#include <SPI.h>
#include <SD.h>
#include <DHT.h>

#define DHTPIN     7
#define DHTTYPE    DHT22
#define CS_PIN     10
#define LED_PIN    6

DHT dht(DHTPIN, DHTTYPE);
File logFile;

unsigned long lastLog = 0;
int logCount = 0;

void setup() {
  Serial.begin(9600);
  pinMode(LED_PIN, OUTPUT);

  Serial.println("=================================");
  Serial.println("   SD Card Data Logger");
  Serial.println("   Arduino Uno | Wokwi");
  Serial.println("=================================");

  dht.begin();

  if (!SD.begin(CS_PIN)) {
    Serial.println("[ERROR] SD Card init failed!");
    while (true) {
      digitalWrite(LED_PIN, HIGH); delay(200);
      digitalWrite(LED_PIN, LOW);  delay(200);
    }
  }
  Serial.println("[OK] SD Card initialized.");

  // Write CSV header
  logFile = SD.open("datalog.csv", FILE_WRITE);
  if (logFile) {
    logFile.println("Log#,Temperature(C),Humidity(%),Status");
    logFile.close();
    Serial.println("[OK] datalog.csv created.");
  } else {
    Serial.println("[ERROR] Could not create file.");
  }

  Serial.println("Logging every 3 seconds...\n");
}

void loop() {
  if (millis() - lastLog >= 3000) {
    lastLog = millis();

    float temp = dht.readTemperature();
    float hum  = dht.readHumidity();

    if (isnan(temp) || isnan(hum)) {
      Serial.println("[WARN] Sensor read failed, skipping...");
      return;
    }

    logCount++;
    String status = "Normal";
    if (temp > 35)       status = "HIGH TEMP";
    else if (hum > 80)   status = "HIGH HUMIDITY";
    else if (temp < 15)  status = "LOW TEMP";

    // Log to SD
    logFile = SD.open("datalog.csv", FILE_WRITE);
    if (logFile) {
      logFile.print(logCount);
      logFile.print(",");
      logFile.print(temp);
      logFile.print(",");
      logFile.print(hum);
      logFile.print(",");
      logFile.println(status);
      logFile.close();

      // Blink LED to confirm log
      digitalWrite(LED_PIN, HIGH); delay(100);
      digitalWrite(LED_PIN, LOW);

      Serial.print("[LOG #"); Serial.print(logCount); Serial.print("] ");
      Serial.print("Temp: "); Serial.print(temp); Serial.print(" C | ");
      Serial.print("Hum: ");  Serial.print(hum);  Serial.print(" % | ");
      Serial.println("Status: " + status);
    } else {
      Serial.println("[ERROR] Failed to open file for writing.");
    }
  }
}