using System;
using System.Collections.Generic;
using System.Linq;
using Robust.Client.ResourceManagement;
using Robust.Client.UserInterface;
using Robust.Shared;
using Robust.Shared.Configuration;
using Robust.Shared.Console;
using Robust.Shared.IoC;
using Robust.Shared.Log;
using Robust.Shared.Maths;
using Robust.Shared.Timing;
using Stopwatch = Robust.Shared.Timing.Stopwatch;

namespace Robust.Client.Graphics;

internal interface ILoadingScreenManager
{
    void BeginLoadingSection(string sectionName);

    /// <summary>
    /// Start a loading bar "section" for the given method.
    /// Must be ended with EndSection.
    /// </summary>
    void BeginLoadingSection(object method);

    void EndLoadingSection();

    /// <summary>
    /// Will run the giving function and add a custom "section" for it on the loading screen.
    /// </summary>
    void LoadingStep(Action action, object method);
}

/// <summary>
/// Manager that creates and displays a basic splash screen and loading bar.
/// </summary>
internal sealed partial class LoadingScreenManager : ILoadingScreenManager
{
    [Dependency] private IResourceCache _resourceCache = default!;
    [Dependency] private IClydeInternal _clyde = default!;
    [Dependency] private IConfigurationManager _cfg = default!;
    [Dependency] private ILogManager _logManager = default!;

    private ISawmill _sawmill = default!;

    private readonly Stopwatch _sw = new();

    #region UI constants

    private const int LoadingBarWidth = 250;
    private const int LoadingBarHeight = 20;
    private const int LoadingBarOutlineOffset = 5;
    private static readonly Vector2i LogoLoadingBarOffset = (0, 20);
    private static readonly Vector2i LoadTimesIndent = (20, 0);

    private const int NumLongestLoadTimes = 5;

    private static readonly Color LoadingBarColor = Color.White;

    #endregion

    #region Cvars

    private string _splashLogo = "";
    private bool _showLoadingBar;
    private bool _showDebug;

    #endregion

    private const string FontLocation = "/EngineFonts/NotoSans/NotoSans-Regular.ttf";
    private const int FontSize = 11;
    private VectorFont? _font;

    // Number of loading sections for the loading bar. This has to be manually set!
    private int _numberOfLoadingSections;

    // The name of the section and how much time it took to load
    internal readonly List<(string Name, TimeSpan LoadTime)> Times = [];

    private int _currentSection;
    private string? _currentSectionName;

    private bool _currentlyInSection;
    private bool _finished;

    public void Initialize(int sections)
    {
        if (_finished)
            return;

        _clyde.VsyncEnabled = false;

        _numberOfLoadingSections = sections;

        _sawmill = _logManager.GetSawmill("loading");

        _splashLogo = _cfg.GetCVar(CVars.DisplaySplashLogo);
        _showLoadingBar = _cfg.GetCVar(CVars.LoadingShowBar);
        _showDebug = _cfg.GetCVar(CVars.LoadingShowDebug);

        if (_resourceCache.TryGetResource<FontResource>(FontLocation, out var fontResource))
            _font = new VectorFont(fontResource, FontSize);
        else
            _sawmill.Error($"Could not load font: {FontLocation}");
    }

    public void BeginLoadingSection(string sectionName) => BeginLoadingSection(sectionName, false);
    public void BeginLoadingSection(string sectionName, bool dontRender)
    {
        if (_finished)
            return;

        if (_currentlyInSection)
            throw new InvalidOperationException("You cannot begin more than one section at a time!");

        _currentlyInSection = true;

        _currentSectionName = sectionName;

        if (_clyde.IsInitialized)
        {
            _clyde.MainWindow.SetWindowProgress(
                WindowProgressState.Normal,
                _currentSection / (float)_numberOfLoadingSections);
        }

        if (!dontRender)
        {
            // This ensures that if the screen was resized or something the new size is properly updated to clyde.
            _clyde.ProcessInput(new FrameEventArgs((float)_sw.Elapsed.TotalSeconds));
            _sw.Restart();
            _clyde.Render();
        }
        else
        {
            _sw.Restart();
        }
    }

    /// <summary>
    /// Start a loading bar "section" for the given method.
    /// Must be ended with EndSection.
    /// </summary>
    public void BeginLoadingSection(object method)
    {
        if (_finished)
            return;

        BeginLoadingSection(method.GetType().Name);
    }

    public void EndLoadingSection()
    {
        if (_finished)
            return;

        var time = _sw.Elapsed;
        if (_currentSectionName != null)
            Times.Add((_currentSectionName, time));
        _currentSection++;
        _currentlyInSection = false;
    }

    /// <summary>
    /// Will run the giving function and add a custom "section" for it on the loading screen.
    /// </summary>
    public void LoadingStep(Action action, object method)
    {
        if (_finished)
            return;

