#region License
/*
 * WebSocketFrame.cs
 *
 * The MIT License
 *
 * Copyright (c) 2012-2021 sta.blockhead
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#endregion

#region Contributors
/*
 * Contributors:
 * - Chris Swiedler
 */
#endregion

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace WebSocketSharp
{
  internal class WebSocketFrame : IEnumerable<byte>
  {
    #region Private Fields

    private byte[]      _extPayloadLength;
    private Fin         _fin;
    private Mask        _mask;
    private byte[]      _maskingKey;
    private Opcode      _opcode;
    private PayloadData _payloadData;
    private byte        _payloadLength;
    private Rsv         _rsv1;
    private Rsv         _rsv2;
    private Rsv         _rsv3;

    #endregion

    #region Private Constructors

    private WebSocketFrame ()
    {
    }

    #endregion

    #region Internal Constructors

    internal WebSocketFrame (Opcode opcode, PayloadData payloadData, bool mask)
      : this (Fin.Final, opcode, payloadData, false, mask)
    {
    }

    internal WebSocketFrame (
      Fin fin, Opcode opcode, byte[] data, bool compressed, bool mask
    )
      : this (fin, opcode, new PayloadData (data), compressed, mask)
    {
    }

    internal WebSocketFrame (
      Fin fin,
      Opcode opcode,
      PayloadData payloadData,
      bool compressed,
      bool mask
    )
    {
      _fin = fin;
      _opcode = opcode;

      _rsv1 = opcode.IsData () && compressed ? Rsv.On : Rsv.Off;
      _rsv2 = Rsv.Off;
      _rsv3 = Rsv.Off;

      var len = payloadData.Length;

      if (len < 126) {
        _payloadLength = (byte) len;
        _extPayloadLength = WebSocket.EmptyBytes;
      }
      else if (len < 0x010000) {
        _payloadLength = (byte) 126;
        _extPayloadLength = ((ushort) len).InternalToByteArray (ByteOrder.Big);
      }
      else {
        _payloadLength = (byte) 127;
        _extPayloadLength = len.InternalToByteArray (ByteOrder.Big);
      }

      if (mask) {
        _mask = Mask.On;
        _maskingKey = createMaskingKey ();

        payloadData.Mask (_maskingKey);
      }
      else {
        _mask = Mask.Off;
        _maskingKey = WebSocket.EmptyBytes;
      }

      _payloadData = payloadData;
    }

    #endregion

    #region Internal Properties

    internal ulong ExactPayloadLength {
      get {
        return _payloadLength < 126
               ? _payloadLength
               : _payloadLength == 126
                 ? _extPayloadLength.ToUInt16 (ByteOrder.Big)
                 : _extPayloadLength.ToUInt64 (ByteOrder.Big);
      }
    }

    internal int ExtendedPayloadLengthWidth {
      get {
        return _payloadLength < 126
               ? 0
               : _payloadLength == 126
                 ? 2
                 : 8;
      }
    }

    #endregion

    #region Public Properties

    public byte[] ExtendedPayloadLength {
      get {
        return _extPayloadLength;
      }
    }

    public Fin Fin {
      get {
        return _fin;
      }
    }

    public bool IsBinary {
      get {
        return _opcode == Opcode.Binary;
      }
    }

    public bool IsClose {
      get {
        return _opcode == Opcode.Close;
      }
    }

    public bool IsCompressed {
      get {
        return _rsv1 == Rsv.On;
      }
    }

    public bool IsContinuation {
      get {
        return _opcode == Opcode.Cont;
      }
    }

    public bool IsControl {
      get {
        return _opcode >= Opcode.Close;
      }
    }

    public bool IsData {
      get {
        return _opcode == Opcode.Text || _opcode == Opcode.Binary;
      }
    }

    public bool IsFinal {
      get {
        return _fin == Fin.Final;
      }
    }

    public bool IsFragment {
      get {
        return _fin == Fin.More || _opcode == Opcode.Cont;
      }
    }

    public bool IsMasked {
      get {
        return _mask == Mask.On;
      }
    }

