Add pipe pressure damage

Content.Server/NodeContainer/NodeGroups/PipeNet.cs

@@ -3,6 +3,8 @@
 using Content.Server.Atmos.EntitySystems;
 using Content.Server.NodeContainer.Nodes;
 using Content.Shared.Atmos;
+using Content.Shared.Damage;
+using Robust.Shared.Random;
 using Robust.Shared.Utility;
 
 namespace Content.Server.NodeContainer.NodeGroups
@@ -21,6 +23,9 @@ public sealed class PipeNet : BaseNodeGroup, IPipeNet
         [ViewVariables] public GasMixture Air { get; set; } = new() {Temperature = Atmospherics.T20C};
 
         [ViewVariables] private AtmosphereSystem? _atmosphereSystem;
+        [ViewVariables] private DamageableSystem? _damage;
+        [ViewVariables] private IEntityManager? _entMan;
+        [ViewVariables] private IRobustRandom? _random;
 
         public EntityUid? Grid { get; private set; }
 
@@ -38,11 +43,53 @@ public override void Initialize(Node sourceNode, IEntityManager entMan)
 
             _atmosphereSystem = entMan.EntitySysManager.GetEntitySystem<AtmosphereSystem>();
             _atmosphereSystem.AddPipeNet(Grid.Value, this);
+            _damage = entMan.EntitySysManager.GetEntitySystem<DamageableSystem>();
+            _entMan = entMan;
+            _random = IoCManager.Resolve<IRobustRandom>();
+        }
+
+        /// <summary>
+        /// Calculate pressure damage for pipe. There is no damage if the pressure is below MaxPressure,
+        /// and damage scales exponentially beyond that.
+        /// </summary>
+        private int PressureDamage(PipeNode pipe)
+        {
+            const float tau = 10; // number of atmos ticks to break pipe at nominal overpressure
+            var diff = pipe.Air.Pressure - pipe.MaxPressure;
+            const float alpha = 100/tau;
+            return diff > 0 ? (int)(alpha*float.Exp(diff / pipe.MaxPressure)) : 0;
         }
 
         public void Update()
         {
             _atmosphereSystem?.React(Air, this);
+
+            // Check each pipe node for overpressure and apply damage if needed
+            foreach (var node in Nodes)
+            {
+                if (node is PipeNode pipe && pipe.MaxPressure > 0)
+                {
+                    // Prefer damaging pipes that are already damaged. This means that only one pipe
+                    // fails instead of the whole pipenet bursting at the same time.
+                    const float baseChance = 0.5f;
+                    float p = baseChance;
+                    if (_entMan != null && _entMan.TryGetComponent<DamageableComponent>(pipe.Owner, out var damage))
+                    {
+                        p += (float)damage.TotalDamage * (1 - baseChance);
+                    }
+
+                    if (_random != null && _random.Prob(1-p))
+                        continue;
+
+                    int dam = PressureDamage(pipe);
+                    if (dam > 0)
+                    {
+                        var dspec = new DamageSpecifier();
+                        dspec.DamageDict.Add("Structural", dam);
+                        _damage?.TryChangeDamage(pipe.Owner, dspec);
+                    }
+                }
+            }
         }
 
         public override void LoadNodes(List<Node> groupNodes)

Content.Server/NodeContainer/Nodes/PipeNode.cs

@@ -102,6 +102,12 @@ public GasMixture Air
 
         private const float DefaultVolume = 200f;
 
+        /// <summary>
+        ///     Pressure beyond which this pipe node starts taking damage. Set to zero for no pressure damage.
+        /// </summary>
+        [DataField]
+        public float MaxPressure = 0;
+
         public override void Initialize(EntityUid owner, IEntityManager entMan)
         {
             base.Initialize(owner, entMan);

Resources/Prototypes/Entities/Structures/Piping/Atmospherics/pipes.yml

@@ -83,6 +83,7 @@
         !type:PipeNode
         nodeGroupID: Pipe
         pipeDirection: Longitudinal
+        maxPressure: 6750
   - type: Sprite
     layers:
       - state: pipeStraight
@@ -102,6 +103,7 @@
         !type:PipeNode
         nodeGroupID: Pipe
         pipeDirection: SWBend
+        maxPressure: 6750
   - type: Sprite
     layers:
       - state: pipeBend
@@ -121,6 +123,7 @@
         !type:PipeNode
         nodeGroupID: Pipe
         pipeDirection: TSouth
+        maxPressure: 6750
   - type: Sprite
     layers:
       - state: pipeTJunction
@@ -142,6 +145,7 @@
         !type:PipeNode
         nodeGroupID: Pipe
         pipeDirection: Fourway
+        maxPressure: 6750
   - type: Sprite
     layers:
       - state: pipeFourway