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

using Content.Shared.CCVar;
using Content.Shared.Explosion;
using Content.Shared.GameTicking;
using Robust.Client.GameObjects;
using Robust.Client.Graphics;
using Robust.Client.ResourceManagement;
using Robust.Shared.Configuration;
using Robust.Shared.Map;
using Robust.Shared.Prototypes;

namespace Content.Client.Explosion;

/// <summary>
///     This system is responsible for showing the client-side explosion effects (light source & fire-overlay). The
///     fire overlay code is just a bastardized version of the atmos plasma fire overlay and uses the same texture.
/// </summary>
public sealed class ExplosionOverlaySystem : EntitySystem
{
    private ExplosionOverlay _overlay = default!;

    [Dependency] private readonly IPrototypeManager _protoMan = default!;
    [Dependency] private readonly IMapManager _mapMan = default!;
    [Dependency] private readonly IResourceCache _resCache = default!;
    [Dependency] private readonly IConfigurationManager _cfg = default!;

    /// <summary>
    ///     For how many seconds should an explosion stay on-screen once it has finished expanding?
    /// </summary>
    public float ExplosionPersistence = 0.3f;

    public override void Initialize()
    {
        base.Initialize();

        SubscribeNetworkEvent<ExplosionEvent>(OnExplosion);
        SubscribeNetworkEvent<ExplosionOverlayUpdateEvent>(HandleExplosionUpdate);
        SubscribeLocalEvent<MapChangedEvent>(OnMapChanged);
        SubscribeAllEvent<RoundRestartCleanupEvent>(OnReset);

        _cfg.OnValueChanged(CCVars.ExplosionPersistence, SetExplosionPersistence, true);

        var overlayManager = IoCManager.Resolve<IOverlayManager>();
        _overlay = new ExplosionOverlay();
        if (!overlayManager.HasOverlay<ExplosionOverlay>())
            overlayManager.AddOverlay(_overlay);
    }

    private void OnReset(RoundRestartCleanupEvent ev)
    {
        // Not sure if round restart cleans up client-side entities, but better safe than sorry.
        foreach (var exp in _overlay.CompletedExplosions)
        {
            QueueDel(exp.LightEntity);
        }
        if (_overlay.ActiveExplosion != null)
            QueueDel(_overlay.ActiveExplosion.LightEntity);
        
        _overlay.CompletedExplosions.Clear();
        _overlay.ActiveExplosion = null;
        _overlay.Index = 0;
    }

    private void OnMapChanged(MapChangedEvent ev)
    {
        if (ev.Created)
            return;

        if (_overlay.ActiveExplosion?.Map == ev.Map)
            _overlay.ActiveExplosion = null;

        _overlay.CompletedExplosions.RemoveAll(exp => exp.Map == ev.Map);
    }

    private void SetExplosionPersistence(float value) => ExplosionPersistence = value;

    public override void FrameUpdate(float frameTime)
    {
        base.FrameUpdate(frameTime);

        // increment the lifetime of completed explosions, and remove them if they have been ons screen for more
        // than ExplosionPersistence seconds
        for (int i = _overlay.CompletedExplosions.Count - 1; i>= 0; i--) 
        {
            var explosion = _overlay.CompletedExplosions[i];

            if (_mapMan.IsMapPaused(explosion.Map))
                continue;

            explosion.Lifetime += frameTime;

            if (explosion.Lifetime >= ExplosionPersistence)
            {
                EntityManager.QueueDeleteEntity(explosion.LightEntity);

                // Remove-swap
                _overlay.CompletedExplosions[i] = _overlay.CompletedExplosions[^1];
                _overlay.CompletedExplosions.RemoveAt(_overlay.CompletedExplosions.Count - 1);
            }
        }
    }

    /// <summary>
    ///     The server has processed some explosion. This updates the client-side overlay so that the area covered
    ///     by the fire-visual matches up with the area that the explosion has affected.
    /// </summary>
    private void HandleExplosionUpdate(ExplosionOverlayUpdateEvent args)
    {
        if (args.ExplosionId != _overlay.ActiveExplosion?.Explosionid && !IsNewer(args.ExplosionId))
        {
            // out of order events. Ignore.
            return;
        }

        _overlay.Index = args.Index;

        if (_overlay.ActiveExplosion == null)
        {
            // no active explosion... events out of order?
            return;
        }

        if (args.Index != int.MaxValue)
            return;

