import java.security.SecureRandom;
import java.io.IOException;
import java.nio.file.Paths;
import java.nio.file.Files;
import java.util.List;
import picocli.CommandLine;
import picocli.CommandLine.Option;

public class Main implements Runnable {
    private static SecureRandom random;

    @Option(names = {"-x", "--xkcd"}, description = "Will generate an xkcd-style password (See xkcd 936)")
    private boolean xkcd = false;

    @Option(names = {"-s", "--simple"}, description = "Will generate a password of specified length without special characters")
    private boolean simple = false;

    @Option(names = {"-l", "--length"}, description = "Will generate a regular password with the provided amount of characters (or words for XKCD passwords). Defaults to 32.")
    private int length = 32;

    @Option(names = {"-h", "--help"}, usageHelp = true, description = "Displays this help message and exits.")
    private boolean help;

    private static String generate_simple_password(int count) {
        String simpleCharacters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
        String password = "";
        int randomIndex;
        char randomChar;
        for (int i = 0; i < count; i++) {
            randomIndex = random.nextInt(simpleCharacters.length());
            randomChar = simpleCharacters.charAt(randomIndex);
            password = password + randomChar;
        }
        return password;
    }

    private static String generate_regular_password(int count) {
        String characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890!@#$%^&*";
        String password = "";
        int randomIndex;
        char randomChar;
        for (int i = 0; i < count; i++) {
            randomIndex = random.nextInt(characters.length());
            randomChar = characters.charAt(randomIndex);
            password = password + randomChar;
        }
        return password;
    }

    private static String generate_xkcd_password(int count) {
            String password = "";
        try {
            List<String> dictionary = Files.readAllLines(Paths.get("/usr/share/dict/words"));

            int randomIndex;
            String randomWord;
            for (int i = 0; i < count; i++) {
                randomIndex = random.nextInt(dictionary.size());
                randomWord = dictionary.get(randomIndex);
                password = password + randomWord;
                password = password + " ";
            }
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("An error occured while reading /usr/share/dict/words - Is the file present?");
            System.exit(2);
        }
        return password;
    }
    public static void main(String[] args) {
        random = new SecureRandom();
        int exitCode = new CommandLine(new Main()).execute(args);
        System.exit(exitCode);
    }

    @Override
    public void run() {
        if (xkcd && simple) {
            System.out.println("Error: Only use one of xkcd (-x), simple (-s) or regular (-r) at once.");
            System.exit(2);
        }
        if (xkcd) {
            System.out.println(generate_xkcd_password(length));
            System.exit(0);
        }
        else if (simple) {
            System.out.println(generate_simple_password(length));
            System.exit(0);
        }
        else {
            System.out.println(generate_regular_password(length));
            System.exit(0);
        }
    }
}