Change all of body system to use entities and components (#2074)

* Early commit

* Early commit 2

* merging master broke my git

* does anyone even read these

* life is fleeting

* it just works

* this time passing integration tests

* Remove hashset yaml serialization for now

* You got a license for those nullables?

* No examine, no context menu, part and mechanism parenting and visibility

* Fix wrong brain sprite state

* Removing layers was a mistake

* just tear body system a new one and see if it still breathes

* Remove redundant code

* Add that comment back

* Separate damage and body, component states, stomach rework

* Add containers for body parts

* Bring layers back pls

* Fix parts magically changing color

* Reimplement sprite layer visibility

* Fix tests

* Add leg test

* Active legs is gone

Crab rave

* Merge fixes, rename DamageState to CurrentState

* Remove IShowContextMenu and ICanExamine

Content.Shared/GameObjects/Components/Body/Behavior/SharedStomachBehaviorComponent.cs

@@ -0,0 +1,171 @@
+#nullable enable
+using System.Collections.Generic;
+using System.Linq;
+using Content.Shared.Chemistry;
+using Content.Shared.GameObjects.Components.Body.Networks;
+using Content.Shared.GameObjects.Components.Chemistry;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
+using Robust.Shared.ViewVariables;
+
+namespace Content.Shared.GameObjects.Components.Body.Behavior
+{
+    /// <summary>
+    /// Where reagents go when ingested. Tracks ingested reagents over time, and
+    /// eventually transfers them to <see cref="SharedBloodstreamComponent"/> once digested.
+    /// </summary>
+    public abstract class SharedStomachBehaviorComponent : MechanismBehaviorComponent
+    {
+        public override string Name => "Stomach";
+
+        private float _accumulatedFrameTime;
+
+        /// <summary>
+        ///     Updates digestion status of ingested reagents.
+        ///     Once reagents surpass _digestionDelay they are moved to the
+        ///     bloodstream, where they are then metabolized.
+        /// </summary>
+        /// <param name="frameTime">
+        ///     The time since the last update in seconds.
+        /// </param>
+        public override void Update(float frameTime)
+        {
+            if (Body == null)
+            {
+                return;
+            }
+
+            _accumulatedFrameTime += frameTime;
+
+            // Update at most once per second
+            if (_accumulatedFrameTime < 1)
+            {
+                return;
+            }
+
+            _accumulatedFrameTime -= 1;
+
+            if (!Body.Owner.TryGetComponent(out SharedSolutionContainerComponent? solution) ||
+                !Body.Owner.TryGetComponent(out SharedBloodstreamComponent? bloodstream))
+            {
+                return;
+            }
+
+            // Add reagents ready for transfer to bloodstream to transferSolution
+            var transferSolution = new Solution();
+
+            // Use ToList here to remove entries while iterating
+            foreach (var delta in _reagentDeltas.ToList())
+            {
+                //Increment lifetime of reagents
+                delta.Increment(frameTime);
+                if (delta.Lifetime > _digestionDelay)
+                {
+                    solution.TryRemoveReagent(delta.ReagentId, delta.Quantity);
+                    transferSolution.AddReagent(delta.ReagentId, delta.Quantity);
+                    _reagentDeltas.Remove(delta);
+                }
+            }
+
+            // Transfer digested reagents to bloodstream
+            bloodstream.TryTransferSolution(transferSolution);
+        }
+
+        /// <summary>
+        ///     Max volume of internal solution storage
+        /// </summary>
+        public ReagentUnit MaxVolume
+        {
+            get => Owner.TryGetComponent(out SharedSolutionContainerComponent? solution) ? solution.MaxVolume : ReagentUnit.Zero;
+            set
+            {
+                if (Owner.TryGetComponent(out SharedSolutionContainerComponent? solution))
+                {
+                    solution.MaxVolume = value;
+                }
+            }
+        }
+
+        /// <summary>
+        ///     Initial internal solution storage volume
+        /// </summary>
+        [ViewVariables]
+        protected ReagentUnit InitialMaxVolume { get; private set; }
+
+        /// <summary>
+        ///     Time in seconds between reagents being ingested and them being
+        ///     transferred to <see cref="SharedBloodstreamComponent"/>
+        /// </summary>
+        [ViewVariables]
+        private float _digestionDelay;
+
+        /// <summary>
+        ///     Used to track how long each reagent has been in the stomach
+        /// </summary>
+        [ViewVariables]
+        private readonly List<ReagentDelta> _reagentDeltas = new List<ReagentDelta>();
+
+        public override void ExposeData(ObjectSerializer serializer)
+        {
+            base.ExposeData(serializer);
+            serializer.DataField(this, s => s.InitialMaxVolume, "maxVolume", ReagentUnit.New(100));
+            serializer.DataField(ref _digestionDelay, "digestionDelay", 20);
+        }
+
+        public bool CanTransferSolution(Solution solution)
+        {
+            if (!Owner.TryGetComponent(out SharedSolutionContainerComponent? solutionComponent))
+            {
+                return false;
+            }
+
+            // TODO: For now no partial transfers. Potentially change by design
+            if (!solutionComponent.CanAddSolution(solution))
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        public bool TryTransferSolution(Solution solution)
+        {
+            if (!CanTransferSolution(solution))
+                return false;
+
+            if (!Owner.TryGetComponent(out SharedSolutionContainerComponent? solutionComponent))
+            {
+                return false;
+            }
+
+            // Add solution to _stomachContents
+            solutionComponent.TryAddSolution(solution, false, true);
+            // Add each reagent to _reagentDeltas. Used to track how long each reagent has been in the stomach
+            foreach (var reagent in solution.Contents)
+            {
+                _reagentDeltas.Add(new ReagentDelta(reagent.ReagentId, reagent.Quantity));
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        ///     Used to track quantity changes when ingesting & digesting reagents
+        /// </summary>
+        protected class ReagentDelta
+        {
+            public readonly string ReagentId;
+            public readonly ReagentUnit Quantity;
+            public float Lifetime { get; private set; }
+
+            public ReagentDelta(string reagentId, ReagentUnit quantity)
+            {
+                ReagentId = reagentId;
+                Quantity = quantity;
+                Lifetime = 0.0f;
+            }
+
+            public void Increment(float delta) => Lifetime += delta;
+        }
+    }
+}