[PBE-537] Possibility to send system messages (#126)

* Possibility to send system messages

* wip: created MessageRequestType enum

* Remove invalid MessageRequestType values + Add StringEnumConverter

* Add default regular message type + ignore default values during serialization

---------

Co-authored-by: Daniel Sierpiński <33436839+sierpinskid@users.noreply.github.com>

src/Models/MessageRequest.cs

@@ -1,11 +1,25 @@
 using System;
 using System.Collections.Generic;
+using System.Runtime.Serialization;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
 
 namespace StreamChat.Models
 {
+    [JsonConverter(typeof(StringEnumConverter))]
+    public enum MessageRequestType
+    {
+        [EnumMember(Value = @"regular")]
+        Regular = 0,
+
+        [EnumMember(Value = @"system")]
+        System = 1,
+    }
+
     public class MessageRequest : CustomDataBase
     {
         public string Id { get; set; }
+        public MessageRequestType Type { get; set; }
         public string Text { get; set; }
         public string Mml { get; set; }
         public UserRequest User { get; set; }

src/Utils/JsonSerializerSettings.cs

@@ -13,6 +13,7 @@ internal static class StreamJsonConverter
                 NamingStrategy = new SnakeCaseNamingStrategy(),
             },
             NullValueHandling = NullValueHandling.Ignore,
+            DefaultValueHandling = DefaultValueHandling.Ignore,
         };
 
         internal static string SerializeObject(object obj) => JsonConvert.SerializeObject(obj, Settings);

src/Utils/Utils.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.Serialization;
+
+namespace StreamChat.Utils
+{
+    public static class Utils
+    {
+        /// <summary>
+        /// Return enum value string representation respecting optional <see cref="EnumMemberAttribute"/> that overrides string representation
+        /// </summary>
+        public static string ToEnumMemberString<T>(this T value)
+            where T : Enum
+        {
+            return typeof(T)
+                .GetTypeInfo()
+                .DeclaredMembers
+                .SingleOrDefault(x => x.Name == value.ToString())
+                ?.GetCustomAttribute<EnumMemberAttribute>(false)
+                ?.Value ?? value.ToString();
+        }
+    }
+}

tests/MessageClientTests.cs

@@ -8,6 +8,7 @@
 using StreamChat.Clients;
 using StreamChat.Exceptions;
 using StreamChat.Models;
+using StreamChat.Utils;
 
 namespace StreamChatTests
 {
@@ -74,6 +75,19 @@ public async Task TestSendMessageAsync()
             actualMsg.Attachments[0].GetData<string>("baz").Should().BeEquivalentTo("bazky");
         }
 
+        [Test]
+        public async Task TestSendSystemMessageAsync()
+        {
+            var expectedMessage = new MessageRequest { Text = Guid.NewGuid().ToString(), Type = MessageRequestType.System };
+
+            var msgResp = await _messageClient.SendMessageAsync(_channel.Type, _channel.Id, expectedMessage, _user.Id);
+
+            var channel = await _channelClient.GetOrCreateAsync(_channel.Type, _channel.Id, new ChannelGetRequest { Watch = false, State = true });
+            var actualMsg = channel.Messages.First(m => m.Id == msgResp.Message.Id);
+            actualMsg.User.Id.Should().BeEquivalentTo(_user.Id);
+            actualMsg.Type.Should().BeEquivalentTo(MessageRequestType.System.ToEnumMemberString());
+        }
+
         [Test]
         public async Task TestUpdateMessageAsync()
         {