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

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

        public readonly SemaphoreSlim ContextAccess = new(1, 1);

        public HashSet<ChatChannel> Channels { get; } = new();
        public HashSet<ChatConnection> Connections { get; } = new();
        public HashSet<ChatUser> Users { get; } = new();
        public IEventStorage Events { get; }
        public HashSet<ChannelUserAssoc> ChannelUsers { get; } = new();
        public Dictionary<long, RateLimiter> UserRateLimiters { get; } = new();
        public Dictionary<long, ChatChannel> UserLastChannel { get; } = new();

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

        public void Update() {
            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);

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

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

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

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

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

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

        public void UpdateUser(
            ChatUser user,
            string userName = null,
            string nickName = null,
            ChatColour? colour = null,
            ChatUserStatus? status = null,
            string statusText = null,
            int? rank = null,
            ChatUserPermissions? perms = null,
            bool silent = false
        ) {
            if(user == null)
                throw new ArgumentNullException(nameof(user));

            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 != 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(hasChanged)
                SendToUserChannels(user, new UserUpdatePacket(user, previousName));
        }

        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));

            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) {
            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));

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

            Users.Add(user);

            ChannelUsers.Add(new ChannelUserAssoc(user.UserId, chan.Name));
            UserLastChannel[user.UserId] = chan;
        }

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

            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.IsOwner(user))
                    RemoveChannel(chan);
            }
        }

        public void SwitchChannel(ChatUser user, ChatChannel chan, string password) {
            if(UserLastChannel.TryGetValue(user.UserId, out ChatChannel ulc) && chan == ulc) {
                ForceChannel(user);
                return;
            }

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

                if(!string.IsNullOrEmpty(chan.Password) && 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) {
            if(!Channels.Contains(chan))
                return;

            ChatChannel oldChan = UserLastChannel[user.UserId];

            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);

            ChannelUsers.Remove(new ChannelUserAssoc(user.UserId, oldChan.Name));
            ChannelUsers.Add(new ChannelUserAssoc(user.UserId, chan.Name));
            UserLastChannel[user.UserId] = chan;

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

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

            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));

            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
            IEnumerable<ChatConnection> conns = Connections.Where(c => c.IsAuthed && IsInChannel(c.User, channel));
            foreach(ChatConnection conn in conns)
                conn.Send(packet);
        }

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

            IEnumerable<ChatChannel> chans = Channels.Where(c => IsInChannel(user, c));
            IEnumerable<ChatConnection> conns = Connections.Where(conn => conn.IsAuthed && ChannelUsers.Any(cu => cu.UserId == conn.User.UserId && chans.Any(chan => chan.NameEquals(cu.ChannelName))));
            foreach(ChatConnection conn in conns)
                conn.Send(packet);
        }

        public IPAddress[] GetRemoteAddresses(ChatUser user) {
            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));

            if(chan == null && !UserLastChannel.TryGetValue(user.UserId, out chan))
                throw new ArgumentException("no channel???");

            SendTo(user, new UserChannelForceJoinPacket(chan));
        }

        public void UpdateChannel(ChatChannel channel, 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));

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

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

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

            // TODO: 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
            foreach(ChatUser user in Users.Where(u => u.Rank >= channel.Rank)) {
                SendTo(user, new ChannelUpdatePacket(channel.Name, channel));
            }
        }

        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
            foreach(ChatUser user in Users.Where(u => u.Rank >= channel.Rank))
                SendTo(user, new ChannelDeletePacket(channel));
        }
    }
}