package somiba;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Collection;
import java.util.Iterator;

public class Util {

    private static final String HEX_ALPHABET[] = { "0", "1", "2", "3", "4",
            "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

    /**
     * Encode byte array in hexadecimal notation.
     * 
     * @param in the byte array to encode
     * @return hex-encoded string representation of the byte array.
     */
    public static String hexEncode(byte in[]) {
        if (in == null || in.length == 0) {
            return null;
        }
        StringBuilder out = new StringBuilder(in.length * 2);
        for (int i = 0; i < in.length; i++) {
            byte b = (byte) (in[i] & 0xF0);
            b = (byte) (b >>> 4);
            b = (byte) (b & 0x0F);
            out.append(HEX_ALPHABET[b]);
            b = (byte) (in[i] & 0x0F);
            out.append(HEX_ALPHABET[b]);
        }
        return new String(out);
    }

    /**
     * Generate MD5 digest of a string.
     * 
     * @param in the string to digest.
     * @return hexadecimal-encoded MD5-digest of the input string.
     */
    public static String md5Digest(String in) {
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            byte[] digest = messageDigest.digest(in.getBytes());
            return hexEncode(digest);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("Failed to get MD5 digest", e);
        }
    }

    public static boolean isEmpty(String s) {
        return s == null || s.length() == 0 || s.trim().length() == 0;
    }

    public static String join(Collection<?> collection, String delimiter) {
        StringBuilder out = new StringBuilder();
        for (Iterator<?> i = collection.iterator(); i.hasNext();) {
            out.append(i.next());
            if (i.hasNext()) {
                out.append(delimiter);
            }
        }
        return out.toString();
    }
    
 }