#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Pin Definitions
const int ldrPin = A0;    // LDR (Photoresistor) connected to A0
const int buzzerPin = 9;  // Buzzer connected to digital pin 9
const int heartRateThreshold = 50; // Heart rate threshold for the alert

// Variables
int heartRate = 0;       // Variable to store calculated heart rate
int ldrValue = 0;        // Raw LDR value from analog input

// Initialize LCD (20x4) with I2C address
LiquidCrystal_I2C lcd(0x3F, 20, 4); // Replace 0x3F with 0x27 if needed

void setup() {
  // Initialize Serial Monitor (for debugging)
  Serial.begin(9600);
  
  // Initialize Buzzer
  pinMode(buzzerPin, OUTPUT);
  digitalWrite(buzzerPin, LOW); // Ensure buzzer is off initially
  
  // Initialize LCD
  lcd.begin(20, 4);  
  lcd.backlight();  // Turn on LCD backlight
  lcd.setCursor(0, 0);
  lcd.print("Smartwatch Project");
  delay(2000);
  lcd.clear();
  
  // Display initial message
  lcd.setCursor(0, 0);
  lcd.print("Heart Rate Monitor");
  lcd.setCursor(0, 1);
  lcd.print("Initializing...");
  delay(2000);
  lcd.clear();
}

void loop() {
  // Read the value from the LDR
  ldrValue = analogRead(ldrPin);

  // Simulate heart rate using the LDR value
  heartRate = calculateHeartRate(ldrValue);
  
  // Display heart rate on the LCD
  lcd.setCursor(0, 0);
  lcd.print("Heart Rate: ");
  lcd.print(heartRate);
  lcd.print(" BPM"); // Beats Per Minute
  
  // Check if the heart rate is below the threshold
  if (heartRate < heartRateThreshold) {
    lcd.setCursor(0, 1);
    lcd.print("WARNING: Low HR!   ");
    activateBuzzer(); // Alert the user
  } else {
    lcd.setCursor(0, 1);
    lcd.print("HR is Normal       ");
    deactivateBuzzer(); // Ensure the buzzer is off
  }

  // Debugging output in Serial Monitor
  Serial.print("LDR Value: ");
  Serial.print(ldrValue);
  Serial.print(" | Heart Rate: ");
  Serial.println(heartRate);
  
  delay(1000); // Wait 1 second before the next reading
}

// Function to simulate heart rate based on LDR value
int calculateHeartRate(int ldrValue) {
  // Map the LDR value (0-1023) to a heart rate range (60-120 BPM)
  return map(ldrValue, 0, 1023, 60, 120);
}

// Function to activate the buzzer
void activateBuzzer() {
  digitalWrite(buzzerPin, HIGH); // Turn on the buzzer
}

// Function to deactivate the buzzer
void deactivateBuzzer() {
  digitalWrite(buzzerPin, LOW); // Turn off the buzzer
}