unsigned long startTime;
float currentMin;
float currentMax;
float currentSum;
int samples;
float tenMins[600];
float tenMinAverages[300];

void setup() {
  Serial.begin(112500);
  delay(2000);
  startTime = millis();
  Serial.println("-------------------- PROGRAM START --------------------");
  currentMin = 1000;
  currentMax = -20;
  samples = 0;
  currentSum = 0;
  int i;
  for(i=0; i < 300; i++){
    tenMinAverages[i] = 0;
  }
  for(i=0; i < 600; i++){
    tenMins[i] = 0;
  }
}

void loop() {
  float reading; // voltage read by thermistor
  unsigned long interval; // time between readings in ms
  char input; // input taken to generate report
  interval = 1000;
  if(millis() >= startTime + interval){ // watiting 1000 ms
    startTime = millis(); // resetting the timer
    reading = analogRead(33); // read the pin
    Serial.println(returnCelsius(reading)); // print the temperature
    setMax(returnCelsius(reading)); // pass the temperature to various functions to find averages, min, max, last 10 min array and running sum
    setMin(returnCelsius(reading));
    samples++; // increment number of samples taken
    lastTenMins(returnCelsius(reading));
    sumNewTemp(returnCelsius(reading));
    averagesList();
  }
  if(Serial.available() > 0){ // checking for input needed to generate report
    input = Serial.read();
    if(input == '0'){
      report();
    }
  }
}

float returnCelsius(float reading){ // converts voltage reading to degrees celsius | This function is adapted from code written by user "E" at https://arduinodiy.wordpress.com/2015/11/10/measuring-temperature-with-ntc-the-steinhart-hart-formula/
  float resistance;
  float temperature;
  resistance = (4095/reading) - 1;
  resistance = 10000.0*resistance;
  temperature = resistance/10000.0;
  temperature = log(temperature);
  temperature /= 3950;
  temperature += 1.0 / 298.15;
  temperature = 1.0 / temperature;
  temperature -= 273.15;
  return temperature;
}

float setMax(float temp){ // keeps track of maximum temperature recorded
  if(temp > currentMax){
    currentMax = temp;
  }
  return currentMax;
}


float setMin(float temp){ // keeps track of minimum temperature
  if(temp < currentMin){
    currentMin = temp;
  }
  return currentMin;
}

void lastTenMins(float latestTemp){ // this function manages an array that contains the readings over the last 10 mins
  int i;
  int j;
  if(samples < 600){ // first fills the array
    tenMins[samples - 1] = latestTemp;
  } else {
    for(i=0; i<600; i++){ // then for every new value passed once the array is full, shift every value array to the left once
      j = i - 1;
      if (j == -1){
        continue;
      }
      tenMins[j] = tenMins[i];
    }
    tenMins[599] = latestTemp; // then set the last value to the newest value
  }
}

float averageTenMins(){ //average of the last 10 mins
  int i;
  float sum;
  sum = 0;
  for(i=0; i < 600; i++){
    sum += tenMins[i];
  }
  return sum/600;
}

float cumulativeAverage(){ // calculates total average based on the running sum
  return currentSum/samples;
}

void averagesList(){ // maintains an array of the average of every 10 minute period that has passed
  if(samples != 0 && samples%600 == 0){
    tenMinAverages[(samples/600) - 1] = averageTenMins();
  }
}

float sumNewTemp(float temperature){ // maintains the running sum of temperatures
  currentSum += temperature;
  return currentSum;
}

void report(){ // prints a report to console
  int i;
  Serial.print("Program has been logging for: ");
  Serial.print(millis()/60000);
  Serial.println(" minutes");
  Serial.print("Max recorded Temperature: ");
  Serial.print(currentMax);
  Serial.println("oC");
  Serial.print("Min recorded Temperature: ");
  Serial.print(currentMin);
  Serial.println("oC");
  Serial.print("Overall average Temperature: ");
  Serial.print(cumulativeAverage());
  Serial.println("oC");
  Serial.print("Average Temperature over last 10 minutes: ");
  Serial.print(averageTenMins());
  Serial.println("oC");
  Serial.println("Here are the 10 minute averages since program began: (all in degrees celsius)");
  for(i=0; i < 200; i++){
    if(tenMinAverages[i] != 0.0){
      Serial.print("~~~");
      Serial.println(tenMinAverages[i]);
    } else {
      continue;
    }
  }
}