using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LeatherApp.Utils
{
    public static class HexUtil
    {
        public static byte[] joinByteList(List<byte[]> buffList)    
        {
            int len = 0;
            foreach (byte[] b in buffList)
                len += b.Length;

            byte[] result = new byte[len];
            len = 0;
            foreach (byte[] b in buffList)
            {
                b.CopyTo(result, len);
                len += b.Length;
            }
            return result;
        }
        public static byte[] subBytes(byte[] buff, int start, int len = 0)
        {
            if (len < 1)
                return buff.Skip(start).ToArray();
            else
                return buff.Skip(start).Take(len).ToArray();
        }
        public static string toHexString(this byte[] bytes)
        {
            string byteStr = string.Empty;
            if (bytes != null || bytes.Length > 0)
            {
                foreach (var item in bytes)
                {
                    byteStr += string.Format("{0:X2}", item);
                }
            }
            return byteStr;
        }
        public static bool Equals(byte[] buff1, byte[] buff2)
        {
            if (buff1 == null || buff1 == null || buff1.Length != buff2.Length)
                return false;
            for (int i = 0; i < buff1.Length; i++)
                if (buff1[i] != buff2[i]) return false;
            return true;

        }
        public static IEnumerable<long> IndexOf(byte[] source, int start, byte[] pattern)
        {
            if (source == null)
            {
                throw new ArgumentNullException(nameof(source));
            }

            if (pattern == null)
            {
                throw new ArgumentNullException(nameof(pattern));
            }

            long valueLength = source.LongLength;
            long patternLength = pattern.LongLength;
            if ((valueLength == 0) || (patternLength == 0) || (patternLength > valueLength))
            {
                yield break;
            }

            var badCharacters = new long[256];
            for (var i = 0; i < 256; i++)
            {
                badCharacters[i] = patternLength;
            }

            var lastPatternByte = patternLength - 1;
            for (long i = 0; i < lastPatternByte; i++)
            {
                badCharacters[pattern[i]] = lastPatternByte - i;
            }

            long index = start;
            while (index <= valueLength - patternLength)
            {
                for (var i = lastPatternByte; source[index + i] == pattern[i]; i--)
                {
                    if (i == 0)
                    {
                        yield return index;
                        break;
                    }
                }

                index += badCharacters[source[index + lastPatternByte]];
            }
        }
    }
}