Blood Regeneration Affects Hunger/Thirst (#1007)

# Description
Makes natural blood regeneration use up some hunger and thirst, and halt
completely when you are starving/dying of thirst.

This is necessary to fix two issues:
1. It being possible to feed off of your own blood, by repeatedly
drawing your blood and injecting it back with a syringe. (I actually
know a few people on floof who do that on a daily basis)
2. Hunger and thirst having no real impact on gameplay, besides giving
you a mildly annoying depression overlay when low.

This PR also slightly refactors the blood deficiency trait so that it's
no longer completely hardcoded in the bloodstream system.

<details><summary><h1>Media</h1></summary>
<p>


https://github.com/user-attachments/assets/f8634de5-19bd-44a5-ada2-62f4504bf3d4

</p>
</details>

# Changelog
:cl:
- add: Blood regeneration now uses up hunger and thirst, and comes to a
halt when you are very hungry or thirst.
- fix: It is no longer feasible to drink your own blood to satiate your
own hunger.

Content.Server/Body/Components/BloodstreamComponent.cs

@@ -1,5 +1,6 @@
 using Content.Server.Body.Systems;
 using Content.Server.Chemistry.EntitySystems;
+using Content.Server.Traits;
 using Content.Server.Traits.Assorted;
 using Content.Shared.Chemistry.Components;
 using Content.Shared.Chemistry.Reagent;
@@ -83,6 +84,13 @@ public sealed partial class BloodstreamComponent : Component
         [DataField]
         public FixedPoint2 BloodRefreshAmount = 1.0f;
 
+        /// <summary>
+        ///     How much hunger/thirst is used to regenerate one unit of blood. Set to zero to disable.
+        ///     The actual thirst/hunger rate will scale with <see cref="BloodRefreshAmount"/>.
+        /// </summary>
+        /// <remarks>Those will have no effect if the entity has no hunger/thirst components.</remarks>
+        public float BloodRegenerationHunger = 1f, BloodRegenerationThirst = 1f;
+
         /// <summary>
         ///     How much blood needs to be in the temporary solution in order to create a puddle?
         /// </summary>
@@ -172,18 +180,5 @@ public sealed partial class BloodstreamComponent : Component
         /// </summary>
         [ViewVariables(VVAccess.ReadWrite)]
         public TimeSpan StatusTime;
-
-        /// <summary>
-        ///     If this is true, the entity will not passively regenerate blood,
-        ///     and instead will slowly lose blood.
-        /// </summary>
-        [DataField]
-        public bool HasBloodDeficiency = false;
-
-        /// <summary>
-        ///     How much percentage of max blood volume should be removed with blood deficiency in each update interval?
-        /// </summary>
-        [DataField]
-        public float BloodDeficiencyLossPercentage;
     }
 }

Content.Server/Body/Events/NaturalBloodRegenerationAttemptEvent.cs

@@ -0,0 +1,15 @@
+using Content.Shared.FixedPoint;
+
+namespace Content.Server.Body.Events;
+
+/// <summary>
+///     Raised on a mob when its bloodstream tries to perform natural blood regeneration.
+/// </summary>
+[ByRefEvent]
+public sealed class NaturalBloodRegenerationAttemptEvent : CancellableEntityEventArgs
+{
+    /// <summary>
+    ///     How much blood the mob will regenerate on this tick. Can be negative.
+    /// </summary>
+    public FixedPoint2 Amount;
+}

Content.Server/Body/Systems/BloodstreamSystem.cs

@@ -1,4 +1,5 @@
 using Content.Server.Body.Components;
+using Content.Server.Body.Events;
 using Content.Server.Chemistry.Containers.EntitySystems;
 using Content.Server.Chemistry.ReactionEffects;
 using Content.Server.Fluids.EntitySystems;
@@ -14,6 +15,8 @@
 using Content.Shared.Drunk;
 using Content.Shared.FixedPoint;
 using Content.Shared.Mobs.Systems;
+using Content.Shared.Nutrition.Components;
+using Content.Shared.Nutrition.EntitySystems;
 using Content.Shared.Popups;
 using Content.Shared.Rejuvenate;
 using Content.Shared.Speech.EntitySystems;
@@ -39,6 +42,8 @@ public sealed class BloodstreamSystem : EntitySystem
     [Dependency] private readonly SharedStutteringSystem _stutteringSystem = default!;
     [Dependency] private readonly AlertsSystem _alertsSystem = default!;
     [Dependency] private readonly ForensicsSystem _forensicsSystem = default!;
+    [Dependency] private readonly HungerSystem _hunger = default!;
+    [Dependency] private readonly ThirstSystem _thirst = default!;
 
     public override void Initialize()
     {
@@ -118,17 +123,9 @@ public override void Update(float frameTime)
             if (!_solutionContainerSystem.ResolveSolution(uid, bloodstream.BloodSolutionName, ref bloodstream.BloodSolution, out var bloodSolution))
                 continue;
 
