public class SecureChannel {

    static final String negResponse = "-1";

    // Complete the secureChannel function below.
    static String secureChannel(int operation, String message, String key) {

        switch (operation) {
            case 1:
                return encoded(message, key);
            case 2:
                return decoded(message, key);
            default:
                return negResponse;
        }

    }


    private static String isEmpty(String message, String key) {
        if (message == null || key == null)
            return negResponse;

        if (message.isEmpty() && key.isEmpty())
            return message;

        if (!message.isEmpty() && key.isEmpty())
            return message;

        if (message.isEmpty() && !key.isEmpty())
            return negResponse;


        return null;

    }

    /**
     * Input:
     * 2
     * Oppeeen
     * 123
     * <p>
     * Output:
     * Open
     *
     * @param message
     * @param key
     * @return
     */
    private static String decoded(String message, String key) {
        String corner = isEmpty(message, key);
        if (corner != null)
            return corner;


        if (key.equals("0"))
            return message;

        int index = 0;
        final StringBuilder res = new StringBuilder();

        char keys[] = key.toCharArray();

        int i;
        for (i = 0; i < keys.length; i++) {

            if (index < message.length()) {
                char current = message.charAt(index);
                if (Character.isDigit(keys[i])) {
                    int keyV = keys[i] - '0';
                    int x = 1;
                    while (x + index < message.length() && message.charAt(x + index) == current) {

                        x++;
                    }

                    if (x == keyV) { //this is correct
                        res.append(current);
                    } else
                        return negResponse;
                    index = index + x;
                } else
                    return negResponse;

            } else
                break;
        }

        return getMessage(message, index, res, keys, i);


    }

    private static String getMessage(String message, int index, StringBuilder res, char[] keys, int i) {
        if (index < message.length()) {
            String remaining = message.substring(index);
            res.append(remaining);
        }
        return res.toString();

    }

    /**
     * Message: Open
     * Key: 123
     * <p>
     * Output:
     * Oppeeen
     *
     * @param message
     * @param key
     * @return
     */
    private static String encoded(String message, String key) {
        String corner = isEmpty(message, key);
        if (corner != null)
            return corner;


        int index = 0;
        final StringBuilder res = new StringBuilder();

        char keys[] = key.toCharArray();

        int i;
        for (i = 0; i < keys.length; i++) {

            if (index < message.length()) {
                char current = message.charAt(index);

                if (Character.isDigit(keys[i])) {
                    int keyV = keys[i] - '0';

                    for (int x = 0; x < keyV; x++) {
                        res.append(current);
                    }

                    index++;
                } else
                    return negResponse;
            } else
                break;

        }

        return getMessage(message, index, res, keys, i);

    }

    public static void main(String args[]) {


        System.out.println(secureChannel(2, "open", "aad"));

        System.out.println(secureChannel(2, "", ""));


        System.out.println(secureChannel(2, "Oppeeennnn", "1234"));


        System.out.println(secureChannel(1, "abcdefgh", ""));
        System.out.println(secureChannel(2, "aaabbbcccdddeeefffggghhh", ""));


        System.out.println(secureChannel(1, "abcdefgh", "0"));
        System.out.println(secureChannel(2, "bcdefgh", "0"));


        System.out.println(secureChannel(1, "abcdefgh", ""));
        System.out.println(secureChannel(2, "aaabbbcccdddeeefffggghhh", ""));


        System.out.println(secureChannel(1, "abcdefgh", "33333333333"));
        System.out.println(secureChannel(2, "aaabbbcccdddeeefffggghhh", "33333333333"));


        System.out.println(secureChannel(1, null, "9999"));
        System.out.println(secureChannel(2, null, "9999"));

        System.out.println(secureChannel(1, "", "9999"));
        System.out.println(secureChannel(2, "", "9999"));

        System.out.println(secureChannel(1, "Ope", "12345"));
        System.out.println(secureChannel(2, "Oppeee", "12345"));


        System.out.println(secureChannel(1, "open", "123"));
        System.out.println(secureChannel(2, "Oppeeen", "123"));


        System.out.println(secureChannel(1, "open", "1234"));
        System.out.println(secureChannel(2, "oppeeennnn", "123"));


        System.out.println(secureChannel(1, "o", "1234"));
        System.out.println(secureChannel(2, "opp", "123"));
    }
}