using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.IO;
using System.Reflection;
using System.Linq;
using System.Text.RegularExpressions;

namespace System.Net.ApiService {

    public class StateObject {
        // Client  socket.  
        public Socket workSocket = null;
        // Size of receive buffer.  
        public const int BufferSize = 2048;
        // Receive buffer.  
        public byte[] buffer = new byte[BufferSize];
        // Received data string.  
        public MemoryStream Content = new MemoryStream();

        public StringBuilder RawHeader = new StringBuilder();

        public RequestHeader Request;

        public ApiServer server;
    }

    public class ApiServer {

        public static ManualResetEvent allDone = new ManualResetEvent(false);

        protected ushort _port;

        protected HttpMethod _allowedMethods = HttpMethod.GET | HttpMethod.POST;

        private List<RouteElements> _routes = new List<RouteElements>();
        protected string _serverName = "BlackPro_SimpleApi";

        // TODO: wwwDirectory entsprechend einer Hosts.ini Datei anpassen, anhand der Request.Host wird ein entsprechender wwwDirectory / FavIcon / Robots.txt verwendet, der in der Hosts.ini hinterlegt wurde
        //       Das soll Multiple V-Hosts in zukunft erlauben
        protected string? _wwwDirectory = "/www";
        protected bool bUseWebDirectory = true;

        protected bool bUseCompression = false;

        protected bool bAllowEmptyResponse = false;
        protected Socket listener;
        protected bool bRunning;
        protected Thread th;

        protected string[] _allowedEncodingTypes = new string[] {
            "text/html",
            "application/javascript",
            "text/javascript",
            "application/json",
            "text/json",
            "text/css",
            "text/stylesheet",
            "text/xml",
            "application/xml"
        };

        public HttpMethod AllowedMethods {
            get => this._allowedMethods;
            set => this._allowedMethods = value;
        }

        public RouteElements[] Routes {
            get { return this._routes.ToArray(); }
        }

        public bool Running {
            get { return this.bRunning; }
        }

        public bool AllowEmptyResponse {
            get { return this.bAllowEmptyResponse; }
            set { this.bAllowEmptyResponse = value; }
        }

        public bool Compression {
            get {
                return this.bUseCompression;
            }
            set {
                this.bUseCompression = value;
            }
        }

        public string ServerName {
            get {
                return this._serverName;
            }
            set {
                this._serverName = value;
            }
        }

        public bool UseWebDirectory {
            get {
                return this.bUseWebDirectory;
            }
        }

        public string WebDirectory {
            get {
                return this._wwwDirectory;
            }
            set {
                this._wwwDirectory = value;
                this.bUseWebDirectory = this._wwwDirectory != null && Directory.Exists(this._wwwDirectory) && this._wwwDirectory != "";
            }
        }

        public ushort Port {
            get {
                return this._port;
            }
            set {
                this._port = value;
                if (this.bRunning) {
                    this.Stop();
                    this.Start();
                }
            }
        }




        public ApiServer() {
        }

        public ApiServer(ushort port) {
            this._port = port;
        }

        public ApiServer(string www_Directory, ushort port) {
            this._port = port;
            this._wwwDirectory = www_Directory;
        }

        public void Stop() {
            this.bRunning = false;
            System.Diagnostics.Debug.WriteLine("Stop");
            try {
                allDone.Set();
                this.th.Abort();
                this.listener.Close();
                this.listener.Dispose();
                this.listener = null;
            } catch {

            }
        }

        public void Start() {
            if (this.bRunning == true)
                return;
            this.bRunning = true;
            this.th = new Thread(new ThreadStart(this.StartListen));
            //this.th.ThreadState = new object[] { this.listener, this._port, this };
            System.Diagnostics.Debug.WriteLine("Start");
            this.th.Start();
        }

        protected void StartListen() {
            // Establish the local endpoint for the socket.  
            // The DNS name of the computer  
            // running the listener is "host.contoso.com".  
            IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
            //IPAddress ipAddress = ipHostInfo.AddressList[0];
            IPAddress ipAddress = new IPAddress(new byte[] { 127, 0, 0, 1 });
            IPEndPoint localEndPoint = new IPEndPoint(ipAddress, this._port);

            // Create a TCP/IP socket.  
            System.Diagnostics.Debug.WriteLine("Create listener");
            //this.listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            this.listener = new Socket(ipAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

            // Bind the socket to the local endpoint and listen for incoming connections.  
            try {
                System.Diagnostics.Debug.WriteLine("Bind listener");
                this.listener.Bind(localEndPoint);
                System.Diagnostics.Debug.WriteLine("Listen on port: " + this._port);
                this.listener.Listen(100);

                while (this.bRunning) {
                    // Set the event to nonsignaled state.
                    System.Diagnostics.Debug.WriteLine("Reset");
                    allDone.Reset();

