source: binary-improvements/MapRendering/API/GetLog.cs

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

namespace AllocsFixes.WebAPIs {
        [UsedImplicitly]
        public class GetLog : AbsWebAPI {
                private const int MAX_COUNT = 1000;
                
                private static readonly byte[] jsonKeyFirstLine = JsonWriter.GetEncodedPropertyNameWithBeginObject ("firstLine");
                private static readonly byte[] jsonKeyLastLine = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("lastLine");
                private static readonly byte[] jsonKeyEntries = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("entries");

                private static readonly byte[] jsonKeyEntDate = JsonWriter.GetEncodedPropertyNameWithBeginObject ("date");
                private static readonly byte[] jsonKeyEntTime = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("time");
                private static readonly byte[] jsonKeyEntUptime = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("uptime");
                private static readonly byte[] jsonKeyEntMsg = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("msg");
                private static readonly byte[] jsonKeyEntTrace = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("trace");
                private static readonly byte[] jsonKeyEntType = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("type");

                public override void HandleRequest (RequestContext _context) {
                        if (_context.Request.QueryString ["count"] == null || !int.TryParse (_context.Request.QueryString ["count"], out var count)) {
                                count = 50;
                        }

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

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

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

                        if (_context.Request.QueryString ["firstLine"] == null || !int.TryParse (_context.Request.QueryString ["firstLine"], out var firstLine)) {
                                firstLine = count > 0 ? LogBuffer.Instance.OldestLine : LogBuffer.Instance.LatestLine;
                        }

                        List<LogBuffer.LogEntry> logEntries = LogBuffer.Instance.GetRange (ref firstLine, count, out var lastLine);

                        JsonWriter writer = new JsonWriter ();
                        
                        writer.WriteRaw (jsonKeyFirstLine);
                        writer.WriteInt32 (firstLine);
                        
                        writer.WriteRaw (jsonKeyLastLine);
                        writer.WriteInt32 (lastLine);
                        
                        writer.WriteRaw (jsonKeyEntries);
                        writer.WriteBeginArray ();
                        
                        bool first = true;

                        foreach (LogBuffer.LogEntry logEntry in logEntries) {
                                if (!first) {
                                        writer.WriteValueSeparator ();
                                }

                                first = false;
                                
                                var logEntryTimestamp = logEntry.Timestamp;

                                writer.WriteRaw (jsonKeyEntDate);
                                writer.WriteString ($"{logEntryTimestamp.Year:0000}-{logEntryTimestamp.Month:00}-{logEntryTimestamp.Day:00}");
                                
                                writer.WriteRaw (jsonKeyEntTime);
                                writer.WriteString ($"{logEntryTimestamp.Hour:00}:{logEntryTimestamp.Minute:00}:{logEntryTimestamp.Second:00}");
                                
                                writer.WriteRaw (jsonKeyEntUptime);
                                writer.WriteString (logEntry.Uptime.ToString());
                                
                                writer.WriteRaw (jsonKeyEntMsg);
                                writer.WriteString (logEntry.Message);
                                
                                writer.WriteRaw (jsonKeyEntTrace);
                                writer.WriteString (logEntry.Trace);
                                
                                writer.WriteRaw (jsonKeyEntType);
                                writer.WriteString (logEntry.Type.ToStringCached ());

                                writer.WriteEndObject ();
                        }

                        writer.WriteEndArray ();
                        
                        writer.WriteEndObject ();
                        WebUtils.WriteJsonData (_context.Response, ref writer);
                }
        }
}