#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

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

// Pin Definitions
const int relayPin       = 5;
const int buzzerPin      = 4;

const int setButtonPin   = A3;
const int upButtonPin    = A2;
const int downButtonPin  = A1;
const int startButtonPin = A0;

// Variables
int timerSeconds = 0;
bool setupMode = false;
bool timerRunning = false;

// ============================================================================
// BEEP FUNCTION
// ============================================================================
void beepButton() {
  digitalWrite(buzzerPin, HIGH);
  delay(50);
  digitalWrite(buzzerPin, LOW);
}

// ============================================================================
// SETUP
// ============================================================================
void setup() {

  pinMode(relayPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);

  pinMode(setButtonPin, INPUT_PULLUP);
  pinMode(upButtonPin, INPUT_PULLUP);
  pinMode(downButtonPin, INPUT_PULLUP);
  pinMode(startButtonPin, INPUT_PULLUP);

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);

  // Splash Screen ------------------------------------------------------------
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);

  display.setTextSize(2);
  display.setCursor(45, 0);
  display.print("SAN");

  display.setCursor(10, 20);
  display.print("Creations");

  display.setTextColor(SSD1306_BLACK, SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(20, 50);
  display.print(" SANTOSH MISHRA ");

  display.display();
  delay(3000);

  // Welcome Screen -----------------------------------------------------------
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);

  display.setTextSize(2);
  display.setCursor(23, 0);
  display.print("UV CURE");

  display.setCursor(23, 15);
  display.print("STATION");

  display.drawLine(0, 30, 127, 30, SSD1306_WHITE);
  display.drawLine(0, 35, 127, 35, SSD1306_WHITE);

  display.setTextSize(1);
  display.setCursor(15, 43);
  display.print(" Press SETUP to ");

  display.setCursor(33, 53);
  display.print(" set TIME ");

  display.display();
  delay(2000);
  display.clearDisplay();
}

// ============================================================================
// MAIN LOOP
// ============================================================================
void loop() {
  checkButtons();

  if (setupMode) {
    displaySetupMode();
  } else if (timerRunning) {
    displayTimer();
  }
}

// ============================================================================
// CHECK FOR SETUP BUTTON
// ============================================================================
void checkButtons() {
  if (digitalRead(setButtonPin) == LOW) {
    beepButton();                     // *** SOUND FEEDBACK ***
    setupMode = true;
    while (digitalRead(setButtonPin) == LOW) delay(10);
  }
}

// ============================================================================
// SETUP MODE SCREEN
// ============================================================================
void displaySetupMode() {

  displaySetupScreen();

  unsigned long pressStart = 0;
  bool upPressed = false;
  bool downPressed = false;

  while (setupMode) {

    // ------------------------------------------------------------------------
    // UP BUTTON → short press = +30 sec, long press = +60 sec
    // ------------------------------------------------------------------------
    if (digitalRead(upButtonPin) == LOW && !upPressed) {
      upPressed = true;
      pressStart = millis();
    }

    if (digitalRead(upButtonPin) == HIGH && upPressed) {
      unsigned long duration = millis() - pressStart;

      beepButton();  // *** SOUND ***

      if (duration < 600) timerSeconds += 30; 
      else               timerSeconds += 60;

      displaySetupScreen();
      upPressed = false;
    }

    // ------------------------------------------------------------------------
    // DOWN BUTTON → short press = -30 sec, long press = -60 sec
    // ------------------------------------------------------------------------
    if (digitalRead(downButtonPin) == LOW && !downPressed) {
      downPressed = true;
      pressStart = millis();
    }

    if (digitalRead(downButtonPin) == HIGH && downPressed) {
      unsigned long duration = millis() - pressStart;

      beepButton();  // *** SOUND ***

      if (duration < 600)
        timerSeconds = max(0, timerSeconds - 30);
      else
        timerSeconds = max(0, timerSeconds - 60);

      displaySetupScreen();
      downPressed = false;
    }

    // ------------------------------------------------------------------------
    // START BUTTON
    // ------------------------------------------------------------------------
    if (digitalRead(startButtonPin) == LOW) {
      beepButton();               // *** SOUND ***

      setupMode = false;
      timerRunning = true;

      digitalWrite(relayPin, HIGH);

      beepButton(); // start beep
      delay(200);
    }

    delay(20); // debounce
  }
}

// ============================================================================
// DRAW SETUP SCREEN
// ============================================================================
void displaySetupScreen() {
  display.clearDisplay();

  // Draw Box
  display.drawLine(25, 30, 120, 30, SSD1306_WHITE);
  display.drawLine(25, 45, 120, 45, SSD1306_WHITE);
  display.drawLine(25, 30, 25, 45, SSD1306_WHITE);
  display.drawLine(120, 30, 120, 45, SSD1306_WHITE);

  // Title
  display.setTextSize(2);
  display.setCursor(30, 0);
  display.print("Setup");
  display.drawLine(0, 25, 127, 25, SSD1306_WHITE);

  display.setTextSize(1);
  display.setCursor(30, 50);
  display.print("Press Start");

  // Timer Value
  display.setCursor(30, 35);
  display.print("Seconds: " + String(timerSeconds));

  display.display();
}

// ============================================================================
// TIMER RUNNING SCREEN
// ============================================================================
void displayTimer() {

  display.clearDisplay();

  display.setTextSize(4);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(20, 15);

  display.print(timerSeconds / 60);
  display.print(":");

  if (timerSeconds % 60 < 10) display.print("0");
  display.print(timerSeconds % 60);

  display.display();

  delay(1000);

  if (--timerSeconds < 0) {
    digitalWrite(relayPin, LOW);

    digitalWrite(buzzerPin, HIGH);
    delay(2000);
    digitalWrite(buzzerPin, LOW);

    timerRunning = false;
    timerSeconds = 0;
    setupMode = true;
  }
}