#include <LiquidCrystal_I2C.h>

#define LDR_PIN_0 0
#define LDR_PIN_1 1
#define LDR_PIN_2 2
#define LDR_PIN_3 3
#define LDR_PIN_4 4
#define LDR_PIN_5 5
#define LDR_PIN_6 6

LiquidCrystal_I2C lcd(0x27, 20, 4);

int readLightSensors() {
  if (digitalRead(LDR_PIN_2) == HIGH && digitalRead(LDR_PIN_3) == HIGH) {
    return 7;
  } else if (digitalRead(LDR_PIN_1) == HIGH && digitalRead(LDR_PIN_3) == HIGH) {
    return 8;
  } else if (digitalRead(LDR_PIN_0) == HIGH && digitalRead(LDR_PIN_3) == HIGH) {
    return 9;
  } else if (digitalRead(LDR_PIN_2) == HIGH && digitalRead(LDR_PIN_4) == HIGH) {
    return 4;
  } else if (digitalRead(LDR_PIN_1) == HIGH && digitalRead(LDR_PIN_4) == HIGH) {
    return 5;
  } else if (digitalRead(LDR_PIN_0) == HIGH && digitalRead(LDR_PIN_4) == HIGH) {
    return 6;
  } else if (digitalRead(LDR_PIN_2) == HIGH && digitalRead(LDR_PIN_5) == HIGH) {
    return 1;
  } else if (digitalRead(LDR_PIN_1) == HIGH && digitalRead(LDR_PIN_5) == HIGH) {
    return 2;
  } else if (digitalRead(LDR_PIN_0) == HIGH && digitalRead(LDR_PIN_5) == HIGH) {
    return 3;
  } else if (digitalRead(LDR_PIN_2) == HIGH && digitalRead(LDR_PIN_6) == HIGH) {
    return -1; // Placeholder for special character #
  } else if (digitalRead(LDR_PIN_1) == HIGH && digitalRead(LDR_PIN_6) == HIGH) {
    return 0;
  } else if (digitalRead(LDR_PIN_0) == HIGH && digitalRead(LDR_PIN_6) == HIGH) {
    return -2; // Placeholder for special character *
  } else {
    return -3; // Placeholder for no valid key
  }
}

void setup() {
  pinMode(LDR_PIN_0, INPUT);
  pinMode(LDR_PIN_1, INPUT);
  pinMode(LDR_PIN_2, INPUT);
  pinMode(LDR_PIN_3, INPUT);
  pinMode(LDR_PIN_4, INPUT);
  pinMode(LDR_PIN_5, INPUT);
  pinMode(LDR_PIN_6, INPUT);
  
  lcd.init();
  lcd.backlight();
}

void loop() {
  lcd.setCursor(0, 0);
  lcd.print("Keypad: ");
  int key = readLightSensors();

  if (key >= 0) {
    lcd.print(key);
  } else if (key == -1) {
    lcd.print("#");
  } else if (key == 0) {
    lcd.print("*");
  } else {
    lcd.print(" ");
  }

  delay(100);
}