// 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.

#nullable enable

using System;
using System.Diagnostics;
using System.Linq;
using osu.Framework.Allocation;
using osu.Framework.Configuration;
using osu.Framework.Extensions.Color4Extensions;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Colour;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Effects;
using osu.Framework.Graphics.Shapes;
using osu.Framework.Graphics.Sprites;
using osu.Framework.Input.Events;
using osu.Framework.Platform;
using osu.Framework.Platform.Windows;
using osu.Framework.Screens;
using osu.Framework.Utils;
using osu.Game.Graphics;
using osu.Game.Graphics.Containers;
using osu.Game.Graphics.Sprites;
using osu.Game.Overlays;
using osuTK;
using osuTK.Input;

namespace osu.Game.Screens.Utility
{
    public class LatencyComparerScreen : OsuScreen
    {
        private FrameSync previousFrameSyncMode;
        private double previousActiveHz;

        private readonly OsuTextFlowContainer statusText;

        public override bool HideOverlaysOnEnter => true;

        public override bool CursorVisible => mainArea.Count == 0;

        public override float BackgroundParallaxAmount => 0;

        private readonly OsuTextFlowContainer explanatoryText;

        private readonly Container<LatencyArea> mainArea;

        private readonly Container resultsArea;

        /// <summary>
        /// The rate at which the game host should attempt to run.
        /// </summary>
        private const int target_host_update_frames = 4000;

        [Cached]
        private readonly OverlayColourProvider overlayColourProvider = new OverlayColourProvider(OverlayColourScheme.Orange);

        [Resolved]
        private OsuColour colours { get; set; } = null!;

        [Resolved]
        private FrameworkConfigManager config { get; set; } = null!;

        private const int rounds_to_complete = 5;

        private const int rounds_to_complete_certified = 20;

        private int round;
        private int correctCount;
        private int targetRoundCount = rounds_to_complete;

        private int difficultyLevel = 1;

        private double lastPoll;
        private int pollingMax;

        [Resolved]
        private GameHost host { get; set; } = null!;

        public LatencyComparerScreen()
        {
            InternalChildren = new Drawable[]
            {
                new Box
                {
                    Colour = overlayColourProvider.Background6,
                    RelativeSizeAxes = Axes.Both,
                },
                mainArea = new Container<LatencyArea>
                {
                    RelativeSizeAxes = Axes.Both,
                },
                // Make sure the edge between the two comparisons can't be used to ascertain latency.
                new Box
                {
                    Name = "separator",
                    Colour = ColourInfo.GradientHorizontal(overlayColourProvider.Background6, overlayColourProvider.Background6.Opacity(0)),
                    Width = 100,
                    RelativeSizeAxes = Axes.Y,
                    Anchor = Anchor.TopCentre,
                    Origin = Anchor.TopLeft,
                },
                new Box
                {
                    Name = "separator",
                    Colour = ColourInfo.GradientHorizontal(overlayColourProvider.Background6.Opacity(0), overlayColourProvider.Background6),
                    Width = 100,
                    RelativeSizeAxes = Axes.Y,
                    Anchor = Anchor.TopCentre,
                    Origin = Anchor.TopRight,
                },
                explanatoryText = new OsuTextFlowContainer(cp => cp.Font = OsuFont.Default.With(size: 20))
                {
                    Anchor = Anchor.BottomCentre,
                    Origin = Anchor.BottomCentre,
                    TextAnchor = Anchor.TopCentre,
                    RelativeSizeAxes = Axes.X,
                    AutoSizeAxes = Axes.Y,
                    Text = @"Welcome to the latency comparer!
Use the arrow keys, Z/X/J/K to move the square.
You can click the targets but you don't have to.
Use the Tab key to change focus.
Do whatever you need to try and perceive the difference in latency, then choose your best side.
",
                },
                resultsArea = new Container
                {
                    RelativeSizeAxes = Axes.Both,
                },
                statusText = new OsuTextFlowContainer(cp => cp.Font = OsuFont.Default.With(size: 40))
                {
                    Anchor = Anchor.TopCentre,
                    Origin = Anchor.TopCentre,
                    TextAnchor = Anchor.TopCentre,
                    Y = 150,
                    RelativeSizeAxes = Axes.X,
                    AutoSizeAxes = Axes.Y,
                },
            };
        }

        protected override bool OnMouseMove(MouseMoveEvent e)
        {
            if (lastPoll > 0)
                pollingMax = (int)Math.Max(pollingMax, 1000 / (Clock.CurrentTime - lastPoll));
            lastPoll = Clock.CurrentTime;
            return base.OnMouseMove(e);
        }