-            // Removes blood for Blood Deficiency constantly.
-            if (bloodstream.HasBloodDeficiency)
-            {
-                if (!_mobStateSystem.IsDead(uid))
-                    RemoveBlood(uid, bloodstream.BloodMaxVolume * bloodstream.BloodDeficiencyLossPercentage, bloodstream);
-            }
-            // Adds blood to their blood level if it is below the maximum.
-            else if (bloodSolution.Volume < bloodSolution.MaxVolume && !_mobStateSystem.IsDead(uid))
-            {
-                TryModifyBloodLevel(uid, bloodstream.BloodRefreshAmount, bloodstream);
-            }
+            // Try to apply natural blood regeneration/bloodloss
+            if (!_mobStateSystem.IsDead(uid))
+                TryDoNaturalRegeneration((uid, bloodstream), bloodSolution);
 
             // Removes blood from the bloodstream based on bleed amount (bleed rate)
             // as well as stop their bleeding to a certain extent.
@@ -498,4 +495,35 @@ private void RemoveBlood(EntityUid uid, FixedPoint2 amount, BloodstreamComponent
 
         bloodSolution.RemoveReagent(component.BloodReagent, amount);
     }
+
+    /// <summary>
+    ///     Tries to apply natural blood regeneration/loss to the entity. Returns true if succesful.
+    /// </summary>
+    private bool TryDoNaturalRegeneration(Entity<BloodstreamComponent> ent, Solution bloodSolution)
+    {
+        var ev = new NaturalBloodRegenerationAttemptEvent { Amount = ent.Comp.BloodRefreshAmount };
+        RaiseLocalEvent(ent, ref ev);
+
+        if (ev.Cancelled || (ev.Amount > 0 && bloodSolution.Volume >= bloodSolution.MaxVolume))
+            return false;
+
+        var usedHunger = ev.Amount * ent.Comp.BloodRegenerationHunger;
+        var usedThirst = ev.Amount * ent.Comp.BloodRegenerationThirst;
+
+        // First, check if the entity has enough hunger/thirst
+        var hungerComp = CompOrNull<HungerComponent>(ent);
+        var thirstComp = CompOrNull<ThirstComponent>(ent);
+        if (usedHunger > 0 && hungerComp is not null && (hungerComp.CurrentHunger < usedHunger || hungerComp.CurrentThreshold <= HungerThreshold.Starving)
+            ||  usedThirst > 0 && thirstComp is not null && (thirstComp.CurrentThirst < usedThirst || thirstComp.CurrentThirstThreshold <= ThirstThreshold.Parched))
+            return false;
+
+        // Then actually expend hunger and thirst (if necessary) and regenerate blood.
+        if (usedHunger > 0 && hungerComp is not null)
+            _hunger.ModifyHunger(ent, (float) -usedHunger, hungerComp);
+
+        if (usedThirst > 0 && thirstComp is not null)
+            _thirst.ModifyThirst(ent, thirstComp, (float) -usedThirst);
+
+        return TryModifyBloodLevel(ent, ev.Amount, ent.Comp);
+    }
 }

Content.Server/Traits/BloodDeficiencyComponent.cs

@@ -11,4 +11,10 @@ public sealed partial class BloodDeficiencyComponent : Component
     // </summary>
     [DataField(required: true)]
     public float BloodLossPercentage;
+
+    /// <summary>
+    ///     Whether the effects of this trait should be active.
+    /// </summary>
+    [DataField]
+    public bool Active = true;
 }

Content.Server/Traits/BloodDeficiencySystem.cs

@@ -1,23 +1,24 @@
-using Content.Server.Body.Systems;
 using Content.Server.Body.Components;
-using Content.Shared.Damage;
+using Content.Server.Body.Events;
+using Content.Server.Traits.Assorted;
+using Content.Shared.FixedPoint;
 
