sharp-chat/SharpChat/Packet/ChatMessageAddPacket.cs

using System;
using System.Text;

namespace SharpChat.Packet {
    public class ChatMessageAddPacket : ServerPacket {
        public DateTimeOffset Created { get; }
        public long UserId { get; }
        public string Text { get; }
        public bool IsAction { get; }
        public bool IsPrivate { get; }

        public ChatMessageAddPacket(
            long msgId,
            DateTimeOffset created,
            long userId,
            string text,
            bool isAction,
            bool isPrivate
        ) : base(msgId) {
            Created = created;
            UserId = userId < 0 ? -1 : userId;
            Text = text;
            IsAction = isAction;
            IsPrivate = isPrivate;
        }

        public override string Pack() {
            StringBuilder sb = new();

            sb.Append('2');
            sb.Append('\t');

            sb.Append(Created.ToUnixTimeSeconds());
            sb.Append('\t');

            sb.Append(UserId);
            sb.Append('\t');

            if(IsAction)
                sb.Append("<i>");

            sb.Append(
                Text.Replace("<", "&lt;")
                    .Replace(">", "&gt;")
                    .Replace("\n", " <br/> ")
                    .Replace("\t", "    ")
            );

            if(IsAction)
                sb.Append("</i>");

            sb.Append('\t');
            sb.Append(SequenceId);
            sb.AppendFormat(
                "\t1{0}0{1}{2}",
                IsAction ? '1' : '0',
                IsAction ? '0' : '1',
                IsPrivate ? '1' : '0'
            );

            return sb.ToString();
        }
    }
}