sharp-chat/SharpChat.SockChat/SockChatContext.cs

using SharpChat.Events;
using SharpChat.EventStorage;
using SharpChat.SockChat;
using SharpChat.SockChat.PacketsS2C;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;

namespace SharpChat {
    public class SockChatContext : IChatEventHandler {
        public readonly SemaphoreSlim ContextAccess = new(1, 1);

        public ChannelsContext Channels { get; } = new();
        public ConnectionsContext Connections { get; } = new();
        public UsersContext Users { get; } = new();
        public IEventStorage EventStorage { get; }
        public ChatEventDispatcher Events { get; } = new();
        public ChannelsUsersContext ChannelsUsers { get; } = new();
        public Dictionary<long, RateLimiter> UserRateLimiters { get; } = new();

        public SockChatContext(IEventStorage evtStore) {
            EventStorage = evtStore;
            Events.Subscribe(evtStore);
            Events.Subscribe(this);
        }

        public void HandleEvent(ChatEventInfo info) {
            // user status should be stored outside of the UserInfo class so we don't need to do this:
            UserInfo? userInfo = Users.Get(info.SenderId);

            switch(info.Type) {
                case "user:connect":
                    SendTo(info.ChannelName, new UserConnectS2CPacket(
                        info.Id,
                        info.Created,
                        info.SenderId,
                        userInfo == null ? SockChatUtility.GetUserName(info) : SockChatUtility.GetUserNameWithStatus(userInfo),
                        info.SenderColour,
                        info.SenderRank,
                        info.SenderPerms
                    ));
                    break;

                case "user:disconnect":
                    SendTo(info.ChannelName, new UserDisconnectS2CPacket(
                        info.Id,
                        info.Created,
                        info.SenderId,
                        userInfo == null ? SockChatUtility.GetUserName(info) : SockChatUtility.GetUserNameWithStatus(userInfo),
                        info.Data is UserDisconnectEventData userDisconnect ? userDisconnect.Reason : UserDisconnectReason.Leave
                    ));
                    break;

                case "chan:join":
                    SendTo(info.ChannelName, new UserChannelJoinS2CPacket(
                        info.SenderId,
                        userInfo == null ? SockChatUtility.GetUserName(info) : SockChatUtility.GetUserNameWithStatus(userInfo),
                        info.SenderColour,
                        info.SenderRank,
                        info.SenderPerms
                    ));
                    break;

                case "chan:leave":
                    SendTo(info.ChannelName, new UserChannelLeaveS2CPacket(info.SenderId));
                    break;

                case "msg:delete":
                    if(info.Data is not MessageDeleteEventData msgDelete)
                        break;

                    MessageDeleteS2CPacket msgDelPacket = new(msgDelete.MessageId);

                    if(info.IsBroadcast) {
                        Send(msgDelPacket);
                    } else if(info.ChannelName.StartsWith('@')) {
                        long[] targetIds = info.ChannelName[1..].Split('-', 3).Select(u => long.TryParse(u, out long up) ? up : -1).ToArray();
                        if(targetIds.Length != 2)
                            return;

                        UserInfo[] users = Users.GetMany(targetIds);
                        UserInfo? target = users.FirstOrDefault(u => u.UserId != info.SenderId);
                        if(target == null)
                            return;

                        foreach(UserInfo user in users)
                            SendTo(user, msgDelPacket);
                    } else {
                        SendTo(info.ChannelName, msgDelPacket);
                    }
                    break;

                case "msg:add":
                    if(info.Data is not MessageAddEventData msgAdd)
                        break;

                    if(info.IsBroadcast) {
                        Send(new MessageBroadcastS2CPacket(info.Id, info.Created, msgAdd.Text));
                    } else if(info.ChannelName.StartsWith('@')) {
                        // The channel name returned by GetDMChannelName should not be exposed to the user, instead @<Target User> should be displayed
                        // e.g. nook sees @Arysil and Arysil sees @nook

                        long[] targetIds = info.ChannelName[1..].Split('-', 3).Select(u => long.TryParse(u, out long up) ? up : -1).ToArray();
                        if(targetIds.Length != 2)
                            return;

                        UserInfo[] users = Users.GetMany(targetIds);
                        UserInfo? target = users.FirstOrDefault(u => u.UserId != info.SenderId);
                        if(target == null)
                            return;

