#include <Arduino.h>

// Define the Hamming(7, 4) lookup table
const byte hammingTable[16] = {
  0b0000000, 0b0000111, 0b0001011, 0b0001100,
  0b0010101, 0b0010010, 0b0011110, 0b0011001,
  0b0100111, 0b0100000, 0b0101100, 0b0101011,
  0b0110010, 0b0110101, 0b0111001, 0b0111110
};

// Function to encode a 4-bit message using Hamming(7, 4) code
byte hammingEncode(byte message) {
  byte encodedMessage = 0;

  // Set the data bits in the encoded message
  encodedMessage |= (message & 0x0F);

  // Calculate and set the parity bits
  encodedMessage |= ((encodedMessage & 0x01) ^ ((encodedMessage >> 1) & 0x01) ^ ((encodedMessage >> 2) & 0x01)) << 4;
  encodedMessage |= (((encodedMessage >> 1) & 0x01) ^ ((encodedMessage >> 3) & 0x01) ^ ((encodedMessage >> 4) & 0x01)) << 5;
  encodedMessage |= (((encodedMessage >> 2) & 0x01) ^ ((encodedMessage >> 3) & 0x01) ^ ((encodedMessage >> 5) & 0x01)) << 6;

  return encodedMessage;
}

// Function to decode a 7-bit received message using Hamming(7, 4) code
byte hammingDecode(byte receivedMessage) {
  byte syndrome = 0;

  // Calculate the syndrome bits
  syndrome |= (((receivedMessage >> 1) & 0x01) ^ ((receivedMessage >> 3) & 0x01) ^ ((receivedMessage >> 5) & 0x01) ^ ((receivedMessage >> 7) & 0x01)) << 2;
  syndrome |= (((receivedMessage >> 2) & 0x01) ^ ((receivedMessage >> 3) & 0x01) ^ ((receivedMessage >> 6) & 0x01) ^ ((receivedMessage >> 7) & 0x01)) << 1;
  syndrome |= (((receivedMessage >> 4) & 0x01) ^ ((receivedMessage >> 5) & 0x01) ^ ((receivedMessage >> 6) & 0x01) ^ ((receivedMessage >> 7) & 0x01));

  // Check if the received message is valid
  if (syndrome != 0) {
    // Correct the bit with the error
    receivedMessage ^= (1 << (7 - syndrome));
  }

  // Extract and return the decoded 4-bit message
  return receivedMessage & 0x0F;
}

void setup() {
  Serial.begin(9600);

  byte originalMessage = 0b1010;
  byte encodedMessage = hammingEncode(originalMessage);

  Serial.print("Original Message: ");
  Serial.println(originalMessage, BIN);

  Serial.print("Encoded Message: ");
  Serial.println(encodedMessage, BIN);

  byte receivedMessage = encodedMessage;
  byte decodedMessage = hammingDecode(receivedMessage);

  Serial.print("Received Message: ");
  Serial.println(receivedMessage, BIN);

  Serial.print("Decoded Message: ");
  Serial.println(decodedMessage, BIN);
}

void loop() {
  // Empty loop
}