// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json;
using osu.Game.Online.API.Requests;
using osu.Game.Online.Chat;

namespace osu.Game.Online.Notifications
{
    public partial class NotificationsClient
    {
        public Action<Channel>? ChannelJoined;
        public Action<List<Message>>? NewMessages;
        public Action? PresenceReceived;

        private bool enableChat;
        private long lastMessageId;

        public bool EnableChat
        {
            get => enableChat;
            set
            {
                enableChat = value;
                Task.Run(startChatIfEnabledAsync);
            }
        }

        private async Task onConnectedAsync()
        {
            await startChatIfEnabledAsync();
        }

        private async Task startChatIfEnabledAsync()
        {
            if (!EnableChat)
                return;

            await sendMessage(new StartChatRequest(), CancellationToken.None);

            var fetchReq = new GetUpdatesRequest(lastMessageId);

            fetchReq.Success += updates =>
            {
                if (updates?.Presence != null)
                {
                    foreach (var channel in updates.Presence)
                        handleJoinedChannel(channel);

                    //todo: handle left channels

                    handleMessages(updates.Messages);
                }

                PresenceReceived?.Invoke();
            };

            api.Queue(fetchReq);
        }

        private Task onMessageReceivedAsync(SocketMessage message)
        {
            switch (message.Event)
            {
                case "chat.message.new":
                    Debug.Assert(message.Data != null);

                    NewChatMessageData? messageData = JsonConvert.DeserializeObject<NewChatMessageData>(message.Data.ToString());
                    Debug.Assert(messageData != null);

                    List<Message> messages = messageData.Messages.Where(m => m.Sender.OnlineID != api.LocalUser.Value.OnlineID).ToList();

                    foreach (var msg in messages)
                        handleJoinedChannel(new Channel(msg.Sender) { Id = msg.ChannelId });

                    handleMessages(messages);
                    break;
            }

            return Task.CompletedTask;
        }

        private void handleJoinedChannel(Channel channel)
        {
            // we received this from the server so should mark the channel already joined.
            channel.Joined.Value = true;
            ChannelJoined?.Invoke(channel);
        }

        private void handleMessages(List<Message> messages)
        {
            NewMessages?.Invoke(messages);
            lastMessageId = messages.LastOrDefault()?.Id ?? lastMessageId;
        }
    }
}