package com.ifish.jpush.utils;

import java.io.CharArrayWriter;
import java.io.IOException;

public class Base64 {
    static final char[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
            .toCharArray();

    public static char[] encode(byte[] content) {
        CharArrayWriter cw = new CharArrayWriter(4 * content.length / 3);

        int idx = 0;

        int x = 0;

        for (int i = 0; i < content.length; ++i) {
            if (idx == 0)
                x = (content[i] & 0xFF) << 16;
            else if (idx == 1)
                x |= (content[i] & 0xFF) << 8;
            else {
                x |= content[i] & 0xFF;
            }

            if (++idx == 3) {
                cw.write(alphabet[(x >> 18)]);
                cw.write(alphabet[(x >> 12 & 0x3F)]);
                cw.write(alphabet[(x >> 6 & 0x3F)]);
                cw.write(alphabet[(x & 0x3F)]);

                idx = 0;
            }
        }

        if (idx == 1) {
            cw.write(alphabet[(x >> 18)]);
            cw.write(alphabet[(x >> 12 & 0x3F)]);
            cw.write(61);
            cw.write(61);
        }

        if (idx == 2) {
            cw.write(alphabet[(x >> 18)]);
            cw.write(alphabet[(x >> 12 & 0x3F)]);
            cw.write(alphabet[(x >> 6 & 0x3F)]);
            cw.write(61);
        }

        return cw.toCharArray();
    }

    public static byte[] decode(char[] message) throws IOException {
        byte[] buff = new byte[4];
        byte[] dest = new byte[message.length];

        int bpos = 0;
        int destpos = 0;

        for (int i = 0; i < message.length; ++i) {
            int c = message[i];

            if ((c != 10) && (c != 13) && (c != 32)) {
                if (c == 9)
                    continue;

                if ((c >= 65) && (c <= 90)) {
                    buff[(bpos++)] = (byte) (c - 65);
                } else if ((c >= 97) && (c <= 122)) {
                    buff[(bpos++)] = (byte) (c - 97 + 26);
                } else if ((c >= 48) && (c <= 57)) {
                    buff[(bpos++)] = (byte) (c - 48 + 52);
                } else if (c == 43) {
                    buff[(bpos++)] = 62;
                } else if (c == 47) {
                    buff[(bpos++)] = 63;
                } else if (c == 61) {
                    buff[(bpos++)] = 64;
                } else {
                    throw new IOException("Illegal char in base64 code.");
                }

                if (bpos == 4) {
                    bpos = 0;

                    if (buff[0] == 64)
                        break;

                    if (buff[1] == 64)
                        throw new IOException("Unexpected '=' in base64 code.");

                    int v;
                    if (buff[2] == 64) {
                        v = (buff[0] & 0x3F) << 6 | buff[1] & 0x3F;
                        dest[(destpos++)] = (byte) (v >> 4);
                        break;
                    }
                    if (buff[3] == 64) {
                        v = (buff[0] & 0x3F) << 12 | (buff[1] & 0x3F) << 6
                                | buff[2] & 0x3F;
                        dest[(destpos++)] = (byte) (v >> 10);
                        dest[(destpos++)] = (byte) (v >> 2);
                        break;
                    }

                    v = (buff[0] & 0x3F) << 18 | (buff[1] & 0x3F) << 12
                            | (buff[2] & 0x3F) << 6 | buff[3] & 0x3F;
                    dest[(destpos++)] = (byte) (v >> 16);
                    dest[(destpos++)] = (byte) (v >> 8);
                    dest[(destpos++)] = (byte) v;
                }
            }
        }

        byte[] res = new byte[destpos];
        System.arraycopy(dest, 0, res, 0, destpos);

        return res;
    }
}