                    // Start an asynchronous socket to listen for connections.
                    System.Diagnostics.Debug.WriteLine("Begin Accept");
                    this.listener.BeginAccept(new AsyncCallback(Async_AcceptCallback), new object[] { this.listener, this });
                    //Accept(this, this.listener);
                    

                    // Wait until a connection is made before continuing.
                    System.Diagnostics.Debug.WriteLine("WaitOne");
                    allDone.WaitOne();
                    System.Diagnostics.Debug.WriteLine("Wait done");
                }

                System.Diagnostics.Debug.WriteLine("Stop Listen");

            } catch (Exception e) {
                System.Diagnostics.Debug.WriteLine(e);
            }
        }

        protected static void Accept(ApiServer server, Socket listener) {
            // Get the socket that handles the client request.  
            Socket handler = listener.Accept();
            System.Diagnostics.Debug.WriteLine("AcceptCallback");
            allDone.Set();

            // Create the state object.  
            StateObject state = new StateObject();
            state.workSocket = handler;
            state.server = server;
            System.Diagnostics.Debug.WriteLine("Begin Receive");
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(Async_ReadRequestCallback), state);
        }

        protected static void Async_AcceptCallback(IAsyncResult ar) {
            // Signal the main thread to continue.
            System.Diagnostics.Debug.WriteLine("AcceptCallback");
            allDone.Set();

            // Get the socket that handles the client request.  
            Socket listener = (Socket)((object[])ar.AsyncState)[0];
            Socket handler = listener.EndAccept(ar);

            // Create the state object.  
            StateObject state = new StateObject();
            state.workSocket = handler;
            state.server = (ApiServer)((object[])ar.AsyncState)[1];
            System.Diagnostics.Debug.WriteLine("Begin Receive");
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(Async_ReadRequestCallback), state);
        }

        protected static void Async_ReadRequestCallback(IAsyncResult ar) {
            System.Diagnostics.Debug.WriteLine("ReadRequestCallback");
            String content = String.Empty;

            // Retrieve the state object and the handler socket  
            // from the asynchronous state object.  
            StateObject state = (StateObject)ar.AsyncState;
            Socket handler = state.workSocket;

            // Read data from the client socket.
            int bytesRead = handler.EndReceive(ar);

            if (bytesRead > 0) {
                // There  might be more data, so store the data received so far.
                string line = Encoding.ASCII.GetString(state.buffer, 0, bytesRead);

                if (state.RawHeader.Length == 0) {
                    string[] xline = line.Split("\r\n\r\n", 2);
                    state.RawHeader.Append(xline[0]);
                    if (xline.Length > 0) {
                        for (int i = 20; i < bytesRead; i++)
                            if (state.buffer[i] == '\r' && state.buffer[i + 1] == '\n' && state.buffer[i + 2] == '\r' && state.buffer[i + 3] == '\n') {
                                state.Content.Write(state.buffer,i+4,bytesRead-i-4);
                                break;
                            }
                    }
                    state.Request = new RequestHeader(state.RawHeader.ToString());
                } else {
                    state.Content.Write(state.buffer, 0, bytesRead);
                }

                Response resp = new Response();
                RequestEventArgs req = new RequestEventArgs();
                req.Response = resp;
                req.Request = state.Request;
                req.Socket = handler;
                req.SendAnyResponse = true;


                // Check if more data is incomming
                bool ContinueRead = false;
                HttpMethod requestsWithContent = HttpMethod.POST | HttpMethod.PUT | HttpMethod.PATCH;
                if ((state.Request.Method | requestsWithContent) == requestsWithContent && state.Request.ContentLength > 0) {
                    ContinueRead = (state.Request.ContentLength > 0 && state.Request.ContentLength < state.Content.Length) || (state.Request.Boundary.Length > 0 && !line.EndsWith("--" + state.Request.Boundary + "--"));

                    if (!ContinueRead && state.Request.Boundary.Length > 0) {
                        // TODO: Resolver boundary here
                        /*
                        --boundary\r\n
                        Content-Disposition: form-data; name="field1"\r\n
                        \r\n
                        Hier steht der Content, bis der nächste boundary beginnt\r\n
                        --boundary\r\n
                        Content-Disposition: form-data; name="field2"; filename="example.txt"\r\n
                        \r\n
                        Hier steht der Zweite Content, bis der finale boundary tag beginnt\r\n
                        --boundary--
                        */
                    }
                }


                if (ContinueRead) {
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(Async_ReadRequestCallback), state);
                } else {

