/*  Copyright (C) 2015-2021 Andreas Shimokawa, Carsten Pfeiffer

    This file is part of Gadgetbridge.

    Gadgetbridge is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published
    by the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Gadgetbridge is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
package nodomain.freeyourgadget.gadgetbridge.util;

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.CRC32;

public class CheckSums {
    public static int getCRC8(byte[] seq) {
        int len = seq.length;
        int i = 0;
        byte crc = 0x00;

        while (len-- > 0) {
            byte extract = seq[i++];
            for (byte tempI = 8; tempI != 0; tempI--) {
                byte sum = (byte) ((crc & 0xff) ^ (extract & 0xff));
                sum = (byte) ((sum & 0xff) & 0x01);
                crc = (byte) ((crc & 0xff) >>> 1);
                if (sum != 0) {
                    crc = (byte) ((crc & 0xff) ^ 0x8c);
                }
                extract = (byte) ((extract & 0xff) >>> 1);
            }
        }
        return (crc & 0xff);
    }

    //thanks http://stackoverflow.com/questions/13209364/convert-c-crc16-to-java-crc16
    public static int getCRC16(byte[] seq) {
        return getCRC16(seq, 0xFFFF);
    }
    
    public static int getCRC16(byte[] seq, int crc) {
        for (byte b : seq) {
            crc = ((crc >>> 8) | (crc << 8)) & 0xffff;
            crc ^= (b & 0xff);//byte to int, trunc sign
            crc ^= ((crc & 0xff) >> 4);
            crc ^= (crc << 12) & 0xffff;
            crc ^= ((crc & 0xFF) << 5) & 0xffff;
        }
        crc &= 0xffff;
        return crc;
    }
    
    public static int getCRC16ansi(byte[] seq) {
        int crc = 0xffff;
        int polynomial = 0xA001;

        for (int i = 0; i < seq.length; i++) {
            crc ^= seq[i] & 0xFF;
            for (int j = 0; j < 8; j++) {
                if ((crc & 1) != 0) {
                    crc = (crc >>> 1) ^ polynomial;
                } else {
                    crc = crc >>> 1;
                }
            }
        }

        return crc & 0xFFFF;
    }

    public static int getCRC32(byte[] seq) {
        CRC32 crc = new CRC32();
        crc.update(seq);
        return (int) (crc.getValue());
    }

    public static int getCRC32(byte[] seq,int offset, int length) {
        CRC32 crc = new CRC32();
        crc.update(seq,offset,length);
        return (int) (crc.getValue());
    }

    public static void main(String[] args) throws IOException {
        if (args == null || args.length == 0) {
            throw new IllegalArgumentException("Pass the files to be checksummed as arguments");
        }
        for (String name : args) {
            try (FileInputStream in = new FileInputStream(name)) {
                byte[] bytes = readAll(in, 1000 * 1000);
                System.out.println(name + " : " + getCRC16(bytes));
            }
        }
    }

    // copy&paste of FileUtils.readAll() to have it free from Android dependencies
    private static byte[] readAll(InputStream in, long maxLen) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream(Math.max(8192, in.available()));
        byte[] buf = new byte[8192];
        int read;
        long totalRead = 0;
        while ((read = in.read(buf)) > 0) {
            out.write(buf, 0, read);
            totalRead += read;
            if (totalRead > maxLen) {
                throw new IOException("Too much data to read into memory. Got already " + totalRead);
            }
        }
        return out.toByteArray();
    }

    // https://github.com/ThePBone/GalaxyBudsClient/blob/master/GalaxyBudsClient/Utils/CRC16.cs

    private static int[] Crc16Tab =
            {0, 4129, 8258, 12387, 16516, 20645, 24774, 28903, 33032, 37161, 41290,
                    45419, 49548, 53677, 57806, 61935, 4657, 528, 12915, 8786, 21173, 17044, 29431, 25302,
                    37689, 33560, 45947, 41818, 54205, 50076, 62463, 58334, 9314, 13379, 1056, 5121, 25830,
                    29895, 17572, 21637, 42346, 46411, 34088, 38153, 58862, 62927, 50604, 54669, 13907,
                    9842, 5649, 1584, 30423, 26358, 22165, 18100, 46939, 42874, 38681, 34616, 63455, 59390,
                    55197, 51132, 18628, 22757, 26758, 30887, 2112, 6241, 10242, 14371, 51660, 55789,
                    59790, 63919, 35144, 39273, 43274, 47403, 23285, 19156, 31415, 27286, 6769, 2640,
                    14899, 10770, 56317, 52188, 64447, 60318, 39801, 35672, 47931, 43802, 27814, 31879,
                    19684, 23749, 11298, 15363, 3168, 7233, 60846, 64911, 52716, 56781, 44330, 48395,
                    36200, 40265, 32407, 28342, 24277, 20212, 15891, 11826, 7761, 3696, 65439, 61374,
                    57309, 53244, 48923, 44858, 40793, 36728, 37256, 33193, 45514, 41451, 53516, 49453,
                    61774, 57711, 4224, 161, 12482, 8419, 20484, 16421, 28742, 24679, 33721, 37784, 41979,
                    46042, 49981, 54044, 58239, 62302, 689, 4752, 8947, 13010, 16949, 21012, 25207, 29270,
                    46570, 42443, 38312, 34185, 62830, 58703, 54572, 50445, 13538, 9411, 5280, 1153, 29798,
                    25671, 21540, 17413, 42971, 47098, 34713, 38840, 59231, 63358, 50973, 55100, 9939,
                    14066, 1681, 5808, 26199, 30326, 17941, 22068, 55628, 51565, 63758, 59695, 39368,
                    35305, 47498, 43435, 22596, 18533, 30726, 26663, 6336, 2273, 14466, 10403, 52093,
                    56156, 60223, 64286, 35833, 39896, 43963, 48026, 19061, 23124, 27191, 31254, 2801,
                    6864, 10931, 14994, 64814, 60687, 56684, 52557, 48554, 44427, 40424, 36297, 31782,
                    27655, 23652, 19525, 15522, 11395, 7392, 3265, 61215, 65342, 53085, 57212, 44955,
                    49082, 36825, 40952, 28183, 32310, 20053, 24180, 11923, 16050, 3793, 7920};

    // // https://github.com/ThePBone/GalaxyBudsClient/blob/master/GalaxyBudsClient/Utils/CRC16.cs
    public static int crc16_ccitt(byte[] data) {

        int i2 = 0;
        for (int i3 = 0; i3 < data.length; i3++)
            i2 = Crc16Tab[((i2 >> 8) ^ data[i3]) & 255] ^ (i2 << 8);

        return 65535 & i2;
    }
}