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/*
 * Copyright (C) 2015-2017 S.Violet
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Project GitHub: https://github.com/shepherdviolet/thistle
 * Email: [email protected]
 */

package sviolet.thistle.util.conversion;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.zip.DataFormatException;
import java.util.zip.Deflater;
import java.util.zip.Inflater;

/**
 * Base64工具

 *
 * @author SOMEONE
 */
public class Base64Utils {

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

    private static final byte[] DECODING_TABLE;

    static {
        DECODING_TABLE = new byte[128];
        for (int i = 0; i < 128; i++) {
            DECODING_TABLE[i] = (byte) -1;
        }
        for (int i = 'A'; i <= 'Z'; i++) {
            DECODING_TABLE[i] = (byte) (i - 'A');
        }
        for (int i = 'a'; i <= 'z'; i++) {
            DECODING_TABLE[i] = (byte) (i - 'a' + 26);
        }
        for (int i = '0'; i <= '9'; i++) {
            DECODING_TABLE[i] = (byte) (i - '0' + 52);
        }
        DECODING_TABLE['+'] = 62;
        DECODING_TABLE['/'] = 63;
    }

    /**
     * bytes编码为String
     *
     * @param data bytes
     */
    public static String encodeToString(byte[] data) {
        try {
            return new String(encode(data), "utf-8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * bytes编码为Url专用的String, 用于Http的Url参数, 否则+号会变空格
     *
     * @param data bytes
     */
    public static String encodeToUrlEncodedString(byte[] data){
        try {
            return URLEncoder.encode(encodeToString(data), "UTF-8");
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * bytes编码为Base64 bytes
     *
     * @param data bytes
     */
    public static byte[] encode(byte[] data) {
        if (data == null){
            return new byte[0];
        }

        byte[] bytes;
        int modulus = data.length % 3;
        if (modulus == 0) {
            bytes = new byte[(4 * data.length) / 3];
        } else {
            bytes = new byte[4 * ((data.length / 3) + 1)];
        }
        int dataLength = (data.length - modulus);
        int a1;
        int a2;
        int a3;
        for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
            a1 = data[i] & 0xff;
            a2 = data[i + 1] & 0xff;
            a3 = data[i + 2] & 0xff;
            bytes[j] = ENCODING_TABLE[(a1 >>> 2) & 0x3f];
            bytes[j + 1] = ENCODING_TABLE[((a1 << 4) | (a2 >>> 4)) & 0x3f];
            bytes[j + 2] = ENCODING_TABLE[((a2 << 2) | (a3 >>> 6)) & 0x3f];
            bytes[j + 3] = ENCODING_TABLE[a3 & 0x3f];
        }
        int b1;
        int b2;
        int b3;
        int d1;
        int d2;
        switch (modulus) {
            case 0:
                break;
            case 1:
                d1 = data[data.length - 1] & 0xff;
                b1 = (d1 >>> 2) & 0x3f;
                b2 = (d1 << 4) & 0x3f;
                bytes[bytes.length - 4] = ENCODING_TABLE[b1];
                bytes[bytes.length - 3] = ENCODING_TABLE[b2];
                bytes[bytes.length - 2] = (byte) '=';
                bytes[bytes.length - 1] = (byte) '=';
                break;
            case 2:
                d1 = data[data.length - 2] & 0xff;
                d2 = data[data.length - 1] & 0xff;
                b1 = (d1 >>> 2) & 0x3f;
                b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
                b3 = (d2 << 2) & 0x3f;
                bytes[bytes.length - 4] = ENCODING_TABLE[b1];
                bytes[bytes.length - 3] = ENCODING_TABLE[b2];
                bytes[bytes.length - 2] = ENCODING_TABLE[b3];
                bytes[bytes.length - 1] = (byte) '=';
                break;
            default:
                break;
        }
        return bytes;
    }

    /**
     * Base64 bytes解码为bytes
     */
    public static byte[] decode(byte[] data) {
        if (data == null){
            return new byte[0];
        }

        byte[] bytes;
        byte b1;
        byte b2;
        byte b3;
        byte b4;
        data = discardNonBase64Bytes(data);
        if (data[data.length - 2] == '=') {
            bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
        } else if (data[data.length - 1] == '=') {
            bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
        } else {
            bytes = new byte[((data.length / 4) * 3)];
        }
        for (int i = 0, j = 0; i < (data.length - 4); i += 4, j += 3) {
            b1 = DECODING_TABLE[data[i]];
            b2 = DECODING_TABLE[data[i + 1]];
            b3 = DECODING_TABLE[data[i + 2]];
            b4 = DECODING_TABLE[data[i + 3]];
            bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[j + 2] = (byte) ((b3 << 6) | b4);
        }
        if (data[data.length - 2] == '=') {
            b1 = DECODING_TABLE[data[data.length - 4]];
            b2 = DECODING_TABLE[data[data.length - 3]];
            bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
        } else if (data[data.length - 1] == '=') {
            b1 = DECODING_TABLE[data[data.length - 4]];
            b2 = DECODING_TABLE[data[data.length - 3]];
            b3 = DECODING_TABLE[data[data.length - 2]];
            bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
        } else {
            b1 = DECODING_TABLE[data[data.length - 4]];
            b2 = DECODING_TABLE[data[data.length - 3]];
            b3 = DECODING_TABLE[data[data.length - 2]];
            b4 = DECODING_TABLE[data[data.length - 1]];
            bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
        }
        return bytes;
    }

