tbd-station-14/Content.Client/Explosion/ExplosionOverlay.cs

using JetBrains.Annotations;
using Robust.Client.Graphics;
using Robust.Shared.Enums;
using Robust.Shared.Map;
using Robust.Shared.Prototypes;
using Robust.Shared.Random;

namespace Content.Client.Explosion;

[UsedImplicitly]
public sealed class ExplosionOverlay : Overlay
{
    /// <summary>
    ///     The explosion that needs to be drawn. This explosion is currently being processed by the server and
    ///     expanding outwards.
    /// </summary>
    internal Explosion? ActiveExplosion;

    /// <summary>
    ///     This index specifies what parts of the currently expanding explosion should be drawn.
    /// </summary>
    public int Index;

    /// <summary>
    ///     These explosions have finished expanding, but we will draw for a few more frames. This is important for
    ///     small explosions, as otherwise they disappear far too quickly.
    /// </summary>
    internal List<Explosion> CompletedExplosions = new ();

    [Dependency] private readonly IEyeManager _eyeManager = default!;
    [Dependency] private readonly IRobustRandom _robustRandom = default!;
    [Dependency] private readonly IMapManager _mapManager = default!;

    public override OverlaySpace Space => OverlaySpace.WorldSpaceBelowFOV;

    /// <summary>
    ///     How intense does the explosion have to be at a tile to advance to the next fire texture state?
    /// </summary>
    public const int IntensityPerState = 12;

    private ShaderInstance _shader;

    public ExplosionOverlay()
    {
        IoCManager.InjectDependencies(this);
        _shader = IoCManager.Resolve<IPrototypeManager>().Index<ShaderPrototype>("unshaded").Instance();
    }

    protected override void Draw(in OverlayDrawArgs args)
    {
        var drawHandle = args.WorldHandle;
        drawHandle.UseShader(_shader);

        if (ActiveExplosion != null)
        {
            DrawExplosion(drawHandle, args.WorldBounds, ActiveExplosion, Index);
        }

        foreach (var exp in CompletedExplosions)
        {
            DrawExplosion(drawHandle, args.WorldBounds, exp, exp.Intensity.Count);
        }

        drawHandle.SetTransform(Matrix3.Identity);
    }

    private void DrawExplosion(DrawingHandleWorld drawHandle, Box2Rotated worldBounds, Explosion exp, int index)
    {
        if (exp.Map != _eyeManager.CurrentMap)
            return;

        Box2 gridBounds;
        foreach (var (gridId, tiles) in exp.Tiles)
        {
            if (!_mapManager.TryGetGrid(gridId, out var grid))
                continue;

            gridBounds = grid.InvWorldMatrix.TransformBox(worldBounds);
            drawHandle.SetTransform(grid.WorldMatrix);

            DrawTiles(drawHandle, gridBounds, index, tiles, exp);
        }

        if (exp.SpaceTiles == null)
            return;

        gridBounds = Matrix3.Invert(exp.SpaceMatrix).TransformBox(worldBounds);
        drawHandle.SetTransform(exp.SpaceMatrix);
        
        DrawTiles(drawHandle, gridBounds, index, exp.SpaceTiles, exp);
    }

    private void DrawTiles(
        DrawingHandleWorld drawHandle,
        Box2 gridBounds,
        int index,
        Dictionary<int, List<Vector2i>> tileSets,
        Explosion exp)
    {
        for (var j = 0; j < index; j++)
        {
            if (!tileSets.TryGetValue(j, out var tiles))
                continue;

            var frameIndex = (int) Math.Min(exp.Intensity[j] / IntensityPerState, exp.FireFrames.Count - 1);
            var frames = exp.FireFrames[frameIndex];

            foreach (var tile in tiles)
            {
                Vector2 bottomLeft = (tile.X, tile.Y);

                if (!gridBounds.Contains((bottomLeft + 0.5f) * 1f))
                    continue;

                var texture = _robustRandom.Pick(frames);
                drawHandle.DrawTexture(texture, bottomLeft, exp.FireColor);
            }
        }
    }
}