Add "Member left" message

Signed-off-by: mctaylors <cantsendmails@mctaylors.ru>

locale/Messages.resx

@@ -585,4 +585,13 @@
   <data name="ButtonReportIssue" xml:space="preserve">
       <value>Report an issue</value>
   </data>
+  <data name="DefaultLeaveMessage" xml:space="preserve">
+      <value>See you soon, {0}!</value>
+  </data>
+  <data name="SettingsSendLeaveMessages" xml:space="preserve">
+      <value>Send leave messages</value>
+  </data>
+  <data name="SettingsLeaveMessage" xml:space="preserve">
+      <value>Leave message</value>
+  </data>
 </root>

locale/Messages.ru.resx

@@ -585,4 +585,13 @@
   <data name="ButtonReportIssue" xml:space="preserve">
       <value>Сообщить о проблеме</value>
   </data>
+  <data name="DefaultLeaveMessage" xml:space="preserve">
+      <value>До скорой встречи, {0}!</value>
+  </data>
+  <data name="SettingsSendLeaveMessages" xml:space="preserve">
+      <value>Отправлять сообщения о выходе</value>
+  </data>
+  <data name="SettingsLeaveMessage" xml:space="preserve">
+      <value>Сообщение о выходе</value>
+  </data>
 </root>

locale/Messages.tt-ru.resx

@@ -585,4 +585,13 @@
   <data name="ButtonReportIssue" xml:space="preserve">
       <value>зарепортить баг</value>
   </data>
+  <data name="DefaultLeaveMessage" xml:space="preserve">
+      <value>ну, мы потеряли {0}</value>
+  </data>
+  <data name="SettingsSendLeaveMessages" xml:space="preserve">
+      <value>разглашать о том что сбежал шизоид</value>
+  </data>
+  <data name="SettingsLeaveMessage" xml:space="preserve">
+      <value>до свидания (типо настройка)</value>
+  </data>
 </root>

src/Commands/SettingsCommandGroup.cs

@@ -39,6 +39,7 @@ public class SettingsCommandGroup : CommandGroup
     {
         GuildSettings.Language,
         GuildSettings.WelcomeMessage,
+        GuildSettings.LeaveMessage,
         GuildSettings.ReceiveStartupMessages,
         GuildSettings.RemoveRolesOnMute,
         GuildSettings.ReturnRolesOnRejoin,

src/Data/GuildSettings.cs

@@ -24,6 +24,18 @@ public static class GuildSettings
     /// <seealso cref="GuildMemberJoinedResponder" />
     public static readonly Option<string> WelcomeMessage = new("WelcomeMessage", "default");
 
+    /// <summary>
+    ///     Controls what message should be sent in <see cref="PublicFeedbackChannel" /> when member leaves the server.
+    /// </summary>
+    /// <remarks>
+    ///     <list type="bullet">
+    ///         <item>No message will be sent if set to "off", "disable" or "disabled".</item>
+    ///         <item><see cref="Messages.DefaultLeaveMessage" /> will be sent if set to "default" or "reset"</item>
+    ///     </list>
+    /// </remarks>
+    /// <seealso cref="GuildMemberLeftResponder" />
+    public static readonly Option<string> LeaveMessage = new("LeaveMessage", "default");
+
     /// <summary>
     ///     Controls whether or not the <see cref="Messages.Ready" /> message should be sent
     ///     in <see cref="PrivateFeedbackChannel" /> on startup.

src/Data/Options/AllOptionsEnum.cs

@@ -14,6 +14,7 @@ public enum AllOptionsEnum
 {
     [UsedImplicitly] Language,
     [UsedImplicitly] WelcomeMessage,
+    [UsedImplicitly] LeaveMessage,
     [UsedImplicitly] ReceiveStartupMessages,
     [UsedImplicitly] RemoveRolesOnMute,
     [UsedImplicitly] ReturnRolesOnRejoin,

src/Messages.Designer.cs

@@ -1036,5 +1036,23 @@ namespace Octobot {
                 return ResourceManager.GetString("ButtonReportIssue", resourceCulture);
             }
         }
+
+        internal static string DefaultLeaveMessage {
+            get {
+                return ResourceManager.GetString("DefaultLeaveMessage", resourceCulture);
+            }
+        }
+
+        internal static string SettingsLeaveMessage {
+            get {
+                return ResourceManager.GetString("SettingsLeaveMessage", resourceCulture);
+            }
+        }
+
+        internal static string SettingsSendLeaveMessages {
+            get {
+                return ResourceManager.GetString("SettingsSendLeaveMessages", resourceCulture);
+            }
+        }
     }
 }

src/Responders/GuildMemberLeftResponder.cs

@@ -0,0 +1,67 @@
+using JetBrains.Annotations;
+using Octobot.Data;
+using Octobot.Extensions;
+using Octobot.Services;
+using Remora.Discord.API.Abstractions.Gateway.Events;
+using Remora.Discord.API.Abstractions.Rest;
+using Remora.Discord.Extensions.Embeds;
+using Remora.Discord.Gateway.Responders;
+using Remora.Results;
+
+namespace Octobot.Responders;
+
+/// <summary>
+///     Handles sending a guild's <see cref="GuildSettings.LeaveMessage" /> if one is set.
+/// </summary>
+/// <seealso cref="GuildSettings.LeaveMessage" />
+[UsedImplicitly]
+public class GuildMemberLeftResponder : IResponder<IGuildMemberRemove>
+{
+    private readonly IDiscordRestChannelAPI _channelApi;
+    private readonly IDiscordRestGuildAPI _guildApi;
+    private readonly GuildDataService _guildData;
+
+    public GuildMemberLeftResponder(
+        IDiscordRestChannelAPI channelApi, GuildDataService guildData, IDiscordRestGuildAPI guildApi)
+    {
+        _channelApi = channelApi;
+        _guildData = guildData;
+        _guildApi = guildApi;
+    }
+
+    public async Task<Result> RespondAsync(IGuildMemberRemove gatewayEvent, CancellationToken ct = default)
+    {
+        var user = gatewayEvent.User;
+        var data = await _guildData.GetData(gatewayEvent.GuildID, ct);
+        var cfg = data.Settings;
+
+        if (GuildSettings.PublicFeedbackChannel.Get(cfg).Empty()
+            || GuildSettings.LeaveMessage.Get(cfg) is "off" or "disable" or "disabled")
+        {
+            return Result.FromSuccess();
+        }
+
+        Messages.Culture = GuildSettings.Language.Get(cfg);
+        var leaveMessage = GuildSettings.LeaveMessage.Get(cfg) is "default" or "reset"
+            ? Messages.DefaultLeaveMessage
+            : GuildSettings.LeaveMessage.Get(cfg);
+
+        var guildResult = await _guildApi.GetGuildAsync(gatewayEvent.GuildID, ct: ct);
+        if (!guildResult.IsDefined(out var guild))
+        {
+            return Result.FromError(guildResult);
+        }
+
+        var embed = new EmbedBuilder()
+            .WithSmallTitle(string.Format(leaveMessage, user.GetTag(), guild.Name), user)
+            .WithGuildFooter(guild)
+            .WithTimestamp(DateTimeOffset.UtcNow)
+            .WithColour(ColorsList.Black)
+            .Build();
+
+        return await _channelApi.CreateMessageWithEmbedResultAsync(
+            GuildSettings.PublicFeedbackChannel.Get(cfg), embedResult: embed,
+            allowedMentions: Octobot.NoMentions, ct: ct);
+    }
+}
+