    /**
     * Base64 String解码为bytes
     */
    public static byte[] decode(String data) {
        if (data == null){
            return new byte[0];
        }

        byte[] bytes;
        byte b1;
        byte b2;
        byte b3;
        byte b4;
        data = discardNonBase64Chars(data);
        if (data.charAt(data.length() - 2) == '=') {
            bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
        } else if (data.charAt(data.length() - 1) == '=') {
            bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
        } else {
            bytes = new byte[((data.length() / 4) * 3)];
        }
        for (int i = 0, j = 0; i < (data.length() - 4); i += 4, j += 3) {
            b1 = DECODING_TABLE[data.charAt(i)];
            b2 = DECODING_TABLE[data.charAt(i + 1)];
            b3 = DECODING_TABLE[data.charAt(i + 2)];
            b4 = DECODING_TABLE[data.charAt(i + 3)];
            bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[j + 2] = (byte) ((b3 << 6) | b4);
        }
        if (data.charAt(data.length() - 2) == '=') {
            b1 = DECODING_TABLE[data.charAt(data.length() - 4)];
            b2 = DECODING_TABLE[data.charAt(data.length() - 3)];
            bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
        } else if (data.charAt(data.length() - 1) == '=') {
            b1 = DECODING_TABLE[data.charAt(data.length() - 4)];
            b2 = DECODING_TABLE[data.charAt(data.length() - 3)];
            b3 = DECODING_TABLE[data.charAt(data.length() - 2)];
            bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
        } else {
            b1 = DECODING_TABLE[data.charAt(data.length() - 4)];
            b2 = DECODING_TABLE[data.charAt(data.length() - 3)];
            b3 = DECODING_TABLE[data.charAt(data.length() - 2)];
            b4 = DECODING_TABLE[data.charAt(data.length() - 1)];
            bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
        }
        return bytes;
    }

    private static byte[] discardNonBase64Bytes(byte[] data) {
        byte[] temp = new byte[data.length];
        int bytesCopied = 0;
        for (int i = 0; i < data.length; i++) {
            if (isValidBase64Byte(data[i])) {
                temp[bytesCopied++] = data[i];
            }
        }
        byte[] newData = new byte[bytesCopied];
        System.arraycopy(temp, 0, newData, 0, bytesCopied);
        return newData;
    }

    private static String discardNonBase64Chars(String data) {
        StringBuffer sb = new StringBuffer();
        int length = data.length();
        for (int i = 0; i < length; i++) {
            if (isValidBase64Byte((byte) (data.charAt(i)))) {
                sb.append(data.charAt(i));
            }
        }
        return sb.toString();
    }

    private static boolean isValidBase64Byte(byte b) {
        if (b == '=') {
            return true;
        } else if ((b < 0) || (b >= 128)) {
            return false;
        } else if (DECODING_TABLE[b] == -1) {
            return false;
        }
        return true;
    }

    /**
     * bytes编码(压缩)为Base64 bytes
     */
    public static byte[] compressBytes(byte[] input) {
        if (input == null){
            return new byte[0];
        }

        int cachesize = 1024;

        Deflater compresser = new Deflater();

        compresser.reset();
        compresser.setInput(input);
        compresser.finish();
        byte[] output;
        ByteArrayOutputStream o = new ByteArrayOutputStream(input.length);
        try {
            byte[] buf = new byte[cachesize];
            int got;
            while (!compresser.finished()) {
                got = compresser.deflate(buf);
                o.write(buf, 0, got);
            }
            output = o.toByteArray();
        } finally {
            try {
                o.close();
            } catch (IOException ignore) {
            }
        }
        return output;
    }

    /**
     * Base64 bytes解码(解压缩)为bytes
     */
    public static byte[] decompressBytes(byte[] input) throws DataFormatException {
        if (input == null){
            return new byte[0];
        }

        int cacheSize = 1024;
        Inflater decompresser = new Inflater();

        byte[] output;
        decompresser.reset();
        decompresser.setInput(input);
        ByteArrayOutputStream o = new ByteArrayOutputStream(input.length);
        try {
            byte[] buf = new byte[cacheSize];
            int got;
            while (!decompresser.finished()) {
                got = decompresser.inflate(buf);
                o.write(buf, 0, got);
            }
            output = o.toByteArray();
        } finally {
            try {
                o.close();
            } catch (IOException ignore) {
            }
        }
        return output;
    }

}