package com.yutou.tools.Tools;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Scanner;
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 GoogleAccount {
    public static final boolean isDev=true;
    // 生成的key长度( Generate secret key length)
    private static final int SECRET_SIZE = 10;

    private static final String SEED = "g8GjEvTbW5oVSV7avL47357438reyhreyuryetredLDVKs2m0QN7vxRs2im5MDaNCWGmcD2rvcZx";
    // Java实现随机数算法
    private static final String RANDOM_NUMBER_ALGORITHM = "SHA1PRNG";
    // 最多可偏移的时间
    int window_size = 3; // default 3 - max 17

    /**
     * set the windows size. This is an integer value representing the number of
     * 30 second windows we allow The bigger the window, the more tolerant of
     * clock skew we are.
     *
     * @param s window size - must be >=1 and <=17. Other values are ignored
     */
    public void setWindowSize(int s) {
        if (s >= 1 && s <= 17) {
            window_size = s;
        }
    }

    /**
     * Generate a random secret key. This must be saved by the server and
     * associated with the users account to verify the code displayed by Google
     * Authenticator. The user must register this secret on their device.
     * 生成一个随机秘钥
     *
     * @return secret key
     */
    public static String generateSecretKey() {
        SecureRandom sr = null;
        try {
            sr = SecureRandom.getInstance(RANDOM_NUMBER_ALGORITHM);
            sr.setSeed(Base64.decodeBase64(SEED));
            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;
    }

    /**
     * Return a URL that generates and displays a QR barcode. The user scans
     * this bar code with the Google Authenticator application on their
     * smartphone to register the auth code. They can also manually enter the
     * secret if desired
     *
     * @param user   user id (e.g. fflinstone)
     * @param host   host or system that the code is for (e.g. myapp.com)
     * @param secret the secret that was previously generated for this user
     * @return the URL for the QR code to scan
     */
    public static String getQRBarcodeURL(String user, String host, String secret) {
        String format = "http://www.google.com/chart?chs=200x200&chld=M%%7C0&cht=qr&chl=otpauth://totp/%s@%s?secret=%s";
        return String.format(format, user, host, secret);
    }

    /**
     * 生成一个google身份验证器，识别的字符串，只需要把该方法返回值生成二维码扫描就可以了。
     *
     * @param user   账号
     * @param secret 密钥
     * @return
     */
    public static String getQRBarcode(String user, String secret) {
        String format = "otpauth://totp/%s?secret=%s";
        return String.format(format, user, secret);
    }

    /**
     * Check the code entered by the user to see if it is valid 验证code是否合法
     *
     * @param secret The users secret.
     * @param code   The code displayed on the users device
     * @param timeMsec      The time in msec (System.currentTimeMillis() for example)
     * @return
     */
    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;
    }

    public static void main(String[] args) {
        String secret=GoogleAccount.generateSecretKey();
        String uname=isDev?"yutou(dev)":"yutou";
        String qrcode = GoogleAccount.getQRBarcode(uname, secret);
        System.out.println("qrcode:" + qrcode + ",key:" + secret);
        while (true){
            String code=new Scanner(System.in).nextLine();
            GoogleAccount account=new GoogleAccount();
            boolean check=account.check_code(secret,Long.parseLong(code),System.currentTimeMillis());
            System.out.println("验证结果:"+check);
        }
    }
}
