sharp-chat/SharpChat/ChatContext.cs

using SharpChat.Events;
using SharpChat.EventStorage;
using SharpChat.Packet;
using System;
using System.Collections.Generic;
using System.Linq;

namespace SharpChat {
    public class ChatContext {
        public HashSet<ChatChannel> Channels { get; } = new();
        public readonly object ChannelsAccess = new();

        public HashSet<ChatUser> Users { get; } = new();
        public readonly object UsersAccess = new();

        public IEventStorage Events { get; }
        public readonly object EventsAccess = new();

        public ChatContext(IEventStorage evtStore) {
            Events = evtStore ?? throw new ArgumentNullException(nameof(evtStore));
        }

        public void Update() {
            lock(UsersAccess)
                foreach(ChatUser user in Users) {
                    IEnumerable<ChatUserSession> timedOut = user.GetDeadSessions();

                    foreach(ChatUserSession sess in timedOut) {
                        user.RemoveSession(sess);
                        sess.Dispose();
                        Logger.Write($"Nuked session {sess.Id} from {user.Username} (timeout)");
                    }

                    if(!user.HasSessions)
                        UserLeave(null, user, UserDisconnectReason.TimeOut);
                }
        }

        public void BanUser(ChatUser user, TimeSpan duration, UserDisconnectReason reason = UserDisconnectReason.Kicked) {
            if(duration > TimeSpan.Zero)
                user.Send(new ForceDisconnectPacket(ForceDisconnectReason.Banned, DateTimeOffset.Now + duration));
            else
                user.Send(new ForceDisconnectPacket(ForceDisconnectReason.Kicked));

            user.Close();
            UserLeave(user.Channel, user, reason);
        }

        public void HandleJoin(ChatUser user, ChatChannel chan, ChatUserSession sess, int maxMsgLength) {
            lock(EventsAccess) {
                if(!chan.HasUser(user)) {
                    chan.Send(new UserConnectPacket(DateTimeOffset.Now, user));
                    Events.AddEvent(new UserConnectEvent(DateTimeOffset.Now, user, chan));
                }

                sess.Send(new AuthSuccessPacket(user, chan, sess, maxMsgLength));
                sess.Send(new ContextUsersPacket(chan.GetUsers(new[] { user })));

                foreach(IChatEvent msg in Events.GetTargetEventLog(chan.Name))
                    sess.Send(new ContextMessagePacket(msg));

                lock(ChannelsAccess)
                    sess.Send(new ContextChannelsPacket(Channels.Where(c => c.Rank <= user.Rank)));

                if(!chan.HasUser(user))
                    chan.UserJoin(user);

                lock(UsersAccess)
                    Users.Add(user);
            }
        }

        public void UserLeave(ChatChannel chan, ChatUser user, UserDisconnectReason reason = UserDisconnectReason.Leave) {
            user.Status = ChatUserStatus.Offline;

            if(chan == null) {
                foreach(ChatChannel channel in user.GetChannels()) {
                    UserLeave(channel, user, reason);
                }
                return;
            }

            if(chan.IsTemporary && chan.Owner == user)
                lock(ChannelsAccess)
                    RemoveChannel(chan);

            lock(EventsAccess) {
                chan.UserLeave(user);
                chan.Send(new UserDisconnectPacket(DateTimeOffset.Now, user, reason));
                Events.AddEvent(new UserDisconnectEvent(DateTimeOffset.Now, user, chan, reason));
            }
        }

        public void SwitchChannel(ChatUser user, ChatChannel chan, string password) {
            if(user.CurrentChannel == chan) {
                //user.Send(true, "samechan", chan.Name);
                user.ForceChannel();
                return;
            }

            if(!user.Can(ChatUserPermissions.JoinAnyChannel) && chan.Owner != user) {
                if(chan.Rank > user.Rank) {
                    user.Send(new LegacyCommandResponse(LCR.CHANNEL_INSUFFICIENT_HIERARCHY, true, chan.Name));
                    user.ForceChannel();
                    return;
                }

                if(chan.Password != password) {
                    user.Send(new LegacyCommandResponse(LCR.CHANNEL_INVALID_PASSWORD, true, chan.Name));
                    user.ForceChannel();
                    return;
                }
            }

            ForceChannelSwitch(user, chan);
        }

        public void ForceChannelSwitch(ChatUser user, ChatChannel chan) {
            lock(ChannelsAccess)
                if(!Channels.Contains(chan))
                    return;

            ChatChannel oldChan = user.CurrentChannel;

            lock(EventsAccess) {
                oldChan.Send(new UserChannelLeavePacket(user));
                Events.AddEvent(new UserChannelLeaveEvent(DateTimeOffset.Now, user, oldChan));
                chan.Send(new UserChannelJoinPacket(user));
                Events.AddEvent(new UserChannelJoinEvent(DateTimeOffset.Now, user, chan));

                user.Send(new ContextClearPacket(chan, ContextClearMode.MessagesUsers));
                user.Send(new ContextUsersPacket(chan.GetUsers(new[] { user })));

                foreach(IChatEvent msg in Events.GetTargetEventLog(chan.Name))
                    user.Send(new ContextMessagePacket(msg));

                user.ForceChannel(chan);
                oldChan.UserLeave(user);
                chan.UserJoin(user);
            }

            if(oldChan.IsTemporary && oldChan.Owner == user)
                lock(ChannelsAccess)
                    RemoveChannel(oldChan);
        }

        public void Send(IServerPacket packet) {
            lock(UsersAccess)
                foreach(ChatUser user in Users)
                    user.Send(packet);
        }

        public void UpdateChannel(ChatChannel channel, string name = null, bool? temporary = null, int? hierarchy = null, string password = null) {
            if(channel == null)
                throw new ArgumentNullException(nameof(channel));
            if(!Channels.Contains(channel))
                throw new ArgumentException("Provided channel is not registered with this manager.", nameof(channel));

            string prevName = channel.Name;
            int prevHierarchy = channel.Rank;
            bool nameUpdated = !string.IsNullOrWhiteSpace(name) && name != prevName;

            if(nameUpdated) {
                if(!ChatChannel.CheckName(name))
                    throw new ArgumentException("Name contains invalid characters.", nameof(name));

                channel.Name = name;
            }

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

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

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

            // Users that no longer have access to the channel/gained access to the channel by the hierarchy change should receive delete and create packets respectively
            lock(UsersAccess)
                foreach(ChatUser user in Users.Where(u => u.Rank >= channel.Rank)) {
                    user.Send(new ChannelUpdatePacket(prevName, channel));

                    if(nameUpdated)
                        user.ForceChannel();
                }
        }

        public void RemoveChannel(ChatChannel channel) {
            if(channel == null || !Channels.Any())
                return;

            ChatChannel defaultChannel = Channels.FirstOrDefault();
            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(ChatUser user in channel.GetUsers())
                SwitchChannel(user, defaultChannel, string.Empty);

            // Broadcast deletion of channel
            lock(UsersAccess)
                foreach(ChatUser user in Users.Where(u => u.Rank >= channel.Rank))
                    user.Send(new ChannelDeletePacket(channel));
        }
    }
}