                    // Check known files and check allowed HTTP-Method
                    if ((state.Request.Path == "/ping" || state.Request.Path == "ping") && state.Request.Method == HttpMethod.GET) {
                        resp.FromString(200, "pong");
                    } else if (state.Request.Path == "/favicon.ico" && state.Request.Method == HttpMethod.GET) {
                        resp.FromFile("favicon.ico");
                    } else if (state.Request.Path == "/robots.txt" && state.Request.Method == HttpMethod.GET) {
                        resp.FromFile("robots.txt");
                    } else {

                        if(state.Request.ContentLength>0 && state.Request.ContentLength<2048) {
                            state.Request.SetPostData(state.Content.ToString());
                        }

                        if ((state.Request.Method | state.server._allowedMethods) != state.server._allowedMethods) {
                            resp.Error(Response.eErrorCode.MethodNotAllowed);
                        } else {
                            state.server.RequestAttr(req);
                            state.server.OnRequest(req);
                        }
                    }


                    // Generate response header
                    List<string> response_header = new List<string>();

                    if (state.server.bAllowEmptyResponse && req.Response.Length == 0) {
                        SetDefaultResponse(req.Response);
                    }

                    response_header.Add("HTTP/1.1 " + req.Response.Code + " " + req.Response.CodeName);
                    response_header.Add("Server: " + state.server.ServerName);
                    response_header.Add("Date: " + DateTime.Now.ToString("r"));
                    bool bUseBRCompression = false;
                    bool bUseGZCompression = false;
                    bool bUseDeflateCompression = false;
                    Span<byte> compressed_content = new Span<byte>();
                    int bytesWritten;
                    if (req.Response.Code >= 200 && req.Response.Code < 300 && resp.FilePath == "" && state.server.bUseCompression) {
                        if (state.server._allowedEncodingTypes.Contains(req.Response.ContentType)) {
                            if ((state.Request.AcceptEncoding & RequestHeader.eEncoder.br) == state.Request.AcceptEncoding) {
                                if (System.IO.Compression.BrotliEncoder.TryCompress(resp.Content, compressed_content, out bytesWritten)) {
                                    bUseBRCompression = true;
                                }
                            } else if ((state.Request.AcceptEncoding & RequestHeader.eEncoder.gzip) == state.Request.AcceptEncoding) {
                                using (MemoryStream mem = new MemoryStream()) {
                                    using (System.IO.Compression.GZipStream gzip = new IO.Compression.GZipStream(mem, IO.Compression.CompressionLevel.Optimal)) {
                                        gzip.Write(resp.Content, 0, resp.Content.Length);
                                    }
                                    compressed_content = mem.ToArray();
                                }
                                bUseGZCompression = true;
                            } else if ((state.Request.AcceptEncoding & RequestHeader.eEncoder.deflate) == state.Request.AcceptEncoding) {
                                using (MemoryStream mem = new MemoryStream()) {
                                    using (System.IO.Compression.DeflateStream defl = new IO.Compression.DeflateStream(mem, IO.Compression.CompressionLevel.Optimal)) {
                                        defl.Write(resp.Content, 0, resp.Content.Length);
                                    }
                                    compressed_content = mem.ToArray();
                                }
                                bUseDeflateCompression = true;
                            }
                        }
                    }

                    if (req.Response.Code >= 300 && req.Response.Code < 400 && req.Response.RedirectLocation != "") {
                        response_header.Add("Location: " + req.Response.RedirectLocation);
                    } else if (req.Response.Code >= 500) {
                        // Nothing to do on 500 errors
                    } else {
                        if (bUseBRCompression || bUseGZCompression || bUseDeflateCompression)
                            response_header.Add("Content-Length: " + compressed_content.Length);
                        else
                            response_header.Add("Content-Length: " + req.Response.Length);
                        if (req.Response.ContentType == "") {
                            response_header.Add("Content-Type: " + req.Response.ContentType);
                        }
                        response_header.Add("Accept-Ranges: bytes");
                        response_header.Add("Age: 0");
                        response_header.Add("Accept-Ranges: bytes");
                        if (resp.CacheControl != null && resp.CacheControl.IsSet) {
                            response_header.Add("Cache-Control: " + resp.CacheControl);
                        }
                        if (bUseBRCompression)
                            response_header.Add("Content-Encoding: bz");
                        else if (bUseGZCompression)
                            response_header.Add("Content-Encoding: gzip");
                        else if (bUseDeflateCompression)
                            response_header.Add("Content-Encoding: deflate");
                        response_header.Add("Connection: " + (resp.Connection == Response.eConnection.KeepAlive ? "keep-alive" : "Close"));
                    }

                    string response_header_string = "";
                    foreach (string s in response_header)
                        response_header_string += s + "\r\n";
                    response_header_string += "\r\n";



