#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <PID_v1.h>  // Include the PID library

// Pin definitions for Arduino Mega
#define BUTTON_MENU 22
#define BUTTON_UP 23
#define BUTTON_DOWN 24
#define BUTTON_OK 25
#define TEMP_SENSOR A1  // Temperature sensor input pin
#define LED_PIN 29      // LED output pin

// LCD setup
LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27, 16 columns, 2 rows

// Menu variables
enum MenuState { MAIN_MENU, SET_TEMP, SET_MAX_TEMP, SET_PID, SET_MODE };
MenuState menuState = MAIN_MENU;
bool inMenu = false;
unsigned long menuButtonPressTime = 0;
bool menuButtonHeld = false;
int selectedMenuItem = 0;
double setpoint = 25.0;
double maxTemperature = 300.0;
double kp = 2.0, ki = 0.5, kd = 0.1; // PID parameters
enum Mode { AUTONOMOUS, SLAVE };
Mode currentMode = AUTONOMOUS;
double tempIncrement = 1.0; // Temperature increment value

// Timing variables
unsigned long lastButtonPressTime = 0;
unsigned long debounceDelay = 300; // 300 ms debounce time
unsigned long lastDisplayUpdateTime = 0;
unsigned long displayUpdateInterval = 1500; // Update display every 1.5 seconds
unsigned long menuTimeout = 3000; // Menu timeout in 3 seconds
unsigned long lastInteractionTime = 0;

// PID control variables
double input = 0, output = 0; // Input from the sensor and output to the LED
PID myPID(&input, &output, &setpoint, kp, ki, kd, DIRECT); // PID object

// PID parameter selection
enum PIDState { SELECTING, ADJUSTING };
PIDState pidState = SELECTING;
int selectedPID = 0; // 0: Kp, 1: Ki, 2: Kd

void setup() {
  // Initialize LCD
  lcd.init();
  lcd.backlight();

  // Initialize buttons
  pinMode(BUTTON_MENU, INPUT);
  pinMode(BUTTON_UP, INPUT);
  pinMode(BUTTON_DOWN, INPUT);
  pinMode(BUTTON_OK, INPUT);

  // Initialize LED and PID controller
  pinMode(LED_PIN, OUTPUT);
  myPID.SetMode(AUTOMATIC);
  myPID.SetOutputLimits(0, 255); // Set limits for PWM output (0 to 255)

  // Display welcome message
  lcd.clear();
  lcd.print("Temp Controller");
  delay(1000);
  lcd.clear();
  lastDisplayUpdateTime = millis(); // Update display timer
}

void loop() {
  readButtons();

  // Read the temperature sensor value
  input = analogRead(TEMP_SENSOR) * (maxTemperature / 1023.0); // Convert analog input to temperature value

  // Compute PID output and control LED brightness
  myPID.Compute();
  analogWrite(LED_PIN, output); // Adjust LED brightness based on PID output

  if (inMenu) {
    unsigned long currentMillis = millis();
    if (currentMillis - lastInteractionTime >= menuTimeout) {
      inMenu = false; // Exit menu after 3 seconds of inactivity
      menuState = MAIN_MENU;
    }
    displayMenu(); // Continuously update the menu display
  } else {
    unsigned long currentMillis = millis();
    if (currentMillis - lastDisplayUpdateTime >= displayUpdateInterval) {
      lastDisplayUpdateTime = currentMillis;

      // Main screen display
      lcd.setCursor(0, 0);
      lcd.print("Temp: ");
      lcd.print(input, 1);
      lcd.print("C   "); // Clear remaining characters

      lcd.setCursor(0, 1);
      lcd.print("Mode: ");
      lcd.print(currentMode == AUTONOMOUS ? "AUTO " : "SLAVE"); // Add space to clear the line
    }
  }
}

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

  // Handle MENU button
  if (digitalRead(BUTTON_MENU) == HIGH) {
    if (!menuButtonHeld) {
      menuButtonPressTime = currentMillis;
      menuButtonHeld = true;
    } else if (currentMillis - menuButtonPressTime > 3000) {
      inMenu = true;
      menuButtonHeld = false;
      menuState = MAIN_MENU;
      lastInteractionTime = currentMillis; // Reset the inactivity timer
      lcd.clear(); // Clear LCD when menu is accessed
    }
  } else {
    menuButtonHeld = false;
  }

