Added .imageonlychannel / .imageonly to prevent users from posting anything but images in the channel

src/NadekoBot/Modules/Administration/Services/AdministrationService.cs

@@ -1,9 +1,7 @@
-using System;
-using Discord;
+using Discord;
 using Discord.Commands;
 using Discord.WebSocket;
 using Microsoft.EntityFrameworkCore;
-using NadekoBot.Common;
 using NadekoBot.Common.Collections;
 using NadekoBot.Common.Replacements;
 using NadekoBot.Services;
@@ -24,14 +22,11 @@ namespace NadekoBot.Modules.Administration.Services
 
         private readonly DbService _db;
         private readonly ILogCommandService _logService;
-        private readonly IEmbedBuilderService _eb;
 
-        public AdministrationService(Bot bot, CommandHandler cmdHandler, DbService db,
-            ILogCommandService logService, IEmbedBuilderService eb)
+        public AdministrationService(Bot bot, CommandHandler cmdHandler, DbService db, ILogCommandService logService)
         {
             _db = db;
             _logService = logService;
-            _eb = eb;
 
             DeleteMessagesOnCommand = new ConcurrentHashSet<ulong>(bot.AllGuildConfigs
                 .Where(g => g.DeleteMessageOnCommand)

src/NadekoBot/Modules/Administration/Services/ImageOnlyChannelService.cs

@@ -0,0 +1,187 @@
+using System;
+using System.Collections.Concurrent;
+using System.Linq;
+using System.Net;
+using System.Threading.Channels;
+using System.Threading.Tasks;
+using Discord;
+using Discord.Net;
+using Discord.WebSocket;
+using LinqToDB;
+using Microsoft.Extensions.Caching.Memory;
+using NadekoBot.Common.Collections;
+using NadekoBot.Common.ModuleBehaviors;
+using NadekoBot.Extensions;
+using NadekoBot.Services;
+using Serilog;
+
+namespace NadekoBot.Modules.Administration.Services
+{
+    public sealed class ImageOnlyChannelService : IEarlyBehavior
+    {
+        private readonly IMemoryCache _ticketCache;
+        private readonly DiscordSocketClient _client;
+        private readonly DbService _db;
+        private readonly ConcurrentDictionary<ulong, ConcurrentHashSet<ulong>> _enabledOn;
+
+        private Channel<IUserMessage> _deleteQueue = Channel.CreateBounded<IUserMessage>(new BoundedChannelOptions(100)
+        {
+            FullMode = BoundedChannelFullMode.DropOldest,
+            SingleReader = true,
+            SingleWriter = false,
+        });
+
+
+        public ImageOnlyChannelService(IMemoryCache ticketCache, DiscordSocketClient client, DbService db)
+        {
+            _ticketCache = ticketCache;
+            _client = client;
+            _db = db;
+
+            var uow = _db.GetDbContext();
+            _enabledOn = uow.ImageOnlyChannels
+                .ToList()
+                .GroupBy(x => x.GuildId)
+                .ToDictionary(x => x.Key, x => new ConcurrentHashSet<ulong>(x.Select(x => x.ChannelId)))
+                .ToConcurrent();
+            
+            _ = Task.Run(DeleteQueueRunner);
+            
+            _client.ChannelDestroyed += ClientOnChannelDestroyed;
+        }
+
+        private Task ClientOnChannelDestroyed(SocketChannel ch)
+        {
+            if (ch is not IGuildChannel gch)
+                return Task.CompletedTask;
+
+            if (_enabledOn.TryGetValue(gch.GuildId, out var channels) && channels.TryRemove(ch.Id))
+                ToggleImageOnlyChannel(gch.GuildId, ch.Id, true);
+
+            return Task.CompletedTask;
+        }
+
+        private async Task DeleteQueueRunner()
+        {
+            while (true)
+            {
+                var toDelete = await _deleteQueue.Reader.ReadAsync();
+                try
+                {
+                    await toDelete.DeleteAsync();
+                    await Task.Delay(1000);
+                }
+                catch (HttpException ex) when (ex.HttpCode == HttpStatusCode.Forbidden)
+                {
+                    // disable if bot can't delete messages in the channel
