':
      if (currentValue != 0) {
        result = previousValue / currentValue;
      } else {
        lcd.clear();
        lcd.print("Error: Div by 0");
        delay(1000);
        displayCurrentInput();
        return;
      }
      break;
  }

  // Show the result on the LCD and store it as the previous value for next operation
  previousValue = result;
  lcd.clear();
  lcd.print("Result: Rp");
  lcd.print(result, 0);  // Display result with no decimal points for Rupiah
}