//#define USE_FASTPID         // Required for PID control
//#define USE_DS18B20
//#define READ_VOLTAGE        // Enable voltage mode
#define USE_PTC_THERMISTOR
#define USE_NTC_THERMISTOR

//-------------Debugging messages 
//#define DEBUG_PID

#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <math.h>

#ifdef USE_FASTPID
#include <FastPID.h>
#endif

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Thermistor setup (for temp modes)
const int thermistorPin = A0;
const float seriesResistor = 10000.0;
const float nominalResistance = 1000.0;
const float nominalTemperature = 25.0;
const float bCoefficient = 3950.0;  // NTC
const float tempCoefficient = 0.007;  // PTC

// Voltage feedback pin
#define PIN_VOLTAGE_FEEDBACK A1  // Measures output voltage after MOSFET

// Button & output
#define BUTTON_UP 2
#define BUTTON_DOWN 3
#define PWM_OUTPUT 5    // Drives MOSFET

// Button debounce
unsigned long lastDebounceTimeUp = 0;
unsigned long lastDebounceTimeDown = 0;
const unsigned long debounceDelay = 50;
bool lastUpState = HIGH;
bool lastDownState = HIGH;
unsigned long lastButtonPressTime = 0;
const unsigned int displayDuration = 3000;
bool showSetTemp = false;

// Temps or Voltage
float currentTemp = 0;  // Temp or voltage feedback
float setTemp = 0.0;    // Temp or voltage setpoint (default 0)
int pidOutput = 0;

#ifdef USE_DS18B20
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
#define ONE_WIRE_BUS 4
#endif

#ifdef USE_FASTPID
const float Kp = 2.0;  // Tune these for voltage control
const float Ki = 0.5;
const float Kd = 5.0;
FastPID pid(Kp, Ki, Kd, 100, false);  // 100 Hz, no clamping
#endif

void setup() {
  Serial.begin(9600);
#ifdef USE_DS18B20
  sensors.begin();
#endif
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);

  pinMode(BUTTON_UP, INPUT_PULLUP);
  pinMode(BUTTON_DOWN, INPUT_PULLUP);
  pinMode(PWM_OUTPUT, OUTPUT);
#ifdef READ_VOLTAGE
  pinMode(PIN_VOLTAGE_FEEDBACK, INPUT);
#endif
}

void loop() {
  handleButtons();

#ifdef READ_VOLTAGE
  currentTemp = reading_voltage();  // Feedback from A1
#else
#ifdef USE_PTC_THERMISTOR
  currentTemp = readPTCThermistor();
#else
#ifdef USE_NTC_THERMISTOR
  currentTemp = readThermistor();
#endif
#endif
#endif

#ifdef USE_FASTPID
  pidOutput = pid.step(setTemp, currentTemp);  // Adjust PWM to match setpoint
#else
  pidOutput = (currentTemp < setTemp) ? 255 : 0;
#endif

  analogWrite(PWM_OUTPUT, pidOutput);  // Drive MOSFET
  updateDisplay();

#ifdef USE_DS18B20
  sensors.requestTemperatures();
  Serial.print("DS Temp: ");
  Serial.print(sensors.getTempCByIndex(0));
  Serial.print(" C | ");
#endif

#ifdef DEBUG_PID
  Serial.print("Feedback: ");
  Serial.print(currentTemp);
#endif
  
#ifdef READ_VOLTAGE
  Serial.print(" V | Setpoint: ");
//#else
 // Serial.print(" C | Setpoint: ");
#endif

#ifdef DEBUG_PID
  Serial.print(setTemp);
  Serial.print(" | PWM: ");
  Serial.println(pidOutput);
#endif  

  delay(200);
}

#ifdef READ_VOLTAGE
float reading_voltage() {
  int val = analogRead(PIN_VOLTAGE_FEEDBACK);
  float voltage = 5.0 * val / 1023.0;  // 0-5V (adjust to 3.3V if needed)
  return voltage;
}
#endif

#ifdef USE_PTC_THERMISTOR
float readPTCThermistor() {
  int adcValue = analogRead(thermistorPin);
  float resistance = seriesResistor * (1023.0 / adcValue - 1.0);
  float temperature = nominalTemperature + (resistance - nominalResistance) / (nominalResistance * tempCoefficient);
  return temperature;
}
#endif

#ifdef USE_NTC_THERMISTOR
float readThermistor() {
  int adcValue = analogRead(thermistorPin);
  float resistance = seriesResistor * (1023.0 / adcValue - 1.0);
  float steinhart = resistance / nominalResistance;
  steinhart = log(steinhart);
  steinhart /= bCoefficient;
  steinhart += 1.0 / (nominalTemperature + 273.15);
  steinhart = 1.0 / steinhart;
  return steinhart - 273.15;
}
#endif

void updateDisplay() {
  display.clearDisplay();
  int currentTempInt = (int)round(currentTemp);
  int setTempInt = (int)round(setTemp);

  if (showSetTemp && (millis() - lastButtonPressTime < displayDuration)) {
    updateDisplayInfo(setTempInt, currentTempInt);
  } else {
    updateDisplayInfo(currentTempInt, setTempInt);
    showSetTemp = false;

