#include <SD.h>

#define CS_PIN 10

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("");

  // 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!");
  }
  writeText(400);
}

void writeText(int distance) {
  File myFile = SD.open("test.txt", FILE_WRITE);

  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to test.txt...");
    myFile.println("the distance is ");
    myFile.println(distance);
    // close the file:
    myFile.close();
    Serial.println("done.");
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

void readText() {
  File textFile = SD.open("test.txt");
  if (textFile) {
    Serial.print("wokwi.txt: ");
    while (textFile.available()) {
      Serial.write(textFile.read());
    }
    textFile.close();
  } else {
    Serial.println("error opening wokwi.txt!");
  }
}

long readUltrasonicDistance(int triggerPin, int echoPin) {
	pinMode(triggerPin, OUTPUT);  // Clear the trigger
	digitalWrite(triggerPin, LOW);
	delayMicroseconds(2);
	// Sets the trigger pin to HIGH state for 10 microseconds
	digitalWrite(triggerPin, HIGH);
	delayMicroseconds(10);
	digitalWrite(triggerPin, LOW);
	pinMode(echoPin, INPUT);
	// Reads the echo pin, and returns
	// the sound wave travel time in microseconds
	return pulseIn(echoPin, HIGH);
}

void loop() {
  int distance = 0.0344/2 * readUltrasonicDistance(2, 3);
  if (distance < 50) {
    writeText(distance);
    readText();
  }
  delay(200);
}

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();
  }
}