                        foreach(UserInfo user in users)
                            SendTo(user, new MessageAddS2CPacket(
                                info.Id,
                                DateTimeOffset.Now,
                                info.SenderId,
                                info.SenderId == user.UserId ? $"{SockChatUtility.GetUserName(target)} {msgAdd.Text}" : msgAdd.Text,
                                msgAdd.IsAction,
                                true
                            ));
                    } else {
                        ChannelInfo? channel = Channels.Get(info.ChannelName, SockChatUtility.SanitiseChannelName);
                        if(channel != null)
                            SendTo(channel, new MessageAddS2CPacket(
                                info.Id,
                                DateTimeOffset.Now,
                                info.SenderId,
                                msgAdd.Text,
                                msgAdd.IsAction,
                                false
                            ));
                    }
                    break;
            }
        }

        public void Update() {
            ConnectionInfo[] timedOut = Connections.GetTimedOut();
            foreach(ConnectionInfo conn in timedOut) {
                Connections.Remove(conn);
                if(conn is SockChatConnectionInfo scConn)
                    scConn.Close(1002);

                Logger.Write($"<{conn.RemoteEndPoint}> Nuked timed out connection from user #{conn.UserId}.");
            }

            foreach(UserInfo user in Users.All)
                if(!Connections.HasUser(user)) {
                    HandleDisconnect(user, UserDisconnectReason.TimeOut);
                    Logger.Write($"Timed out {user} (no more connections).");
                }
        }

        public void SafeUpdate() {
            ContextAccess.Wait();
            try {
                Update();
            } finally {
                ContextAccess.Release();
            }
        }

        public ChannelInfo[] GetUserChannels(UserInfo user) {
            return Channels.GetMany(ChannelsUsers.GetUserChannelNames(user));
        }

        public UserInfo[] GetChannelUsers(ChannelInfo channel) {
            return Users.GetMany(ChannelsUsers.GetChannelUserIds(channel));
        }

        public void UpdateUser(
            UserInfo user,
            string? userName = null,
            string? nickName = null,
            Colour? colour = null,
            UserStatus? status = null,
            string? statusText = null,
            int? rank = null,
            UserPermissions? perms = null,
            bool? isSuper = null,
            bool silent = false
        ) {
            bool hasChanged = false;
            string? previousName = null;

            if(userName != null && !user.UserName.Equals(userName)) {
                user.UserName = userName;
                hasChanged = true;
            }

            if(nickName != null && !user.NickName.Equals(nickName)) {
                if(!silent)
                    previousName = string.IsNullOrWhiteSpace(user.NickName) ? user.UserName : user.NickName;

                user.NickName = nickName;
                hasChanged = true;
            }

            if(colour.HasValue && !user.Colour.Equals(colour.Value)) {
                user.Colour = colour.Value;
                hasChanged = true;
            }

            if(status.HasValue && user.Status != status.Value) {
                user.Status = status.Value;
                hasChanged = true;
            }

            if(statusText != null && !user.StatusText.Equals(statusText)) {
                user.StatusText = statusText;
                hasChanged = true;
            }

            if(rank != null && user.Rank != rank) {
                user.Rank = (int)rank;
                hasChanged = true;
            }

            if(perms.HasValue && user.Permissions != perms) {
                user.Permissions = perms.Value;
                hasChanged = true;
            }

            if(isSuper.HasValue && user.IsSuper != isSuper) {
                user.IsSuper = isSuper.Value;
                hasChanged = true;
            }

            if(hasChanged) {
                if(previousName != null)
                    SendToUserChannels(user, new UserUpdateNotificationS2CPacket(previousName, SockChatUtility.GetUserNameWithStatus(user)));

                SendToUserChannels(user, new UserUpdateS2CPacket(
                    user.UserId,
                    SockChatUtility.GetUserNameWithStatus(user),
                    user.Colour,
                    user.Rank,
                    user.Permissions
                ));
            }
        }

        public void BanUser(UserInfo user, TimeSpan duration, UserDisconnectReason reason = UserDisconnectReason.Kicked) {
            if(duration > TimeSpan.Zero) {
                DateTimeOffset expires = duration >= TimeSpan.MaxValue ? DateTimeOffset.MaxValue : DateTimeOffset.Now + duration;
                SendTo(user, new ForceDisconnectS2CPacket(expires));
            } else
                SendTo(user, new ForceDisconnectS2CPacket());

            ConnectionInfo[] conns = Connections.GetUser(user);
            foreach(ConnectionInfo conn in conns) {
                Connections.Remove(conn);
                if(conn is SockChatConnectionInfo scConn)
                    scConn.Close(1000);

                Logger.Write($"<{conn.RemoteEndPoint}> Nuked connection from banned user #{conn.UserId}.");
            }

