import java.io.IOException;
import java.io.OutputStream;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.Mac;

public class CipherHmacOutputStream_PLAINTEXT_HMAC extends CipherOutputStream {
    private Cipher cipher;
    private Mac mac;
    private byte[] iv;

    public CipherHmacOutputStream_PLAINTEXT_HMAC(OutputStream os, Cipher c, Mac m, byte[] iv) {
        super(os, c);
        cipher = c;
        mac = m;
    }

    @Override
    public void write(int b) throws IOException {
        mac.update((byte) b);
        super.write(b);
    }

    @Override
    public void write(byte[] b) throws IOException {
        mac.update(b);
        super.write(b);
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        mac.update(b, off, len);
        super.write(b, off, len);
    }

    @Override
    public void close() throws IOException {
        writeHmac();
        super.close();
    }

    private void writeHmac() throws IOException {
        // Add IV & algorithm details
        try {
            mac.update(iv);
            mac.update(cipher.getAlgorithm().getBytes("UTF8"));
            mac.update(cipher.getParameters().getEncoded());

            byte[] macBytes = mac.doFinal();
            super.write(macBytes);
        }
        catch (Exception e) {
            throw new IOException(e);
        }
    }
}