using System;
using Tesses.WebServer;
using System.Threading.Tasks;
using Tesses.WebServer.WebSocket;
using System.Threading;
using System.Text;
using Newtonsoft.Json;
using System.Security.Cryptography;
using System.Collections.Generic;
using System.Linq;
using System.Collections;
using System.IO;

namespace Tesses.WebServer
{
    public static class WebSocketExtensions
    {
        
        internal static bool FirstEquals<T1,T2>(this Dictionary<T1,List<T2>> dict,T1 t,T2 t2)
        {
            T2 firstVal;
            return dict.TryGetFirst(t,out firstVal) && firstVal.Equals(t2);
        }
        internal static bool AnyEquals<T1,T2>(this Dictionary<T1,List<T2>> dict,T1 t,T2 t2)
        {
            List<T2> items;
            if(dict.TryGetValue(t,out items))
            {
                foreach(var item in items)
                {
                    if(item.Equals(t2)) return true;
                }
            }
            return false;
           
        }
        public static void StartWebSocketConnection(this ServerContext ctx,Action<Action<WebSocketMessage>,Action<byte[]>,CancellationToken> opened,Action<WebSocketMessage> arrived,Action<bool> closed)
        {
           var t=ctx.StartWebSocketConnectionAsync(async(s,p,c)=>await Task.Run(()=>opened(
                (mm)=>{
                    Task.Run(async()=>await s(mm)).Wait();
                },(data)=>{
                    Task.Run(async()=>await p(data)).Wait();
                },c)),async(m)=>await Task.Run(()=>arrived(m)),closed);
            Task.Run(()=>t).Wait();
        }
        public static async Task StartWebSocketConnectionAsync(this ServerContext ctx,Func<Func<WebSocketMessage,Task>,Func<byte[],Task>,CancellationToken,Task> opened,Func<WebSocketMessage,Task> arrived,Action<bool> closed)
        {
            WebSocketServer server=new WebSocketServer(ctx);
            server.MessageArrived+=async(sender,e)=>{
                try{
                await arrived(e.Message);
                }catch(Exception ex)
                {
                    _=ex;
                }
            };
            server.WebSocketClosed+=(sender,e)=>{
                
                     closed(e.Clean);
                
            };
         
            using(var cts=new CancellationTokenSource()){
            Thread t=new Thread(async()=>{
                try{
                    await opened(server.SendMessageAsync,server.Ping,cts.Token);
                }catch(Exception ex)
                {
                    _=ex;
                }
            });
            t.Start();
            await server.StartAsync();
            cts.Cancel();
            t.Join();
            }
        }
    }
}
namespace Tesses.WebServer.WebSocket
{
    public class WebSocketMessage
    {
        public static WebSocketMessage Create(string text)
        {
            WebSocketMessage msg=new WebSocketMessage();
            msg.Text = text;
            return msg;
        }
        public static WebSocketMessage Create(byte[] data)
        {
            WebSocketMessage msg=new WebSocketMessage();
            msg.Data=data;
            return msg;
        }
        public static WebSocketMessage Create(object data)
        {
            WebSocketMessage msg=new WebSocketMessage();
            msg.EncodeJson(data);
            return msg;
        }
        private WebSocketMessage()
        {
            Data=new byte[0];
            
        }
        internal WebSocketMessage(byte[] message,bool binary)
        {
            data=message;
            Binary=binary;
        }
        private byte[] data;
        public bool Binary {get;private set;}
        public byte[] Data {get{return data;} private set{data=value; Binary=true;}}

        public T DecodeJson<T>()
        {
            return JsonConvert.DeserializeObject<T>(Text);
        }
        private void EncodeJson(object data)
        {
           Text=JsonConvert.SerializeObject(data);
        }
        internal IEnumerable<(byte[] array,int)> GetPackets()
        {
            int read=0;
            int offset=0;
            byte[] buffer=new byte[4096];
            do
            {
                read = Math.Min(buffer.Length,data.Length-offset);
                Array.Copy(data,offset,buffer,0,read);
                yield return (buffer,read);
                offset+=read;