                    Send(handler, response_header_string, resp.Content);
                }
            }
        }

        protected static void SetDefaultResponse(Response res) {
            switch (res.ContentType.ToLower().Trim()) {
                case "":
                case "text/html":
                    res.FromString("<html></html>", "text/html");
                    break;
                case "text/stylesheet":
                case "text/css":
                    res.FromString("");
                    break;
                case "text/javascript":
                case "application/javascript":
                case "text/x-javascript":
                case "application/x-javascript":
                    res.FromString("");
                    break;
            }
        }

        private static void Send(Socket handler, String data, byte[] Content) {
            // Convert the string data to byte data using ASCII encoding.  
            byte[] byteData = Encoding.ASCII.GetBytes(data);

            // Begin sending the data to the remote device.  
            handler.BeginSend(byteData, 0, byteData.Length, 0, new AsyncCallback(SendResponseHeaderCallback), new object[] { handler, Content });
        }

        private static void SendResponseHeaderCallback(IAsyncResult ar) {
            try {
                // Retrieve the socket from the state object.  
                Socket handler = (Socket)((object[])ar.AsyncState)[0];
                byte[] Content = (byte[])((object[])ar.AsyncState)[1];

                // Complete sending the data to the remote device.  
                int bytesSent = handler.EndSend(ar);

                handler.BeginSend(Content, 0, Content.Length, 0, new AsyncCallback(SendResponseContentCallback), handler);
            } catch (Exception e) {
                System.Diagnostics.Debug.WriteLine(e);
            }
        }

        private static void SendResponseContentCallback(IAsyncResult ar) {
            try {
                // Retrieve the socket from the state object.  
                Socket handler = (Socket)ar.AsyncState;

                // Complete sending the data to the remote device.  
                int bytesSent = handler.EndSend(ar);
                //Console.WriteLine("Sent {0} bytes to client.", bytesSent);

                handler.Shutdown(SocketShutdown.Both);
                handler.Close();

            } catch (Exception e) {
                System.Diagnostics.Debug.WriteLine(e);
            }
        }





        public void RegisterClass(object[] instances) {
            foreach (object o in instances)
                this.RegisterClass(o);
        }

        public void RegisterClass(Type[] t) {
            foreach (Type o in t)
                this.RegisterClass(o);
        }

        public void RegisterClass(object instance) {
            Type t = instance.GetType();
            MethodInfo[] methodInfos = t.GetMethods(BindingFlags.Public | BindingFlags.Static);
            Route r = t.GetCustomAttribute<Route>();
            string baseRoute = "";
            if (r != null) {
                baseRoute = r.Path;
            }
            foreach (MethodInfo mi in methodInfos) {
                Route[] ris = mi.GetCustomAttributes<Route>().ToArray();
                foreach (Route ri in ris) {
                    this._routes.Add(new RouteElements(instance, mi, ri, baseRoute));
                }
            }
        }

        public void RegisterClass(Type t) {
            Route r = t.GetCustomAttribute<Route>();
            string baseRoute = "";
            if (r != null) {
                baseRoute = r.Path;
            }
            MethodInfo[] methodInfos = t.GetMethods(BindingFlags.Public | BindingFlags.Static);
            foreach (MethodInfo mi in methodInfos) {
                Route[] ris = mi.GetCustomAttributes<Route>().ToArray();
                foreach (Route ri in ris) {
                    this._routes.Add(new RouteElements(t, mi, ri, baseRoute));
                }
            }
        }



        protected void RequestAttr(RequestEventArgs e) {
            RequestHeader rh;
            foreach (RouteElements re in this._routes) {
                rh = e.Request;
                bool bIsMethod = (rh.Method | re.Method) == re.Method;
                if (rh.Path != null && re.Pattern.IsMatch(rh.Path) && bIsMethod) {
                    ParameterInfo[] pis = re.Function.GetParameters();

