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package mixin.java.sdk.algorithm;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

public class Util {

    public static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();

    public static String bytesToHex(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        for ( int j = 0; j < bytes.length; j++ ) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = HEX_ARRAY[v >>> 4];
            hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
        }
        return new String(hexChars);
    }

    public static byte[] hexToBytes(String s) {
        int len = s.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
                    + Character.digit(s.charAt(i+1), 16));
        }
        return data;
    }

    /**
     * Returns SHA-256 hash of data.
     * @param data
     */
    public static byte[] hash(byte[] data) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-256");
            md.update(data);
            return md.digest();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("SHA-256 not implemented");
        }
    }

    /**
     * Pads bytes array to length with zeros.
     * @param bytes
     * @param length
     */
    static byte[] paddedByteArray(byte[] bytes, int length) {
        byte[] finalBytes = new byte[length];
        Arrays.fill(finalBytes, (byte) 0);
        System.arraycopy(bytes, 0, finalBytes, 0, bytes.length);
        return finalBytes;
    }

    /**
     * Pads string to length with zeros.
     * @param string
     * @param length
     */
    static byte[] paddedByteArray(String string, int length) {
        return Util.paddedByteArray(string.getBytes(), length);
    }

    /**
     * Remove zeros from the end of bytes array.
     * @param bytes
     */
    static String paddedByteArrayToString(byte[] bytes) {
        return new String(bytes).split("\0")[0];
    }

    /**
     * Get the version of the SDK
     * @return version
     */
    public static String getSdkVersion() {
        String clientVersion = "dev";
        String implementationVersion = Util.class.getPackage().getImplementationVersion();
        if (implementationVersion != null) {
            clientVersion = implementationVersion;
        }
        return clientVersion;
    }


}