using Esiur.Net.IIP;
using System;
using System.Collections.Generic;
using System.Text;
using System.Xml.Linq;

namespace Esiur.Data;


public struct TransmissionDataUnit
{
    public TransmissionDataUnitIdentifier Identifier;
    public int Index;
    public TransmissionDataUnitClass Class;
    public uint Offset;
    public ulong ContentLength;
    public byte Exponent;
    public byte[] Data;
    public byte[] Metadata;

    public ulong Size;

    public TransmissionDataUnit(TransmissionDataUnitIdentifier identifier,
                                byte[] data, uint offset,
                                ulong length, byte[] metadata = null,
                                byte exponent = 0)
    {
        Identifier = identifier;
        Index = (byte)identifier & 0x7;
        Class = (TransmissionDataUnitClass)((byte)identifier >> 6);
        Offset = offset;
        ContentLength = length;
        Exponent = exponent;
        Data = data;
        Metadata = metadata;

        Size = Class == TransmissionDataUnitClass.Fixed ? 1 + length: 1 + length +
    }

    public byte[] GetTypeMetadata()
    {
        if (Class != TransmissionDataUnitClass.Typed)
            throw new Exception("Class has no metadata.");

        var size = Data[Offset];
        return Data.Clip(Offset + 1, size);

    }
    public bool MatchType(TransmissionDataUnit with)
    {
        if (Identifier != with.Identifier)
            return false;

        if (Class == TransmissionDataUnitClass.Typed)
            if (!Metadata.SequenceEqual(with.Metadata))
                return false;

        return true;
    }

    public byte[] Compose()
    {
        return null;
    }

    public static byte[] Compose(TransmissionDataUnitIdentifier identifier, byte[] data, byte[] typeMetadata)
    {

        if (data == null || data.Length == 0)
            return new byte[] { (byte)identifier };

        var cls = (TransmissionDataUnitClass)((int)identifier >> 6);
        if (cls == TransmissionDataUnitClass.Fixed)
        {
            return DC.Combine(new byte[] { (byte)identifier }, 0, 1, data, 0, (uint)data.Length);
        }
        else if (cls == TransmissionDataUnitClass.Dynamic
            || cls == TransmissionDataUnitClass.Extension)
        {
            var len = (ulong)data.LongLength;

            if (len == 0)
            {
                return new byte[1] { (byte)identifier };
            }
            else if (len <= 0xFF)
            {
                var rt = new byte[2 + len];
                rt[0] = (byte)((byte)identifier | 0x8);
                rt[1] = (byte)len;
                Buffer.BlockCopy(data, 0, rt, 2, (int)len);
                return rt;
            }
            else if (len <= 0xFF_FF)
            {
                var rt = new byte[3 + len];
                rt[0] = (byte)((byte)identifier | 0x10);
                rt[1] = (byte)((len >> 8) & 0xFF);
                rt[2] = (byte)(len & 0xFF);
                Buffer.BlockCopy(data, 0, rt, 3, (int)len);
                return rt;
            }
            else if (len <= 0xFF_FF_FF)
            {
                var rt = new byte[4 + len];
                rt[0] = (byte)((byte)identifier | 0x18);
                rt[1] = (byte)((len >> 16) & 0xFF);
                rt[2] = (byte)((len >> 8) & 0xFF);
                rt[3] = (byte)(len & 0xFF);
                Buffer.BlockCopy(data, 0, rt, 4, (int)len);
                return rt;
            }
            else if (len <= 0xFF_FF_FF_FF)
            {
                var rt = new byte[5 + len];
                rt[0] = (byte)((byte)identifier | 0x20);
                rt[1] = (byte)((len >> 24) & 0xFF);
                rt[2] = (byte)((len >> 16) & 0xFF);
                rt[3] = (byte)((len >> 8) & 0xFF);
                rt[4] = (byte)(len & 0xFF);
                Buffer.BlockCopy(data, 0, rt, 5, (int)len);
                return rt;
            }
            else if (len <= 0xFF_FF_FF_FF_FF)
            {
                var rt = new byte[6 + len];
                rt[0] = (byte)((byte)identifier | 0x28);
                rt[1] = (byte)((len >> 32) & 0xFF);
                rt[2] = (byte)((len >> 24) & 0xFF);
                rt[3] = (byte)((len >> 16) & 0xFF);
                rt[4] = (byte)((len >> 8) & 0xFF);
                rt[5] = (byte)(len & 0xFF);
                Buffer.BlockCopy(data, 0, rt, 6, (int)len);
                return rt;
            }
            else if (len <= 0xFF_FF_FF_FF_FF_FF)
            {
                var rt = new byte[7 + len];
                rt[0] = (byte)((byte)identifier | 0x30);
                rt[1] = (byte)((len >> 40) & 0xFF);
                rt[2] = (byte)((len >> 32) & 0xFF);
                rt[3] = (byte)((len >> 24) & 0xFF);
                rt[4] = (byte)((len >> 16) & 0xFF);
                rt[5] = (byte)((len >> 8) & 0xFF);
                rt[6] = (byte)(len & 0xFF);
                Buffer.BlockCopy(data, 0, rt, 7, (int)len);
                return rt;
            }
            else //if (len <= 0xFF_FF_FF_FF_FF_FF_FF)
            {
                var rt = new byte[8 + len];
                rt[0] = (byte)((byte)identifier | 0x38);
                rt[1] = (byte)((len >> 48) & 0xFF);
                rt[2] = (byte)((len >> 40) & 0xFF);
                rt[3] = (byte)((len >> 32) & 0xFF);
                rt[4] = (byte)((len >> 24) & 0xFF);
                rt[5] = (byte)((len >> 16) & 0xFF);
                rt[6] = (byte)((len >> 8) & 0xFF);
                rt[7] = (byte)(len & 0xFF);
                Buffer.BlockCopy(data, 0, rt, 8, (int)len);
                return rt;
            }
        }
        else if (cls == TransmissionDataUnitClass.Typed)
        {

