add PreconditionRequirement and RelatedModule requirement

Assets/Engine/Runtime/Requirements/OrientationRequirement.cs

@@ -11,6 +11,12 @@ namespace EscapeRoomEngine.Engine.Runtime.Requirements
 
         public static bool TryOrienting(Module module, Space space)
         {
+            if (module.description.orientationRequirements.Count == 0)
+            {
+                // don't evaluate requirements if there are none
+                return true;
+            }
+            
             var orientationCandidates = Candidates(
                 Module.EveryOrientation,
                 module.description.orientationRequirements,

Assets/Engine/Runtime/Requirements/PlacementRequirement.cs

@@ -14,6 +14,12 @@ namespace EscapeRoomEngine.Engine.Runtime.Requirements
 
         public static bool TryPlacing(Module module, Space space)
         {
+            if (module.description.placementRequirements.Count == 0)
+            {
+                // don't evaluate requirements if there are none
+                return true;
+            }
+            
             var placementCandidates = Candidates(
                 space.rrDimensions.EveryPosition,
                 module.description.placementRequirements,

Assets/Engine/Runtime/Requirements/PreconditionRequirement.cs

@@ -0,0 +1,44 @@
+using System.Collections.Generic;
+using EscapeRoomEngine.Engine.Runtime.Modules;
+using UnityEngine;
+using Logger = EscapeRoomEngine.Engine.Runtime.Utilities.Logger;
+using LogType = EscapeRoomEngine.Engine.Runtime.Utilities.LogType;
+
+namespace EscapeRoomEngine.Engine.Runtime.Requirements
+{
+    public abstract class PreconditionRequirement : Requirement<bool>
+    {
+        protected static readonly HashSet<bool> TrueSet = new(new[] { true }), FalseSet = new(new[] { false });
+
+        protected abstract override IEnumerable<bool> GenerateCandidates(Module module, Space space);
+
+        public static bool CheckPreconditions(Module module, Space space)
+        {
+            Debug.Log($"{module}, {module.description.preconditionRequirements}");
+            if (module.description.preconditionRequirements.Count == 0)
+            {
+                // don't evaluate requirements if there are none
+                return true;
+            }
+            
+            var preconditionsMet = Candidates(
+                    TrueSet,
+                    module.description.preconditionRequirements,
+                    module, space)
+                .Contains(true);
+
+            Logger.Log(
+                preconditionsMet
+                    ? $"Preconditions for {module} satisfied"
+                    : $"Could not satisfy preconditions for {module}",
+                LogType.ModulePlacement);
+
+            return preconditionsMet;
+        }
+
+        protected static HashSet<bool> SetFor(bool value)
+        {
+            return value ? TrueSet : FalseSet;
+        }
+    }
+}

Assets/Engine/Runtime/Requirements/PreconditionRequirement.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: a73316a9f52d4c5982f9c7936e322ec4
+timeCreated: 1668945634

Assets/Engine/Runtime/Requirements/RelatedModule.cs

@@ -0,0 +1,20 @@
+using System.Collections.Generic;
+using EscapeRoomEngine.Engine.Runtime.Modules;
+using NaughtyAttributes;
+using UnityEngine;
+
+namespace EscapeRoomEngine.Engine.Runtime.Requirements
+{
+    [CreateAssetMenu(menuName = "Requirements/Related Module")]
+    class RelatedModule : PreconditionRequirement
+    {
+        [InfoBox("A related module that must be added to the same space successfully before this module is added.")]
+        [Required]
+        public ModuleDescription relatedModule;
+        
+        protected override IEnumerable<bool> GenerateCandidates(Module module, Space space)
+        {
+            return new []{ space.AddModuleWithRequirements(Module.CreateModuleByType(space, relatedModule)) };
+        }
+    }
+}

Assets/Engine/Runtime/Requirements/RelatedModule.cs.meta

@@ -0,0 +1,3 @@
+fileFormatVersion: 2
+guid: 6e3f3bf07aae4a03834a7943c255f37d
+timeCreated: 1668947627