[Feature] Modify guild features (#2605)

* initial commit

* Update src/Discord.Net.Core/Entities/Guilds/GuildProperties.cs

---------

Co-authored-by: Casmir <68127614+csmir@users.noreply.github.com>

src/Discord.Net.Core/Entities/Guilds/GuildFeature.cs

@@ -34,11 +34,11 @@ namespace Discord
         /// </summary>
         Commerce = 1L << 4,
         /// <summary>
-        ///     The guild can enable welcome screen, Membership Screening, stage channels and discovery, and receives community updates.
+        ///     The guild can enable welcome screen, Membership Screening, stage channels and discovery, and receives community updates. This feature is mutable.
         /// </summary>
         Community = 1L << 5,
         /// <summary>
-        ///     The guild is able to be discovered in the directory.
+        ///     The guild is able to be discovered in the directory. This feature is mutable.
         /// </summary>
         Discoverable = 1L << 6,
         /// <summary>
@@ -185,5 +185,13 @@ namespace Discord
         ///     The guild has been set as a support server on the App Directory.
         /// </summary>
         DeveloperSupportServer = 1L << 42,
+        /// <summary>
+        ///     The guild has invites disabled. This feature is mutable.
+        /// </summary>
+        InvitesDisabled = 1L << 43,
+        /// <summary>
+        ///     The guild has auto moderation enabled.
+        /// </summary>
+        AutoModeration = 1L << 44
     }
 }

src/Discord.Net.Core/Entities/Guilds/GuildProperties.cs

@@ -113,5 +113,10 @@ namespace Discord
         ///     Gets or sets if the boost progress bar is enabled.
         /// </summary>
         public Optional<bool> IsBoostProgressBarEnabled { get; set; }
+
+        /// <summary>
+        ///     Gets or sets the guild features enabled in this guild. Features that are not mutable will be ignored.
+        /// </summary>
+        public Optional<GuildFeature> Features { get; set; }
     }
 }

src/Discord.Net.Rest/API/Rest/ModifyGuildParams.cs

@@ -37,5 +37,7 @@ namespace Discord.API.Rest
         public string PreferredLocale { get; set; }
         [JsonProperty("premium_progress_bar_enabled")]
         public Optional<bool> IsBoostProgressBarEnabled { get; set; }
+        [JsonProperty("features")]
+        public Optional<GuildFeatures> GuildFeatures { get; set; }
     }
 }

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -39,7 +39,8 @@ namespace Discord.Rest
                 VerificationLevel = args.VerificationLevel,
                 ExplicitContentFilter = args.ExplicitContentFilter,
                 SystemChannelFlags = args.SystemChannelFlags,
-                IsBoostProgressBarEnabled = args.IsBoostProgressBarEnabled
+                IsBoostProgressBarEnabled = args.IsBoostProgressBarEnabled,
+                GuildFeatures = args.Features.IsSpecified ? new GuildFeatures(args.Features.Value, Array.Empty<string>()) : Optional.Create<GuildFeatures>(),
             };
 
             if (apiArgs.Banner.IsSpecified)

src/Discord.Net.Rest/Net/Converters/GuildFeaturesConverter.cs

@@ -2,6 +2,7 @@ using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using System;
 using System.Collections.Generic;
+using System.Text;
 
 namespace Discord.Net.Converters
 {
@@ -36,9 +37,52 @@ namespace Discord.Net.Converters
 
             return new GuildFeatures(features, experimental.ToArray());
         }
+
         public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
         {
-            throw new NotImplementedException();
+            var guildFeatures = (GuildFeatures)value;
+
+            var enumValues = Enum.GetValues(typeof(GuildFeature));
+
+            writer.WriteStartArray();
+
+            foreach (var enumValue in enumValues)
+            {
+                var val = (GuildFeature)enumValue;
+                if (val is GuildFeature.None)
+                    continue;
+
+                if (guildFeatures.Value.HasFlag(val))
+                {
+                    writer.WriteValue(FeatureToApiString(val));
+                }
+            }
+            writer.WriteEndArray();
+        }
+
+        private string FeatureToApiString(GuildFeature feature)
+        {
+            var builder = new StringBuilder();
+            var firstChar = true;
+
+            foreach (var c in feature.ToString().ToCharArray())
+            {
+                if (char.IsUpper(c))
+                {
+                    if (firstChar)
+                        firstChar = false;
+                    else
+                        builder.Append("_");
+
+                    builder.Append(c);
+                }
+                else
+                {
+                    builder.Append(char.ToUpper(c));
+                }
+            }
+
+            return builder.ToString();
         }
     }
 }