            var len = 1 + (ulong)typeMetadata.LongLength + (ulong)data.LongLength;

            if (len == 0)
            {
                return new byte[1] { (byte)identifier };
            }
            else if (len <= 0xFF)
            {
                var rt = new byte[2 + len];
                rt[0] = (byte)((byte)identifier | 0x8);
                rt[1] = (byte)len;

                Buffer.BlockCopy(typeMetadata, 0, rt, 2, typeMetadata.Length);
                Buffer.BlockCopy(data, 0, rt, 2 + typeMetadata.Length, data.Length);
                return rt;
            }
            else if (len <= 0xFF_FF)
            {
                var rt = new byte[3 + len];
                rt[0] = (byte)((byte)identifier | 0x10);
                rt[1] = (byte)((len >> 8) & 0xFF);
                rt[2] = (byte)(len & 0xFF);

                Buffer.BlockCopy(typeMetadata, 0, rt, 3, typeMetadata.Length);
                Buffer.BlockCopy(data, 0, rt, 3 + typeMetadata.Length, data.Length);
                return rt;
            }
            else if (len <= 0xFF_FF_FF)
            {
                var rt = new byte[4 + len];
                rt[0] = (byte)((byte)identifier | 0x18);
                rt[1] = (byte)((len >> 16) & 0xFF);
                rt[2] = (byte)((len >> 8) & 0xFF);
                rt[3] = (byte)(len & 0xFF);

                Buffer.BlockCopy(typeMetadata, 0, rt, 4, typeMetadata.Length);
                Buffer.BlockCopy(data, 0, rt, 4 + typeMetadata.Length, data.Length);

                return rt;
            }
            else if (len <= 0xFF_FF_FF_FF)
            {
                var rt = new byte[5 + len];
                rt[0] = (byte)((byte)identifier | 0x20);
                rt[1] = (byte)((len >> 24) & 0xFF);
                rt[2] = (byte)((len >> 16) & 0xFF);
                rt[3] = (byte)((len >> 8) & 0xFF);
                rt[4] = (byte)(len & 0xFF);

                Buffer.BlockCopy(typeMetadata, 0, rt, 5, typeMetadata.Length);
                Buffer.BlockCopy(data, 0, rt, 5 + typeMetadata.Length, data.Length);

                return rt;
            }
            else if (len <= 0xFF_FF_FF_FF_FF)
            {
                var rt = new byte[6 + len];
                rt[0] = (byte)((byte)identifier | 0x28);
                rt[1] = (byte)((len >> 32) & 0xFF);
                rt[2] = (byte)((len >> 24) & 0xFF);
                rt[3] = (byte)((len >> 16) & 0xFF);
                rt[4] = (byte)((len >> 8) & 0xFF);
                rt[5] = (byte)(len & 0xFF);

