source: TFP-WebServer/WebServer/src/WebAPI/APIs/LogApi.cs@ 479

using System.Collections.Generic;
using JetBrains.Annotations;
using Utf8Json;

namespace Webserver.WebAPI.APIs {
        [UsedImplicitly]
        public class LogApi : AbsRestApi {
                private const int maxCount = 1000;

                private static readonly byte[] jsonKeyEntries = JsonWriter.GetEncodedPropertyNameWithBeginObject ("entries");
                private static readonly byte[] jsonKeyFirstLine = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("firstLine");
                private static readonly byte[] jsonKeyLastLine = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("lastLine");

                private static readonly byte[] jsonIdKey = JsonWriter.GetEncodedPropertyNameWithBeginObject ("id");
                private static readonly byte[] jsonMsgKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("msg");
                private static readonly byte[] jsonTypeKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("type");
                private static readonly byte[] jsonTraceKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("trace");
                private static readonly byte[] jsonIsotimeKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("isotime");
                private static readonly byte[] jsonUptimeKey = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("uptime");

                public LogApi () : base ("Log") {
                }

                protected override void HandleRestGet (RequestContext _context) {
                        if (_context.QueryParameters ["count"] == null || !int.TryParse (_context.QueryParameters ["count"], out int count)) {
                                count = 50;
                        }

                        if (count == 0) {
                                count = 1;
                        }

                        if (count > maxCount) {
                                count = maxCount;
                        }

                        if (count < -maxCount) {
                                count = -maxCount;
                        }

                        if (_context.QueryParameters ["firstLine"] == null || !int.TryParse (_context.QueryParameters ["firstLine"], out int firstLine)) {
                                firstLine = count > 0 ? LogBuffer.Instance.OldestLine : LogBuffer.Instance.LatestLine;
                        }
                        
                        PrepareEnvelopedResult (out JsonWriter writer);
                        
                        writer.WriteRaw (jsonKeyEntries);
                        
                        List<LogBuffer.LogEntry> logEntries = LogBuffer.Instance.GetRange (ref firstLine, count, out int lastLine);

                        writer.WriteBeginArray ();

                        for (int i = 0; i < logEntries.Count; i++) {
                                LogBuffer.LogEntry logEntry = logEntries [i];
                                
                                if (i > 0) {
                                        writer.WriteValueSeparator ();
                                }

                                WriteLogMessageObject (ref writer, logEntry);
                        }

                        writer.WriteEndArray ();

                        writer.WriteRaw (jsonKeyFirstLine);
                        writer.WriteInt32 (firstLine);
                        
                        writer.WriteRaw (jsonKeyLastLine);
                        writer.WriteInt32 (lastLine);
                        
                        writer.WriteEndObject ();

                        SendEnvelopedResult (_context, ref writer);
                }

                public static void WriteLogMessageObject (ref JsonWriter _writer, LogBuffer.LogEntry _logEntry) {
                        _writer.WriteRaw (jsonIdKey);
                        _writer.WriteInt32 (_logEntry.MessageId);
                        
                        _writer.WriteRaw (jsonMsgKey);
                        _writer.WriteString (_logEntry.Message);

                        _writer.WriteRaw (jsonTypeKey);
                        _writer.WriteString (_logEntry.Type.ToStringCached ());

                        _writer.WriteRaw (jsonTraceKey);
                        _writer.WriteString (_logEntry.Trace);

                        _writer.WriteRaw (jsonIsotimeKey);
                        _writer.WriteString (_logEntry.IsoTime);

                        _writer.WriteRaw (jsonUptimeKey);
                        _writer.WriteString (_logEntry.Uptime.ToString ());

                        _writer.WriteEndObject ();
                }
        }
}