package com.bcxin.signature.util.SM;

import org.bouncycastle.crypto.digests.SM3Digest;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.util.encoders.Hex;

import java.io.UnsupportedEncodingException;

public class SM3Utils {
    /**
     * SM3值的长度
     */
    private static final int BYTE_LENGTH = 32;
    /**
     * SM3分组长度
     */
    private static final int BLOCK_LENGTH = 64;
    /**
     * 缓冲区长度
     */
    private static final int BUFFER_LENGTH = BLOCK_LENGTH * 1;
    /**
     * 缓冲区
     */
    private byte[] xBuf = new byte[BUFFER_LENGTH];
    /**
     * 缓冲区偏移量
     */
    private int xBufOff;
    /**
     * 初始向量
     */
    private byte[] V = SM3.iv.clone();
    private int cntBlock = 0;

    public SM3Utils() {
    }

    /**
     * SM3结果输出
     *
     * @param out    保存SM3结构的缓冲区
     * @param outOff 缓冲区偏移量
     * @return
     */
    public int doFinal(byte[] out, int outOff) {
        byte[] tmp = doFinal();
        System.arraycopy(tmp, 0, out, 0, tmp.length);
        return BYTE_LENGTH;
    }

    /**
     * 明文输入
     *
     * @param in    明文输入缓冲区
     * @param inOff 缓冲区偏移量
     * @param len   明文长度
     */
    public void update(byte[] in, int inOff, int len) {
        int partLen = BUFFER_LENGTH - xBufOff;
        int inputLen = len;
        int dPos = inOff;
        if (partLen < inputLen) {
            System.arraycopy(in, dPos, xBuf, xBufOff, partLen);
            inputLen -= partLen;
            dPos += partLen;
            doUpdate();
            while (inputLen > BUFFER_LENGTH) {
                System.arraycopy(in, dPos, xBuf, 0, BUFFER_LENGTH);
                inputLen -= BUFFER_LENGTH;
                dPos += BUFFER_LENGTH;
                doUpdate();
            }
        }
        System.arraycopy(in, dPos, xBuf, xBufOff, inputLen);
        xBufOff += inputLen;
    }

    private void doUpdate() {
        byte[] B = new byte[BLOCK_LENGTH];
        for (int i = 0; i < BUFFER_LENGTH; i += BLOCK_LENGTH) {
            System.arraycopy(xBuf, i, B, 0, B.length);
            doHash(B);
        }
        xBufOff = 0;
    }

    private void doHash(byte[] B) {
        byte[] tmp = SM3.CF(V, B);
        System.arraycopy(tmp, 0, V, 0, V.length);
        cntBlock++;
    }

    private byte[] doFinal() {
        byte[] B = new byte[BLOCK_LENGTH];
        byte[] buffer = new byte[xBufOff];
        System.arraycopy(xBuf, 0, buffer, 0, buffer.length);
        byte[] tmp = SM3.padding(buffer, cntBlock);
        for (int i = 0; i < tmp.length; i += BLOCK_LENGTH) {
            System.arraycopy(tmp, i, B, 0, B.length);
            doHash(B);
        }
        return V;
    }

    public void update(byte in) {
        byte[] buffer = new byte[]{in};
        update(buffer, 0, 1);
    }

    public int getDigestSize() {
        return BYTE_LENGTH;
    }

    /**
     * 铭文输入，密文输出
     *
     * @param msg
     * @return
     */
    public String sm3(String msg) {
        byte[] sm = new byte[32];
        byte[] psw = msg.getBytes();
        update(psw, 0, psw.length);
        doFinal(sm, 0);
        return new String(Hex.encode(sm));
    }
    /**
     * 铭文输入，密文输出
     *
     * @param msg
     * @return
     */
    public byte[] sm3(byte[] psw) {
        byte[] sm = new byte[32];
        update(psw, 0, psw.length);
        doFinal(sm, 0);
        return sm;
    }
    public static String hmac(String key, String src) throws UnsupportedEncodingException {
        byte[] keyData = key.getBytes("UTF-8");
        byte[] srcData = src.getBytes("UTF-8");
        KeyParameter keyParameter = new KeyParameter(keyData);
        SM3Digest digest = new SM3Digest();
        HMac mac = new HMac(digest);
        mac.init(keyParameter);
        mac.update(srcData, 0 , srcData.length);
        byte[] result = new byte[mac.getMacSize()];
        mac.doFinal(result, 0);

        return Hex.toHexString(result);
    }
}