                Buffer.BlockCopy(typeMetadata, 0, rt, 6, typeMetadata.Length);
                Buffer.BlockCopy(data, 0, rt, 6 + typeMetadata.Length, data.Length);

                return rt;
            }
            else if (len <= 0xFF_FF_FF_FF_FF_FF)
            {
                var rt = new byte[7 + len];
                rt[0] = (byte)((byte)identifier | 0x30);
                rt[1] = (byte)((len >> 40) & 0xFF);
                rt[2] = (byte)((len >> 32) & 0xFF);
                rt[3] = (byte)((len >> 24) & 0xFF);
                rt[4] = (byte)((len >> 16) & 0xFF);
                rt[5] = (byte)((len >> 8) & 0xFF);
                rt[6] = (byte)(len & 0xFF);

                Buffer.BlockCopy(typeMetadata, 0, rt, 7, typeMetadata.Length);
                Buffer.BlockCopy(data, 0, rt, 7 + typeMetadata.Length, data.Length);

                return rt;
            }
            else //if (len <= 0xFF_FF_FF_FF_FF_FF_FF)
            {
                var rt = new byte[8 + len];
                rt[0] = (byte)((byte)identifier | 0x38);
                rt[1] = (byte)((len >> 48) & 0xFF);
                rt[2] = (byte)((len >> 40) & 0xFF);
                rt[3] = (byte)((len >> 32) & 0xFF);
                rt[4] = (byte)((len >> 24) & 0xFF);
                rt[5] = (byte)((len >> 16) & 0xFF);
                rt[6] = (byte)((len >> 8) & 0xFF);
                rt[7] = (byte)(len & 0xFF);

                Buffer.BlockCopy(typeMetadata, 0, rt, 8, typeMetadata.Length);
                Buffer.BlockCopy(data, 0, rt, 8 + typeMetadata.Length, data.Length);

                return rt;
            }
        }

        throw new Exception("Not supported class type.");
    }

    public static (ulong, TransmissionDataUnit?) Parse(byte[] data, uint offset, uint ends)
    {
        var h = data[offset++];

        var cls = (TransmissionDataUnitClass)(h >> 6);

        if (cls == TransmissionDataUnitClass.Fixed)
        {
            var exp = (h & 0x38) >> 3;

            if (exp == 0)
                return (1, new TransmissionDataUnit((TransmissionDataUnitIdentifier)h, data, offset, 0));

            ulong cl = (ulong)(1 << (exp - 1));

            if (ends - offset < cl)
                return (cl - (ends - offset), null);

            //offset += (uint)cl;

            return (1 + cl, new TransmissionDataUnit((TransmissionDataUnitIdentifier)h, data, offset, cl, null, (byte)exp));
        }
        else if (cls == TransmissionDataUnitClass.Typed)
        {
            ulong cll = (ulong)(h >> 3) & 0x7;

            if (ends - offset < cll)
                return (cll - (ends - offset), null);

            ulong cl = 0;

            for (uint i = 0; i < cll; i++)
                cl = cl << 8 | data[offset++];

            if (ends - offset < cl)
                return (cl - (ends - offset), null);

            var metaData = DC.Clip(data, offset + 1, data[offset]);
            offset += data[offset];

            return (1 + cl + cll, new TransmissionDataUnit((TransmissionDataUnitIdentifier)(h & 0xC7), data, offset, cl, metaData));
        }
        else 
        {
            ulong cll = (ulong)(h >> 3) & 0x7;

            if (ends - offset < cll)
                return (cll - (ends - offset), null);

            ulong cl = 0;

            for (uint i = 0; i < cll; i++)
                cl = cl << 8 | data[offset++];

            if (ends - offset < cl)
                return (cl - (ends - offset), null);


            return (1 + cl + cll, new TransmissionDataUnit((TransmissionDataUnitIdentifier)(h & 0xC7), data, offset, cl));

        }
    }

}