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

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] = {19, 18, 5, 17};
byte colPins[COLS] = {16, 4, 2, 15};

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

RTC_DS1307 rtc;

#define EEPROM_ADDRESS  0x50
char inputBuffer[100]; // Increased buffer size to accommodate date and time
int inputIndex = 0;
float volume = 0;
float price = 90.0;

float rate;
float  vol = 0;
long code = 0;
#define EEPROM_SIZE 512

void setup() {
  Serial.begin(115200);
  Wire.begin();
  rtc.begin();
}

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

  if (key >= '0' && key <= '9') {
    inputBuffer[inputIndex++] = key;
    code = code * 10 + (key - '0');
    rate = 1000.0 / price;
    vol = (code * rate);
    volume = round(vol * 100.0) / 100000.0;
   
    delay(100);
  }
  
  if (key == 'D') {
    inputBuffer[inputIndex] = '\0'; // Null-terminate the string
    saveToEEPROM(inputBuffer);
    inputIndex = 0; // Reset the input index
    code = 0;
  }

  if (Serial.available() > 0) {
    String command = Serial.readStringUntil('\n');
    if (command == "show") {
      viewSavedData();
    }
  }
}

void saveToEEPROM(char* inputBuffer) {
  if (inputBuffer) {
    DateTime now = rtc.now();
    String dateTimeStr = String(now.year()) + "-" + String(now.month()) + "-" + String(now.day()) +
                 " " + String(now.hour()) + ":" + String(now.minute()) + ":" + String(now.second());

    String dataToStore = "Rs." + String(inputBuffer) + " - " + volume +"litre" + "-" + dateTimeStr + "\n";
    
    int eepromAddress = 0;

    // Find the first available EEPROM address
    while (eepromAddress < EEPROM_SIZE) {
      Wire.beginTransmission(EEPROM_ADDRESS);
      Wire.write(eepromAddress >> 8);
      Wire.write(eepromAddress & 0xFF);
      Wire.endTransmission(false);
      Wire.requestFrom(EEPROM_ADDRESS, 1);

      if (Wire.available()) {
        char data = Wire.read();
        if (data == '\0') {
          break; // Found an empty slot
        }
      } else {
        break;
      }

      eepromAddress++;
    }

    if (eepromAddress < EEPROM_SIZE) {
      // Write each byte of the string to EEPROM
      for (int i = 0; i < dataToStore.length(); i++) {
        Wire.beginTransmission(EEPROM_ADDRESS);
        Wire.write(eepromAddress >> 8);
        Wire.write(eepromAddress & 0xFF);
        Wire.write(dataToStore[i]);
        Wire.endTransmission();
        delay(5);
        eepromAddress++;
        if (eepromAddress >= EEPROM_SIZE) {
          Serial.println("Error: EEPROM memory full");
          delay(1000000000);
          break;
        }
      }
      
      Serial.println("Data saved to EEPROM: " + dataToStore);
      delay(1000);
    } else {
      Serial.println("Error: EEPROM memory full");
    }
  }
}

void viewSavedData() {
  int eepromAddress = 0;
  char buffer[EEPROM_SIZE];
  int bytesRead = 0;
  Serial.print("Data read from EEPROM: \n");
  while (true) {
    Wire.beginTransmission(EEPROM_ADDRESS);
    Wire.write(eepromAddress >> 8);
    Wire.write(eepromAddress & 0xFF);
    Wire.endTransmission(false);
    Wire.requestFrom(EEPROM_ADDRESS, 1);

    if (Wire.available()) {
      char data = Wire.read();
      buffer[bytesRead] = data;
      bytesRead++;

      if (data == '\0' || bytesRead >= EEPROM_SIZE) {
        // Print the current entry and move to the next line
        buffer[bytesRead] = '\0';
        Serial.println(buffer);

        if (data == '\0') {
          break; // Reached the end of EEPROM
        }

        bytesRead = 0; // Reset for the next entry
      }
    } else {
      break;
    }

    eepromAddress++;
  }

  delay(1000);
}