    public bool IsPing {
      get {
        return _opcode == Opcode.Ping;
      }
    }

    public bool IsPong {
      get {
        return _opcode == Opcode.Pong;
      }
    }

    public bool IsText {
      get {
        return _opcode == Opcode.Text;
      }
    }

    public ulong Length {
      get {
        return 2
               + (ulong) (_extPayloadLength.Length + _maskingKey.Length)
               + _payloadData.Length;
      }
    }

    public Mask Mask {
      get {
        return _mask;
      }
    }

    public byte[] MaskingKey {
      get {
        return _maskingKey;
      }
    }

    public Opcode Opcode {
      get {
        return _opcode;
      }
    }

    public PayloadData PayloadData {
      get {
        return _payloadData;
      }
    }

    public byte PayloadLength {
      get {
        return _payloadLength;
      }
    }

    public Rsv Rsv1 {
      get {
        return _rsv1;
      }
    }

    public Rsv Rsv2 {
      get {
        return _rsv2;
      }
    }

    public Rsv Rsv3 {
      get {
        return _rsv3;
      }
    }

    #endregion

    #region Private Methods

    private static byte[] createMaskingKey ()
    {
      var key = new byte[4];

      WebSocket.RandomNumber.GetBytes (key);

      return key;
    }

    private static string dump (WebSocketFrame frame)
    {
      var len = frame.Length;
      var cnt = (long) (len / 4);
      var rem = (int) (len % 4);

      int cntDigit;
      string cntFmt;

      if (cnt < 10000) {
        cntDigit = 4;
        cntFmt = "{0,4}";
      }
      else if (cnt < 0x010000) {
        cntDigit = 4;
        cntFmt = "{0,4:X}";
      }
      else if (cnt < 0x0100000000) {
        cntDigit = 8;
        cntFmt = "{0,8:X}";
      }
      else {
        cntDigit = 16;
        cntFmt = "{0,16:X}";
      }

      var spFmt = String.Format ("{{0,{0}}}", cntDigit);

      var headerFmt = String.Format (
                        @"
{0} 01234567 89ABCDEF 01234567 89ABCDEF
{0}+--------+--------+--------+--------+\n",
                        spFmt
                      );

      var lineFmt = String.Format (
                      "{0}|{{1,8}} {{2,8}} {{3,8}} {{4,8}}|\n", cntFmt
                    );

      var footerFmt = String.Format (
                        "{0}+--------+--------+--------+--------+", spFmt
                      );

      var buff = new StringBuilder (64);

      Func<Action<string, string, string, string>> linePrinter =
        () => {
          long lineCnt = 0;

          return (arg1, arg2, arg3, arg4) => {
                   buff.AppendFormat (
                     lineFmt, ++lineCnt, arg1, arg2, arg3, arg4
                   );
                 };
        };

      var printLine = linePrinter ();
      var bytes = frame.ToArray ();

      buff.AppendFormat (headerFmt, String.Empty);

      for (long i = 0; i <= cnt; i++) {
        var j = i * 4;

        if (i < cnt) {
          printLine (
            Convert.ToString (bytes[j], 2).PadLeft (8, '0'),
            Convert.ToString (bytes[j + 1], 2).PadLeft (8, '0'),
            Convert.ToString (bytes[j + 2], 2).PadLeft (8, '0'),
            Convert.ToString (bytes[j + 3], 2).PadLeft (8, '0')
          );

          continue;
        }

        if (rem > 0) {
          printLine (
            Convert.ToString (bytes[j], 2).PadLeft (8, '0'),
            rem >= 2
            ? Convert.ToString (bytes[j + 1], 2).PadLeft (8, '0')
            : String.Empty,
            rem == 3
            ? Convert.ToString (bytes[j + 2], 2).PadLeft (8, '0')
            : String.Empty,
            String.Empty
          );
        }
      }

      buff.AppendFormat (footerFmt, String.Empty);

      return buff.ToString ();
    }

    private static string print (WebSocketFrame frame)
    {
      // Payload Length
      var payloadLen = frame._payloadLength;

