Add EntManager + ProtoManager helpers for random picks (#4869)

* Add EntManager + ProtoManager helpers for random picks

Lets us cleanup content a bit from these being re-implemented.

* weh

RELEASE-NOTES.md

@@ -39,8 +39,7 @@ END TEMPLATE-->
 
 ### New features
 
-* You can now specify CVar overrides via environment variable with the `ROBUST_CVAR_*` prefix. For example `ROBUST_CVAR_game__hostname=foobar` would set the appropriate CVar. Double underscores in the environment variable name are replaced with ".".
-* Added non-generic variant of `GetCVar` to `IConfigurationManager`.
+* Add TryGetRandom to EntityManager to get a random entity with the specified component and TryGetRandom to IPrototypeManager to return a random prototype of the specified type.
 
 ### Bugfixes
 

Robust.Shared/GameObjects/EntityManagerExt.cs

@@ -1,4 +1,7 @@
-namespace Robust.Shared.GameObjects
+using Robust.Shared.Collections;
+using Robust.Shared.Random;
+
+namespace Robust.Shared.GameObjects
 {
     public static class EntityManagerExt
     {
@@ -19,5 +22,79 @@
 
             return default;
         }
+
+        /// <summary>
+        /// Picks an entity at random with the supplied component.
+        /// </summary>
+        public static bool TryGetRandom<TComp1>(this IEntityManager entManager, IRobustRandom random, out EntityUid entity, bool includePaused = false) where TComp1 : IComponent
+        {
+            var entities = new ValueList<EntityUid>();
+
+            if (includePaused)
+            {
+                var query = entManager.AllEntityQueryEnumerator<TComp1>();
+
+                while (query.MoveNext(out var uid, out _))
+                {
+                    entities.Add(uid);
+                }
+            }
+            else
+            {
+                var query = entManager.EntityQueryEnumerator<TComp1>();
+
+                while (query.MoveNext(out var uid, out _))
+                {
+                    entities.Add(uid);
+                }
+            }
+
+            if (entities.Count == 0)
+            {
+                entity = EntityUid.Invalid;
+                return false;
+            }
+
+            entity = random.Pick(entities);
+            return true;
+        }
+
+        /// <summary>
+        /// Picks an entity at random with the supplied components.
+        /// </summary>
+        public static bool TryGetRandom<TComp1, TComp2>(this IEntityManager entManager, IRobustRandom random, out EntityUid entity, bool includePaused = false)
+            where TComp1 : IComponent
+            where TComp2 : IComponent
+        {
+            var entities = new ValueList<EntityUid>();
+
+            if (includePaused)
+            {
+                var query = entManager.AllEntityQueryEnumerator<TComp1, TComp2>();
+
+                while (query.MoveNext(out var uid, out _, out _))
+                {
+                    entities.Add(uid);
+                }
+            }
+            else
+            {
+                var query = entManager.EntityQueryEnumerator<TComp1, TComp2>();
+
+                while (query.MoveNext(out var uid, out _, out _))
+                {
+                    entities.Add(uid);
+                }
+            }
+
+            if (entities.Count == 0)
+            {
+                entity = EntityUid.Invalid;
+                return false;
+            }
+
+            entity = random.Pick(entities);
+            return true;
+        }
     }
 }

Robust.Shared/Prototypes/IPrototypeManager.cs

@@ -3,6 +3,7 @@ using System.Collections.Frozen;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
+using Robust.Shared.Random;
 using Robust.Shared.Serialization.Manager;
 using Robust.Shared.Serialization.Manager.Attributes;
 using Robust.Shared.Serialization.Markdown;
@@ -386,6 +387,11 @@ public interface IPrototypeManager
     ///     For example: /Prototypes/Guidebook
     /// </param>
     void AbstractDirectory(ResPath path);
+
+    /// <summary>
+    /// Tries to get a random prototype.
+    /// </summary>
+    bool TryGetRandom<T>(IRobustRandom random, [NotNullWhen(true)] out IPrototype? prototype) where T : class, IPrototype;
 }
 
 internal interface IPrototypeManagerInternal : IPrototypeManager

Robust.Shared/Prototypes/PrototypeManager.cs

@@ -1082,6 +1082,34 @@ namespace Robust.Shared.Prototypes
             _prototypeDataCache[prototype.ID] = data;
             return data;
         }
+
+        public bool TryGetRandom<T>(IRobustRandom random, [NotNullWhen(true)] out IPrototype? prototype) where T : class, IPrototype
+        {
+            var count = Count<T>();
+
+            if (count == 0)
+            {
+                prototype = null;
+                return false;
+            }
+
+            var index = 0;
+
+            var picked = random.Next(count);
+
+            foreach (var proto in EnumeratePrototypes<T>())
+            {
+                if (index == picked)
+                {
+                    prototype = proto;
+                    return true;
+                }
+
+                index++;
+            }
+
+            throw new ArgumentOutOfRangeException($"Unable to pick valid prototype for {typeof(T)}?");
+        }
     }
 
     public sealed class InvalidPrototypeNameException : Exception