#include <OneWire.h>
#include <DallasTemperature.h>
#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);

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

#define BUZZER_PIN 4
#define MODE_BUTTON 12
#define CONFIRM_BUTTON 13
#define RETURN_BUTTON 14

int mode = 0; // 0: Not selected, 1: Hot Mode, 2: Cold Mode
int activeMode = 0; // The mode that has been confirmed
float temperature = 0.0;
bool isModeActive = false;

unsigned long lastTempRequest = 0;
unsigned long tempInterval = 1000; // 1 second interval for temperature updates

void setup() {
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(MODE_BUTTON, INPUT_PULLUP);
  pinMode(CONFIRM_BUTTON, INPUT_PULLUP);
  pinMode(RETURN_BUTTON, INPUT_PULLUP);

  sensors.begin();
  
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  display.display();
  delay(2000);
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
}

void loop() {
  handleButtons();

  unsigned long currentMillis = millis();

  if (isModeActive && currentMillis - lastTempRequest >= tempInterval) {
    lastTempRequest = currentMillis;
    sensors.requestTemperatures();
    temperature = sensors.getTempCByIndex(0);
  }

  display.clearDisplay();
  
  if (isModeActive) {
    if (activeMode == 1) {
      display.setCursor(0, 0);
      centerTextOnDisplay("Hot Mode");
      checkTemperatureHotMode();
    } else if (activeMode == 2) {
      display.setCursor(0, 0);
      centerTextOnDisplay("Cold Mode");
      checkTemperatureColdMode();
    }
    centerTextOnDisplay("Temp: " + String(temperature) + " C");
  } else {
    displayModeSelectionScreen();
  }
  
  display.display();
}

void handleButtons() {
  static unsigned long lastButtonPress = 0;
  unsigned long debounceDelay = 50; // 50 milliseconds debounce

  // Track the previous and current state of the MODE_BUTTON
  static bool lastModeButtonState = HIGH;
  bool modeButtonState = digitalRead(MODE_BUTTON);

  // Detect the falling edge: button pressed down and released
  if (modeButtonState == LOW && lastModeButtonState == HIGH) {
    if (millis() - lastButtonPress > debounceDelay) {
      mode = (mode + 1) % 3; // Cycle through 0, 1, 2 (0: Not selected)
      lastButtonPress = millis(); // Update debounce timer
    }
  }

  // Track the previous and current state of the CONFIRM_BUTTON
  static bool lastConfirmButtonState = HIGH;
  bool confirmButtonState = digitalRead(CONFIRM_BUTTON);

  if (confirmButtonState == LOW && lastConfirmButtonState == HIGH) {
    if (millis() - lastButtonPress > debounceDelay) {
      if (mode != 0) {
        activeMode = mode; // Lock the mode
        isModeActive = true; // Activate the mode
      }
      lastButtonPress = millis(); // Update debounce timer
    }
  }

  // Track the previous and current state of the RETURN_BUTTON
  static bool lastReturnButtonState = HIGH;
  bool returnButtonState = digitalRead(RETURN_BUTTON);

  if (returnButtonState == LOW && lastReturnButtonState == HIGH) {
    if (millis() - lastButtonPress > debounceDelay) {
      activeMode = 0; // Deactivate the mode
      isModeActive = false; // Return to selection
      mode = 0; // Reset mode selection
      lastButtonPress = millis(); // Update debounce timer
    }
  }

  // Update the last button states
  lastModeButtonState = modeButtonState;
  lastConfirmButtonState = confirmButtonState;
  lastReturnButtonState = returnButtonState;
}

void checkTemperatureHotMode() {
  if (temperature > 50.0) {
    digitalWrite(BUZZER_PIN, HIGH); // Beep quickly
  } else if (temperature < 45.0) {
    digitalWrite(BUZZER_PIN, LOW); // Stop buzzer
  }
}

void checkTemperatureColdMode() {
  if (temperature > 20.0) {
    digitalWrite(BUZZER_PIN, HIGH); // Beep quickly
  } else if (temperature < 10.0) {
    digitalWrite(BUZZER_PIN, LOW); // Stop buzzer
  }
}

void displayModeSelectionScreen() {
  display.setTextSize(2);
  display.setCursor(0, 0);
  centerTextOnDisplay("MODE");
  display.setCursor(0, 16);
  centerTextOnDisplay("SELECTION");

  display.setTextSize(1);
  display.setCursor(0, 40);
  
  if (mode == 1) {
    centerTextOnDisplay("> Hot Mode");
  } else {
    centerTextOnDisplay("  Hot Mode");
  }
  
  display.setCursor(0, 50);
  if (mode == 2) {
    centerTextOnDisplay("> Cold Mode");
  } else {
    centerTextOnDisplay("  Cold Mode");
  }
}

void centerTextOnDisplay(String text) {
  int16_t x1, y1;
  uint16_t w, h;
  
  display.getTextBounds(text, 0, 0, &x1, &y1, &w, &h);
  display.setCursor((SCREEN_WIDTH - w) / 2, display.getCursorY());
  display.println(text);
}