Octobot/src/Responders/MessageDeletedResponder.cs

using Boyfriend.Data;
using Boyfriend.Services;
using JetBrains.Annotations;
using Remora.Discord.API.Abstractions.Gateway.Events;
using Remora.Discord.API.Abstractions.Objects;
using Remora.Discord.API.Abstractions.Rest;
using Remora.Discord.Extensions.Embeds;
using Remora.Discord.Extensions.Formatting;
using Remora.Discord.Gateway.Responders;
using Remora.Results;

namespace Boyfriend.Responders;

/// <summary>
///     Handles logging the contents of a deleted message and the user who deleted the message
///     to a guild's <see cref="GuildSettings.PrivateFeedbackChannel" /> if one is set.
/// </summary>
[UsedImplicitly]
public class MessageDeletedResponder : IResponder<IMessageDelete> {
    private readonly IDiscordRestAuditLogAPI _auditLogApi;
    private readonly IDiscordRestChannelAPI  _channelApi;
    private readonly GuildDataService        _dataService;
    private readonly IDiscordRestUserAPI     _userApi;

    public MessageDeletedResponder(
        IDiscordRestAuditLogAPI auditLogApi, IDiscordRestChannelAPI channelApi,
        GuildDataService        dataService, IDiscordRestUserAPI    userApi) {
        _auditLogApi = auditLogApi;
        _channelApi = channelApi;
        _dataService = dataService;
        _userApi = userApi;
    }

    public async Task<Result> RespondAsync(IMessageDelete gatewayEvent, CancellationToken ct = default) {
        if (!gatewayEvent.GuildID.IsDefined(out var guildId)) return Result.FromSuccess();

        var cfg = await _dataService.GetSettings(guildId, ct);
        if (GuildSettings.PrivateFeedbackChannel.Get(cfg).Empty()) return Result.FromSuccess();

        var messageResult = await _channelApi.GetChannelMessageAsync(gatewayEvent.ChannelID, gatewayEvent.ID, ct);
        if (!messageResult.IsDefined(out var message)) return Result.FromError(messageResult);
        if (string.IsNullOrWhiteSpace(message.Content)) return Result.FromSuccess();

        var auditLogResult = await _auditLogApi.GetGuildAuditLogAsync(
            guildId, actionType: AuditLogEvent.MessageDelete, limit: 1, ct: ct);
        if (!auditLogResult.IsDefined(out var auditLogPage)) return Result.FromError(auditLogResult);

        var auditLog = auditLogPage.AuditLogEntries.Single();
        if (!auditLog.Options.IsDefined(out var options))
            return Result.FromError(new ArgumentNullError(nameof(auditLog.Options)));

        var user = message.Author;
        if (options.ChannelID == gatewayEvent.ChannelID
            && DateTimeOffset.UtcNow.Subtract(auditLog.ID.Timestamp).TotalSeconds <= 2) {
            var userResult = await _userApi.GetUserAsync(auditLog.UserID!.Value, ct);
            if (!userResult.IsDefined(out user)) return Result.FromError(userResult);
        }

        Messages.Culture = GuildSettings.Language.Get(cfg);

        var embed = new EmbedBuilder()
            .WithSmallTitle(
                string.Format(
                    Messages.CachedMessageDeleted,
                    message.Author.GetTag()), message.Author)
            .WithDescription(
                $"{Mention.Channel(gatewayEvent.ChannelID)}\n{message.Content.InBlockCode()}")
            .WithActionFooter(user)
            .WithTimestamp(message.Timestamp)
            .WithColour(ColorsList.Red)
            .Build();
        if (!embed.IsDefined(out var built)) return Result.FromError(embed);

        return (Result)await _channelApi.CreateMessageAsync(
            GuildSettings.PrivateFeedbackChannel.Get(cfg), embeds: new[] { built },
            allowedMentions: Boyfriend.NoMentions, ct: ct);
    }
}