            HandleDisconnect(user, reason);
        }

        public void HandleChannelEventLog(string channelName, Action<ISockChatS2CPacket> handler) {
            foreach(ChatEventInfo info in EventStorage.GetChannelEventLog(channelName)) {
                switch(info.Type) {
                    case "msg:add":
                        if(info.Data is not MessageAddEventData msgAdd)
                            break;

                        handler(new MessageAddLogS2CPacket(
                            info.Id,
                            info.Created,
                            info.SenderId,
                            info.SenderName,
                            info.SenderColour,
                            info.SenderRank,
                            info.SenderPerms,
                            msgAdd.Text,
                            msgAdd.IsAction,
                            info.ChannelName.StartsWith('@'),
                            info.IsBroadcast,
                            false
                        ));
                        break;

                    case "user:connect":
                        handler(new UserConnectLogS2CPacket(
                            info.Id,
                            info.Created,
                            SockChatUtility.GetUserName(info)
                        ));
                        break;

                    case "user:disconnect":
                        handler(new UserDisconnectLogS2CPacket(
                            info.Id,
                            info.Created,
                            SockChatUtility.GetUserName(info),
                            info.Data is UserDisconnectEventData userDisconnect ? userDisconnect.Reason : UserDisconnectReason.Leave
                        ));
                        break;

                    case "chan:join":
                        handler(new UserChannelJoinLogS2CPacket(
                            info.Id,
                            info.Created,
                            SockChatUtility.GetUserName(info)
                        ));
                        break;

                    case "chan:leave":
                        handler(new UserChannelLeaveLogS2CPacket(
                            info.Id,
                            info.Created,
                            SockChatUtility.GetUserName(info)
                        ));
                        break;
                }
            }
        }

        public void HandleJoin(UserInfo user, ChannelInfo chan, SockChatConnectionInfo conn, int maxMsgLength) {
            if(!ChannelsUsers.Has(chan, user))
                Events.Dispatch("user:connect", chan, user);

            conn.Send(new AuthSuccessS2CPacket(
                user.UserId,
                SockChatUtility.GetUserNameWithStatus(user),
                user.Colour,
                user.Rank,
                user.Permissions,
                chan.Name,
                maxMsgLength
            ));
            conn.Send(new UsersPopulateS2CPacket(GetChannelUsers(chan).Except(new[] { user }).Select(
                user => new UsersPopulateS2CPacket.ListEntry(
                    user.UserId,
                    SockChatUtility.GetUserNameWithStatus(user),
                    user.Colour,
                    user.Rank,
                    user.Permissions,
                    true
                )
            ).OrderByDescending(user => user.Rank).ToArray()));

            HandleChannelEventLog(chan.Name, p => conn.Send(p));

            conn.Send(new ChannelsPopulateS2CPacket(Channels.GetMany(isPublic: true, minRank: user.Rank).Select(
                channel => new ChannelsPopulateS2CPacket.ListEntry(channel.Name, channel.HasPassword, channel.IsTemporary)
            ).ToArray()));

            if(Users.Get(userId: user.UserId) == null)
                Users.Add(user);

            ChannelsUsers.Join(chan.Name, user.UserId);
        }

        public void HandleDisconnect(UserInfo user, UserDisconnectReason reason = UserDisconnectReason.Leave) {
            UpdateUser(user, status: UserStatus.Offline);
            Users.Remove(user.UserId);

            ChannelInfo[] channels = GetUserChannels(user);
            ChannelsUsers.DeleteUser(user);

            foreach(ChannelInfo chan in channels) {
                Events.Dispatch("user:disconnect", chan, user, new UserDisconnectEventData(reason));

                if(chan.IsTemporary && chan.IsOwner(user))
                    RemoveChannel(chan);
            }
        }

        public void SwitchChannel(UserInfo user, ChannelInfo chan, string password) {
            if(ChannelsUsers.IsUserLastChannel(user, chan)) {
                ForceChannel(user);
                return;
            }

            if(!user.Permissions.HasFlag(UserPermissions.JoinAnyChannel) && chan.IsOwner(user)) {
                if(chan.Rank > user.Rank) {
                    SendTo(user, new ChannelRankTooLowErrorS2CPacket(chan.Name));
                    ForceChannel(user);
                    return;
                }

                if(!string.IsNullOrEmpty(chan.Password) && chan.Password.Equals(password)) {
                    SendTo(user, new ChannelPasswordWrongErrorS2CPacket(chan.Name));
                    ForceChannel(user);
                    return;
                }
            }