        BeginLoadingSection(method as string ?? method.GetType().Name);
        action();
        EndLoadingSection();
    }

    public void Finish()
    {
        if (_finished)
            return;

        if (_currentSection != _numberOfLoadingSections)
            _sawmill.Error($"The number of seen loading sections isn't equal to the total number of loading sections! Seen: {_currentSection}, Total: {_numberOfLoadingSections}");

        _clyde.MainWindow.SetWindowProgress(WindowProgressState.None, 1);

        _finished = true;
    }

    #region Drawing functions

    /// <summary>
    /// Draw out the splash and loading screen.
    /// </summary>
    public void DrawLoadingScreen(IRenderHandle handle, Vector2i screenSize)
    {
        if (_finished)
            return;

        var scale = UserInterfaceManager.CalculateUIScale(_clyde.MainWindow.ContentScale.X, _cfg);

        // Start at the center!
        var location = screenSize / 2;

        DrawSplash(handle, ref location, scale);

        DrawLoadingBar(handle, ref location, scale);

        if (_showDebug)
        {
            DrawCurrentLoading(handle, ref location, scale);

            DrawTopTimes(handle, ref location, scale);
        }
    }

    private void DrawSplash(IRenderHandle handle, ref Vector2i startLocation, float scale)
    {
        if (string.IsNullOrEmpty(_splashLogo))
            return;

        if (!_resourceCache.TryGetResource<TextureResource>(_splashLogo, out var textureResource))
            return;

        var drawSize = textureResource.Texture.Size * scale;

        handle.DrawingHandleScreen.DrawTextureRect(textureResource.Texture, UIBox2.FromDimensions(startLocation - drawSize / 2, drawSize));
        startLocation += Vector2i.Up * (int)drawSize.Y / 2;
    }

    private void DrawLoadingBar(IRenderHandle handle, ref Vector2i location, float scale)
    {
        var barWidth = (int)(LoadingBarWidth * scale);
        var barHeight = (int)(LoadingBarHeight * scale);
        var outlineOffset = (int)(LoadingBarOutlineOffset * scale);

        // Always do the offsets, it looks a lot better!
        location.X -= barWidth / 2;
        location += (Vector2i)(LogoLoadingBarOffset * scale);

        if (!_showLoadingBar)
            return;

        var sectionWidth = barWidth / _numberOfLoadingSections;

        var barTopLeft = location;
        var barBottomRight = new Vector2i(_currentSection * sectionWidth % barWidth, barHeight);
        var barBottomRightMax = new Vector2i(barWidth, barHeight);

        var outlinePosition = barTopLeft + Vector2i.DownLeft * outlineOffset;
        var outlineSize = barBottomRightMax + Vector2i.UpRight * 2 * outlineOffset;

        // Outline
        handle.DrawingHandleScreen.DrawRect(UIBox2.FromDimensions(outlinePosition, outlineSize), LoadingBarColor, false);

        // Progress bar
        handle.DrawingHandleScreen.DrawRect(UIBox2.FromDimensions(barTopLeft, barBottomRight), LoadingBarColor);

        location += Vector2i.Up * outlineSize;
    }

    // Draw the currently loading section to the screen.
    private void DrawCurrentLoading(IRenderHandle handle, ref Vector2i location, float scale)
    {
        if (_font == null || _currentSectionName == null)
            return;

        handle.DrawingHandleScreen.DrawString(_font, location, _currentSectionName, scale, Color.White);
        location += Vector2i.Up * _font.GetLineHeight(scale);
    }

    // Draw the slowest loading times to the screen.
    private void DrawTopTimes(IRenderHandle handle, ref Vector2i location, float scale)
    {
        if (_font == null)
            return;

        location += (Vector2i)(LoadTimesIndent * scale);

        var offset = 0;
        var x = 0;
        Times.Sort((a, b) => b.LoadTime.CompareTo(a.LoadTime));

        foreach (var (name, time) in Times)
        {
            if (x >= NumLongestLoadTimes)
                break;

            var entry = $"{time.TotalSeconds:F2} - {name}";
            handle.DrawingHandleScreen.DrawString(_font, location + new Vector2i(0, offset), entry, scale, Color.White);
            offset += _font.GetLineHeight(scale);
            x++;
        }

        location += Vector2i.Up * offset;
    }

    #endregion // Drawing functions
}

internal sealed partial class ShowTopLoadingTimesCommand : IConsoleCommand
{
    [Dependency] private LoadingScreenManager _mgr = default!;

    public string Command => "loading_top";
    public string Description => "";
    public string Help => "";

    public void Execute(IConsoleShell shell, string argStr, string[] args)
    {
        var sorted = _mgr.Times.Where(x => x.LoadTime > TimeSpan.FromSeconds(0.01)).OrderByDescending(x => x.LoadTime);
        foreach (var (name, time) in sorted)
        {
            shell.WriteLine($"{time.TotalSeconds:F2} - {name}");
        }
    }
}