package site.huozhu.home.util.secret;

import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;

/**
 * Created by chuanxue.mcx on 2016/12/17.
 */
public class Base64ForRobot {

    // map 6-bit int to char
    private static final char[] chars64 = { 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
                                            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
                                            't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
                                            'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
                                            '8', '9', '+', '/' };

    // map char to 6-bit int
    private static final int[]  ints64  = new int[128];
    static {
        for (int i = 0; i < 64; i++) {
            ints64[chars64[i]] = i;
        }
    }

    public static String encodeStr(String newStr) {
        if (newStr == null || newStr.length() == 0) return null;
        String encoded = encode(newStr.getBytes());
        if (encoded == null || encoded.length() == 0) return null;

        try {
            return java.net.URLEncoder.encode(encoded, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            return null;
        }

    }

    /** Convert byte array into Base64 string */
    @SuppressWarnings("UnusedAssignment")
    public static final String encode(byte[] unencoded) {
        // Take 24-bits from three octets, translate into four encoded chars.
        // If necessary, pad with 0 bits on the right at the end
        // Use = signs as padding at the end to ensure encodedLength % 4 == 0
        if (unencoded == null || unencoded.length == 0) return null;
        ByteArrayOutputStream out = null;
        try {

            out = new ByteArrayOutputStream((int) (unencoded.length * 1.37));
            int byteCount = 0;
            int carryOver = 0;

            for (int i = 0; i < unencoded.length; i++) {
                int bc = (byteCount % 3);
                byte b = unencoded[i];
                int lookup = 0;

                // First byte use first six bits, save last two bits
                if (bc == 0) {
                    lookup = (b >> 2) & 0x3F;
                    carryOver = b & 0x03; // last two bits
                    out.write(chars64[lookup]);
                } else if (bc == 1) {
                    // Second byte use previous two bits and first four new bits,
                    // save last four bits
                    lookup = ((carryOver << 4) | ((b >> 4) & 0x0F));
                    carryOver = b & 0x0F; // last four bits
                    out.write(chars64[lookup]);
                } else if (bc == 2) {
                    // Third byte use previous four bits and first two new bits,
                    // then use last six new bits
                    lookup = ((carryOver << 2) | ((b >> 6) & 0x03));
                    out.write(chars64[lookup]);

                    lookup = b & 0x3F; // last six bits
                    out.write(chars64[lookup]);
                    carryOver = 0;
                }
                byteCount++;
            }

            if (byteCount % 3 == 1) { // one leftover
                int lookup = (carryOver << 4) & 0xF0;
                out.write(chars64[lookup]);
                out.write('=');
                out.write('=');
            } else if (byteCount % 3 == 2) { // two leftovers
                int lookup = (carryOver << 2) & 0x3C;
                out.write(chars64[lookup]);
                out.write('=');
            }

            String out_str = out.toString();
            return out_str;
        } finally {
            if (out != null) {
                try {
                    out.close();
                } catch (Throwable e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /** Decode Base64 string back to byte array */
    public static final byte[] decode(String encoded) {
        if (encoded == null || encoded.length() == 0) return null;

        byte[] bytes = encoded.getBytes();
        ByteArrayOutputStream out = null;
        try {
            out = new ByteArrayOutputStream((int) (bytes.length * 0.67));
            int byteCount = 0;
            int carryOver = 0;

            DECODE_LOOP: for (int i = 0; i < bytes.length; i++) {
                int ch = bytes[i];

                // Read the next non-whitespace character
                // if (Character.isWhitespace((char)ch))
                // continue;

                // The '=' sign is just padding; geffective end of stream
                if (ch == '=') break DECODE_LOOP;

                // Convert from raw form to 6-bit form
                int newbits = ints64[ch];

                int bc = (byteCount % 4);
                if (bc == 0) {
                    // First char save all six bits, go for another
                    carryOver = newbits & 0x3F;
                } else if (bc == 1) {
                    // second char use 6 previous bits and first 2 new bits
                    int data = ((carryOver << 2) + ((newbits >> 4) & 0x03));
                    out.write(data);
                    carryOver = newbits & 0x0F; // save 4 bits
                } else if (bc == 2) {
                    // Third char use previous four bits and first four new bits,
                    // save last two bits
                    int data = ((carryOver << 4) + ((newbits >> 2) & 0x0F));
                    out.write(data);
                    carryOver = newbits & 0x03; // save 2 bits
                } else if (bc == 3) {
                    // Fourth char use previous two bits and all six new bits
                    int data = ((carryOver << 6) + (newbits & 0x3F));
                    out.write(data);
                    carryOver = 0;
                }
                byteCount++;
            }
            byte[] byte_arr = out.toByteArray();
            return byte_arr;
        } finally {
            if (out != null) {
                try {
                    out.close();
                } catch (Throwable e) {
                    e.printStackTrace();
                }
            }
        }
    }
}
