Delta-v/Content.Server/Xenoarchaeology/XenoArtifacts/Effects/Systems/DiseaseArtifactSystem.cs

using System.Linq;
using Content.Server.Xenoarchaeology.XenoArtifacts.Events;
using Content.Server.Xenoarchaeology.XenoArtifacts.Effects.Components;
using Content.Shared.Disease;
using Content.Server.Disease;
using Content.Server.Disease.Components;
using Robust.Shared.Prototypes;
using Content.Shared.Interaction;

namespace Content.Server.Xenoarchaeology.XenoArtifacts.Effects.Systems
{
    /// <summary>
    /// Handles disease-producing artifacts
    /// </summary>
    public sealed class DiseaseArtifactSystem : EntitySystem
    {
        [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
        [Dependency] private readonly DiseaseSystem _disease = default!;
        [Dependency] private readonly EntityLookupSystem _lookup = default!;
        [Dependency] private readonly SharedInteractionSystem _interactionSystem = default!;

        public override void Initialize()
        {
            base.Initialize();
            SubscribeLocalEvent<DiseaseArtifactComponent, ArtifactNodeEnteredEvent>(OnNodeEntered);
            SubscribeLocalEvent<DiseaseArtifactComponent, ArtifactActivatedEvent>(OnActivate);
        }

        /// <summary>
        /// Makes sure this artifact is assigned a disease
        /// </summary>
        private void OnNodeEntered(EntityUid uid, DiseaseArtifactComponent component, ArtifactNodeEnteredEvent args)
        {
            if (component.SpawnDisease != null || !component.DiseasePrototypes.Any())
                return;
            var diseaseName = component.DiseasePrototypes[args.RandomSeed % component.DiseasePrototypes.Count];

            if (!_prototypeManager.TryIndex<DiseasePrototype>(diseaseName, out var disease))
            {
                Logger.ErrorS("disease", $"Invalid disease {diseaseName} selected from random diseases.");
                return;
            }

            component.SpawnDisease = disease;
        }

        /// <summary>
        /// When activated, blasts everyone in LOS within n tiles
        /// with a high-probability disease infection attempt
        /// </summary>
        private void OnActivate(EntityUid uid, DiseaseArtifactComponent component, ArtifactActivatedEvent args)
        {
            if (component.SpawnDisease == null) return;

            var xform = Transform(uid);
            var carrierQuery = GetEntityQuery<DiseaseCarrierComponent>();

            foreach (var entity in _lookup.GetEntitiesInRange(xform.Coordinates, component.Range))
            {
                if (!carrierQuery.TryGetComponent(entity, out var carrier)) continue;

                if (!_interactionSystem.InRangeUnobstructed(uid, entity, component.Range))
                    continue;

                _disease.TryInfect(carrier, component.SpawnDisease, forced: true);
            }
        }
    }
}