package com.qkwl.common.google;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;


import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;


import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;



public class GoogleAuthenticator {


// taken from Google pam docs - we probably don't need to mess with these
public static final int SECRET_SIZE = 10;
public static final String SEED = "g8GjEvTbW5oVSV7avLBdwIHqGlUYNzKFI7izOF8GwLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";
public static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";


int window_size = 3; // default 3 - max 17 (from google docs)



public void setWindowSize(int s) {
if (s >= 1 && s <= 17)
window_size = s;
}



public static String generateSecretKey() {


SecureRandom sr = null;
try {
sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
sr.setSeed(Base64.decodeBase64(SEED.getBytes()));
byte[] buffer = sr.generateSeed(SECRET_SIZE);
Base32 codec = new Base32();
byte[] bEncodedKey = codec.encode(buffer);
String encodedKey = new String(bEncodedKey);
return encodedKey;


} catch (NoSuchAlgorithmException e) {
// should never occur... configuration error
}
return null;
}



public static String getQRBarcodeURL(String user, String host, String secret) {
// String format =
// "https://www.google.com/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s%%3Fsecret%%3D%s";
String format = "otpauth://totp/%s--%s?secret=%s";
return String.format(format, user, host, secret);
}// otpauth://totp/OKCoin:sbicrgw@vip.qq.com?secret=LQQZJ6ITK5CKS6YA



public boolean check_code(String secret, long code, long timeMsec) {
Base32 codec = new Base32();
byte[] decodedKey = codec.decode(secret);


// convert unix msec time into a 30 second "window"
// this is per the TOTP spec (see the RFC for details)
long t = (timeMsec / 1000L) / 30L;
// Window is used to check codes generated in the near past.
// You can use this value to tune how far you're willing to go.


for (int i = -window_size; i <= window_size; ++i) {
long hash;
try {
hash = verify_code(decodedKey, t + i);
} catch (Exception e) {
// Yes, this is bad form - but
// the exceptions thrown would be rare and a static
// configuration problem
e.printStackTrace();
throw new RuntimeException(e.getMessage());
// return false;
}
if (hash == code) {
return true;
}
}
// The validation code is invalid.
return false;
}


private static int verify_code(byte[] key, long t) throws NoSuchAlgorithmException, InvalidKeyException {
byte[] data = new byte[8];
long value = t;
for (int i = 8; i-- > 0; value >>>= 8) {
data[i] = (byte) value;
}


SecretKeySpec signKey = new SecretKeySpec(key, "HmacSHA1");
Mac mac = Mac.getInstance("HmacSHA1");
mac.init(signKey);
byte[] hash = mac.doFinal(data);


int offset = hash[20 - 1] & 0xF;


// We're using a long because Java hasn't got unsigned int.
long truncatedHash = 0;
for (int i = 0; i < 4; ++i) {
truncatedHash <<= 8;
// We are dealing with signed bytes:
// we just keep the first byte.
truncatedHash |= (hash[offset + i] & 0xFF);
}


truncatedHash &= 0x7FFFFFFF;
truncatedHash %= 1000000;


return (int) truncatedHash;
}