mrgameeng/src/MrGameEng.UI/EcsInspectorUi.cs

using System;
using Microsoft.Xna.Framework;
using MrGameEng.Graphics;
using Myra.Graphics2D;
using Myra.Graphics2D.Brushes;
using Myra.Graphics2D.UI;

namespace MrGameEng.Inspector;

/// <summary>
/// Myra overlay of the ECS inspector — a Chrome-DevTools-style side panel. The top bar switches the
/// Entities/Performance tabs and arms world-pick; the Entities tab shows archetypes → entities →
/// the selected entity's components and editable fields; the Performance tab shows renderer
/// timings. A thin border tracks the selected entity in the world each frame. Rebuilds lazily on
/// <see cref="EcsInspector.ListRevision"/>/<see cref="EcsInspector.DetailRevision"/> changes.
/// </summary>
internal sealed class EcsInspectorUi
{
    private const int PanelWidth = 540;
    private static readonly Color Accent = new(120, 200, 255);

    private readonly EcsInspector _inspector;
    private readonly Renderer2D _renderer;
    private readonly Desktop _desktop;

    private readonly VerticalStackPanel _archetypeList = Stack();
    private readonly VerticalStackPanel _entityList = Stack();
    private readonly VerticalStackPanel _detailList = Stack();
    private readonly Label _stats = new();
    private readonly Label _perf = new() { Wrap = false };
    private readonly Label _pickLabel = new() { Text = "Pick" };
    private readonly Widget _entitiesSection;
    private readonly Panel _highlight;
    private readonly VerticalStackPanel _panel;

    private int _lastListRevision = -1;
    private int _lastDetailRevision = -1;

    public EcsInspectorUi(EcsInspector inspector, Renderer2D renderer)
    {
        _inspector = inspector;
        _renderer = renderer;

        var tabEntities = MakeButton("Entities", () => _inspector.SetTab(InspectorTab.Entities));
        var tabPerf = MakeButton("Performance", () => _inspector.SetTab(InspectorTab.Performance));
        var pick = new Button { Content = _pickLabel };
        pick.Click += (_, _) => _inspector.ArmPick(!_inspector.PickArmed);

        var search = new TextBox { HintText = "filter components", Width = 160 };
        search.TextChanged += (_, _) => _inspector.SetSearch(search.Text ?? "");

        var bar = new HorizontalStackPanel { Spacing = 6 };
        bar.Widgets.Add(tabEntities);
        bar.Widgets.Add(tabPerf);
        bar.Widgets.Add(pick);
        bar.Widgets.Add(search);

        _entitiesSection = BuildEntitiesSection();

        _panel = new VerticalStackPanel
        {
            Spacing = 6,
            Padding = new Thickness(8),
            Width = PanelWidth,
            HorizontalAlignment = HorizontalAlignment.Right,
            VerticalAlignment = VerticalAlignment.Stretch,
            Background = new SolidBrush(new Color(8, 10, 14, 235)),
        };
        _panel.Widgets.Add(bar);
        _panel.Widgets.Add(_stats);
        _panel.Widgets.Add(new HorizontalSeparator());
        _panel.Widgets.Add(_entitiesSection);
        _panel.Widgets.Add(_perf);

        _highlight = new Panel
        {
            Border = new SolidBrush(Accent),
            BorderThickness = new Thickness(2),
            Visible = false,
        };

        var root = new Panel();
        root.Widgets.Add(_highlight);
        root.Widgets.Add(_panel);
        _desktop = new Desktop { Root = root };
    }

    public void Render()
    {
        if (!_inspector.IsOpen)
        {
            return;
        }

        // Stats and perf are cheap text updates — refresh every frame so they stay live.
        var perf = _inspector.Performance();
        UpdateStats(perf);
        if (_inspector.ActiveTab == InspectorTab.Performance)
        {
            UpdatePerf(perf);
        }

        if (_inspector.ListRevision != _lastListRevision)
        {
            _lastListRevision = _inspector.ListRevision;
            RebuildLists();
        }

        if (_inspector.DetailRevision != _lastDetailRevision)
        {
            _lastDetailRevision = _inspector.DetailRevision;
            RebuildDetails();
        }

        UpdateHighlight();
        _desktop.Render();
    }

    /// <summary>True when the physical screen point is over the panel (so a pick click is ignored).</summary>
    public bool IsOverPanel(Point screen) => _panel.Bounds.Contains(screen);

    private Widget BuildEntitiesSection()
    {
        var section = new VerticalStackPanel { Spacing = 4 };
        section.Widgets.Add(Header("Archetypes"));
        section.Widgets.Add(new ScrollViewer { Content = _archetypeList, Height = 150 });
        section.Widgets.Add(Header("Entities"));
        section.Widgets.Add(new ScrollViewer { Content = _entityList, Height = 150 });
        section.Widgets.Add(Header("Selected"));
        section.Widgets.Add(new ScrollViewer { Content = _detailList, Height = 320 });
        return section;
    }

    private void RebuildLists()
    {
        var entitiesTab = _inspector.ActiveTab == InspectorTab.Entities;
        _entitiesSection.Visible = entitiesTab;
        _perf.Visible = !entitiesTab;
        _pickLabel.Text = _inspector.PickArmed ? "Pick*" : "Pick";

