source: TFP-WebServer/WebServer/src/WebUtils.cs@ 468

using System;
using System.Collections.Specialized;
using System.Diagnostics.CodeAnalysis;
using System.Net;
using System.Text;
using UnityEngine.Profiling;
using Utf8Json;
using Webserver.WebAPI;
using HttpListenerRequest = SpaceWizards.HttpListener.HttpListenerRequest;
using HttpListenerResponse = SpaceWizards.HttpListener.HttpListenerResponse;

namespace Webserver {
        public static class WebUtils {
                static WebUtils () {
                        JsonWriter writer = new JsonWriter ();
                        writer.WriteBeginArray ();
                        writer.WriteEndArray ();
                        JsonEmptyData = writer.ToUtf8ByteArray ();
                }

                // ReSharper disable once MemberCanBePrivate.Global
                public const string MimePlain = "text/plain";
                public const string MimeHtml = "text/html";
                // ReSharper disable once MemberCanBePrivate.Global
                public const string MimeJson = "application/json";
                
                private static readonly CustomSampler envelopeBuildSampler = CustomSampler.Create ("JSON_EnvelopeBuilding");
                private static readonly CustomSampler netWriteSampler = CustomSampler.Create ("JSON_Write");

                public static void WriteText (HttpListenerResponse _resp, string _text, HttpStatusCode _statusCode = HttpStatusCode.OK, string _mimeType = null) {
                        _resp.StatusCode = (int)_statusCode;
                        _resp.ContentType = _mimeType ?? MimePlain;
                        _resp.ContentEncoding = Encoding.UTF8;

                        if (string.IsNullOrEmpty (_text)) {
                                _resp.ContentLength64 = 0;
                        } else {
                                byte[] buf = Encoding.UTF8.GetBytes (_text);
                                _resp.ContentLength64 = buf.Length;
                                _resp.OutputStream.Write (buf, 0, buf.Length);
                        }
                }

                public static bool IsSslRedirected (HttpListenerRequest _req) {
                        string proto = _req.Headers ["X-Forwarded-Proto"];
                        return !string.IsNullOrEmpty (proto) && proto.Equals ("https", StringComparison.OrdinalIgnoreCase);
                }
                
                public static string GenerateGuid () {
                        return Guid.NewGuid ().ToString ();
                }

                [SuppressMessage ("ReSharper", "MemberCanBePrivate.Global")]
                public static void WriteJsonData (HttpListenerResponse _resp, ref JsonWriter _jsonWriter, HttpStatusCode _statusCode = HttpStatusCode.OK) {
                        ArraySegment<byte> jsonData = _jsonWriter.GetBuffer ();

                        netWriteSampler.Begin ();
                        _resp.StatusCode = (int)_statusCode;
                        _resp.ContentType = MimeJson;
                        _resp.ContentEncoding = Encoding.UTF8;
                        _resp.ContentLength64 = jsonData.Count;
                        _resp.OutputStream.Write (jsonData.Array!, 0, jsonData.Count);
                        netWriteSampler.End ();
                }
                
                public static readonly byte[] JsonEmptyData;

                private static readonly byte[] jsonRawDataKey = JsonWriter.GetEncodedPropertyNameWithBeginObject ("data"); // {"data":

                private static readonly byte[] jsonRawMetaKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("meta"); // ,"meta":
                private static readonly byte[] jsonRawMetaServertimeKey = JsonWriter.GetEncodedPropertyNameWithBeginObject ("serverTime"); // {"serverTime":
                private static readonly byte[] jsonRawMetaRequestMethodKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("requestMethod"); // ,"requestMethod":
                private static readonly byte[] jsonRawMetaRequestSubpathKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("requestSubpath"); // ,"requestSubpath":
                private static readonly byte[] jsonRawMetaRequestBodyKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("requestBody"); // ,"requestBody":
                private static readonly byte[] jsonRawMetaErrorCodeKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("errorCode"); // ,"errorCode":
                private static readonly byte[] jsonRawMetaExceptionMessageKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("exceptionMessage"); // ,"exceptionMessage":
                private static readonly byte[] jsonRawMetaExceptionTraceKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("exceptionTrace"); // ,"exceptionTrace":
                
                public static void PrepareEnvelopedResult (out JsonWriter _writer) {
                        _writer = new JsonWriter ();
                        _writer.WriteRaw (jsonRawDataKey);
                }

                public static void SendEnvelopedResult (RequestContext _context, ref JsonWriter _writer, HttpStatusCode _statusCode = HttpStatusCode.OK,
                        byte[] _jsonInputData = null, string _errorCode = null, Exception _exception = null) {
                        
                        envelopeBuildSampler.Begin ();
                        
                        _writer.WriteRaw (jsonRawMetaKey);

                        _writer.WriteRaw (jsonRawMetaServertimeKey);
                        JsonCommons.WriteDateTime (ref _writer, DateTime.Now);

                        if (!string.IsNullOrEmpty (_errorCode)) {
                                _writer.WriteRaw (jsonRawMetaRequestMethodKey);
                                _writer.WriteString (_context.Request.HttpMethod);

                                _writer.WriteRaw (jsonRawMetaRequestSubpathKey);
                                _writer.WriteString (_context.RequestPath);

                                _writer.WriteRaw (jsonRawMetaRequestBodyKey);
                                if (_jsonInputData != null) {
                                        _writer.WriteRaw (_jsonInputData);
                                } else {
                                        _writer.WriteNull ();
                                }

                                _writer.WriteRaw (jsonRawMetaErrorCodeKey);
                                _writer.WriteString (_errorCode);

                                if (_exception != null) {
                                        _writer.WriteRaw (jsonRawMetaExceptionMessageKey);
                                        _writer.WriteString (_exception.Message);

                                        _writer.WriteRaw (jsonRawMetaExceptionTraceKey);
                                        _writer.WriteString (_exception.StackTrace);
                                }
                        }
                        
                        _writer.WriteEndObject (); // End of "meta" object
                        _writer.WriteEndObject (); // End of overall result object
                        
                        envelopeBuildSampler.End ();

                        WriteJsonData (_context.Response, ref _writer, _statusCode);
                }

                public static void SendEmptyResponse (RequestContext _context, HttpStatusCode _statusCode = HttpStatusCode.OK, byte[] _jsonInputData = null, string _errorCode = null, Exception _exception = null) {
                        PrepareEnvelopedResult (out JsonWriter writer);
                        writer.WriteRaw (JsonEmptyData);
                        SendEnvelopedResult (_context, ref writer, _statusCode, _jsonInputData, _errorCode, _exception);
                }


                public static bool TryGetValue (this NameValueCollection _nameValueCollection, string _name, out string _result) {
                        _result = _nameValueCollection [_name];
                        return _result != null;
                }
        }
}