#include <WiFi.h>
#include "time.h"
#include <SPI.h>
#include <SD.h>
#include <DHT.h>

#define SD_CS 5
#define DHTPIN 4
#define DHTTYPE DHT22

DHT dht(DHTPIN, DHTTYPE);
File dataFile;

// WiFi credentials
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// NTP settings (India time)
const char* ntpServer = "pool.ntp.org";
const long gmtOffset_sec = 19800;
const int daylightOffset_sec = 0;

// Store previous values
float lastTemp = -1000;
float lastHum  = -1000;

void setup() {
  Serial.begin(115200);

  // Connect WiFi
  WiFi.begin(ssid, password);
  Serial.print("Connecting WiFi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWiFi Connected");

  // Setup time
  configTime(gmtOffset_sec, daylightOffset_sec, ntpServer);

  // Init DHT
  dht.begin();

  // Init SD Card
  if (!SD.begin(SD_CS)) {
    Serial.println("SD Card initialization failed!");
    return;
  }
  Serial.println("SD Card initialized");

  // Create file and write header
  dataFile = SD.open("/sensor.csv", FILE_WRITE);
  if (dataFile) {
    dataFile.println("Time,Temperature,Humidity");
    dataFile.close();
  }
}

void loop() {
  float temp = dht.readTemperature();
  float hum = dht.readHumidity();

  if (isnan(temp) || isnan(hum)) {
    Serial.println("DHT read failed!");
    return;
  }

  // Check threshold condition
  if (abs(temp - lastTemp) > 0.5 || abs(hum - lastHum) > 0.5) {

    // Get time
    struct tm timeinfo;
    if (!getLocalTime(&timeinfo)) {
      Serial.println("Failed to get time");
      return;
    }

    char timeString[30];
    strftime(timeString, sizeof(timeString), "%Y-%m-%d %H:%M:%S", &timeinfo);

    // Write to SD card
    dataFile = SD.open("/sensor.csv", FILE_APPEND);
    if (dataFile) {
      dataFile.print(timeString);
      dataFile.print(",");
      dataFile.print(temp);
      dataFile.print(",");
      dataFile.println(hum);
      dataFile.close();
    }

    Serial.println("\n✅ New Data Logged!");

    // 🔥 READ FULL FILE AND PRINT
    dataFile = SD.open("/sensor.csv", FILE_READ);
    if (dataFile) {
      Serial.println("----- FULL LOG FILE -----");
      while (dataFile.available()) {
        Serial.write(dataFile.read());
      }
      dataFile.close();
      Serial.println("\n-------------------------");
    }

    // Update last values
    lastTemp = temp;
    lastHum  = hum;

  } else {
    Serial.println("No significant change in Sensor Data");
  }

  delay(2000);
}