struct BoilerData {
  int16_t tempSensor1;
  int16_t tempSensor2;
  int16_t tempSensor3;
};

constexpr size_t maxCycleCount = 10;
BoilerData historicalData[maxCycleCount];

size_t nextHistoricalEntry = 0;
bool HistoricalDataIsFull = false;


void addHistoricalData(int16_t sensor1, int16_t sensor2, int16_t sensor3) {
  historicalData[nextHistoricalEntry].tempSensor1 = sensor1;
  historicalData[nextHistoricalEntry].tempSensor2 = sensor2;
  historicalData[nextHistoricalEntry].tempSensor3 = sensor3;

  nextHistoricalEntry = (nextHistoricalEntry + 1) % maxCycleCount; // Move to the next index, cycling if necessary

  if (nextHistoricalEntry == 0) HistoricalDataIsFull = true; // If nextHistoricalEntry is back to 0, then we kknow the array is full
}

void printHistoricalDataAtIndex(size_t idx) {
  Serial.print(idx + 1); // for display start numbering at 1 (in C++ arrays starts at index 0)
  Serial.write('\t');
  Serial.print(historicalData[idx].tempSensor1);
  Serial.write('\t');
  Serial.print(historicalData[idx].tempSensor2);
  Serial.write('\t');
  Serial.println(historicalData[idx].tempSensor3);
}

void printHistoricalData() {

  Serial.println(F("\n-----------------------------"));
  // print the number of valid samples
  if (HistoricalDataIsFull) Serial.print(maxCycleCount);
  else Serial.print(nextHistoricalEntry);

  Serial.println(F(" Historical Data sample(s)"));
  Serial.println(F("-----------------------------"));
  Serial.println(F("#\tsensor1\tsensor2\tsensor3"));
  if (HistoricalDataIsFull) {
    // the array has been fill up so we have to go through all entries
    // because we use a circular buffer, the oldest entry is no longer at index 0
    // but it is at nextHistoricalEntry (the one we should overwrite)
    // so this is our start index, and we want to print maxCycleCount entries
    // we use modulo so that our index stays within the bounds of our array
    for (size_t i = nextHistoricalEntry; i < nextHistoricalEntry + maxCycleCount; ++i) {
      printHistoricalDataAtIndex(i % maxCycleCount); // Ensure the index stays within bounds
    }
  } else {
    for (size_t i = 0; i < nextHistoricalEntry; ++i) {
      // the array is not full yet, so we print samples from index 0 to nextHistoricalEntry (not included)
      printHistoricalDataAtIndex(i);
    }
  }
}

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

void loop() {
  addHistoricalData(random(200), random(200), random(200)); // add a new random entrty
  printHistoricalData();
  delay(1000);
}