        public override void OnEntering(ScreenTransitionEvent e)
        {
            base.OnEntering(e);

            previousFrameSyncMode = config.Get<FrameSync>(FrameworkSetting.FrameSync);
            previousActiveHz = host.UpdateThread.ActiveHz;
            config.SetValue(FrameworkSetting.FrameSync, FrameSync.Unlimited);
            host.UpdateThread.ActiveHz = target_host_update_frames;
            // host.AllowBenchmarkUnlimitedFrames = true;
        }

        public override bool OnExiting(ScreenExitEvent e)
        {
            // host.AllowBenchmarkUnlimitedFrames = false;
            config.SetValue(FrameworkSetting.FrameSync, previousFrameSyncMode);
            host.UpdateThread.ActiveHz = previousActiveHz;
            return base.OnExiting(e);
        }

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

        protected override bool OnKeyDown(KeyDownEvent e)
        {
            switch (e.Key)
            {
                case Key.Tab:
                    var firstArea = mainArea.FirstOrDefault(a => !a.IsActiveArea.Value);
                    if (firstArea != null)
                        firstArea.IsActiveArea.Value = true;
                    return true;
            }

            return base.OnKeyDown(e);
        }

        private void showResults()
        {
            mainArea.Clear();

            var displayMode = host.Window.CurrentDisplayMode.Value;

            string exclusive = "unknown";

            if (host.Window is WindowsWindow windowsWindow)
                exclusive = windowsWindow.FullscreenCapability.ToString();

            statusText.Clear();

            float successRate = (float)correctCount / targetRoundCount;
            bool isPass = successRate == 1;

            statusText.AddParagraph($"You scored {correctCount} out of {targetRoundCount} ({successRate:0%})!", cp => cp.Colour = isPass ? colours.Green : colours.Red);
            statusText.AddParagraph($"Level {difficultyLevel} ({mapDifficultyToTargetFrameRate(difficultyLevel):N0} hz)",
                cp => cp.Font = OsuFont.Default.With(size: 24));

            statusText.AddParagraph(string.Empty);
            statusText.AddParagraph(string.Empty);
            statusText.AddIcon(isPass ? FontAwesome.Regular.CheckCircle : FontAwesome.Regular.TimesCircle, cp => cp.Colour = isPass ? colours.Green : colours.Red);
            statusText.AddParagraph(string.Empty);

            if (!isPass && difficultyLevel > 1)
            {
                statusText.AddParagraph("To complete certification, decrease the difficulty level until you can get 20 tests correct in a row!", cp => cp.Font = OsuFont.Default.With(size: 24));
                statusText.AddParagraph(string.Empty);
            }

            statusText.AddParagraph($"Polling: {pollingMax} hz Monitor: {displayMode.RefreshRate:N0} hz Exclusive: {exclusive}", cp => cp.Font = OsuFont.Default.With(size: 15));

            statusText.AddParagraph($"Input: {host.InputThread.Clock.FramesPerSecond} hz "
                                    + $"Update: {host.UpdateThread.Clock.FramesPerSecond} hz "
                                    + $"Draw: {host.DrawThread.Clock.FramesPerSecond} hz"
                , cp => cp.Font = OsuFont.Default.With(size: 15));

            int certificationRemaining = !isPass ? rounds_to_complete_certified : rounds_to_complete_certified - correctCount;

            if (isPass && certificationRemaining <= 0)
            {
                Drawable background;
                Drawable certifiedText;

                resultsArea.AddRange(new[]
                {
                    background = new Box
                    {
                        Colour = overlayColourProvider.Background4,
                        RelativeSizeAxes = Axes.Both,
                    },
                    (certifiedText = new OsuSpriteText
                    {
                        Alpha = 0,
                        Font = OsuFont.TorusAlternate.With(size: 80, weight: FontWeight.Bold),
                        Text = "Certified!",
                        Blending = BlendingParameters.Additive,
                    }).WithEffect(new GlowEffect
                    {
                        Colour = overlayColourProvider.Colour1,
                    }).With(e =>
                    {
                        e.Anchor = Anchor.Centre;
                        e.Origin = Anchor.Centre;
                    })
                });

                background.FadeInFromZero(1000, Easing.OutQuint);

                certifiedText.FadeInFromZero(500, Easing.InQuint);

                certifiedText
                    .ScaleTo(10)
                    .ScaleTo(1, 600, Easing.InQuad)
                    .Then()
                    .ScaleTo(1.05f, 10000, Easing.OutQuint);
                return;
            }

            string cannotIncreaseReason = string.Empty;

