nadekobot/src/NadekoBot/Modules/Administration/Services/PruneService.cs

#nullable disable
namespace NadekoBot.Modules.Administration.Services;

public class PruneService : INService
{
    //channelids where prunes are currently occuring
    private readonly ConcurrentHashSet<ulong> _pruningGuilds = new();
    private readonly TimeSpan _twoWeeks = TimeSpan.FromDays(14);
    private readonly ILogCommandService _logService;

    public PruneService(ILogCommandService logService)
        => this._logService = logService;

    public async Task PruneWhere(ITextChannel channel, int amount, Func<IMessage, bool> predicate)
    {
        ArgumentNullException.ThrowIfNull(channel, nameof(channel));
        
        if (amount <= 0)
            throw new ArgumentOutOfRangeException(nameof(amount));

        if (!_pruningGuilds.Add(channel.GuildId))
            return;

        try
        {
            IMessage[] msgs;
            IMessage lastMessage = null;
            msgs = (await channel.GetMessagesAsync(50).FlattenAsync().ConfigureAwait(false)).Where(predicate).Take(amount).ToArray();
            while (amount > 0 && msgs.Any())
            {
                lastMessage = msgs[msgs.Length - 1];

                var bulkDeletable = new List<IMessage>();
                var singleDeletable = new List<IMessage>();
                foreach (var x in msgs)
                {
                    _logService.AddDeleteIgnore(x.Id);

                    if (DateTime.UtcNow - x.CreatedAt < _twoWeeks)
                        bulkDeletable.Add(x);
                    else
                        singleDeletable.Add(x);
                }

                if (bulkDeletable.Count > 0)
                    await Task.WhenAll(Task.Delay(1000), channel.DeleteMessagesAsync(bulkDeletable)).ConfigureAwait(false);

                foreach (var group in singleDeletable.Chunk(5))
                    await Task.WhenAll(Task.Delay(1000), Task.WhenAll(group.Select(x => x.DeleteAsync()))).ConfigureAwait(false);

                //this isn't good, because this still work as if i want to remove only specific user's messages from the last
                //100 messages, Maybe this needs to be reduced by msgs.Length instead of 100
                amount -= 50;
                if(amount > 0)
                    msgs = (await channel.GetMessagesAsync(lastMessage, Direction.Before, 50).FlattenAsync().ConfigureAwait(false)).Where(predicate).Take(amount).ToArray();
            }
        }
        catch
        {
            //ignore
        }
        finally
        {
            _pruningGuilds.TryRemove(channel.GuildId);
        }
    }
}