Entity Tables (EntitySpawnEntry replacement) (#30579)

* Entity table code

* entity table examples

* fix dat shit

* access

* tests tests tests

* sloth review

Content.Shared/EntityTable/EntitySelectors/EntityTableSelector.cs

@@ -0,0 +1,49 @@
+using Content.Shared.EntityTable.ValueSelector;
+using JetBrains.Annotations;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Random;
+
+namespace Content.Shared.EntityTable.EntitySelectors;
+
+[ImplicitDataDefinitionForInheritors, UsedImplicitly(ImplicitUseTargetFlags.WithInheritors)]
+public abstract partial class EntityTableSelector
+{
+    /// <summary>
+    /// The number of times this selector is run
+    /// </summary>
+    [DataField]
+    public NumberSelector Rolls = new ConstantNumberSelector(1);
+
+    /// <summary>
+    /// A weight used to pick between selectors.
+    /// </summary>
+    [DataField]
+    public float Weight = 1;
+
+    /// <summary>
+    /// A simple chance that the selector will run.
+    /// </summary>
+    [DataField]
+    public double Prob = 1;
+
+    public IEnumerable<EntProtoId> GetSpawns(System.Random rand,
+        IEntityManager entMan,
+        IPrototypeManager proto)
+    {
+        var rolls = Rolls.Get(rand, entMan, proto);
+        for (var i = 0; i < rolls; i++)
+        {
+            if (!rand.Prob(Prob))
+                continue;
+
+            foreach (var spawn in GetSpawnsImplementation(rand, entMan, proto))
+            {
+                yield return spawn;
+            }
+        }
+    }
+
+    protected abstract IEnumerable<EntProtoId> GetSpawnsImplementation(System.Random rand,
+        IEntityManager entMan,
+        IPrototypeManager proto);
+}