Add power selling price (#11395)

Content.Server/Power/Components/BatteryComponent.cs

@@ -29,6 +29,13 @@ namespace Content.Server.Power.Components
         /// </summary>
         [ViewVariables] public bool IsFullyCharged => MathHelper.CloseToPercent(CurrentCharge, MaxCharge);
 
+        /// <summary>
+        /// The price per one joule. Default is 1 credit for 10kJ.
+        /// </summary>
+        [DataField("pricePerJoule")]
+        [ViewVariables(VVAccess.ReadWrite)]
+        public float PricePerJoule = 0.0001f;
+
         /// <summary>
         ///     If sufficient charge is avaiable on the battery, use it. Otherwise, don't.
         /// </summary>

Content.Server/Power/EntitySystems/BatterySystem.cs

@@ -1,3 +1,4 @@
+using Content.Server.Cargo.Systems;
 using Content.Server.Power.Components;
 using Content.Shared.Examine;
 using JetBrains.Annotations;
@@ -12,6 +13,7 @@ namespace Content.Server.Power.EntitySystems
             base.Initialize();
 
             SubscribeLocalEvent<ExaminableBatteryComponent, ExaminedEvent>(OnExamine);
+            SubscribeLocalEvent<BatteryComponent, PriceCalculationEvent>(CalculateBatteryPrice);
 
             SubscribeLocalEvent<NetworkBatteryPreSync>(PreSync);
             SubscribeLocalEvent<NetworkBatteryPostSync>(PostSync);
@@ -64,5 +66,13 @@ namespace Content.Server.Power.EntitySystems
                 batt.CurrentCharge += comp.AutoRechargeRate * frameTime;
             }
         }
+
+        /// <summary>
+        /// Gets the price for the power contained in an entity's battery.
+        /// </summary>
+        private void CalculateBatteryPrice(EntityUid uid, BatteryComponent component, ref PriceCalculationEvent args)
+        {
+            args.Price += component.CurrentCharge * component.PricePerJoule;
+        }
     }
 }