#ifdef USE_DS18B20
    display.setTextSize(1);
    display.setCursor(0, 56);
    display.print("DS:");
    int dsTempInt = (int)round(sensors.getTempCByIndex(0));
    display.print(dsTempInt);
#endif
  }
  display.display();
}

void updateDisplayInfo(int largeTemp, int smallTemp) {

bool upState = digitalRead(BUTTON_UP);
  bool downState = digitalRead(BUTTON_DOWN);
  
  display.setTextSize(2);
  display.setCursor(0, 0);
#ifdef READ_VOLTAGE
  display.print("SetV:");
#else
  display.print("SetT:");
#endif
  display.print(smallTemp);
  display.setCursor(100, 0);
  display.print(upState);
  display.print(downState);

  display.setTextSize(6);
  if (largeTemp < 10) {
    display.setCursor(45, 18);
    display.print(largeTemp);
  } 
  else if (largeTemp < 100) {
    display.setCursor(25, 18);
    display.print(largeTemp);
  } 
  else {
    display.setCursor(2, 18);
    display.print(largeTemp);
  }
}

/*
void updateDisplayButtonsStet() {
  display.clearDisplay();
  bool upState = digitalRead(BUTTON_UP);
  bool downState = digitalRead(BUTTON_DOWN);
  

if (upState != HIGH) {
    // turn LED on:
     display.setTextSize(6);
      display.setCursor(45, 18);
    display.print("UP");
  }
 if (downState != HIGH) {
    // turn LED on:
    display.setTextSize(6);
      display.setCursor(45, 18);
    display.print("Downn");
 } 
 
    display.display();
    delay(200);
    
}
*/
void handleButtons() {
  bool upState = digitalRead(BUTTON_UP);
  bool downState = digitalRead(BUTTON_DOWN);
  String space = "    ";

  // Detect state changes
  if (upState != lastUpState) {
    lastDebounceTimeUp = millis();
    Serial.print("UP pressed - lastDebounceTimeDown ");
    Serial.println(lastDebounceTimeDown);
  }
  if (downState != lastDownState) {
    lastDebounceTimeDown = millis();
    Serial.print("DOWN pressed - lastDebounceTimeDown ");
    Serial.println(lastDebounceTimeDown);
  }

  // Check UP button press
  //if ((millis() - lastDebounceTimeUp) > debounceDelay && upState == LOW && lastUpState == HIGH) {
  if ((millis() - lastDebounceTimeUp) > debounceDelay && upState == LOW && lastUpState == HIGH) {

  //if ((millis() - lastDebounceTimeDown) > debounceDelay && downState == LOW && lastDownState == HIGH)
    
    Serial.print("DOWN pressed - Set Temp decreased to: ");
    Serial.println(setTemp);
  //if (upState != lastUpState) {  
    setTemp += 1;
    if (setTemp > 150) setTemp = 150;

    lastButtonPressTime = millis();
    showSetTemp = true;

    Serial.print("UP pressed - Set Temp increased to: ");
    Serial.println(setTemp);
  }
  else {
    Serial.println("UP NOT pressed");
    
    /*Serial.print("Full condition result: ");
    bool condition = ((millis() - lastDebounceTimeUp) > debounceDelay && upState == LOW && lastUpState == HIGH);
   bool condition2 = (millis() - lastDebounceTimeUp) > debounceDelay;
    Serial.println(condition);*/
     /*Serial.println(condition2);
    Serial.print("millis()-lastDebounceTimeUp >");
    Serial.print(condition2);
    Serial.print(" and ");
    Serial.print("upState");
    Serial.print(upState);
    Serial.print("== LOW");
    Serial.print("and");
    Serial.print("lastUpState");
    Serial.print(lastUpState);
    Serial.println("HIGH");*/
    
    

    
    /*Serial.println(" >debounceDelay && debounceDelay == LOW ");
    Serial.print(debounceDelay);
    Serial.print(space);
    Serial.print(debounceDelay);
    //Serial.print(lastDebounceTimeUp);
    Serial.println(space ==0);
    Serial.print(debounceDelay);
    /Serial.print(" debounceDelay");
    Serial.print(space);
    Serial.print(upState);
    Serial.print(space);
    Serial.println(lastUpState);*/
  }

  // Check DOWN button press
  if ((millis() - lastDebounceTimeDown) > debounceDelay && downState == LOW && lastDownState == HIGH) {
    Serial.print("DOWN pressed - Set Temp decreased to: ");
    Serial.println(setTemp);
  //if (downState != lastDownState) {  
    setTemp -= 1;
    if (setTemp < 0) setTemp = 0;

    lastButtonPressTime = millis();
    showSetTemp = true;

    Serial.print("DOWN pressed - Set Temp decreased to: ");
    Serial.println(setTemp);
  }
  //else Serial.println("DOWN NOT pressed");

  // Save the current state for next cycle
  lastUpState = upState;
  lastDownState = downState;
}