+                    ToggleImageOnlyChannel(((ITextChannel)toDelete.Channel).GuildId, toDelete.Channel.Id, true);
+                }
+            }
+        }
+
+        public bool ToggleImageOnlyChannel(ulong guildId, ulong channelId, bool forceDisable = false)
+        {
+            var newState = false;
+            using var uow = _db.GetDbContext();
+            if (forceDisable 
+                || (_enabledOn.TryGetValue(guildId, out var channels) 
+                    && channels.TryRemove(channelId)))
+            {
+                uow.ImageOnlyChannels.Delete(x => x.ChannelId == channelId);
+            }
+            else
+            {
+                uow.ImageOnlyChannels.Add(new()
+                {
+                    GuildId = guildId,
+                    ChannelId = channelId
+                });
+
+                channels = _enabledOn.GetOrAdd(guildId, new ConcurrentHashSet<ulong>());
+                channels.Add(channelId);
+                newState = true;
+            }
+            
+            uow.SaveChanges();
+            return newState;
+        }
+
+        public async Task<bool> RunBehavior(IGuild guild, IUserMessage msg)
+        {
+            if (msg.Channel is not ITextChannel tch)
+                return false;
+            
+            if (msg.Attachments.Any(x => x is { Height: > 0, Width: > 0 }))
+                return false;
+
+            if (!_enabledOn.TryGetValue(tch.GuildId, out var chs)
+                || !chs.Contains(msg.Channel.Id))
+                return false;
+
+            var user = await tch.Guild.GetUserAsync(msg.Author.Id)
+                       ?? await _client.Rest.GetGuildUserAsync(tch.GuildId, msg.Author.Id);
+            
+            if (user is null)
+                return false;
+            
+            // ignore owner and admin
+            if (user.Id == tch.Guild.OwnerId || user.GuildPermissions.Administrator)
+            {
+                Log.Information("Image-Only: Ignoring owner od admin ({ChannelId})", msg.Channel.Id);
+                return false;
+            }
+
+            // ignore users higher in hierarchy
+            var botUser = await tch.Guild.GetCurrentUserAsync();
+            if (user.GetRoles().Max(x => x.Position) >= botUser.GetRoles().Max(x => x.Position))
+                return false;
+
+            // can't modify channel perms if not admin apparently
+            if (!botUser.GuildPermissions.ManageGuild)
+            {
+                ToggleImageOnlyChannel( tch.GuildId, tch.Id, true);;
+                return false;
+            }
+
+            var shouldLock = AddUserTicket(tch.GuildId, msg.Author.Id);
+            if (shouldLock)
+            {
+                await tch.AddPermissionOverwriteAsync(msg.Author, new(sendMessages: PermValue.Deny));
+                Log.Warning("Image-Only: User {User} [{UserId}] has been banned from typing in the channel [{ChannelId}]",
+                    msg.Author,
+                    msg.Author.Id,
+                    msg.Channel.Id);
+            }
+            
+            try
+            {
+                await _deleteQueue.Writer.WriteAsync(msg);
+            }
+            catch (Exception ex)
+            {
+                Log.Error(ex, "Error deleting message {MessageId} in image-only channel {ChannelId}.",
+                    msg.Id,
+                    tch.Id);
+            }
+
+            return true;
+        }
+
+        private bool AddUserTicket(ulong guildId, ulong userId)
+        {
+            var old = _ticketCache.GetOrCreate($"{guildId}_{userId}", entry =>
+            {
+                entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromDays(1);
+                return 0;
+            });
+
+            _ticketCache.Set($"{guildId}_{userId}", ++old);
+            
+            // if this is the third time that the user posts a
+            // non image in an image-only channel on this server 
+            return old > 2;
+        }
+
+        public int Priority { get; } = 0;
+    }
+}