      // Extended Payload Length
      var extPayloadLen = payloadLen > 125
                          ? frame.ExactPayloadLength.ToString ()
                          : String.Empty;

      // Masking Key
      var maskingKey = BitConverter.ToString (frame._maskingKey);

      // Payload Data
      var payload = payloadLen == 0
                    ? String.Empty
                    : payloadLen > 125
                      ? "---"
                      : !frame.IsText
                        || frame.IsFragment
                        || frame.IsMasked
                        || frame.IsCompressed
                        ? frame._payloadData.ToString ()
                        : utf8Decode (frame._payloadData.ApplicationData);

      var fmt = @"
                    FIN: {0}
                   RSV1: {1}
                   RSV2: {2}
                   RSV3: {3}
                 Opcode: {4}
                   MASK: {5}
         Payload Length: {6}
Extended Payload Length: {7}
            Masking Key: {8}
           Payload Data: {9}";

      return String.Format (
               fmt,
               frame._fin,
               frame._rsv1,
               frame._rsv2,
               frame._rsv3,
               frame._opcode,
               frame._mask,
               payloadLen,
               extPayloadLen,
               maskingKey,
               payload
             );
    }

    private static WebSocketFrame processHeader (byte[] header)
    {
      if (header.Length != 2) {
        var msg = "The header part of a frame could not be read.";

        throw new WebSocketException (msg);
      }

      // FIN
      var fin = (header[0] & 0x80) == 0x80 ? Fin.Final : Fin.More;

      // RSV1
      var rsv1 = (header[0] & 0x40) == 0x40 ? Rsv.On : Rsv.Off;

      // RSV2
      var rsv2 = (header[0] & 0x20) == 0x20 ? Rsv.On : Rsv.Off;

      // RSV3
      var rsv3 = (header[0] & 0x10) == 0x10 ? Rsv.On : Rsv.Off;

      // Opcode
      var opcode = (byte) (header[0] & 0x0f);

      // MASK
      var mask = (header[1] & 0x80) == 0x80 ? Mask.On : Mask.Off;

      // Payload Length
      var payloadLen = (byte) (header[1] & 0x7f);

      if (!opcode.IsSupported ()) {
        var msg = "A frame has an unsupported opcode.";

        throw new WebSocketException (CloseStatusCode.ProtocolError, msg);
      }

      if (!opcode.IsData () && rsv1 == Rsv.On) {
        var msg = "A non data frame is compressed.";

        throw new WebSocketException (CloseStatusCode.ProtocolError, msg);
      }

      if (opcode.IsControl ()) {
        if (fin == Fin.More) {
          var msg = "A control frame is fragmented.";

          throw new WebSocketException (CloseStatusCode.ProtocolError, msg);
        }

        if (payloadLen > 125) {
          var msg = "A control frame has too long payload length.";

          throw new WebSocketException (CloseStatusCode.ProtocolError, msg);
        }
      }

      var frame = new WebSocketFrame ();
      frame._fin = fin;
      frame._rsv1 = rsv1;
      frame._rsv2 = rsv2;
      frame._rsv3 = rsv3;
      frame._opcode = (Opcode) opcode;
      frame._mask = mask;
      frame._payloadLength = payloadLen;

      return frame;
    }

    private static WebSocketFrame readExtendedPayloadLength (
      Stream stream, WebSocketFrame frame
    )
    {
      var len = frame.ExtendedPayloadLengthWidth;

      if (len == 0) {
        frame._extPayloadLength = WebSocket.EmptyBytes;

        return frame;
      }

      var bytes = stream.ReadBytes (len);

      if (bytes.Length != len) {
        var msg = "The extended payload length of a frame could not be read.";

        throw new WebSocketException (msg);
      }

      frame._extPayloadLength = bytes;

      return frame;
    }

    private static void readExtendedPayloadLengthAsync (
      Stream stream,
      WebSocketFrame frame,
      Action<WebSocketFrame> completed,
      Action<Exception> error
    )
    {
      var len = frame.ExtendedPayloadLengthWidth;

