// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using System;
using System.Collections.Generic;
using System.Linq;
using OpenTK;
using OpenTK.Graphics;
using osu.Framework.Allocation;
using osu.Framework.Configuration;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Shapes;
using osu.Framework.Graphics.UserInterface;
using osu.Framework.Input.Events;
using osu.Framework.Threading;
using osu.Game.Configuration;
using osu.Game.Graphics;
using osu.Game.Graphics.Containers;
using osu.Game.Graphics.UserInterface;
using osu.Game.Online.API;
using osu.Game.Online.API.Requests;
using osu.Game.Online.Chat;
using osu.Game.Overlays.Chat;

namespace osu.Game.Overlays
{
    public class ChatOverlay : OsuFocusedOverlayContainer, IOnlineComponent
    {
        private const float textbox_height = 60;
        private const float channel_selection_min_height = 0.3f;

        private ScheduledDelegate messageRequest;

        private readonly Container<DrawableChannel> currentChannelContainer;

        private readonly LoadingAnimation loading;

        private readonly FocusedTextBox textbox;

        private APIAccess api;

        private const int transition_length = 500;

        public const float DEFAULT_HEIGHT = 0.4f;

        public const float TAB_AREA_HEIGHT = 50;

        private GetUpdatesRequest fetchReq;

        private readonly ChatTabControl channelTabs;

        private readonly Container chatContainer;
        private readonly TabsArea tabsArea;
        private readonly Box chatBackground;
        private readonly Box tabBackground;

        public Bindable<double> ChatHeight { get; set; }

        public List<Channel> AvailableChannels { get; private set; } = new List<Channel>();
        private readonly Container channelSelectionContainer;
        private readonly ChannelSelectionOverlay channelSelection;

        public override bool Contains(Vector2 screenSpacePos) => chatContainer.ReceivePositionalInputAt(screenSpacePos) || channelSelection.State == Visibility.Visible && channelSelection.ReceivePositionalInputAt(screenSpacePos);

        public ChatOverlay()
        {
            RelativeSizeAxes = Axes.Both;
            RelativePositionAxes = Axes.Both;
            Anchor = Anchor.BottomLeft;
            Origin = Anchor.BottomLeft;

            const float padding = 5;

            Children = new Drawable[]
            {
                channelSelectionContainer = new Container
                {
                    RelativeSizeAxes = Axes.Both,
                    Height = 1f - DEFAULT_HEIGHT,
                    Masking = true,
                    Children = new[]
                    {
                        channelSelection = new ChannelSelectionOverlay
                        {
                            RelativeSizeAxes = Axes.Both,
                        },
                    },
                },
                chatContainer = new Container
                {
                    Name = @"chat container",
                    Anchor = Anchor.BottomLeft,
                    Origin = Anchor.BottomLeft,
                    RelativeSizeAxes = Axes.Both,
                    Height = DEFAULT_HEIGHT,
                    Children = new[]
                    {
                        new Container
                        {
                            Name = @"chat area",
                            RelativeSizeAxes = Axes.Both,
                            Padding = new MarginPadding { Top = TAB_AREA_HEIGHT },
                            Children = new Drawable[]
                            {
                                chatBackground = new Box
                                {
                                    RelativeSizeAxes = Axes.Both,
                                },
                                currentChannelContainer = new Container<DrawableChannel>
                                {
                                    RelativeSizeAxes = Axes.Both,
                                    Padding = new MarginPadding
                                    {
                                        Bottom = textbox_height
                                    },
                                },
                                new Container
                                {
                                    Anchor = Anchor.BottomLeft,
                                    Origin = Anchor.BottomLeft,
                                    RelativeSizeAxes = Axes.X,
                                    Height = textbox_height,
                                    Padding = new MarginPadding
                                    {
                                        Top = padding * 2,
                                        Bottom = padding * 2,
                                        Left = ChatLine.LEFT_PADDING + padding * 2,
                                        Right = padding * 2,
                                    },
                                    Children = new Drawable[]
                                    {
                                        textbox = new FocusedTextBox
                                        {
                                            RelativeSizeAxes = Axes.Both,
                                            Height = 1,
                                            PlaceholderText = "type your message",
                                            Exit = () => State = Visibility.Hidden,
                                            OnCommit = postMessage,
                                            ReleaseFocusOnCommit = false,
                                            HoldFocus = true,
                                        }
                                    }
                                },
                                loading = new LoadingAnimation(),
                            }
                        },
                        tabsArea = new TabsArea
                        {
                            Children = new Drawable[]
                            {
                                tabBackground = new Box
                                {
                                    RelativeSizeAxes = Axes.Both,
                                    Colour = Color4.Black,
                                },
                                channelTabs = new ChatTabControl
                                {
                                    RelativeSizeAxes = Axes.Both,
                                    OnRequestLeave = removeChannel,
                                },
                            }
                        },
                    },
                },
            };

