#include <SevSeg.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <math.h>

// --- PIN DEFINITIONS ---
#define ONE_WIRE_BUS 2      // DS18B20 Data
#define NTC_PIN A7          // NTC Analog Input
#define BTN_UP A1           // Button to increase temp
#define BTN_DOWN A2         // Button to decrease temp
#define COMPRESSOR_PIN A3   // Output to Relay/MOSFET

// --- CONFIGURATION CONSTANTS ---
#define RESISTOR_ROOM_TEMP 4700 
#define SERIES_RESISTOR 4700    
#define BETA_COEFFICIENT 3950   
#define TEMPERATURE_NOMINAL 25  

// Hysteresis prevents the compressor from turning on/off rapidly at the threshold
// Example: If Set=25.0, On at 25.5, Off at 24.5
float hysteresis = 0.5; 

// --- OBJECTS ---
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
SevSeg sevSeg; 

// --- VARIABLES ---
// Timing
unsigned long timerSensors = 0;
unsigned long timerButtons = 0;     // For debouncing
unsigned long timerInactivity = 0;  // For returning to main menu
const int sensorInterval = 3000;    // Read sensors every 3s
const int buttonDebounce = 300;     // Min time between button presses (ms)
const int editTimeout = 3000;       // Time before returning to sensor view

// State
bool showDS18B20 = true;       // Toggle between sensors
bool isEditing = false;        // Are we currently changing the setpoint?

// Data
float currentDsTemp = 0.0;
float currentNtcTemp = 0.0;
float setPoint = 25.0;         // Default target temperature

void setup() {
  // Hardware Setup
  pinMode(BTN_UP, INPUT_PULLUP);
  pinMode(BTN_DOWN, INPUT_PULLUP);
  pinMode(COMPRESSOR_PIN, OUTPUT);
  
  // Initial States
  digitalWrite(COMPRESSOR_PIN, LOW); 
  Serial.begin(9600);
  sensors.begin();

  // Display Setup (Same as before)
  byte numDigits = 4;
  byte digitPins[] = {11, 12, 13, A0}; 
  byte segmentPins[] = {3, 4, 5, 6, 7, 8, 9, 10}; 
  bool resistorsOnSegments = false; 
  byte hardwareConfig = COMMON_CATHODE; 
  
  sevSeg.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments,
  false, false, false);
  sevSeg.setBrightness(90);
}

void loop() {
  // 1. ALWAYS REFRESH DISPLAY (High Priority)
  sevSeg.refreshDisplay(); 

  unsigned long currentMillis = millis();

  // 2. CHECK BUTTONS
  // Logic: If button pressed, enter "Editing" mode and reset inactivity timer
  if (currentMillis - timerButtons > buttonDebounce) {
    
    if (digitalRead(BTN_UP) == LOW) {
      setPoint += 0.5; // Increase by 0.5 degrees
      isEditing = true;
      timerInactivity = currentMillis;
      timerButtons = currentMillis;
    }
    
    if (digitalRead(BTN_DOWN) == LOW) {
      setPoint -= 0.5; // Decrease by 0.5 degrees
      isEditing = true;
      timerInactivity = currentMillis;
      timerButtons = currentMillis;
    }
  }

  // 3. CHECK TIMEOUT
  // If we are editing but haven't pressed a button in 3 seconds, stop editing
  if (isEditing && (currentMillis - timerInactivity > editTimeout)) {
    isEditing = false;
  }

  // 4. READ SENSORS (Every 3 seconds, unless we are furiously pressing buttons)
  if (currentMillis - timerSensors >= sensorInterval) {
    timerSensors = currentMillis;
    
    // Read DS18B20
    sensors.requestTemperatures(); 
    float t = sensors.getTempCByIndex(0);
    // Filter out errors (-127)
    if (t > -100) currentDsTemp = t;

    // Read NTC
    currentNtcTemp = readNTC();

    // Toggle view for next cycle (only affects display if NOT editing)
    showDS18B20 = !showDS18B20;
    
    // --- COMPRESSOR LOGIC ---
    // We only control compressor based on DS18B20 as requested
    controlCompressor();
  }

  // 5. UPDATE DISPLAY CONTENT
  // Decide what number goes onto the screen buffer
  if (isEditing) {
    // Show the Set Point (blinking or static)
    sevSeg.setNumber(setPoint*10, 1);
  } else {
    // Normal Mode: Cycle sensors
    if (showDS18B20) {
       // Optional: You could modify the library to show "d 25.0" 
       // but for now we just show the temp
       sevSeg.setNumber(currentDsTemp*10, 1);
    } else {
       sevSeg.setNumber(currentNtcTemp, 1);
    }
  }
}

// --- LOGIC: Compressor Control ---
void controlCompressor() {
  // Basic Thermostat: If Temp > Setpoint -> ON
  // With Hysteresis: 
  // ON if Temp > Setpoint + Hysteresis
  // OFF if Temp < Setpoint - Hysteresis
  
  if (currentDsTemp > (setPoint + hysteresis)) {
    digitalWrite(COMPRESSOR_PIN, HIGH);
  } 
  else if (currentDsTemp < (setPoint - hysteresis)) {
    digitalWrite(COMPRESSOR_PIN, LOW);
  }
}

// --- HELPER: Calculate NTC Temperature ---
float readNTC() {
  int analogValue = analogRead(NTC_PIN);
  if (analogValue == 0) return -999;

  float resistance = SERIES_RESISTOR / (1023.0 / analogValue - 1);
  float steinhart;
  steinhart = resistance / RESISTOR_ROOM_TEMP;       
  steinhart = log(steinhart);                        
  steinhart /= BETA_COEFFICIENT;                     
  steinhart += 1.0 / (TEMPERATURE_NOMINAL + 273.15); 
  steinhart = 1.0 / steinhart;                       
  steinhart -= 273.15;                               

  return steinhart;
}