//////////PERFECTLY WORKING//////////////////



#include <LiquidCrystal.h>
#include <Keypad.h>

// —— PIN ASSIGNMENTS ——

// Parallel LCD (4‑bit mode):
//   RS → D11
//    E → D12
//   D4 → D13
//   D5 → D14
//   D6 → D15
//   D7 → D0
LiquidCrystal lcd(11, 12, 13, 14, 15, 0);

// Keypad rows and columns:
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] = {2, 3, 4, 5};  // D2–D5
byte colPins[COLS] = {6, 7, 8, 9};  // D6–D9
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// Push‑button:
const int BUTTON_PIN = 10;        // D10, wired with INPUT_PULLUP

// —— STATE VARIABLES —— 
bool     lcdVisible       = true;
int      lastButtonState  = HIGH;
unsigned long lastDebounceTime = 0;
const unsigned long debounceDelay = 50;

int      pressCount       = 0;
unsigned long firstPressTime   = 0;

#define MAX_CHARS 20
String buffer = "";

// —— SETUP —— 
void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);  // Set button pin to input with pull-up

  lcd.begin(20, 4);  // Initialize 20x4 LCD
  lcd.setCursor(0, 0);
  lcd.print("System Ready");
  delay(1000);
  lcd.clear();
}

// —— MAIN LOOP —— 
void loop() {
  handleButton();
  handleKeypad();
}

// —— BUTTON HANDLER —— 
void handleButton() {
  static int lastState = HIGH;
  static unsigned long lastDebounce = 0;

  int reading = digitalRead(BUTTON_PIN);

  // Debounce check
  if (reading != lastState && (millis() - lastDebounce) > debounceDelay) {
    lastDebounce = millis();

    // Handle visibility directly: pressed = OFF, released = ON
    if (reading == LOW) {
      lcd.noDisplay();
      lcdVisible = false;

      // Count button press for triple-press-clear logic
      if (pressCount == 0) {
        firstPressTime = millis();
      }
      pressCount++;

      if (pressCount == 3 && (millis() - firstPressTime <= 3000)) {
        lcd.clear();
        buffer = "";  // 🔥 Clear buffer too!
        lcd.setCursor(0, 0);
        lcd.print("Display Cleared");
        delay(1000);
        lcd.clear();
        pressCount = 0;
      } else if (millis() - firstPressTime > 3000) {
        pressCount = 1;
        firstPressTime = millis();
      }

    } else if (reading == HIGH) {
      lcd.display();  // Button released: show LCD again
      lcdVisible = true;
    }
  }

  lastState = reading;
}


// —— KEYPAD HANDLER —— 
void handleKeypad() {
  char key = keypad.getKey();
  if (key && lcdVisible) {
    // Maintain rolling buffer of last 20 characters
    if (buffer.length() >= MAX_CHARS) {
      buffer = buffer.substring(1); // Remove first character if buffer exceeds MAX_CHARS
    }
    buffer += key;

    // Update LCD display with the buffer
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print(buffer);
  }
}