import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class CsvWriter {
    private static final String FILE_NAME = "currency_log.csv";
    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

    private static boolean is_header_written = false;

    public static void write(double value) {
        File file = new File(FILE_NAME);
        boolean file_exists = file.exists();

        try (FileWriter writer = new FileWriter(FILE_NAME, true)) {
            if (!is_header_written && !file_exists) {
                writer.write("Дата и время;Курс USD (руб.)\n");
                is_header_written = true;
            }

            String timestamp = LocalDateTime.now().format(FORMATTER);
            String line = timestamp + ";" + value + "\n";
            writer.write(line);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}