      if (len == 0) {
        frame._extPayloadLength = WebSocket.EmptyBytes;

        completed (frame);

        return;
      }

      stream.ReadBytesAsync (
        len,
        bytes => {
          if (bytes.Length != len) {
            var msg = "The extended payload length of a frame could not be read.";

            throw new WebSocketException (msg);
          }

          frame._extPayloadLength = bytes;

          completed (frame);
        },
        error
      );
    }

    private static WebSocketFrame readHeader (Stream stream)
    {
      var bytes = stream.ReadBytes (2);

      return processHeader (bytes);
    }

    private static void readHeaderAsync (
      Stream stream, Action<WebSocketFrame> completed, Action<Exception> error
    )
    {
      stream.ReadBytesAsync (
        2,
        bytes => {
          var frame = processHeader (bytes);

          completed (frame);
        },
        error
      );
    }

    private static WebSocketFrame readMaskingKey (
      Stream stream, WebSocketFrame frame
    )
    {
      if (!frame.IsMasked) {
        frame._maskingKey = WebSocket.EmptyBytes;

        return frame;
      }

      var len = 4;
      var bytes = stream.ReadBytes (len);

      if (bytes.Length != len) {
        var msg = "The masking key of a frame could not be read.";

        throw new WebSocketException (msg);
      }

      frame._maskingKey = bytes;

      return frame;
    }

    private static void readMaskingKeyAsync (
      Stream stream,
      WebSocketFrame frame,
      Action<WebSocketFrame> completed,
      Action<Exception> error
    )
    {
      if (!frame.IsMasked) {
        frame._maskingKey = WebSocket.EmptyBytes;

        completed (frame);

        return;
      }

      var len = 4;

      stream.ReadBytesAsync (
        len,
        bytes => {
          if (bytes.Length != len) {
            var msg = "The masking key of a frame could not be read.";

            throw new WebSocketException (msg);
          }

          frame._maskingKey = bytes;

          completed (frame);
        },
        error
      );
    }

    private static WebSocketFrame readPayloadData (
      Stream stream, WebSocketFrame frame
    )
    {
      var exactLen = frame.ExactPayloadLength;

      if (exactLen > PayloadData.MaxLength) {
        var msg = "A frame has too long payload length.";

        throw new WebSocketException (CloseStatusCode.TooBig, msg);
      }

      if (exactLen == 0) {
        frame._payloadData = PayloadData.Empty;

        return frame;
      }

      var len = (long) exactLen;
      var bytes = frame._payloadLength < 127
                  ? stream.ReadBytes ((int) exactLen)
                  : stream.ReadBytes (len, 1024);

      if (bytes.LongLength != len) {
        var msg = "The payload data of a frame could not be read.";

        throw new WebSocketException (msg);
      }

      frame._payloadData = new PayloadData (bytes, len);

      return frame;
    }

    private static void readPayloadDataAsync (
      Stream stream,
      WebSocketFrame frame,
      Action<WebSocketFrame> completed,
      Action<Exception> error
    )
    {
      var exactLen = frame.ExactPayloadLength;

      if (exactLen > PayloadData.MaxLength) {
        var msg = "A frame has too long payload length.";

        throw new WebSocketException (CloseStatusCode.TooBig, msg);
      }

      if (exactLen == 0) {
        frame._payloadData = PayloadData.Empty;

        completed (frame);

        return;
      }

      var len = (long) exactLen;

      Action<byte[]> comp =
        bytes => {
          if (bytes.LongLength != len) {
            var msg = "The payload data of a frame could not be read.";

            throw new WebSocketException (msg);
          }

          frame._payloadData = new PayloadData (bytes, len);

          completed (frame);
        };

      if (frame._payloadLength < 127) {
        stream.ReadBytesAsync ((int) exactLen, comp, error);

        return;
      }

      stream.ReadBytesAsync (len, 1024, comp, error);
    }

    private static string utf8Decode (byte[] bytes)
    {
      try {
        return Encoding.UTF8.GetString (bytes);
      }
      catch {
        return null;
      }
    }

