sharp-chat/SharpChat/Commands/MessageDeleteCommand.cs

using SharpChat.EventStorage;
using SharpChat.Packet;
using System.Linq;

namespace SharpChat.Commands
{
    public class MessageDeleteCommand : IChatCommand {
        public bool IsMatch(ChatCommandContext ctx) {
            return ctx.NameEquals("delmsg") || (
                ctx.NameEquals("delete")
                && ctx.Args.FirstOrDefault()?.All(char.IsDigit) == true
            );
        }

        public void Dispatch(ChatCommandContext ctx) {
            bool deleteAnyMessage = ctx.User.Can(ChatUserPermissions.DeleteAnyMessage);

            if(!deleteAnyMessage && !ctx.User.Can(ChatUserPermissions.DeleteOwnMessage)) {
                ctx.Chat.SendTo(ctx.User, new CommandNotAllowedErrorPacket(ctx.Name));
                return;
            }

            string? firstArg = ctx.Args.FirstOrDefault();

            if(string.IsNullOrWhiteSpace(firstArg) || !firstArg.All(char.IsDigit) || !long.TryParse(firstArg, out long delSeqId)) {
                ctx.Chat.SendTo(ctx.User, new CommandFormatErrorPacket());
                return;
            }

            StoredEventInfo? delMsg = ctx.Chat.Events.GetEvent(delSeqId);

            if(delMsg == null || delMsg.Sender?.Rank > ctx.User.Rank || (!deleteAnyMessage && delMsg.Sender?.UserId != ctx.User.UserId)) {
                ctx.Chat.SendTo(ctx.User, new MessageDeleteNotAllowedErrorPacket());
                return;
            }

            ctx.Chat.Events.RemoveEvent(delMsg);
            ctx.Chat.Send(new MessageDeletePacket(delMsg.Id));
        }
    }
}