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

namespace EPD.Data
{
    class ByteReader
    {
        private byte[] buffer;
        private int idx;
        private int length;
        public int Length => length;

        public ByteReader(byte[] data, int len)
        {
            buffer = new byte[len];
            Buffer.BlockCopy(data, 0, buffer, 0, len);
            length = len;
            idx = 0;
        }

        public void Append(byte[] data, int len)
        {
            var buf = new byte[Length + len];
            Buffer.BlockCopy(buffer, 0, buf, 0, Length);
            Buffer.BlockCopy(data, 0, buf, Length, len);
            buffer = buf;
            length += len;
        }

        public bool Reset(int curIdx = 0)
        {
            if (curIdx < length)
                idx = curIdx;
            return idx == curIdx;
        }

        public bool ReadByte(out byte data)
        {
            data = buffer[idx];
            idx++;

            return true;
        }

        public bool ReadBytes(byte[] buf, int len)
        {
            if (idx + len <= length)
            {
                Buffer.BlockCopy(buffer, (int)idx, buf, 0, (int)len);
                idx += len;
                return true;
            }
            return false;
        }

        public bool ReadInt(out int data)
        {
            data = 0;
            if (idx + 4 <= length)
            {
                data = BitConverter.ToInt32(buffer, (int)idx);
                idx += 4;
                return true;
            }
            return false;
        }

        public bool ReadUInt16(out UInt16 data)
        {
            data = 0;
            if (idx + 2 <= length)
            {
                data = BitConverter.ToUInt16(buffer, (int)idx);
                idx += 2;
                return true;
            }
            return false;
        }

        public bool ReadInt64(out Int64 data)
        {
            data = 0;
            if (idx + 8 <= length)
            {
                data = BitConverter.ToInt64(buffer, (int)idx);
                idx += 8;
                return true;
            }
            return false;
        }

        public bool ReadString(out string str, int len)
        {
            str = System.Text.Encoding.Default.GetString(buffer, idx, len);
            str = str.Substring(0, str.IndexOf('\0'));
            idx += len;
            return true;
        }
    }
}