            ForceChannelSwitch(user, chan);
        }

        public void ForceChannelSwitch(UserInfo user, ChannelInfo chan) {
            DateTimeOffset now = DateTimeOffset.UtcNow;
            ChannelInfo? oldChan = Channels.Get(ChannelsUsers.GetUserLastChannel(user));

            if(oldChan != null)
                Events.Dispatch("chan:leave", now, oldChan, user);

            Events.Dispatch("chan:join", now, chan, user);

            SendTo(user, new ContextClearS2CPacket(ContextClearS2CPacket.ClearMode.MessagesUsers));
            SendTo(user, new UsersPopulateS2CPacket(GetChannelUsers(chan).Except(new[] { user }).Select(
                user => new UsersPopulateS2CPacket.ListEntry(
                    user.UserId,
                    SockChatUtility.GetUserNameWithStatus(user),
                    user.Colour,
                    user.Rank,
                    user.Permissions,
                    true
                )
            ).OrderByDescending(u => u.Rank).ToArray()));

            HandleChannelEventLog(chan.Name, p => SendTo(user, p));
            ForceChannel(user, chan);

            if(oldChan != null)
                ChannelsUsers.Leave(oldChan, user);
            ChannelsUsers.Join(chan, user);

            if(oldChan != null && oldChan.IsTemporary && oldChan.IsOwner(user))
                RemoveChannel(oldChan);
        }

        public void Send(ISockChatS2CPacket packet) {
            string data = packet.Pack();
            Connections.WithAuthed(conn => {
                if(conn is SockChatConnectionInfo scConn)
                    scConn.Send(data);
            });
        }

        public void SendTo(UserInfo user, ISockChatS2CPacket packet) {
            string data = packet.Pack();
            Connections.WithUser(user, conn => {
                if(conn is SockChatConnectionInfo scConn)
                    scConn.Send(data);
            });
        }

        public void SendTo(ChannelInfo channel, ISockChatS2CPacket packet) {
            SendTo(channel, packet.Pack());
        }

        public void SendTo(ChannelInfo channel, string packet) {
            SendTo(channel.Name, packet);
        }

        public void SendTo(string channelName, ISockChatS2CPacket packet) {
            SendTo(channelName, packet.Pack());
        }

        public void SendTo(string channelName, string packet) {
            long[] userIds = ChannelsUsers.GetChannelUserIds(channelName);
            foreach(long userId in userIds)
                Connections.WithUser(userId, conn => {
                    if(conn is SockChatConnectionInfo scConn)
                        scConn.Send(packet);
                });
        }

        public void SendToUserChannels(UserInfo user, ISockChatS2CPacket packet) {
            ChannelInfo[] chans = GetUserChannels(user);
            string data = packet.Pack();
            foreach(ChannelInfo chan in chans)
                SendTo(chan, data);
        }

        public void ForceChannel(UserInfo user, ChannelInfo? chan = null) {
            chan ??= Channels.Get(ChannelsUsers.GetUserLastChannel(user));
            if(chan != null)
                SendTo(user, new UserChannelForceJoinS2CPacket(chan.Name));
        }

        public void UpdateChannel(
            ChannelInfo channel,
            bool? temporary = null,
            int? minRank = null,
            string? password = null
        ) {
            string prevName = channel.Name;

            if(temporary.HasValue)
                channel.IsTemporary = temporary.Value;

            if(minRank.HasValue)
                channel.Rank = minRank.Value;

            if(password != null)
                channel.Password = password;

            // TODO: Users that no longer have access to the channel/gained access to the channel by the rank change should receive delete and create packets respectively
            // the server currently doesn't keep track of what channels a user is already aware of so can't really simulate this yet.
            foreach(UserInfo user in Users.GetMany(minRank: channel.Rank))
                SendTo(user, new ChannelUpdateS2CPacket(prevName, channel.Name, channel.HasPassword, channel.IsTemporary));
        }

        public void RemoveChannel(ChannelInfo channel) {
            if(channel == null || Channels.PublicCount > 1)
                return;

            ChannelInfo? defaultChannel = Channels.MainChannel;
            if(defaultChannel == null)
                return;

            // Remove channel from the listing
            Channels.Remove(channel);

            // Move all users back to the main channel
            // TODO: Replace this with a kick. SCv2 supports being in 0 channels, SCv1 should force the user back to DefaultChannel.
            foreach(UserInfo user in GetChannelUsers(channel))
                SwitchChannel(user, defaultChannel, string.Empty);

            // Broadcast deletion of channel
            foreach(UserInfo user in Users.GetMany(minRank: channel.Rank))
                SendTo(user, new ChannelDeleteS2CPacket(channel.Name));
        }
    }
}