            if (!isPass)
                cannotIncreaseReason = "You didn't get a perfect score.";
            else if (mapDifficultyToTargetFrameRate(difficultyLevel + 1) > target_host_update_frames)
                cannotIncreaseReason = "You've reached the limits of this comparison mode.";
            else if (mapDifficultyToTargetFrameRate(difficultyLevel + 1) > Clock.FramesPerSecond)
                cannotIncreaseReason = "Game is not running fast enough to test this level";

            resultsArea.Add(new FillFlowContainer
            {
                RelativeSizeAxes = Axes.X,
                AutoSizeAxes = Axes.Y,
                Anchor = Anchor.BottomLeft,
                Origin = Anchor.BottomLeft,
                Spacing = new Vector2(20),
                Padding = new MarginPadding(20),
                Children = new Drawable[]
                {
                    new ButtonWithKeyBind(Key.Enter)
                    {
                        Text = "Continue to next level",
                        BackgroundColour = colours.Red2,
                        Anchor = Anchor.Centre,
                        Origin = Anchor.Centre,
                        Action = () => changeDifficulty(difficultyLevel + 1),
                        Enabled = { Value = string.IsNullOrEmpty(cannotIncreaseReason) },
                        TooltipText = cannotIncreaseReason
                    },
                    new ButtonWithKeyBind(Key.D)
                    {
                        Text = difficultyLevel == 1 ? "Retry" : "Return to last level",
                        BackgroundColour = colours.Green,
                        Anchor = Anchor.Centre,
                        Origin = Anchor.Centre,
                        Action = () => changeDifficulty(Math.Max(difficultyLevel - 1, 1)),
                    },
                    new ButtonWithKeyBind(Key.C)
                    {
                        Text = $"Continue towards certification at this level ({certificationRemaining} more)",
                        Anchor = Anchor.Centre,
                        Origin = Anchor.Centre,
                        Action = () =>
                        {
                            resultsArea.Clear();
                            targetRoundCount += rounds_to_complete;
                            loadNextRound();
                        },
                        TooltipText = isPass ? $"Chain {rounds_to_complete_certified} to confirm your perception!" : "You've reached your limits. Go to the previous level to complete certification!",
                        Enabled = { Value = isPass },
                    },
                }
            });
        }

        private void changeDifficulty(int difficulty)
        {
            Debug.Assert(difficulty > 0);

            resultsArea.Clear();

            correctCount = 0;
            round = 0;
            pollingMax = 0;
            lastPoll = 0;

            targetRoundCount = rounds_to_complete;
            difficultyLevel = difficulty;

            loadNextRound();
        }

        private void loadNextRound()
        {
            round++;
            statusText.Text = $"Level {difficultyLevel}\nRound {round} of {targetRoundCount}";

            mainArea.Clear();

            int betterSide = RNG.Next(0, 2);

            mainArea.AddRange(new[]
            {
                new LatencyArea(Key.Number1, betterSide == 1 ? mapDifficultyToTargetFrameRate(difficultyLevel) : 0)
                {
                    Width = 0.5f,
                    IsActiveArea = { Value = true },
                    ReportUserBest = () => recordResult(betterSide == 0),
                },
                new LatencyArea(Key.Number2, betterSide == 0 ? mapDifficultyToTargetFrameRate(difficultyLevel) : 0)
                {
                    Width = 0.5f,
                    Anchor = Anchor.TopRight,
                    Origin = Anchor.TopRight,
                    ReportUserBest = () => recordResult(betterSide == 1)
                }
            });

            foreach (var area in mainArea)
            {
                area.IsActiveArea.BindValueChanged(active =>
                {
                    if (active.NewValue)
                        mainArea.Children.First(a => a != area).IsActiveArea.Value = false;
                });
            }
        }

        private void recordResult(bool correct)
        {
            // Fading this out will improve the frame rate after the first round due to less text on screen.
            explanatoryText.FadeOut(500, Easing.OutQuint);

            if (correct)
                correctCount++;

            if (round < targetRoundCount)
                loadNextRound();
            else
                showResults();
        }

        private static int mapDifficultyToTargetFrameRate(int difficulty)
        {
            switch (difficulty)
            {
                case 1:
                    return 15;

                case 2:
                    return 30;

                case 3:
                    return 45;

                case 4:
                    return 60;

                case 5:
                    return 120;

                case 6:
                    return 240;

                case 7:
                    return 480;

                case 8:
                    return 720;

                case 9:
                    return 960;

                default:
                    return 1000 + ((difficulty - 10) * 500);
            }
        }
    }
}