Let AI engulf even if running out of atp

src/microbe_stage/systems/MicrobeAISystem.cs

@@ -280,6 +280,8 @@ private void ChooseActions(in Entity entity, ref MicrobeAI ai, ref CompoundAbsor
 
         ref var control = ref entity.Get<MicrobeControl>();
 
+        ref var cellHealth = ref entity.Get<Health>();
+
         ref var compoundStorage = ref entity.Get<CompoundStorage>();
 
         var compounds = compoundStorage.Compounds;
@@ -330,18 +332,30 @@ private void ChooseActions(in Entity entity, ref MicrobeAI ai, ref CompoundAbsor
             control.SetMucocystState(ref organelles, ref compoundStorage, entity, false);
         }
 
+        float atpLevel = compounds.GetCompoundAmount(Compound.ATP);
+
         // If this microbe is out of ATP, pick an amount of time to rest
-        if (compounds.GetCompoundAmount(Compound.ATP) < 1.0f)
+        if (atpLevel < 1.0f)
         {
             // Keep the maximum at 95% full, as there is flickering when near full
             ai.ATPThreshold = 0.95f * speciesFocus / Constants.MAX_SPECIES_FOCUS;
         }
 
         if (ai.ATPThreshold > MathUtils.EPSILON)
         {
-            if (compounds.GetCompoundAmount(Compound.ATP) <
-                compounds.GetCapacityForCompound(Compound.ATP) * ai.ATPThreshold)
+            if (atpLevel < compounds.GetCapacityForCompound(Compound.ATP) * ai.ATPThreshold)
             {
+                if (cellHealth.CurrentHealth > 2 * Constants.ENGULF_NO_ATP_DAMAGE)
+                {
+                    // Even if we are out of ATP and there is microbe nearby, engulf them.
+                    // make sure engulfing doesn't kill the cell
+                    if (CheckForHuntingConditions(ref ai, ref position, ref organelles, ref ourSpecies, ref engulfer,
+                            ref cellProperties, ref control, ref cellHealth, ref compoundStorage, entity, speciesFocus,
+                            speciesAggression, speciesActivity, speciesOpportunism, strain, random, true,
+                            atpLevel))
+                        return;
+                }
+
                 bool outOfSomething = false;
                 foreach (var compound in compounds.Compounds)
                 {
@@ -467,6 +481,37 @@ private void ChooseActions(in Entity entity, ref MicrobeAI ai, ref CompoundAbsor
             }
         }
 
+        // check if species can hunt any prey and if so - engage in chase
+        bool isHunting = CheckForHuntingConditions(ref ai, ref position, ref organelles, ref ourSpecies, ref engulfer,
+            ref cellProperties, ref control, ref health, ref compoundStorage, entity, speciesFocus, speciesAggression,
+            speciesActivity, speciesOpportunism, strain, random, false, atpLevel);
+        if (isHunting)
+            return;
+
+        // There is no reason to be engulfing at this stage
+        control.SetStateColonyAware(entity, MicrobeState.Normal);
+
+        // Otherwise just wander around and look for compounds
+        if (!isSessile)
+        {
+            SeekCompounds(in entity, ref ai, ref position, ref control, ref organelles, ref absorber, compounds,
+                speciesActivity, speciesFocus, random);
+        }
+        else
+        {
+            // This organism is sessile, and will not act until the environment changes
+            control.SetMoveSpeed(0.0f);
+        }
+    }
+
+    private bool CheckForHuntingConditions(ref MicrobeAI ai, ref WorldPosition position,
+        ref OrganelleContainer organelles, ref SpeciesMember ourSpecies,
+        ref Engulfer engulfer, ref CellProperties cellProperties, ref MicrobeControl control, ref Health health,
+        ref CompoundStorage compoundStorage, in Entity entity, float speciesFocus, float speciesAggression,
+        float speciesActivity, float speciesOpportunism, float strain, Random random, bool outOfAtp, float atpLevel)
+    {
+        var compounds = compoundStorage.Compounds;
+
         // If there are no chunks, look for living prey to hunt
         var possiblePrey = GetNearestPreyItem(ref ai, ref position, ref organelles, ref ourSpecies, ref engulfer,
             compounds, speciesFocus, speciesAggression, speciesOpportunism, random);
@@ -482,32 +527,25 @@ private void ChooseActions(in Entity entity, ref MicrobeAI ai, ref CompoundAbsor
             {
                 GD.PrintErr("Microbe AI tried to engage prey with no position: " + e);
                 ai.FocusedPrey = default;
-                return;
+                return false;
             }
 
             bool engulfPrey = cellProperties.CanEngulfObject(ref ourSpecies, ref engulfer, possiblePrey) ==
                 EngulfCheckResult.Ok && position.Position.DistanceSquaredTo(prey) <
                 10.0f * engulfer.EngulfingSize;
 
-            EngagePrey(ref ai, ref control, ref organelles, ref position, compounds, entity, prey, engulfPrey,
-                speciesAggression, speciesFocus, speciesActivity, strain, random);
-            return;
-        }
-
-        // There is no reason to be engulfing at this stage
-        control.SetStateColonyAware(entity, MicrobeState.Normal);
+            // if out of ATP and the prey is out of reach to engulf, do nothing
+            if (outOfAtp && !engulfPrey)
+            {
+                return false;
+            }
 
-        // Otherwise just wander around and look for compounds
-        if (!isSessile)
-        {
-            SeekCompounds(in entity, ref ai, ref position, ref control, ref organelles, ref absorber, compounds,
-                speciesActivity, speciesFocus, random);
-        }
-        else
-        {
-            // This organism is sessile, and will not act until the environment changes
-            control.SetMoveSpeed(0.0f);
+            EngagePrey(ref ai, ref control, ref organelles, ref position, ref compoundStorage, ref health, entity,
+                prey, engulfPrey, speciesAggression, speciesFocus, speciesActivity, strain, random, atpLevel);
+            return true;
         }
+
+        return false;
     }
 
     private (Entity Entity, Vector3 Position, float EngulfSize, CompoundBag Compounds)? GetNearestChunkItem(
@@ -858,10 +896,21 @@ private void FleeFromPredators(ref WorldPosition position, ref MicrobeAI ai, ref
     }
 
     private void EngagePrey(ref MicrobeAI ai, ref MicrobeControl control, ref OrganelleContainer organelles,
-        ref WorldPosition position, CompoundBag ourCompounds, in Entity entity, Vector3 target, bool engulf,
-        float speciesAggression, float speciesFocus, float speciesActivity, float strain, Random random)
+        ref WorldPosition position, ref CompoundStorage compoundStorage, ref Health health, in Entity entity,
+        Vector3 target, bool engulf, float speciesAggression, float speciesFocus, float speciesActivity,
+        float strain, Random random, float atpLevel)
     {
-        control.SetStateColonyAware(entity, engulf ? MicrobeState.Engulf : MicrobeState.Normal);
+        var ourCompounds = compoundStorage.Compounds;
+
+        if (atpLevel <= Constants.ENGULF_NO_ATP_TRIGGER_THRESHOLD)
+        {
+            control.EnterEngulfModeForcedState(ref health, ref compoundStorage, entity, Compound.ATP);
+        }
+        else
+        {
+            control.SetStateColonyAware(entity, engulf ? MicrobeState.Engulf : MicrobeState.Normal);
+        }
+
         ai.TargetPosition = target;
         control.LookAtPoint = ai.TargetPosition;
         if (CanShootToxin(ourCompounds, speciesFocus))