        if (entitiesTab)
        {
            RebuildArchetypes();
            RebuildEntities();
        }
    }

    private void UpdateStats(in PerfSnapshot perf)
    {
        _stats.Text =
            $"entities {perf.Entities} | archetypes {perf.Archetypes} | {perf.Fps} FPS"
            + (_inspector.PickArmed ? " | click an entity…" : "");
    }

    private void UpdatePerf(in PerfSnapshot perf)
    {
        _perf.Text =
            $"FPS         {perf.Fps}\n"
            + $"submit      {perf.SubmitMs:0.00} ms\n"
            + $"sort        {perf.SortMs:0.00} ms\n"
            + $"build       {perf.BuildMs:0.00} ms\n"
            + $"upload      {perf.UploadMs:0.00} ms\n"
            + $"draw        {perf.DrawMs:0.00} ms\n"
            + $"draw calls  {perf.DrawCalls}\n"
            + $"sprites     {perf.SubmittedSprites} drawn, {perf.CulledSprites} culled\n"
            + $"entities    {perf.Entities}";
    }

    private void RebuildArchetypes()
    {
        _archetypeList.Widgets.Clear();
        foreach (var row in _inspector.Archetypes())
        {
            var index = row.Index;
            var button = MakeButton(
                $"[{row.Count}] {row.Signature}",
                () => _inspector.SelectArchetype(index)
            );
            if (index == _inspector.SelectedArchetype)
            {
                Highlight(button);
            }

            _archetypeList.Widgets.Add(button);
        }
    }

    private void RebuildEntities()
    {
        _entityList.Widgets.Clear();
        if (_inspector.SelectedArchetype < 0)
        {
            return;
        }

        foreach (var id in _inspector.EntitiesOf(_inspector.SelectedArchetype))
        {
            var entityId = id;
            var button = MakeButton($"entity {id}", () => _inspector.SelectEntity(entityId));
            if (entityId == _inspector.SelectedEntityId)
            {
                Highlight(button);
            }

            _entityList.Widgets.Add(button);
        }
    }

    private void RebuildDetails()
    {
        _detailList.Widgets.Clear();
        if (_inspector.SelectedEntityId < 0)
        {
            return;
        }

        foreach (var component in _inspector.Inspect(_inspector.SelectedEntityId))
        {
            _detailList.Widgets.Add(new Label { Text = component.TypeName, TextColor = Accent });
            foreach (var field in component.Fields)
            {
                _detailList.Widgets.Add(BuildFieldRow(component.Type, field));
            }
        }
    }

    private Widget BuildFieldRow(Type componentType, FieldRow field)
    {
        var row = new HorizontalStackPanel { Spacing = 8 };
        row.Widgets.Add(
            new Label
            {
                Text = field.Name,
                Width = 140,
                TextColor = new Color(170, 178, 190),
            }
        );

        if (!field.Editable)
        {
            row.Widgets.Add(new Label { Text = field.Value, TextColor = new Color(150, 156, 168) });
            return row;
        }

        var editor = new TextBox
        {
            Text = field.Value,
            Width = 150,
            Padding = new Thickness(4, 2),
            Background = new SolidBrush(new Color(28, 33, 42)),
            Border = new SolidBrush(new Color(70, 82, 100)),
            BorderThickness = new Thickness(1),
        };
        var entityId = _inspector.SelectedEntityId;
        editor.KeyDown += (_, args) =>
        {
            if (args.Data == Microsoft.Xna.Framework.Input.Keys.Enter)
            {
                _inspector.SetField(entityId, componentType, field.Name, editor.Text ?? "");
            }
        };
        row.Widgets.Add(editor);
        if (field.Kind == FieldKind.Enum && field.EnumOptions is { Length: > 0 })
        {
            row.Widgets.Add(
                new Label
                {
                    Text = string.Join(" / ", field.EnumOptions),
                    TextColor = new Color(120, 128, 140),
                }
            );
        }

        return row;
    }

    private void UpdateHighlight()
    {
        if (!_inspector.TryGetSelectedBounds(out var center, out var radius))
        {
            _highlight.Visible = false;
            return;
        }

        var screenCenter = _renderer.WorldToScreen(center);
        var edge = _renderer.WorldToScreen(center + new Vector2(radius, 0f));
        var screenRadius = MathF.Max(4f, MathF.Abs(edge.X - screenCenter.X));
        _highlight.Visible = true;
        _highlight.Left = (int)(screenCenter.X - screenRadius);
        _highlight.Top = (int)(screenCenter.Y - screenRadius);
        _highlight.Width = (int)(screenRadius * 2f);
        _highlight.Height = (int)(screenRadius * 2f);
    }

    private static void Highlight(Button button)
    {
        if (button.Content is Label label)
        {
            label.TextColor = Accent;
        }
    }

    private static VerticalStackPanel Stack() => new() { Spacing = 2 };

    private static Label Header(string text) =>
        new() { Text = text, TextColor = new Color(150, 160, 175) };

    private static Button MakeButton(string text, Action onClick)
    {
        var button = new Button { Content = new Label { Text = text } };
        button.Click += (_, _) => onClick();
        return button;
    }
}