  // Handle button presses within the menu
  if (inMenu && (currentMillis - lastButtonPressTime >= debounceDelay)) {
    if (digitalRead(BUTTON_UP) == HIGH) {
      lastButtonPressTime = currentMillis;
      lastInteractionTime = currentMillis; // Reset the inactivity timer
      if (menuState == MAIN_MENU) {
        selectedMenuItem = (selectedMenuItem - 1 + 4) % 4; // 4 menu items
      } else {
        handleMenuSelection('U'); // 'U' stands for UP button
      }
      lcd.clear(); // Clear LCD on any button press in the menu
      displayMenu(); // Update the display after button press
    }
    if (digitalRead(BUTTON_DOWN) == HIGH) {
      lastButtonPressTime = currentMillis;
      lastInteractionTime = currentMillis; // Reset the inactivity timer
      if (menuState == MAIN_MENU) {
        selectedMenuItem = (selectedMenuItem + 1) % 4;
      } else {
        handleMenuSelection('D'); // 'D' stands for DOWN button
      }
      lcd.clear(); // Clear LCD on any button press in the menu
      displayMenu(); // Update the display after button press
    }
    if (digitalRead(BUTTON_OK) == HIGH) {
      lastButtonPressTime = currentMillis;
      lastInteractionTime = currentMillis; // Reset the inactivity timer
      handleMenuSelection('O'); // 'O' stands for OK button
      lcd.clear(); // Clear LCD on OK button press
      displayMenu(); // Update the display after button press
    }
  }
}

void displayMenu() {
  // Display content only in menu state
  if (inMenu) {
    lcd.setCursor(0, 0);
    switch (menuState) {
      case MAIN_MENU:
        lcd.print("> ");
        if (selectedMenuItem == 0) lcd.print("Set Temp      ");
        else if (selectedMenuItem == 1) lcd.print("Set Max Temp  ");
        else if (selectedMenuItem == 2) lcd.print("Set PID       ");
        else if (selectedMenuItem == 3) lcd.print("Set Mode      ");
        break;

      case SET_TEMP:
        lcd.print("Set Temp:     ");
        lcd.setCursor(0, 1);
        lcd.print(setpoint, 1);
        lcd.print(" C ");
        break;

      case SET_MAX_TEMP:
        lcd.print("Set Max Temp: ");
        lcd.setCursor(0, 1);
        lcd.print(maxTemperature, 1);
        lcd.print(" C ");
        break;

      case SET_PID:
        if (pidState == SELECTING) {
          lcd.print("Select PID:   ");
          lcd.setCursor(0, 1);
          if (selectedPID == 0) lcd.print("> Kp");
          else if (selectedPID == 1) lcd.print("> Ki");
          else if (selectedPID == 2) lcd.print("> Kd");
        } else if (pidState == ADJUSTING) {
          lcd.print("Adjust PID:   ");
          lcd.setCursor(0, 1);
          if (selectedPID == 0) lcd.print("Kp: ");
          else if (selectedPID == 1) lcd.print("Ki: ");
          else if (selectedPID == 2) lcd.print("Kd: ");
          lcd.print(selectedPID == 0 ? kp : selectedPID == 1 ? ki : kd, 1);
        }
        break;

      case SET_MODE:
        lcd.print("Set Mode:     ");
        lcd.setCursor(0, 1);
        lcd.print(currentMode == AUTONOMOUS ? "AUTO " : "SLAVE");
        break;
    }
  }
}

void handleMenuSelection(char button) {
  switch (menuState) {
    case MAIN_MENU:
      if (selectedMenuItem == 0) {
        menuState = SET_TEMP;
      } else if (selectedMenuItem == 1) {
        menuState = SET_MAX_TEMP;
      } else if (selectedMenuItem == 2) {
        menuState = SET_PID;
        pidState = SELECTING; // Start by selecting PID
      } else if (selectedMenuItem == 3) {
        menuState = SET_MODE;
      }
      break;

    case SET_TEMP:
      if (button == 'U') setpoint += tempIncrement;
      else if (button == 'D') setpoint -= tempIncrement;
      else if (button == 'O') menuState = MAIN_MENU; // OK to exit
      break;

    case SET_MAX_TEMP:
      if (button == 'U') maxTemperature += tempIncrement;
      else if (button == 'D') maxTemperature -= tempIncrement;
      else if (button == 'O') menuState = MAIN_MENU; // OK to exit
      break;

    case SET_PID:
      if (pidState == SELECTING) {
        if (button == 'U') selectedPID = (selectedPID - 1 + 3) % 3; // Cycle through PID parameters
        else if (button == 'D') selectedPID = (selectedPID + 1) % 3;
        else if (button == 'O') pidState = ADJUSTING; // OK to adjust selected PID
      } else if (pidState == ADJUSTING) {
        if (button == 'U') {
          if (selectedPID == 0) kp += 0.1;
          else if (selectedPID == 1) ki += 0.1;
          else if (selectedPID == 2) kd += 0.1;
        } else if (button == 'D') {
          if (selectedPID == 0) kp -= 0.1;
          else if (selectedPID == 1) ki -= 0.1;
          else if (selectedPID == 2) kd -= 0.1;
        } else if (button == 'O') {
          pidState = SELECTING; // OK to return to selecting
          myPID.SetTunings(kp, ki, kd); // Update PID parameters
        }
      }
      break;

    case SET_MODE:
      if (button == 'U' || button == 'D') {
        currentMode = (currentMode == AUTONOMOUS) ? SLAVE : AUTONOMOUS;
      } else if (button == 'O') {
        menuState = MAIN_MENU; // OK to exit
      }
      break;
  }
}