#include <OneWire.h>
#include <DallasTemperature.h>
#include <PID_v1.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <EEPROM.h>

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

// DS18B20 settings
#define ONE_WIRE_BUS 2
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

// PID settings
#define SSR_PIN 9  // PWM pin to control SSR
double Setpoint;   // Loaded from EEPROM
double Input;
double Output;
double Kp = 10.0, Ki = 0.5, Kd = 0.1;  // Adjusted for heater response
PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);

// Button settings
#define INC_BUTTON 3
#define DEC_BUTTON 4
int lastIncState = HIGH;
int lastDecState = HIGH;
unsigned long lastDebounceTime = 0;
const long debounceDelay = 10;

// EEPROM settings
#define EEPROM_ADDRESS 0

// Timing
unsigned long previousMillis = 0;
const long interval = 1000;  // 1-second update cycle

void setup() {
  Serial.begin(9600);

  // Initialize OLED
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("PID Heater Control");
  display.display();

  // Initialize DS18B20
  sensors.begin();

  // Initialize PID
  myPID.SetMode(AUTOMATIC);
  myPID.SetOutputLimits(0, 255);  // PWM range
  pinMode(SSR_PIN, OUTPUT);
  digitalWrite(SSR_PIN, LOW);  // SSR off initially

  // Initialize buttons with internal pull-ups
  pinMode(INC_BUTTON, INPUT_PULLUP);
  pinMode(DEC_BUTTON, INPUT_PULLUP);

  // Load setpoint from EEPROM
  EEPROM.get(EEPROM_ADDRESS, Setpoint);
  if (isnan(Setpoint) || Setpoint < 0 || Setpoint > 100) {
    Setpoint = 30.0;  // Default 30°C
    EEPROM.put(EEPROM_ADDRESS, Setpoint);
  }
}

void loop() {
  unsigned long currentMillis = millis();

  // Handle button presses
  int incReading = digitalRead(INC_BUTTON);
  int decReading = digitalRead(DEC_BUTTON);

  // Increase setpoint by 2 degrees
  if (incReading != lastIncState) {
    lastDebounceTime = currentMillis;
  }
  if ((currentMillis - lastDebounceTime) > debounceDelay && incReading == LOW) {
    Setpoint += 0.05;  // Changed from 1.0 to 2.0
    if (Setpoint > 100) Setpoint = 100;
    EEPROM.put(EEPROM_ADDRESS, Setpoint);
  }
  lastIncState = incReading;

  // Decrease setpoint by 2 degrees
  if (decReading != lastDecState) {
    lastDebounceTime = currentMillis;
  }
  if ((currentMillis - lastDebounceTime) > debounceDelay && decReading == LOW) {
    Setpoint -= 0.05;  // Changed from 1.0 to 2.0
    if (Setpoint < 0) Setpoint = 0;
    EEPROM.put(EEPROM_ADDRESS, Setpoint);
  }
  lastDecState = decReading;

  // Update PID and display
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    // Read temperature
    sensors.requestTemperatures();
    Input = sensors.getTempCByIndex(0);

    // Compute PID output
    myPID.Compute();

    // Apply PWM to SSR
    analogWrite(SSR_PIN, Output);  // 0-255 controls SSR duty cycle

    // Update OLED
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println("PID Heater Control");
    display.setCursor(0, 16);
    display.print("Setpoint: ");
    display.print(Setpoint);
    display.println(" C");
    display.setCursor(0, 32);
    display.print("Temp: ");
    display.print(Input);
    display.println(" C");
    display.setCursor(0, 48);
    display.print("Output: ");
    display.print(Output);
    display.println("/255");
    display.display();

    // Serial debug
    Serial.print("Setpoint: ");
    Serial.print(Setpoint);
    Serial.print(" C, Temp: ");
    Serial.print(Input);
    Serial.print(" C, Output: ");
    Serial.println(Output);
  }
}