        // the explosion has finished expanding
        _overlay.Index = 0;
        _overlay.CompletedExplosions.Add(_overlay.ActiveExplosion);
        _overlay.ActiveExplosion = null;
    }

    /// <summary>
    ///     A new explosion occurred. This prepares the client-side light entity and stores the
    ///     explosion/fire-effect overlay data.
    /// </summary>
    private void OnExplosion(ExplosionEvent args)
    {
        if (!_protoMan.TryIndex(args.TypeID, out ExplosionPrototype? type))
            return;

        // spawn in a light source at the epicenter
        var lightEntity = Spawn("ExplosionLight", args.Epicenter);
        var light = EnsureComp<PointLightComponent>(lightEntity);
        light.Energy = light.Radius = args.Intensity.Count;
        light.Color = type.LightColor;

        if (_overlay.ActiveExplosion == null)
        {
            _overlay.ActiveExplosion = new(args, type, lightEntity, _resCache);
            return;
        }

        // we have a currently active explosion. Can happen when events are received out of order. either multiple
        // explosions are happening in one tick, or a new explosion was received before the event telling us the old one
        // finished got through.

        if (IsNewer(args.ExplosionId))
        {
            // This is a newer explosion. Add the old-currently-active explosions to the completed list
            _overlay.CompletedExplosions.Add(_overlay.ActiveExplosion);
            _overlay.ActiveExplosion = new(args, type, lightEntity, _resCache);
        }
        else
        {
            // explosions were out of order. keep the active one, and directly add the received one to the completed
            // list.
            _overlay.CompletedExplosions.Add(new(args, type, lightEntity, _resCache));
            return;
        }
    }

    public bool IsNewer(int explosionId)
    {
        if (_overlay.ActiveExplosion == null)
            return true;

        // If we ever get servers stable enough to live this long, the explosion Id int might overflow.
        return _overlay.ActiveExplosion.Explosionid < explosionId
            || _overlay.ActiveExplosion.Explosionid > int.MaxValue/2 && explosionId < int.MinValue/2;
    }

    public override void Shutdown()
    {
        base.Shutdown();

        _cfg.UnsubValueChanged(CCVars.ExplosionPersistence, SetExplosionPersistence);

        var overlayManager = IoCManager.Resolve<IOverlayManager>();
        if (overlayManager.HasOverlay<ExplosionOverlay>())
            overlayManager.RemoveOverlay<ExplosionOverlay>();
    }
}

internal sealed class Explosion
{
    public readonly Dictionary<int, List<Vector2i>>? SpaceTiles;
    public readonly Dictionary<EntityUid, Dictionary<int, List<Vector2i>>> Tiles;
    public readonly List<float> Intensity;
    public readonly EntityUid LightEntity;
    public readonly MapId Map;
    public readonly int Explosionid;
    public readonly ushort SpaceTileSize;
    public readonly float IntensityPerState;

    public readonly Matrix3 SpaceMatrix;

    /// <summary>
    ///     How long have we been drawing this explosion, starting from the time the explosion was fully drawn.
    /// </summary>
    public float Lifetime;

    /// <summary>
    ///     The textures used for the explosion fire effect. Each fire-state is associated with an explosion
    ///     intensity range, and each stat itself has several textures.
    /// </summary>
    public readonly List<Texture[]> FireFrames = new();

    public readonly Color? FireColor;

    internal Explosion(ExplosionEvent args, ExplosionPrototype type, EntityUid lightEntity, IResourceCache resCache)
    {
        Map = args.Epicenter.MapId;
        SpaceTiles = args.SpaceTiles;
        Tiles = args.Tiles;
        Intensity = args.Intensity;
        SpaceMatrix = args.SpaceMatrix;
        Explosionid = args.ExplosionId;
        FireColor = type.FireColor;
        LightEntity = lightEntity;
        SpaceTileSize = args.SpaceTileSize;
        IntensityPerState = type.IntensityPerState;

        var fireRsi = resCache.GetResource<RSIResource>(type.TexturePath).RSI;
        foreach (var state in fireRsi)
        {
            FireFrames.Add(state.GetFrames(RSI.State.Direction.South));
            if (FireFrames.Count == type.FireStates)
                break;
        }
    }
}