#include <EEPROM.h>
#include <SoftwareSerial.h>

//--- Pin Definitions ---
const int TEMP_SENSOR_PIN = 1;      // ADC1 (Physical pin 7)
const int CONTROL_PIN     = 0;      // PB0 (Physical pin 5)
const int RX_PIN          = 3;      // PB3 (Physical pin 2)
const int TX_PIN          = 4;      // PB4 (Physical pin 3)

//--- EEPROM Addresses ---
const int UPPER_LIMIT_ADDR = 0;
const int LOWER_LIMIT_ADDR = 4; // Use a different address for each value

//--- Global Variables ---
int upperLimitADC = 700;    // Default: Corresponds to ~28°C with the example sensor.  Will be overwritten from EEPROM
int lowerLimitADC = 300;    // Default: Corresponds to ~15°C with the example sensor. Will be overwritten from EEPROM
int temperatureADC;
bool controlPinState = LOW;
SoftwareSerial mySerial(RX_PIN, TX_PIN); // Initialize SoftwareSerial

//--- Function Declarations ---
void readTemperature();
void checkLimitsAndControl();
void updateLimitsFromSerial();
void storeLimitsToEEPROM();
void readLimitsFromEEPROM();
float convertADCtoCelsius(int adc_value); //Added function for converting ADC to celcius

//--- Setup ---
void setup() {
  //--- Initialize I/O Pins ---
  pinMode(CONTROL_PIN, OUTPUT);
  digitalWrite(CONTROL_PIN, controlPinState); //set default value

  //--- Initialize ADC ---
  analogReference(DEFAULT); // Use default VCC as reference
  // No need to set ADPS2, ADPS1, ADPS0 in ADCSRA, because the default value after reset is 0,
  // and it means f_osc/2 as ADC clock source, that is less than 200kHz.

  //--- Initialize Serial Communication ---
  mySerial.begin(9600);
  delay(100); // Give serial port time to initialize

  //--- Read Limits from EEPROM ---
  readLimitsFromEEPROM();

  // Send a startup message
  mySerial.println("ATtiny85 Temperature Monitor");
  mySerial.print("Upper Limit: ");
  mySerial.println(upperLimitADC);
  mySerial.print("Lower Limit: ");
  mySerial.println(lowerLimitADC);
}

//--- Main Loop ---
void loop() {
  readTemperature();
  checkLimitsAndControl();
  updateLimitsFromSerial();
  delay(1000); // Delay 1 second
}

//--- Function Definitions ---

void readTemperature() {
  // Read the analog value from the temperature sensor
  temperatureADC = analogRead(TEMP_SENSOR_PIN);
  // No need to discard first reading, because it is not mentioned in the datasheet.
  // Send the ADC value for debugging
  mySerial.print("Temperature ADC: ");
  mySerial.println(temperatureADC);
}

void checkLimitsAndControl() {
  // Check if the temperature is outside the limits
  if (temperatureADC > upperLimitADC || temperatureADC < lowerLimitADC) {
    if (controlPinState == LOW) {
      controlPinState = HIGH;
      digitalWrite(CONTROL_PIN, controlPinState);
      mySerial.println("Temperature OUT OF limits - Activating control");
    }
  } else {
    if (controlPinState == HIGH) {
      controlPinState = LOW;
      digitalWrite(CONTROL_PIN, controlPinState);
      mySerial.println("Temperature WITHIN limits - Deactivating control");
    }
  }
}

void updateLimitsFromSerial() {
  // Check if there is data available on the serial port
  if (mySerial.available() > 0) {
    String data = mySerial.readStringUntil('\n'); // Read until newline
    data.trim();  // Remove leading/trailing whitespace

    // Parse the data for the limits.  Robust parsing.
    int upperIndex = data.indexOf("UPPER=");
    int lowerIndex = data.indexOf("LOWER=");

    if (upperIndex != -1 && lowerIndex != -1) {
      String upperStr = data.substring(upperIndex + 6, lowerIndex); //extract the upper limit value
      String lowerStr = data.substring(lowerIndex + 6);  // Extract lower limit

      //attempt to convert the string to a number.
      int newUpperLimit = upperStr.toInt();
      int newLowerLimit = lowerStr.toInt();

      if(newUpperLimit != 0 && newLowerLimit != 0){ //check if the conversion was successful
          upperLimitADC = newUpperLimit;
          lowerLimitADC = newLowerLimit;
          storeLimitsToEEPROM(); //save to eeprom
          mySerial.println("Limits Updated and Stored:");
          mySerial.print("Upper Limit: ");
          mySerial.println(upperLimitADC);
          mySerial.print("Lower Limit: ");
          mySerial.println(lowerLimitADC);
      }
      else{
        mySerial.println("Invalid format.  Use UPPER=XXX LOWER=YYY");
      }
    }
     else {
      mySerial.println("Invalid format.  Use UPPER=XXX LOWER=YYY");
    }
  }
}

void storeLimitsToEEPROM() {
  // Store the upper and lower limits in EEPROM
  EEPROM.put(UPPER_LIMIT_ADDR, upperLimitADC);
  EEPROM.put(LOWER_LIMIT_ADDR, lowerLimitADC);
}

void readLimitsFromEEPROM() {
  // Read the upper and lower limits from EEPROM
  EEPROM.get(UPPER_LIMIT_ADDR, upperLimitADC);
  EEPROM.get(LOWER_LIMIT_ADDR, lowerLimitADC);
}

float convertADCtoCelsius(int adc_value) {
    // This is just an example conversion.  You MUST replace this with the
    // correct formula for your specific temperature sensor.
    //
    // For example, if you are using a TMP36:
    //   float voltage = adc_value * (5.0 / 1023.0);  // Convert ADC value to voltage (assuming 5V Vref)
    //   float temperatureC = (voltage - 0.5) * 100; // Convert voltage to temperature in Celsius
    //
    //  If you are using a thermistor, the calculation will be more complex and
    //  involve the Steinhart-Hart equation or a simplified approximation.  You'll
    //  need the thermistor's datasheet values (R0, T0, B) to do this accurately.
    //
    //  This example is for demonstration ONLY.
    return (adc_value * 0.488) - 50; //  (5000mV/1024)  - 50  made up numbers.
}