            }while(read>0);
        }
       

        public string Text {get{return Encoding.UTF8.GetString(Data);} private set{data=Encoding.UTF8.GetBytes(value); Binary=false;}}
    }
    public class WebSocketMessageEventArgs : EventArgs
    {
        public WebSocketMessageEventArgs(WebSocketMessage message)
        {
            Message=message;
        }
        public WebSocketMessage Message {get;private set;}
    }
    public class WebSocketClosedEventArgs : EventArgs
    {
        public WebSocketClosedEventArgs(bool clean)
        {
            Clean=clean;
        }
        public bool Clean {get;private set;}
    }
  
    public class WebSocketServer
    {
        bool hasInit=false;
        ServerContext context;
        public WebSocketServer(ServerContext ctx)
        {
            context=ctx;
        }
        public EventHandler<WebSocketMessageEventArgs> MessageArrived;

        public EventHandler<WebSocketClosedEventArgs> WebSocketClosed;

        private byte[] glenBytes(long len)
        {
            if(len < 126)
            {
                return new byte[]{(byte)len};
            }else if(len <= ushort.MaxValue)
            {
                byte[] num = BitConverter.GetBytes((ushort)len);
                if(BitConverter.IsLittleEndian)
                {
                    Array.Reverse(num);
                }
                return new byte[]{126,num[0],num[1]};
            }else{
                byte[] num = BitConverter.GetBytes(len);
                if(BitConverter.IsLittleEndian)
                {
                    Array.Reverse(num);
                }
                return new byte[]{127,num[0],num[1],num[2],num[3],num[4],num[5],num[6],num[7]};
            }
        }
        
        public async Task SendMessageAsync(WebSocketMessage msg)
        {
            while(!hasInit) ;
            int opCode = msg.Binary ? 0x2 : 0x1;
            (byte[] buff,int len)[] parts = msg.GetPackets().ToArray();
            
            for(int i = 0;i<parts.Length;i++)
            {
                bool fin = i == parts.Length-1;
                int finField = fin ? 0b10000000 : 0;
                int opCode2 = i==0 ? opCode : 0;
                
                byte firstByte= (byte)(finField | (opCode2 & 0xF));
                var b=glenBytes(parts[i].len);
                byte[] message = new byte[1+b.Length + parts[i].len];
                message[0]=firstByte;
                Array.Copy(b,0,message,1,b.Length);
                Array.Copy(parts[i].buff,0,message,1+b.Length,parts[i].len);
                await context.NetworkStream.WriteAsync(message,0,message.Length);
            }

        }
        private async Task PongSend(byte[] msg,long len)
        {
           
           
                int finField = 0b10000000 ;
               
                byte firstByte= (byte)(finField | 0xA);
                var b=glenBytes(len);
                byte[] message = new byte[1+b.Length + len];
                message[0]=firstByte;
                Array.Copy(b,0,message,1,b.Length);
                Array.Copy(msg,0,message,1+b.Length,len);
                await context.NetworkStream.WriteAsync(message,0,message.Length);
            
        }
        private string get_Sec_WebSocketAccept(string headerVal)
        {
            if(string.IsNullOrWhiteSpace(headerVal))
            {
                return "";
            }
            string headerVal2 = $"{headerVal.Trim()}258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
            var res=SHA1.Create().ComputeHash(Encoding.UTF8.GetBytes(headerVal2));
            return Convert.ToBase64String(res);
        }
        private void MaskMessage(byte[] key,byte[] message)
        {
            if(key.Length < 4)
            {
                return;

            }
            for(int i = 0;i<message.Length;i++)
            {
                message[i] ^= key[i % 4];
            }
        }
        private async Task<long> get_long()
        {
            byte[] data = new byte[8];
            await context.NetworkStream.ReadAsync(data,0,data.Length);
            if(BitConverter.IsLittleEndian)
            {
                Array.Reverse(data);
            }
            return BitConverter.ToInt64(data,0);
        }
        
        public async Task Ping(byte[] ping)
        {
            int finField = 0b10000000 ;
               
