using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Discord;
using Discord.WebSocket;
using Microsoft.EntityFrameworkCore;
using NadekoBot.Core.Services;
using NadekoBot.Core.Services.Database.Models;
using Serilog;

namespace NadekoBot.Modules.Administration.Services
{
    public class VcRoleService : INService
    {
        private readonly DbService _db;
        private readonly DiscordSocketClient _client;

        public ConcurrentDictionary<ulong, ConcurrentDictionary<ulong, IRole>> VcRoles { get; }
        public ConcurrentDictionary<ulong, ConcurrentQueue<(bool, IGuildUser, IRole)>> ToAssign { get; }

        public VcRoleService(DiscordSocketClient client, NadekoBot bot, DbService db)
        {
            _db = db;
            _client = client;

            _client.UserVoiceStateUpdated += ClientOnUserVoiceStateUpdated;
            VcRoles = new ConcurrentDictionary<ulong, ConcurrentDictionary<ulong, IRole>>();
            ToAssign = new ConcurrentDictionary<ulong, ConcurrentQueue<(bool, IGuildUser, IRole)>>();
            var missingRoles = new ConcurrentBag<VcRoleInfo>();

            using (var uow = db.GetDbContext())
            {
                var guildIds = client.Guilds.Select(x => x.Id).ToList();
                var configs = uow.Set<GuildConfig>()
                    .AsQueryable()
                    .Include(x => x.VcRoleInfos)
                    .Where(x => guildIds.Contains(x.GuildId))
                    .ToList();
                
                Task.WhenAll(configs.Select(InitializeVcRole));
            }

            Task.Run(async () =>
            {
                while (true)
                {
                    var tasks = ToAssign.Values.Select(queue => Task.Run(async () =>
                    {
                        while (queue.TryDequeue(out var item))
                        {
                            var (add, user, role) = item;
                            if (add)
                            {
                                if (!user.RoleIds.Contains(role.Id))
                                {
                                    try { await user.AddRoleAsync(role).ConfigureAwait(false); } catch { }
                                }
                            }
                            else
                            {
                                if (user.RoleIds.Contains(role.Id))
                                {
                                    try { await user.RemoveRoleAsync(role).ConfigureAwait(false); } catch { }
                                }
                            }

                            await Task.Delay(250).ConfigureAwait(false);
                        }
                    }));

                    await Task.WhenAll(tasks.Append(Task.Delay(1000))).ConfigureAwait(false);
                }
            });

            _client.LeftGuild += _client_LeftGuild;
            bot.JoinedGuild += Bot_JoinedGuild;
        }

        private Task Bot_JoinedGuild(GuildConfig arg)
        {
            // includeall no longer loads vcrole
            // need to load new guildconfig with vc role included 
            using (var uow = _db.GetDbContext())
            {
                var configWithVcRole = uow.GuildConfigsForId(
                    arg.GuildId,
                    set => set.Include(x => x.VcRoleInfos)
                );
                var _ = InitializeVcRole(configWithVcRole);
            }

            return Task.CompletedTask;
        }

        private Task _client_LeftGuild(SocketGuild arg)
        {
            VcRoles.TryRemove(arg.Id, out _);
            ToAssign.TryRemove(arg.Id, out _);
            return Task.CompletedTask;
        }

        private async Task InitializeVcRole(GuildConfig gconf)
        {
            await Task.Yield();
            var g = _client.GetGuild(gconf.GuildId);
            if (g == null)
                return;

            var infos = new ConcurrentDictionary<ulong, IRole>();
            var missingRoles = new List<VcRoleInfo>();
            VcRoles.AddOrUpdate(gconf.GuildId, infos, delegate { return infos; });
            foreach (var ri in gconf.VcRoleInfos)
            {
                var role = g.GetRole(ri.RoleId);
                if (role == null)
                {
                    missingRoles.Add(ri);
                    continue;
                }

                infos.TryAdd(ri.VoiceChannelId, role);
            }

            if (missingRoles.Any())
            {
                using (var uow = _db.GetDbContext())
                {
                    Log.Warning($"Removing {missingRoles.Count} missing roles from {nameof(VcRoleService)}");
                    uow.RemoveRange(missingRoles);
                    await uow.SaveChangesAsync();
                }
            }
        }

        public void AddVcRole(ulong guildId, IRole role, ulong vcId)
        {
            if (role == null)
                throw new ArgumentNullException(nameof(role));

            var guildVcRoles = VcRoles.GetOrAdd(guildId, new ConcurrentDictionary<ulong, IRole>());

            guildVcRoles.AddOrUpdate(vcId, role, (key, old) => role);
            using (var uow = _db.GetDbContext())
            {
                var conf = uow.GuildConfigsForId(guildId, set => set.Include(x => x.VcRoleInfos));
                var toDelete = conf.VcRoleInfos.FirstOrDefault(x => x.VoiceChannelId == vcId); // remove old one
                if(toDelete != null)
                {
                    uow.Remove(toDelete);
                }
                conf.VcRoleInfos.Add(new VcRoleInfo()
                {
                    VoiceChannelId = vcId,
                    RoleId = role.Id,
                }); // add new one
                uow.SaveChanges();
            }
        }

        public bool RemoveVcRole(ulong guildId, ulong vcId)
        {
            if (!VcRoles.TryGetValue(guildId, out var guildVcRoles))
                return false;

            if (!guildVcRoles.TryRemove(vcId, out _))
                return false;

            using (var uow = _db.GetDbContext())
            {
                var conf = uow.GuildConfigsForId(guildId, set => set.Include(x => x.VcRoleInfos));
                var toRemove = conf.VcRoleInfos.Where(x => x.VoiceChannelId == vcId).ToList();
                uow.RemoveRange(toRemove);
                uow.SaveChanges();
            }

            return true;
        }

        private Task ClientOnUserVoiceStateUpdated(SocketUser usr, SocketVoiceState oldState,
            SocketVoiceState newState)
        {

            var gusr = usr as SocketGuildUser;
            if (gusr == null)
                return Task.CompletedTask;

            var oldVc = oldState.VoiceChannel;
            var newVc = newState.VoiceChannel;
            var _ = Task.Run(() =>
            {
                try
                {
                    if (oldVc != newVc)
                    {
                        ulong guildId;
                        guildId = newVc?.Guild.Id ?? oldVc.Guild.Id;

                        if (VcRoles.TryGetValue(guildId, out ConcurrentDictionary<ulong, IRole> guildVcRoles))
                        {
                            //remove old
                            if (oldVc != null && guildVcRoles.TryGetValue(oldVc.Id, out IRole role))
                            {
                                Assign(false, gusr, role);
                            }
                            //add new
                            if (newVc != null && guildVcRoles.TryGetValue(newVc.Id, out role))
                            {
                                Assign(true, gusr, role);
                            }

                        }
                    }
                }
                catch (Exception ex)
                {
                    Log.Warning(ex, "Error in VcRoleService VoiceStateUpdate");
                }
            });
            return Task.CompletedTask;
        }

        private void Assign(bool v, SocketGuildUser gusr, IRole role)
        {
            var queue = ToAssign.GetOrAdd(gusr.Guild.Id, new ConcurrentQueue<(bool, IGuildUser, IRole)>());
            queue.Enqueue((v, gusr, role));
        }
    }
}