Miasma outbreaks give every mob the same disease (#9232)

Content.Server/Atmos/Miasma/MiasmaSystem.cs

@@ -6,6 +6,7 @@ using Content.Server.Temperature.Systems;
 using Content.Server.Body.Components;
 using Content.Shared.Examine;
 using Robust.Shared.Containers;
+using Robust.Shared.Random;
 
 namespace Content.Server.Atmos.Miasma
 {
@@ -13,12 +14,70 @@ namespace Content.Server.Atmos.Miasma
     {
         [Dependency] private readonly AtmosphereSystem _atmosphereSystem = default!;
         [Dependency] private readonly DamageableSystem _damageableSystem = default!;
-        /// Feel free to weak this if there are perf concerns
-        private float UpdateRate = 5f;
+
+        [Dependency] private readonly IRobustRandom _random = default!;
+
+        /// System Variables
+
+        /// Rotting
+
+        /// <summary>
+        /// How often the rotting ticks.
+        /// Feel free to weak this if there are perf concerns.
+        /// </summary>
+        private float _rotUpdateRate = 5f;
+
+        /// Miasma Disease Pool
+        /// Miasma outbreaks are not per-entity,
+        /// so this ensures that each entity in the same incident
+        /// receives the same disease.
+
+        public readonly IReadOnlyList<string> MiasmaDiseasePool = new[]
+        {
+            "VentCough",
+            "AMIV",
+            "SpaceCold",
+            "SpaceFlu",
+            "BirdFlew",
+            "VanAusdallsRobovirus",
+            "BleedersBite",
+            "Plague"
+        };
+
+        /// <summary>
+        /// The current pool disease.
+        /// </summary>
+        private string _poolDisease = "";
+
+        /// <summary>
+        /// The list of diseases in the pool.
+        /// </summary>
+
+        /// <summary>
+        /// This ticks up to PoolRepickTime.
+        /// After that, it resets to 0.
+        /// Any infection will also reset it to 0.
+        /// </summary>
+        private float _poolAccumulator = 0f;
+
+        /// <summmary>
+        /// How long without an infection before we pick a new disease.
+        /// </summary>
+        private TimeSpan _poolRepickTime = TimeSpan.FromMinutes(5);
 
         public override void Update(float frameTime)
         {
             base.Update(frameTime);
+            // Disease pool
+            _poolAccumulator += frameTime;
+
+            if (_poolAccumulator > _poolRepickTime.TotalSeconds)
+            {
+                _poolAccumulator = 0f;
+                _poolDisease = _random.Pick(MiasmaDiseasePool);
+            }
+
+            // Rotting
             foreach (var (rotting, perishable) in EntityQuery<RottingComponent, PerishableComponent>())
             {
                 if (!perishable.Progressing)
@@ -29,10 +88,10 @@ namespace Content.Server.Atmos.Miasma
                     continue;
 
                 perishable.RotAccumulator += frameTime;
-                if (perishable.RotAccumulator < UpdateRate) // This is where it starts to get noticable on larger animals, no need to run every second
+                if (perishable.RotAccumulator < _rotUpdateRate) // This is where it starts to get noticable on larger animals, no need to run every second
                     continue;
 
-                perishable.RotAccumulator -= UpdateRate;
+                perishable.RotAccumulator -= _rotUpdateRate;
 
                 EnsureComp<FliesComponent>(perishable.Owner);
 
@@ -46,7 +105,7 @@ namespace Content.Server.Atmos.Miasma
                     continue;
                 // We need a way to get the mass of the mob alone without armor etc in the future
 
-                float molRate = perishable.MolsPerSecondPerUnitMass * UpdateRate;
+                float molRate = perishable.MolsPerSecondPerUnitMass * _rotUpdateRate;
 
                 var tileMix = _atmosphereSystem.GetTileMixture(Transform(perishable.Owner).Coordinates);
                 if (tileMix != null)
@@ -69,6 +128,9 @@ namespace Content.Server.Atmos.Miasma
             // Fly audiovisual stuff
             SubscribeLocalEvent<FliesComponent, ComponentInit>(OnFliesInit);
             SubscribeLocalEvent<FliesComponent, ComponentShutdown>(OnFliesShutdown);
+
+            // Init disease pool
+            _poolDisease = _random.Pick(MiasmaDiseasePool);
         }
 
         private void OnShutdown(EntityUid uid, RottingComponent component, ComponentShutdown args)
@@ -170,5 +232,12 @@ namespace Content.Server.Atmos.Miasma
             perishable.Progressing = false;
             RemComp<FliesComponent>(uid);
         }
+
+        public string RequestPoolDisease()
+        {
+            // We reset the current time on this outbreak so people don't get unlucky at the transition time
+            _poolAccumulator = 0f;
+            return _poolDisease;
+        }
     }
 }

Content.Server/Chemistry/ReagentEffects/ChemCauseRandomDisease.cs

@@ -7,7 +7,7 @@ using JetBrains.Annotations;
 namespace Content.Server.Chemistry.ReagentEffects
 {
     /// <summary>
-    /// Default metabolism for medicine reagents.
+    /// Causes a random disease from a list, if the user is not already diseased.
     /// </summary>
     [UsedImplicitly]
     public sealed class ChemCauseRandomDisease : ReagentEffect

Content.Server/Chemistry/ReagentEffects/ChemMiasmaPoolSource.cs

@@ -0,0 +1,23 @@
+using Content.Shared.Chemistry.Reagent;
+using JetBrains.Annotations;
+using Content.Server.Atmos.Miasma;
+using Content.Server.Disease;
+
+namespace Content.Server.Chemistry.ReagentEffects
+{
+    /// <summary>
+    /// The miasma system rotates between 1 disease at a time.
+    /// This gives all entities the disease the miasme system is currently on.
+    /// For things ingested by one person, you probably want ChemCauseRandomDisease instead.
+    /// </summary>
+    [UsedImplicitly]
+    public sealed class ChemMiasmaPoolSource : ReagentEffect
+    {
+        public override void Effect(ReagentEffectArgs args)
+        {
+            string disease = EntitySystem.Get<MiasmaSystem>().RequestPoolDisease();
+
+            EntitySystem.Get<DiseaseSystem>().TryAddDisease(args.SolutionEntity, disease);
+        }
+    }
+}