// Copyright (c) 2007-2017 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.Diagnostics;
using System.Linq;
using OpenTK.Graphics;
using osu.Framework.Allocation;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Game.Graphics.Containers;
using osu.Game.Online.Chat;

namespace osu.Game.Overlays.Chat
{
    public class DrawableChannel : Container
    {
        private class ChatLineContainer : FillFlowContainer<ChatLine>
        {
            protected override int Compare(Drawable x, Drawable y)
            {
                var xC = (ChatLine)x;
                var yC = (ChatLine)y;

                return xC.Message.CompareTo(yC.Message);
            }
        }

        public readonly Channel Channel;
        private readonly ChatLineContainer flow;
        private readonly ScrollContainer scroll;

        public DrawableChannel(Channel channel)
        {
            Channel = channel;

            RelativeSizeAxes = Axes.Both;

            Children = new Drawable[]
            {
                scroll = new OsuScrollContainer
                {
                    RelativeSizeAxes = Axes.Both,
                    // Some chat lines have effects that slightly protrude to the bottom,
                    // which we do not want to mask away, hence the padding.
                    Padding = new MarginPadding { Bottom = 5 },
                    Child = flow = new ChatLineContainer
                    {
                        Padding = new MarginPadding { Left = 20, Right = 20 },
                        RelativeSizeAxes = Axes.X,
                        AutoSizeAxes = Axes.Y,
                        Direction = FillDirection.Vertical,
                    },
                }
            };

            Channel.NewMessagesArrived += newMessagesArrived;
            Channel.MessageRemoved += messageRemoved;
            Channel.PendingMessageResolved += pendingMessageResolved;
        }

        [BackgroundDependencyLoader]
        private void load()
        {
            newMessagesArrived(Channel.Messages);
        }

        protected override void LoadComplete()
        {
            base.LoadComplete();
            scrollToEnd();
        }

        protected override void Dispose(bool isDisposing)
        {
            base.Dispose(isDisposing);

            Channel.NewMessagesArrived -= newMessagesArrived;
            Channel.MessageRemoved -= messageRemoved;
            Channel.PendingMessageResolved -= pendingMessageResolved;
        }

        private void newMessagesArrived(IEnumerable<Message> newMessages)
        {
            // Add up to last Channel.MAX_HISTORY messages
            var displayMessages = newMessages.Skip(Math.Max(0, newMessages.Count() - Channel.MAX_HISTORY));

            flow.AddRange(displayMessages.Select(m => new ChatLine(m)));

            if (!IsLoaded) return;

            if (scroll.IsScrolledToEnd(10) || !flow.Children.Any())
                scrollToEnd();

            var staleMessages = flow.Children.Where(c => c.LifetimeEnd == double.MaxValue).ToArray();
            int count = staleMessages.Length - Channel.MAX_HISTORY;

            for (int i = 0; i < count; i++)
            {
                var d = staleMessages[i];
                if (!scroll.IsScrolledToEnd(10))
                    scroll.OffsetScrollPosition(-d.DrawHeight);
                d.Expire();
            }
        }

        private void pendingMessageResolved(Message existing, Message updated)
        {
            var found = flow.Children.LastOrDefault(c => c.Message == existing);
            if (found != null)
            {
                Trace.Assert(updated.Id.HasValue, "An updated message was returned with no ID.");

                flow.Remove(found);
                found.Message = updated;
                flow.Add(found);
            }
        }

        private void messageRemoved(Message removed)
        {
            flow.Children.FirstOrDefault(c => c.Message == removed)?.FadeColour(Color4.Red, 400).FadeOut(600).Expire();
        }

        private void scrollToEnd() => ScheduleAfterChildren(() => scroll.ScrollToEnd());
    }
}