-namespace Content.Server.Traits.Assorted;
+namespace Content.Server.Traits;
 
 public sealed class BloodDeficiencySystem : EntitySystem
 {
     public override void Initialize()
     {
         base.Initialize();
-        SubscribeLocalEvent<BloodDeficiencyComponent, ComponentStartup>(OnStartup);
+        SubscribeLocalEvent<BloodDeficiencyComponent, NaturalBloodRegenerationAttemptEvent>(OnBloodRegen);
     }
 
-    private void OnStartup(EntityUid uid, BloodDeficiencyComponent component, ComponentStartup args)
+    private void OnBloodRegen(Entity<BloodDeficiencyComponent> ent, ref NaturalBloodRegenerationAttemptEvent args)
     {
-        if (!TryComp<BloodstreamComponent>(uid, out var bloodstream))
+        if (!ent.Comp.Active || !TryComp<BloodstreamComponent>(ent.Owner, out var bloodstream))
             return;
 
-        bloodstream.HasBloodDeficiency = true;
-        bloodstream.BloodDeficiencyLossPercentage = component.BloodLossPercentage;
+        args.Amount = FixedPoint2.Min(args.Amount, 0) // If the blood regen amount already was negative, we keep it.
+                      - bloodstream.BloodMaxVolume * ent.Comp.BloodLossPercentage;
     }
 }

Resources/Prototypes/Entities/Mobs/Species/arachne.yml

@@ -108,6 +108,7 @@
     - DoorBumpOpener
   - type: Bloodstream
     bloodReagent: DemonsBlood
+    bloodRegenerationThirst: 4 # 1 unit of demon's blood satiates 4 thirst
   - type: BloodSucker
     webRequired: true
   - type: Arachne

Resources/Prototypes/Entities/Mobs/Species/diona.yml

@@ -33,6 +33,8 @@
         amount: 5
   - type: Bloodstream
     bloodReagent: Sap
+    bloodRegenerationHunger: 1
+    bloodRegenerationThirst: 1 # 1 unit of sap satiates 1 hunger and thirst
   - type: Reactive
     groups:
       Flammable: [ Touch ]

Resources/Prototypes/Entities/Mobs/Species/slime.yml

@@ -35,6 +35,8 @@
         color: "#2cf274"
   - type: Bloodstream
     bloodReagent: Slime # TODO Color slime blood based on their slime color or smth
+    bloodRegenerationHunger: 2
+    bloodRegenerationThirst: 2 # 1 of slime satiates 2 hunger
   - type: Barotrauma
     damage:
       types:

Resources/Prototypes/Entities/Mobs/base.yml

@@ -233,3 +233,5 @@
     bloodlossHealDamage:
       types:
         Bloodloss: -1
+    bloodRegenerationHunger: 1
+    bloodRegenerationThirst: 1.5 # 1 unit of normal blood satiates 1t, 0.3t for vampires, 0.75h, and restores 0.25 blood for non-humans...

Resources/Prototypes/Reagents/biological.yml

@@ -18,7 +18,7 @@
     Drink:
       effects:
       - !type:SatiateThirst
-        factor: 1.5
+        factor: 0.5
         conditions:
           - !type:OrganType
             type: Human
@@ -39,7 +39,7 @@
         - !type:OrganType
           type: Vampiric
         reagent: Protein
-        amount: 0.15
+        amount: 0.125 # See below
       - !type:AdjustReagent
         conditions:
         - !type:OrganType
@@ -50,7 +50,11 @@
       effects:
         - !type:AdjustReagent
           reagent: UncookedAnimalProteins
-          amount: 0.5
+          amount: 0.125 # 0.25 proteins for 1u of blood - restores 0.75 hunger, adds 0.25 blood per unit
+          conditions:
+          - !type:OrganType
+            type: Vampiric
+            shouldHave: false
     Medicine:
       effects:
       - !type:HealthChange
@@ -99,7 +103,7 @@
       # Delicious!
       effects:
       - !type:SatiateHunger
-        factor: 1.5
+        factor: 1
   footstepSound:
     collection: FootstepBlood
     params:
@@ -123,9 +127,9 @@
       # Sweet!
       effects:
       - !type:SatiateHunger
-        factor: 1
+        factor: 0.5
       - !type:SatiateThirst
-        factor: 1
+        factor: 0.5
   footstepSound:
     collection: FootstepBlood
     params: