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

namespace SharpChat {
    public class ChatContext {
        public record ChannelUserAssoc(long UserId, string ChannelName);

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

        public HashSet<ChatConnection> Connections { get; } = new();
        public readonly object ConnectionsAccess = new();

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

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

        public HashSet<ChannelUserAssoc> ChannelUsers { get; } = new();
        public readonly object ChannelUsersAccess = new();

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

        public void Update() {
            lock(ConnectionsAccess) {
                foreach(ChatConnection conn in Connections)
                    if(!conn.IsDisposed && conn.HasTimedOut) {
                        conn.Dispose();
                        Logger.Write($"Nuked connection {conn.Id} associated with {conn.User}.");
                    }

                Connections.RemoveWhere(conn => conn.IsDisposed);

                lock(UsersAccess)
                    foreach(ChatUser user in Users)
                        if(!Connections.Any(conn => conn.User == user)) {
                            HandleDisconnect(user, UserDisconnectReason.TimeOut);
                            Logger.Write($"Timed out {user} (no more connections).");
                        }
            }
        }

        public bool IsInChannel(ChatUser user, ChatChannel channel) {
            lock(ChannelUsersAccess)
                return ChannelUsers.Contains(new ChannelUserAssoc(user.UserId, channel.Name));
        }

        public string[] GetUserChannelNames(ChatUser user) {
            lock(ChannelUsersAccess)
                return ChannelUsers.Where(cu => cu.UserId == user.UserId).Select(cu => cu.ChannelName).ToArray();
        }

        public ChatChannel[] GetUserChannels(ChatUser user) {
            string[] names = GetUserChannelNames(user);
            lock(ChannelsAccess)
                return Channels.Where(c => names.Any(n => c.NameEquals(n))).ToArray();
        }

        public long[] GetChannelUserIds(ChatChannel channel) {
            lock(ChannelUsersAccess)
                return ChannelUsers.Where(cu => channel.NameEquals(cu.ChannelName)).Select(cu => cu.UserId).ToArray();
        }

        public ChatUser[] GetChannelUsers(ChatChannel channel) {
            long[] ids = GetChannelUserIds(channel);
            lock(UsersAccess)
                return Users.Where(u => ids.Contains(u.UserId)).ToArray();
        }

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

            lock(ConnectionsAccess) {
                foreach(ChatConnection conn in Connections)
                    if(conn.User == user)
                        conn.Dispose();
                Connections.RemoveWhere(conn => conn.IsDisposed);
            }

            HandleDisconnect(user, reason);
        }

        public void HandleJoin(ChatUser user, ChatChannel chan, ChatConnection conn, int maxMsgLength) {
            lock(EventsAccess) {
                if(!IsInChannel(user, chan)) {
                    SendTo(chan, new UserConnectPacket(DateTimeOffset.Now, user));
                    Events.AddEvent(new UserConnectEvent(DateTimeOffset.Now, user, chan));
                }

                conn.Send(new AuthSuccessPacket(user, chan, conn, maxMsgLength));
                conn.Send(new ContextUsersPacket(GetChannelUsers(chan).Except(new[] { user }).OrderByDescending(u => u.Rank)));

                foreach(IChatEvent msg in Events.GetChannelEventLog(chan.Name))
                    conn.Send(new ContextMessagePacket(msg));

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

                lock(UsersAccess)
                    Users.Add(user);

                lock(ChannelUsersAccess) {
                    ChannelUsers.Add(new ChannelUserAssoc(user.UserId, chan.Name));
                    user.CurrentChannel = chan;
                }
            }
        }

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

            lock(EventsAccess) {
                lock(UsersAccess)
                    Users.Remove(user);

                lock(ChannelUsersAccess) {
                    ChatChannel[] channels = GetUserChannels(user);

                    foreach(ChatChannel chan in channels) {
                        ChannelUsers.Remove(new ChannelUserAssoc(user.UserId, chan.Name));

                        SendTo(chan, new UserDisconnectPacket(DateTimeOffset.Now, user, reason));
                        Events.AddEvent(new UserDisconnectEvent(DateTimeOffset.Now, user, chan, reason));

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

        public void SwitchChannel(ChatUser user, ChatChannel chan, string password) {
            if(user.CurrentChannel == chan) {
                ForceChannel(user);
                return;
            }

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

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

            ForceChannelSwitch(user, chan);
        }

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

            ChatChannel oldChan = user.CurrentChannel;

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

                SendTo(user, new ContextClearPacket(chan, ContextClearMode.MessagesUsers));
                SendTo(user, new ContextUsersPacket(GetChannelUsers(chan).Except(new[] { user }).OrderByDescending(u => u.Rank)));

                foreach(IChatEvent msg in Events.GetChannelEventLog(chan.Name))
                    SendTo(user, new ContextMessagePacket(msg));

                ForceChannel(user, chan);

                lock(ChannelUsersAccess) {
                    ChannelUsers.Remove(new ChannelUserAssoc(user.UserId, oldChan.Name));
                    ChannelUsers.Add(new ChannelUserAssoc(user.UserId, chan.Name));
                    user.CurrentChannel = chan;
                }
            }

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

        public void Send(IServerPacket packet) {
            if(packet == null)
                throw new ArgumentNullException(nameof(packet));

            lock(ConnectionsAccess)
                foreach(ChatConnection conn in Connections)
                    if(conn.IsAuthed)
                        conn.Send(packet);
        }

        public void SendTo(ChatUser user, IServerPacket packet) {
            if(user == null)
                throw new ArgumentNullException(nameof(user));
            if(packet == null)
                throw new ArgumentNullException(nameof(packet));

            lock(ConnectionsAccess)
                foreach(ChatConnection conn in Connections)
                    if(conn.IsAlive && conn.User == user)
                        conn.Send(packet);
        }

        public void SendTo(ChatChannel channel, IServerPacket packet) {
            if(channel == null)
                throw new ArgumentNullException(nameof(channel));
            if(packet == null)
                throw new ArgumentNullException(nameof(packet));

            // might be faster to grab the users first and then cascade into that SendTo
            lock(ConnectionsAccess) {
                IEnumerable<ChatConnection> conns = Connections.Where(c => c.IsAuthed && IsInChannel(c.User, channel));
                foreach(ChatConnection conn in conns)
                    conn.Send(packet);
            }
        }

        public IPAddress[] GetRemoteAddresses(ChatUser user) {
            lock(ConnectionsAccess)
                return Connections.Where(c => c.IsAlive && c.User == user).Select(c => c.RemoteAddress).Distinct().ToArray();
        }

        public void ForceChannel(ChatUser user, ChatChannel chan = null) {
            if(user == null)
                throw new ArgumentNullException(nameof(user));

            SendTo(user, new UserChannelForceJoinPacket(chan ?? user.CurrentChannel));
        }

        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)) {
                    SendTo(user, new ChannelUpdatePacket(prevName, channel));

                    if(nameUpdated)
                        ForceChannel(user);
                }
        }

        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 GetChannelUsers(channel))
                SwitchChannel(user, defaultChannel, string.Empty);

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