import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;
import java.util.Date;
import java.math.BigInteger;

public class Fibonacci {

    public static void main(String[] args) {
        int length, starting = 1;
        try {
            if (args.length < 1 || args.length > 2) {
                System.out.println("Invalid number of arguments!");
                System.out.println("fibonacci <length> [initial]");
                return;
            }
            length = Integer.parseInt(args[0]);
            if (args.length >= 2)
                starting = Integer.parseInt(args[1]);
            if (length <= 0) {
                System.out.println("Length must be at least one!");
                return;
            }
        } catch (NumberFormatException ex) {
            System.out.println("Not a valid integer!");
            return;
        }

        BigInteger[] results = new BigInteger[length];
        results[0] = BigInteger.ZERO;
        if (length > 1)
            results[1] = BigInteger.valueOf(starting);

        System.out.println("Starting calculation...");
        double startingTime = new Date().getTime();

        for (int i = 2; i < length; i++)
            results[i] = results[i - 1].add(results[i - 2]);

        double endingTime = new Date().getTime();
        System.out.println("Calculation completed in " + String.format("%.3f", (endingTime - startingTime) * 0.001) + " second(s).");
        System.out.println("Results:");

        for (BigInteger i : results)
            System.out.print(i.toString() + " ");

        boolean writeSuccess = false;
        while (!writeSuccess) {
            System.out.println("\nInput a name for the results file (Leave blank to skip).");
            String name = System.console().readLine();
            if (name.isEmpty())
                writeSuccess = true;
            else {
                System.out.println("Attempting to write file " + name + ".");
                try {
                    PrintStream writeOut = new PrintStream(new FileOutputStream(new File(name)));
                    for (BigInteger i : results)
                        writeOut.println(i.toString());
                    writeOut.close();
                    writeSuccess = true;
                } catch (Throwable th) {
                    System.out.println("Error whilst writing file!");
                    th.printStackTrace();
                }
            }
        }

    }

}