                byte firstByte= (byte)(finField | 0x9);
                var b=glenBytes(ping.Length);
                byte[] message = new byte[1+b.Length + ping.Length];
                message[0]=firstByte;
                Array.Copy(b,0,message,1,b.Length);
                Array.Copy(ping,0,message,1+b.Length,ping.Length);
                await context.NetworkStream.WriteAsync(message,0,message.Length);
        }
        private async Task<short> get_short()
        {
            byte[] data = new byte[2];
            await context.NetworkStream.ReadAsync(data,0,data.Length);
            if(BitConverter.IsLittleEndian)
            {
                Array.Reverse(data);
            }
            return BitConverter.ToInt16(data,0);
        }
        private async Task<(byte[] data,long len)> read_packet_async(byte len)
        {
            int realLen=len & 127;
            bool masked=(len & 0b10000000) > 0;
            long realLen2 = realLen >= 126 ? realLen > 126 ? await get_long() : await get_short() : realLen;
            byte[] maskingKey = new byte[4];
            if(masked)
            {
                await context.NetworkStream.ReadAsync(maskingKey,0,maskingKey.Length);
            }
            byte[] data = new byte[realLen2];
            await context.NetworkStream.ReadAsync(data,0,data.Length);
            if(masked)
            {
                MaskMessage(maskingKey,data);
            }
            return (data,realLen2);
        }
        public async Task StartAsync()
        {
            /*
            GET /chatUrl HTTP/1.1
            Host: server.example.com
            Upgrade: websocket

            */
            string sec_websocket_accept="";
            
            
            if(context.RequestHeaders.TryGetFirst("Sec-WebSocket-Key",out sec_websocket_accept))
            {
                sec_websocket_accept=get_Sec_WebSocketAccept(sec_websocket_accept);
            }else{
                return;
            }
            if(!context.RequestHeaders.AnyEquals("Upgrade","websocket"))
            {
                //Console.WriteLine("Doesn't contain Upgrade: websocket");
                return;
            }
            
            if(!context.RequestHeaders.AnyEquals("Sec-WebSocket-Version", "13"))
            {
                //Console.WriteLine("Doesn't contain version 13");
                return;
            }
            context.StatusCode = 101;
            context.ResponseHeaders.Add("Upgrade","websocket");
            if(context.ResponseHeaders.ContainsKey("Connection"))
            {
                context.ResponseHeaders["Connection"].Clear();
            }
            context.ResponseHeaders.Add("Connection","Upgrade");
            context.ResponseHeaders.Add("Sec-WebSocket-Accept",sec_websocket_accept);
            
            await context.WriteHeadersAsync();
            //await context.NetworkStream.FlushAsync();
            await context.NetworkStream.FlushAsync();
            hasInit=true;
            bool isBinary=false;
            MemoryStream strm=new MemoryStream();
            while(context.Connected)
            {

                byte[] frame_start=new byte[2];
                await context.NetworkStream.ReadAsync(frame_start,0,2);
               byte first= frame_start[0];
                bool hasMessage =false;
               int opcode = first & 0xF;
               bool fin = (first | 0b10000000) > 0;
               switch(opcode)
               {
                    case 0x0:
                    if(!hasMessage) break;
                    var (data,len)= await read_packet_async(frame_start[1]);
                    strm.Write(data,0,(int)len);
                        break;
                    case 0x1:
                    case 0x2:
                        hasMessage=true;
                        strm.Dispose();
                        strm=new MemoryStream();
                        isBinary = opcode == 0x2;
                        
                        var (data2,len2)= await read_packet_async(frame_start[1]);
                        strm.Write(data2,0,(int)len2);
                        break;
                    case 0x8:
                        WebSocketClosed?.Invoke(this,new WebSocketClosedEventArgs(true));
                        return;
                    case 0x9:
                        var (data3,len3) =await read_packet_async(frame_start[1]);
                        await PongSend(data3,len3);
                        break;
                    case 0xA:
                        var (data4,len4) =await read_packet_async(frame_start[1]);
                        break;
                    
                        
               }
                if(fin && hasMessage)
                {
                    hasMessage=false;
                    WebSocketMessage msg=new WebSocketMessage(strm.ToArray(),isBinary);
                    MessageArrived?.Invoke(this,new WebSocketMessageEventArgs(msg));
                }
            }
            WebSocketClosed?.Invoke(this,new WebSocketClosedEventArgs(false));
        }
    }
}