                    if (pis.Length == 2 && pis[0].ParameterType == typeof(RequestHeader) && pis[1].ParameterType == typeof(Response)) {
                        re.Function.Invoke(re.Instance, new object[] { e.Request, e.Response });
                    } else if (pis.Length == 1 && pis[0].ParameterType == typeof(RequestHeader)) {
                        if (re.Function.ReturnType == typeof(Response)) {
                            Response r = (Response)re.Function.Invoke(re.Instance, new object[] { rh });
                            if (r != null) {
                                e.Response = r;
                            }
                        } else if (re.Function.ReturnType == typeof(string)) {
                            string r = (string)re.Function.Invoke(re.Instance, new object[] { rh });
                            e.Response.FromString(200, r);
                        } else if (re.Function.ReturnType == typeof(bool)) {
                            bool r = (bool)re.Function.Invoke(re.Instance, new object[] { rh });
                            if (r)
                                e.Response.FromString(200, "{\"status\":\"ok\",\"code\":200,\"value\":1}", "application/json");
                            else
                                e.Response.FromString(200, "{\"status\":\"failed\",\"code\":200,\"value\":0}", "application/json");
                        } else if (re.Function.ReturnType == typeof(object)) {
                            object r = (object)re.Function.Invoke(re.Instance, new object[] { rh });
                            e.Response.FromObject(200, r);
                        }
                    } else if (pis.Length == 1 && pis[0].ParameterType == typeof(Response)) {
                        re.Function.Invoke(re.Instance, new object[] { e.Response });

                        //RegEx
                    } else if (pis.Length == 3 && pis[0].ParameterType == typeof(RequestHeader) && pis[1].ParameterType == typeof(Response) && pis[2].ParameterType == typeof(Match)) {
                        re.Function.Invoke(re.Instance, new object[] { e.Request, e.Response, re.Pattern.Match(rh.Path) });
                    } else if (pis.Length == 2 && pis[0].ParameterType == typeof(RequestHeader) && pis[1].ParameterType == typeof(Match)) {
                        if (re.Function.ReturnType == typeof(Response)) {
                            Response r = (Response)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path) });
                            if (r != null) {
                                e.Response = r;
                            }
                        } else if (re.Function.ReturnType == typeof(string)) {
                            string r = (string)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path) });
                            e.Response.FromString(200, r);
                        } else if (re.Function.ReturnType == typeof(bool)) {
                            bool r = (bool)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path) });
                            if (r)
                                e.Response.FromString(200, "{\"status\":\"ok\",\"code\":200,\"value\":1}", "application/json");
                            else
                                e.Response.FromString(200, "{\"status\":\"failed\",\"code\":200,\"value\":0}", "application/json");
                        } else if (re.Function.ReturnType == typeof(object)) {
                            object r = (object)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path) });
                            e.Response.FromObject(200, r);
                        }
                    } else if (pis.Length == 2 && pis[0].ParameterType == typeof(Response) && pis[1].ParameterType == typeof(Match)) {
                        re.Function.Invoke(re.Instance, new object[] { e.Response, re.Pattern.Match(rh.Path) });


                    } else if (pis.Length == 3 && pis[0].ParameterType == typeof(RequestHeader) && pis[1].ParameterType == typeof(Response) && pis[2].ParameterType == typeof(GroupCollection)) {
                        re.Function.Invoke(re.Instance, new object[] { e.Request, e.Response, re.Pattern.Match(rh.Path).Groups });
                    } else if (pis.Length == 2 && pis[0].ParameterType == typeof(RequestHeader) && pis[1].ParameterType == typeof(GroupCollection)) {
                        if (re.Function.ReturnType == typeof(Response)) {
                            Response r = (Response)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path).Groups });
                            if (r != null) {
                                e.Response = r;
                            }
                        } else if (re.Function.ReturnType == typeof(string)) {
                            string r = (string)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path).Groups });
                            e.Response.FromString(200, r);
                        } else if (re.Function.ReturnType == typeof(bool)) {
                            bool r = (bool)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path).Groups });
                            if (r)
                                e.Response.FromString(200, "{\"status\":\"ok\",\"code\":200,\"value\":1}", "application/json");
                            else
                                e.Response.FromString(200, "{\"status\":\"failed\",\"code\":200,\"value\":0}", "application/json");
                        } else if (re.Function.ReturnType == typeof(object)) {
                            object r = (object)re.Function.Invoke(re.Instance, new object[] { rh, re.Pattern.Match(rh.Path).Groups });
                            e.Response.FromObject(200, r);
                        }
                    } else if (pis.Length == 2 && pis[0].ParameterType == typeof(Response) && pis[1].ParameterType == typeof(GroupCollection)) {
                        re.Function.Invoke(re.Instance, new object[] { e.Response, re.Pattern.Match(rh.Path).Groups });
                    }

                }
            }
        }


        public virtual void OnRequest(RequestEventArgs e) {
            EventHandler<RequestEventArgs> handler = Request;
            if (handler != null) {
                handler(this, e);
            }
        }

        public event EventHandler<RequestEventArgs> Request;
    }
}