    #endregion

    #region Internal Methods

    internal static WebSocketFrame CreateCloseFrame (
      PayloadData payloadData, bool mask
    )
    {
      return new WebSocketFrame (
               Fin.Final, Opcode.Close, payloadData, false, mask
             );
    }

    internal static WebSocketFrame CreatePingFrame (bool mask)
    {
      return new WebSocketFrame (
               Fin.Final, Opcode.Ping, PayloadData.Empty, false, mask
             );
    }

    internal static WebSocketFrame CreatePingFrame (byte[] data, bool mask)
    {
      return new WebSocketFrame (
               Fin.Final, Opcode.Ping, new PayloadData (data), false, mask
             );
    }

    internal static WebSocketFrame CreatePongFrame (
      PayloadData payloadData, bool mask
    )
    {
      return new WebSocketFrame (
               Fin.Final, Opcode.Pong, payloadData, false, mask
             );
    }

    internal static WebSocketFrame ReadFrame (Stream stream, bool unmask)
    {
      var frame = readHeader (stream);

      readExtendedPayloadLength (stream, frame);
      readMaskingKey (stream, frame);
      readPayloadData (stream, frame);

      if (unmask)
        frame.Unmask ();

      return frame;
    }

    internal static void ReadFrameAsync (
      Stream stream,
      bool unmask,
      Action<WebSocketFrame> completed,
      Action<Exception> error
    )
    {
      readHeaderAsync (
        stream,
        frame =>
          readExtendedPayloadLengthAsync (
            stream,
            frame,
            frame1 =>
              readMaskingKeyAsync (
                stream,
                frame1,
                frame2 =>
                  readPayloadDataAsync (
                    stream,
                    frame2,
                    frame3 => {
                      if (unmask)
                        frame3.Unmask ();

                      completed (frame3);
                    },
                    error
                  ),
                error
              ),
            error
          ),
        error
      );
    }

    internal void Unmask ()
    {
      if (_mask == Mask.Off)
        return;

      _payloadData.Mask (_maskingKey);

      _maskingKey = WebSocket.EmptyBytes;
      _mask = Mask.Off;
    }

    #endregion

    #region Public Methods

    public IEnumerator<byte> GetEnumerator ()
    {
      foreach (var b in ToArray ())
        yield return b;
    }

    public void Print (bool dumped)
    {
      var val = dumped ? dump (this) : print (this);

      Console.WriteLine (val);
    }

    public string PrintToString (bool dumped)
    {
      return dumped ? dump (this) : print (this);
    }

    public byte[] ToArray ()
    {
      using (var buff = new MemoryStream ()) {
        var header = (int) _fin;
        header = (header << 1) + (int) _rsv1;
        header = (header << 1) + (int) _rsv2;
        header = (header << 1) + (int) _rsv3;
        header = (header << 4) + (int) _opcode;
        header = (header << 1) + (int) _mask;
        header = (header << 7) + (int) _payloadLength;

        var headerAsUshort = (ushort) header;
        var headerAsBytes = headerAsUshort.InternalToByteArray (ByteOrder.Big);

        buff.Write (headerAsBytes, 0, 2);

        if (_payloadLength > 125) {
          var cnt = _payloadLength == 126 ? 2 : 8;

          buff.Write (_extPayloadLength, 0, cnt);
        }

        if (_mask == Mask.On)
          buff.Write (_maskingKey, 0, 4);

        if (_payloadLength > 0) {
          var bytes = _payloadData.ToArray ();

          if (_payloadLength < 127)
            buff.Write (bytes, 0, bytes.Length);
          else
            buff.WriteBytes (bytes, 1024);
        }

        buff.Close ();

        return buff.ToArray ();
      }
    }

    public override string ToString ()
    {
      var val = ToArray ();

      return BitConverter.ToString (val);
    }

    #endregion

    #region Explicit Interface Implementations

    IEnumerator IEnumerable.GetEnumerator ()
    {
      return GetEnumerator ();
    }

    #endregion
  }
}