            channelTabs.Current.ValueChanged += newChannel => CurrentChannel = newChannel;
            channelTabs.ChannelSelectorActive.ValueChanged += value => channelSelection.State = value ? Visibility.Visible : Visibility.Hidden;
            channelSelection.StateChanged += state =>
            {
                channelTabs.ChannelSelectorActive.Value = state == Visibility.Visible;

                if (state == Visibility.Visible)
                {
                    textbox.HoldFocus = false;
                    if (1f - ChatHeight.Value < channel_selection_min_height)
                        this.TransformBindableTo(ChatHeight, 1f - channel_selection_min_height, 800, Easing.OutQuint);
                }
                else
                    textbox.HoldFocus = true;
            };
        }

        private double startDragChatHeight;
        private bool isDragging;

        public void OpenChannel(Channel channel) => addChannel(channel);

        protected override bool OnDragStart(DragStartEvent e)
        {
            isDragging = tabsArea.IsHovered;

            if (!isDragging)
                return base.OnDragStart(e);

            startDragChatHeight = ChatHeight.Value;
            return true;
        }

        protected override bool OnDrag(DragEvent e)
        {
            if (isDragging)
            {
                double targetChatHeight = startDragChatHeight - (e.MousePosition.Y - e.MouseDownPosition.Y) / Parent.DrawSize.Y;

                // If the channel selection screen is shown, mind its minimum height
                if (channelSelection.State == Visibility.Visible && targetChatHeight > 1f - channel_selection_min_height)
                    targetChatHeight = 1f - channel_selection_min_height;

                ChatHeight.Value = targetChatHeight;
            }

            return true;
        }

        protected override bool OnDragEnd(DragEndEvent e)
        {
            isDragging = false;
            return base.OnDragEnd(e);
        }

        public void APIStateChanged(APIAccess api, APIState state)
        {
            switch (state)
            {
                case APIState.Online:
                    initializeChannels();
                    break;
                default:
                    messageRequest?.Cancel();
                    break;
            }
        }

        public override bool AcceptsFocus => true;

        protected override void OnFocus(FocusEvent e)
        {
            //this is necessary as textbox is masked away and therefore can't get focus :(
            GetContainingInputManager().ChangeFocus(textbox);
            base.OnFocus(e);
        }

        protected override void PopIn()
        {
            this.MoveToY(0, transition_length, Easing.OutQuint);
            this.FadeIn(transition_length, Easing.OutQuint);

            textbox.HoldFocus = true;
            base.PopIn();
        }

        protected override void PopOut()
        {
            this.MoveToY(Height, transition_length, Easing.InSine);
            this.FadeOut(transition_length, Easing.InSine);

            textbox.HoldFocus = false;
            base.PopOut();
        }

        [BackgroundDependencyLoader]
        private void load(APIAccess api, OsuConfigManager config, OsuColour colours)
        {
            this.api = api;
            api.Register(this);

            ChatHeight = config.GetBindable<double>(OsuSetting.ChatDisplayHeight);
            ChatHeight.ValueChanged += h =>
            {
                chatContainer.Height = (float)h;
                channelSelectionContainer.Height = 1f - (float)h;
                tabBackground.FadeTo(h == 1 ? 1 : 0.8f, 200);
            };
            ChatHeight.TriggerChange();

            chatBackground.Colour = colours.ChatBlue;
        }

        private long lastMessageId;

        private readonly List<Channel> careChannels = new List<Channel>();

        private readonly List<DrawableChannel> loadedChannels = new List<DrawableChannel>();

        private void initializeChannels()
        {
            loading.Show();

            messageRequest?.Cancel();

            ListChannelsRequest req = new ListChannelsRequest();
            req.Success += delegate (List<Channel> channels)
            {
                AvailableChannels = channels;

                Scheduler.Add(delegate
                {
                    //todo: decide how to handle default channels for a user now that they are saved server-side.
                    addChannel(channels.Find(c => c.Name == @"#lazer"));
                    addChannel(channels.Find(c => c.Name == @"#osu"));

                    channelSelection.OnRequestJoin = addChannel;
                    channelSelection.OnRequestLeave = removeChannel;
                    channelSelection.Sections = new[]
                    {
                        new ChannelSection
                        {
                            Header = "All Channels",
                            Channels = channels,
                        },
                    };
                });

                messageRequest = Scheduler.AddDelayed(fetchUpdates, 1000, true);
            };

            api.Queue(req);
        }

        private Channel currentChannel;

        protected Channel CurrentChannel
        {
            get
            {
                return currentChannel;
            }

            set
            {
                if (currentChannel == value) return;

                if (value == null)
                {
                    currentChannel = null;
                    textbox.Current.Disabled = true;
                    currentChannelContainer.Clear(false);
                    return;
                }

                currentChannel = value;

                textbox.Current.Disabled = currentChannel.ReadOnly;
                channelTabs.Current.Value = value;

                var loaded = loadedChannels.Find(d => d.Channel == value);
                if (loaded == null)
                {
                    currentChannelContainer.FadeOut(500, Easing.OutQuint);
                    loading.Show();

                    loaded = new DrawableChannel(currentChannel);
                    loadedChannels.Add(loaded);
                    LoadComponentAsync(loaded, l =>
                    {
                        if (currentChannel.MessagesLoaded)
                            loading.Hide();

