#include <OneWire.h>
#include <DallasTemperature.h>
#include <SD.h>
#include <SPI.h>

// Pin assignments
const int oneWireBus = 2;       // DS18B20 data pin
const int ldrPin = A0;          // LDR analog output pin
const int chipSelect = 10;      // SD card module CS pin

// DS18B20 setup
OneWire oneWire(oneWireBus);
DallasTemperature sensors(&oneWire);

void setup() {
  // Start serial communication
  Serial.begin(9600);
  
  // Start DS18B20
  sensors.begin();

  // Initialize SD card
  if (!SD.begin(chipSelect)) {
    Serial.println("SD card initialization failed!");
    return;
  }
  Serial.println("SD card initialized.");

  // Create or open the file on SD card and add headers if new
  File dataFile = SD.open("data.csv", FILE_WRITE);
  if (dataFile) {
    dataFile.println("Timestamp,Temperature (C),Light Level");
    dataFile.close();
  } else {
    Serial.println("Error opening data.csv");
  }
}

void loop() {
  // Request temperature data from DS18B20
  sensors.requestTemperatures();
  float temperatureC = sensors.getTempCByIndex(0);

  // Read light intensity from LDR
  int lightLevel = analogRead(ldrPin);

  // Print to Serial Monitor for verification
  Serial.print("Temperature (C): ");
  Serial.print(temperatureC);
  Serial.print(" | Light Level: ");
  Serial.println(lightLevel);

  // Log data to SD card
  File dataFile = SD.open("data.csv", FILE_WRITE);
  if (dataFile) {
    // Use millis() as a basic timestamp
    unsigned long timestamp = millis();

    // Write to CSV file
    dataFile.print(timestamp);
    dataFile.print(",");
    dataFile.print(temperatureC);
    dataFile.print(",");
    dataFile.println(lightLevel);

    // Close file after writing
    dataFile.close();
    Serial.println("Data written to SD card.");
  } else {
    Serial.println("Error opening data.csv");
  }

  // Delay before next reading
  delay(1000);
}