source: TFP-WebServer/MarkersMod/src/Markers.cs@ 445

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

namespace Examples {
        [UsedImplicitly]
        public class Markers : AbsRestApi {
                private const int numRandomMarkers = 5;

                private const string defaultIcon =
                        "https://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Blue_question_mark_icon.svg/1200px-Blue_question_mark_icon.svg.png";
                
                private readonly Dictionary<string, (int, int, string)> markers = new Dictionary<string, (int, int, string)> ();

                public Markers () {
                        GameRandom random = GameRandomManager.Instance.CreateGameRandom ();
                        
                        for (int i = 0; i < numRandomMarkers; i++) {
                                int lat = random.RandomRange (-1000, 1001);
                                int lng = random.RandomRange (-1000, 1001);

                                markers.Add (WebUtils.GenerateGuid (), (lat, lng, null));
                        }
                        
                        GameRandomManager.Instance.FreeGameRandom (random);
                }

                private static readonly byte[] jsonKeyId = JsonWriter.GetEncodedPropertyNameWithBeginObject ("id");
                private static readonly byte[] jsonKeyLat = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("lat");
                private static readonly byte[] jsonKeyLng = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("lng");
                private static readonly byte[] jsonKeyIcon = JsonWriter.GetEncodedPropertyNameWithPrefixValueSeparator ("icon");

                protected override void HandleRestGet (RequestContext _context) {
                        string id = _context.RequestPath;
                        
                        PrepareEnvelopedResult (out JsonWriter writer);
                        
                        if (string.IsNullOrEmpty (id)) {
                                writer.WriteBeginArray ();

                                bool first = true;
                                foreach ((string markerId, (int, int, string) properties) in markers) {
                                        if (!first) {
                                                writer.WriteValueSeparator ();
                                        }
                                        
                                        first = false;
                                        
                                        writeMarkerJson (ref writer, markerId, properties);
                                }

                                writer.WriteEndArray ();
                                SendEnvelopedResult (_context, ref writer);
                                return;
                        }

                        if (!markers.TryGetValue (id, out (int, int, string) properties2)) {
                                writer.WriteRaw (WebUtils.JsonEmptyData);
                                SendEnvelopedResult (_context, ref writer, HttpStatusCode.NotFound);
                                return;
                        }

                        {
                                writer.WriteBeginArray ();
                                
                                writeMarkerJson (ref writer, id, properties2);
                                
                                writer.WriteEndArray ();
                                SendEnvelopedResult (_context, ref writer);
                        }
                }

                private void writeMarkerJson (ref JsonWriter _writer, string _markerId, (int, int, string) _properties) {
                        _writer.WriteRaw (jsonKeyId);
                        _writer.WriteString (_markerId);
                        _writer.WriteRaw (jsonKeyLat);
                        (int lat, int lng, string icon) = _properties;
                        _writer.WriteInt32 (lat);
                        _writer.WriteRaw (jsonKeyLng);
                        _writer.WriteInt32 (lng);
                        _writer.WriteRaw (jsonKeyIcon);
                        _writer.WriteString (icon ?? defaultIcon);
                        _writer.WriteEndObject ();
                }

                protected override void HandleRestPost (RequestContext _context, IDictionary<string, object> _jsonInput, byte[] _jsonInputData) {
                        if (!JsonCommons.TryGetJsonField (_jsonInput, "lat", out int lat)) {
                                SendEmptyResponse (_context, HttpStatusCode.BadRequest, _jsonInputData, "NO_OR_INVALID_LAT");
                                return;
                        }

                        if (!JsonCommons.TryGetJsonField (_jsonInput, "lng", out int lng)) {
                                SendEmptyResponse (_context, HttpStatusCode.BadRequest, _jsonInputData, "NO_OR_INVALID_LNG");
                                return;
                        }

                        JsonCommons.TryGetJsonField (_jsonInput, "icon", out string icon);
                        if (string.IsNullOrEmpty (icon)) {
                                icon = null;
                        }

                        string newId = WebUtils.GenerateGuid ();
                        markers.Add (newId, (lat, lng, icon));

                        PrepareEnvelopedResult (out JsonWriter writer);
                        writer.WriteString (newId);
                        SendEnvelopedResult (_context, ref writer, HttpStatusCode.Created);
                }

                protected override void HandleRestPut (RequestContext _context, IDictionary<string, object> _jsonInput, byte[] _jsonInputData) {
                        if (!JsonCommons.TryGetJsonField (_jsonInput, "lat", out int lat)) {
                                SendEmptyResponse (_context, HttpStatusCode.BadRequest, _jsonInputData, "NO_OR_INVALID_LAT");
                                return;
                        }

                        if (!JsonCommons.TryGetJsonField (_jsonInput, "lng", out int lng)) {
                                SendEmptyResponse (_context, HttpStatusCode.BadRequest, _jsonInputData, "NO_OR_INVALID_LNG");
                                return;
                        }

                        bool keepIcon = !_jsonInput.TryGetValue ("icon", out _);
                        JsonCommons.TryGetJsonField (_jsonInput, "icon", out string icon);
                        if (string.IsNullOrEmpty (icon)) {
                                icon = null;
                        }

                        string id = _context.RequestPath;

                        if (!markers.TryGetValue (id, out (int, int, string) properties)) {
                                SendEmptyResponse (_context, HttpStatusCode.NotFound, _jsonInputData, "ID_NOT_FOUND");
                                return;
                        }

                        if (keepIcon) {
                                icon = properties.Item3;
                        }
                        markers [id] = (lat, lng, icon);

                        PrepareEnvelopedResult (out JsonWriter writer);
                        writer.WriteRaw (jsonKeyId);
                        writer.WriteString (id);
                        writer.WriteRaw (jsonKeyLat);
                        writer.WriteInt32 (lat);
                        writer.WriteRaw (jsonKeyLng);
                        writer.WriteInt32 (lng);
                        writer.WriteRaw (jsonKeyIcon);
                        writer.WriteString (icon);
                        writer.WriteEndObject ();
                        SendEnvelopedResult (_context, ref writer);
                }

                protected override void HandleRestDelete (RequestContext _context) {
                        string id = _context.RequestPath;

                        SendEmptyResponse (_context, markers.Remove (id) ? HttpStatusCode.NoContent : HttpStatusCode.NotFound);
                }
                
                public override int[] DefaultMethodPermissionLevels () => new[] {
                        AdminWebModules.MethodLevelNotSupported,
                        AdminWebModules.PermissionLevelGuest,
                        AdminWebModules.PermissionLevelUser,
                        AdminWebModules.MethodLevelInheritGlobal,
                        AdminWebModules.MethodLevelInheritGlobal
                };
        }
}