                        currentChannelContainer.Clear(false);
                        currentChannelContainer.Add(loaded);
                        currentChannelContainer.FadeIn(500, Easing.OutQuint);
                    });
                }
                else
                {
                    currentChannelContainer.Clear(false);
                    currentChannelContainer.Add(loaded);
                }
            }
        }

        private void addChannel(Channel channel)
        {
            if (channel == null) return;

            // ReSharper disable once AccessToModifiedClosure
            var existing = careChannels.Find(c => c.Id == channel.Id);

            if (existing != null)
            {
                // if we already have this channel loaded, we don't want to make a second one.
                channel = existing;
            }
            else
            {
                careChannels.Add(channel);
                channelTabs.AddItem(channel);

                if (channel.Type == ChannelType.Public && !channel.Joined)
                {
                    var req = new JoinChannelRequest(channel, api.LocalUser);
                    req.Success += () => addChannel(channel);
                    req.Failure += ex => removeChannel(channel);
                    api.Queue(req);
                    return;
                }
            }

            // let's fetch a small number of messages to bring us up-to-date with the backlog.
            fetchInitialMessages(channel);

            if (CurrentChannel == null)
                CurrentChannel = channel;

            channel.Joined.Value = true;
        }

        private void removeChannel(Channel channel)
        {
            if (channel == null) return;

            if (channel == CurrentChannel) CurrentChannel = null;

            careChannels.Remove(channel);
            loadedChannels.Remove(loadedChannels.Find(c => c.Channel == channel));
            channelTabs.RemoveItem(channel);

            api.Queue(new LeaveChannelRequest(channel, api.LocalUser));
            channel.Joined.Value = false;
        }

        private void fetchInitialMessages(Channel channel)
        {
            var req = new GetMessagesRequest(channel);
            req.Success += messages =>
            {
                channel.AddNewMessages(messages.ToArray());
                if (channel == currentChannel)
                    loading.Hide();
            };

            api.Queue(req);
        }

        private void fetchUpdates()
        {
            if (fetchReq != null) return;

            fetchReq = new GetUpdatesRequest(lastMessageId);

            fetchReq.Success += updates =>
            {
                if (updates?.Presence != null)
                {
                    foreach (var channel in updates.Presence)
                    {
                        if (careChannels.Find(c => c.Id == channel.Id) == null)
                        {
                            channel.Joined.Value = true;
                            addChannel(channel);
                        }
                    }

                    foreach (var group in updates.Messages.GroupBy(m => m.ChannelId))
                        careChannels.Find(c => c.Id == group.Key)?.AddNewMessages(group.ToArray());

                    lastMessageId = updates.Messages.LastOrDefault()?.Id ?? lastMessageId;
                }

                fetchReq = null;
            };

            fetchReq.Failure += delegate
            {
                fetchReq = null;
            };

            api.Queue(fetchReq);
        }

        private void postMessage(TextBox textbox, bool newText)
        {
            var postText = textbox.Text;

            textbox.Text = string.Empty;

            if (string.IsNullOrWhiteSpace(postText))
                return;

            var target = currentChannel;

            if (target == null) return;

            if (!api.IsLoggedIn)
            {
                target.AddNewMessages(new ErrorMessage("Please sign in to participate in chat!"));
                return;
            }

            bool isAction = false;

            if (postText[0] == '/')
            {
                string[] parameters = postText.Substring(1).Split(new[] { ' ' }, 2);
                string command = parameters[0];
                string content = parameters.Length == 2 ? parameters[1] : string.Empty;

                switch (command)
                {
                    case "me":

                        if (string.IsNullOrWhiteSpace(content))
                        {
                            currentChannel.AddNewMessages(new ErrorMessage("Usage: /me [action]"));
                            return;
                        }

                        isAction = true;
                        postText = content;
                        break;

                    case "help":
                        currentChannel.AddNewMessages(new InfoMessage("Supported commands: /help, /me [action]"));
                        return;

                    default:
                        currentChannel.AddNewMessages(new ErrorMessage($@"""/{command}"" is not supported! For a list of supported commands see /help"));
                        return;
                }
            }

            var message = new LocalEchoMessage
            {
                Sender = api.LocalUser.Value,
                Timestamp = DateTimeOffset.Now,
                ChannelId = target.Id,
                IsAction = isAction,
                Content = postText
            };

            var req = new PostMessageRequest(message);

            target.AddLocalEcho(message);
            req.Failure += e => target.ReplaceMessage(message, null);
            req.Success += m => target.ReplaceMessage(message, m);

            api.Queue(req);
        }

        private class TabsArea : Container
        {
            // IsHovered is used
            public override bool HandlePositionalInput => true;

            public TabsArea()
            {
                Name = @"tabs area";
                RelativeSizeAxes = Axes.X;
                Height = TAB_AREA_HEIGHT;
            }
        }
    }
}