Catalogger.NET/Catalogger.Backend/Bot/Responders/Messages/MessageDeleteResponder.cs

using Catalogger.Backend.Cache.InMemoryCache;
using Catalogger.Backend.Database;
using Catalogger.Backend.Database.Queries;
using Catalogger.Backend.Extensions;
using Catalogger.Backend.Services;
using Humanizer;
using NodaTime;
using Remora.Discord.API;
using Remora.Discord.API.Abstractions.Gateway.Events;
using Remora.Discord.API.Abstractions.Objects;
using Remora.Discord.API.Objects;
using Remora.Discord.Extensions.Embeds;
using Remora.Discord.Gateway.Responders;
using Remora.Rest.Core;
using Remora.Results;

namespace Catalogger.Backend.Bot.Responders.Messages;

public class MessageDeleteResponder(
    ILogger logger,
    DatabaseContext db,
    MessageRepository messageRepository,
    WebhookExecutorService webhookExecutor,
    ChannelCache channelCache,
    UserCache userCache,
    IClock clock,
    PluralkitApiService pluralkitApi
) : IResponder<IMessageDelete>
{
    private readonly ILogger _logger = logger.ForContext<MessageDeleteResponder>();

    private static bool MaybePkProxyTrigger(Snowflake id) =>
        id.Timestamp > DateTimeOffset.Now - 1.Minutes();

    public async Task<Result> RespondAsync(IMessageDelete ev, CancellationToken ct = default)
    {
        if (!ev.GuildID.IsDefined())
            return Result.Success;

        if (MaybePkProxyTrigger(ev.ID))
        {
            _logger.Debug(
                "Deleted message {MessageId} is less than 1 minute old, delaying 5 seconds to give PK time to catch up",
                ev.ID
            );
            await Task.Delay(5.Seconds(), ct);
        }

        if (await messageRepository.IsMessageIgnoredAsync(ev.ID.Value, ct))
            return Result.Success;

        var guild = await db.GetGuildAsync(ev.GuildID, ct);
        if (guild.IsMessageIgnored(ev.ChannelID, ev.ID))
            return Result.Success;

        var logChannel = webhookExecutor.GetLogChannel(
            guild,
            LogChannelType.MessageDelete,
            ev.ChannelID
        );
        var msg = await messageRepository.GetMessageAsync(ev.ID.Value, ct);
        // Sometimes a message that *should* be logged isn't stored in the database, notify the user of that
        if (msg == null)
        {
            if (logChannel == null)
                return Result.Success;
            webhookExecutor.QueueLog(
                logChannel.Value,
                new Embed(
                    Title: "Message deleted",
                    Description: $"A message not found in the database was deleted in <#{ev.ChannelID}> ({ev.ChannelID}).",
                    Footer: new EmbedFooter(Text: $"ID: {ev.ID}"),
                    Timestamp: clock.GetCurrentInstant().ToDateTimeOffset()
                )
            );

            return Result.Success;
        }

        // Check if the message is an edit trigger message.
        // If it is, the API will return a valid message for its ID, but the ID won't match either `Id` or `Original`.
        // (We also won't have any system/member information stored for it)
        if (msg is { System: null, Member: null } && MaybePkProxyTrigger(ev.ID))
        {
            var pkMsg = await pluralkitApi.GetPluralKitMessageAsync(ev.ID.Value, ct);
            if (pkMsg != null && pkMsg.Id != ev.ID.Value && pkMsg.Original != ev.ID.Value)
            {
                _logger.Debug(
                    "Deleted message {MessageId} is a `pk;edit` message, ignoring",
                    ev.ID
                );
                return Result.Success;
            }
        }

        logChannel = webhookExecutor.GetLogChannel(
            guild,
            LogChannelType.MessageDelete,
            ev.ChannelID,
            msg.UserId
        );
        if (logChannel == null)
            return Result.Success;

        var user = await userCache.GetUserAsync(DiscordSnowflake.New(msg.UserId));
        var builder = new EmbedBuilder()
            .WithTitle("Message deleted")
            .WithDescription(msg.Content)
            .WithColour(DiscordUtils.Red)
            .WithFooter($"ID: {msg.Id}")
            .WithTimestamp(ev.ID);

        if (user != null)
            builder.WithAuthor(user.Tag(), url: null, iconUrl: user.AvatarUrl());
        if (msg.Member != null)
            builder.WithTitle($"Message by {msg.Username} deleted");

        string channelMention;
        if (!channelCache.TryGet(ev.ChannelID, out var channel))
            channelMention = $"<#{msg.ChannelId}>";
        else if (
            channel.Type
            is ChannelType.AnnouncementThread
                or ChannelType.PrivateThread
                or ChannelType.PublicThread
        )
            channelMention =
                $"<#{channel.ParentID.Value}>\nID: {channel.ParentID.Value}\n\nThread: {channel.Name} (<#{channel.ID}>)";
        else
            channelMention = $"<#{channel.ID}>\nID: {channel.ID}";

        var userMention =
            user != null
                ? $"<@{user.ID}>\n{user.Tag()}\nID: {user.ID}"
                : $"<@{msg.UserId}>\nID: {msg.UserId}";

        builder.AddField("Channel", channelMention, true);
        builder.AddField(
            msg.System != null ? "Linked Discord account" : "Sender",
            userMention,
            true
        );
        if (msg is { System: not null, Member: not null })
        {
            builder.AddField("\u200b", "**PluralKit information**", false);
            builder.AddField("System ID", msg.System, true);
            builder.AddField("Member ID", msg.Member, true);
        }

        if (msg.Metadata != null)
        {
            var attachmentInfo = string.Join(
                "\n",
                msg.Metadata.Attachments.Select(a =>
                    $"{a.Filename} ({a.ContentType}, {a.Size.Bytes().Humanize()})"
                )
            );
            if (!string.IsNullOrWhiteSpace(attachmentInfo))
                builder.AddField("Attachments", attachmentInfo, false);
        }

        webhookExecutor.QueueLog(logChannel.Value, builder.Build().GetOrThrow());
        return Result.Success;
    }
}