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

// #define SD_CS_PIN 5      // Pin connected to the SD card reader's CS pin

// Name of the file to save sensor data
const char* filename = "/sensor_data.txt";
#define THERMISTORPIN 34
const double VCC = 3.3;             // NodeMCU on board 3.3v vcc
const double R2 = 10000;            // 10k ohm series resistor
const double adc_resolution = 4096; // 12-bit adc

const double A = 0.001129148;   // thermistor equation parameters
const double B = 0.000234125;
const double C = 0.0000000876741;
#define CS_PIN 5

int menu = 0;
File root;

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

  Serial.print("Initializing SD card... ");

  if (!SD.begin(CS_PIN)) {
    Serial.println("Card initialization failed!");
    while (true);
  }

  Serial.println("initialization done.");

  Serial.println("Files in the card:");
  root = SD.open("/");
  printDirectory(root, 0);
  Serial.println("");

  // myFile = SD.open("test.txt", FILE_WRITE);
  // Example of reading file from the card:
  // File textFile = SD.open("wokwi.txt");
  // if (textFile) {
  //   Serial.print("wokwi.txt: ");
  //   while (textFile.available()) {
  //     Serial.write(textFile.read());
  //   }
  //   textFile.close();
  // } else {
  //   Serial.println("error opening wokwi.txt!");
  // }
}

void loop() {
  // Read sensor data
  double Vout, Rth, temperature, adc_value; 

  if (Serial.available() > 0) {

    menu = Serial.read();
    if ((menu-48) == 2) {rfile(SD, filename);}
  }
  else{
    adc_value = adc_resolution-analogRead(THERMISTORPIN)+0.5; // switch direction
    Vout = (adc_value * VCC) / adc_resolution; 
    Rth = (VCC * R2 / Vout) - R2; // Formula for R2 as Pull-down: Vcc-Rth-R2-GND

    /*  Steinhart-Hart Thermistor Equation:
    *  Temperature in Kelvin = 1 / (A + B[ln(R)] + C[ln(R)]^3)
    */
    temperature = (1 / (A + (B * log(Rth)) + (C * pow((log(Rth)),3))));   // Temperature in kelvin

    temperature = temperature - 273.15;  // Temperature in degree celsius

    // Prepare data string
    String dataString = "Temperature: " + String(temperature) + " %";


    // Write data to file
    wfile(SD, filename, dataString.c_str());

    // Print data to Serial
    Serial.println(dataString);

    // Wait 2 seconds before next loop
    delay(1000);
  }

}


void printDirectory(File dir, int numTabs) {
  while (true) {

    File entry =  dir.openNextFile();
    if (! entry) {
      // no more files
      break;
    }
    for (uint8_t i = 0; i < numTabs; i++) {
      Serial.print('\t');
    }
    Serial.print(entry.name());
    if (entry.isDirectory()) {
      Serial.println("/");
      printDirectory(entry, numTabs + 1);
    } else {
      // files have sizes, directories do not
      Serial.print("\t\t");
      Serial.println(entry.size(), DEC);
    }
    entry.close();
  }
}

void wfile(fs::FS &fs, const char * path, const char * message) {
  File file = fs.open(path, FILE_APPEND);
  if (!file) {
    Serial.println("Failed to open file for writing");
    return;
  }
  if (file.print(message)) {
    Serial.println("Message written to file");
  } else {
    Serial.println("Write failed");
  }
  file.close();
}

void rfile(fs::FS &fs, const char * path) {
  File file = fs.open(path);
  Serial.println("-------");
  // iff the file is available, read it:
  if (file) {
    while (file.available()) {
      Serial.write(file.read());
    }
    file.close();
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening data.txt");
  }
  Serial.println("-------");
}