#include <Wire.h>
#include <Keypad.h>
#include <LiquidCrystal_I2C.h>

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

// Keypad setup
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}; // Row pins connected to these Arduino pins
byte colPins[cols] = {26, 25, 33, 32}; // Column pins connected to these Arduino pins

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, rows, cols);

// LED Pins
const int greenLEDPin = 15;
const int yellowLEDPin = 16;
const int redLEDPin = 17;

// Push button pin
const int pushButtonPin = 4; // Connected to pin 4 of ESP32

// Touch sensor pins
const int touchSDAPin = 21;
const int touchSCLPin = 22;

void setup() {
  // LCD setup
  lcd.init();
  lcd.backlight();
  
  // LED setup
  pinMode(greenLEDPin, OUTPUT);
  pinMode(yellowLEDPin, OUTPUT);
  pinMode(redLEDPin, OUTPUT);
  
  // Push button setup
  pinMode(pushButtonPin, INPUT_PULLUP);
  
  // Touch sensor setup
  Wire.begin(touchSDAPin, touchSCLPin);
}

void loop() {
  while (true) {
    // Display waiting message and turn on green LED
    displayWaitingMessage();

    // Wait for input from push button or touch sensor
    waitForInput();

    // Once input is received, indicate processing with yellow LED
    digitalWrite(greenLEDPin, LOW);
    digitalWrite(yellowLEDPin, HIGH);
    
    // Display touch sensed message
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Touch sensed!");
    lcd.setCursor(0, 1);
    lcd.print("Let's start...");
    delay(2000); // Display for 2 seconds
    
    // Display calculator message
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Calculator:");
    
    // Perform keypad operation
    String input = "";
    char key = getKey();
    while (key != '*') {
      if (key != NO_KEY) {
        if (key == 'A') {
          input += "+"; // Addition
        } else if (key == 'B') {
          input += "-"; // Subtraction
        } else if (key == 'C') {
          input += "*"; // Multiplication
        } else if (key == 'D') {
          input += "/"; // Division
        } else if (key == '#') {
          input = ""; // Clear input
        } else {
          input += key; // Numeric input
        }
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Calculator:");
        lcd.setCursor(0, 1);
        lcd.print(input);
      }
      key = getKey();
      delay(100);
    }
    
    // Calculate and display result
    float result = calculateResult(input);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Result: ");
    lcd.print(result, 2); // Display result with 2 decimal places
    
    // Turn on red LED
    digitalWrite(redLEDPin, HIGH);
    digitalWrite(yellowLEDPin, LOW); // Turn off yellow LED during result display
    
    // Display result for 3 seconds
    delay(3000);
    
    // Turn off red LED
    digitalWrite(redLEDPin, LOW);
  }
}

char getKey() {
  char key = keypad.getKey();
  return key;
}

void waitForInput() {
  unsigned long startTime = millis();
  while (true) {
    if (keypad.getKey() != NO_KEY || digitalRead(pushButtonPin) == LOW || touchSensorTouched()) {
      return;
    }
    
    // Check if waiting period exceeds 3 seconds
    if (millis() - startTime > 3000) {
      digitalWrite(greenLEDPin, LOW); // Turn off green LED
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print("No Sensation!!!");
      digitalWrite(redLEDPin, HIGH); // Turn on red LED
      delay(3000); // Display message and keep red LED on for 3 seconds
      digitalWrite(redLEDPin, LOW); // Turn off red LED
      startTime = millis(); // Reset start time to keep displaying waiting message
      displayWaitingMessage(); // Re-display waiting message
    }
    
    delay(100); // Check input every 100 milliseconds
  }
}

void displayWaitingMessage() {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Waiting...");
  digitalWrite(greenLEDPin, HIGH);
  digitalWrite(yellowLEDPin, LOW);
  digitalWrite(redLEDPin, LOW);
}

bool touchSensorTouched() {
  // Check if touch sensor is touched
  // Implement your touch sensor logic here
  return false; // Placeholder, replace with actual logic
}

float calculateResult(String input) {
  // Calculate result based on input string
  float result = 0.0;
  // Implement your calculation logic here
  // For example:
  result = eval(input);
  return result;
}

float eval(String expr) {
  // Basic expression evaluator
  // Assumes expr is a valid arithmetic expression without parentheses
  // Supports only +, -, *, /
  int i = 0;
  float leftOperand = 0.0;
  float rightOperand = 0.0;
  char op;
  while (i < expr.length()) {
    if (isdigit(expr[i]) || expr[i] == '.') {
      leftOperand = expr.substring(i).toFloat();
      break;
    }
    i++;
  }
  i++;
  while (i < expr.length()) {
    if (expr[i] == '+' || expr[i] == '-' || expr[i] == '*' || expr[i] == '/') {
      op = expr[i];
      break;
    }
    i++;
  }
  i++;
  while (i < expr.length()) {
    if (isdigit(expr[i]) || expr[i] == '.') {
      rightOperand = expr.substring(i).toFloat();
      break;
    }
    i++;
  }
  switch (op) {
    case '+':
      return leftOperand + rightOperand;
    case '-':
      return leftOperand - rightOperand;
    case '*':
      return leftOperand * rightOperand;
    case '/':
      if (rightOperand != 0) {
        return leftOperand / rightOperand;
      } else {
        return 0.0; // Division by zero
      }
    default:
      return 0.0; // Invalid operator
  }
}