Add condition support to entity tables (#36819)

Content.Shared/EntityTable/Conditions/EntityTableCondition.cs

@@ -0,0 +1,28 @@
+using Content.Shared.EntityTable.EntitySelectors;
+using JetBrains.Annotations;
+using Robust.Shared.Prototypes;
+
+namespace Content.Shared.EntityTable.Conditions;
+
+/// <summary>
+/// Used for implementing conditional logic for <see cref="EntityTableSelector"/>.
+/// </summary>
+[ImplicitDataDefinitionForInheritors, UsedImplicitly(ImplicitUseTargetFlags.WithInheritors)]
+public abstract partial class EntityTableCondition
+{
+    /// <summary>
+    /// If true, inverts the result of the condition.
+    /// </summary>
+    [DataField]
+    public bool Invert;
+
+    public bool Evaluate(IEntityManager entMan, IPrototypeManager proto)
+    {
+        var res = EvaluateImplementation(entMan, proto);
+
+        // XOR eval to invert the result.
+        return res ^ Invert;
+    }
+
+    public abstract bool EvaluateImplementation(IEntityManager entMan, IPrototypeManager proto);
+}