added state checkers for programmatically checking state before actio…

…n evaluation or execution

MountainGoap/Action.cs

@@ -61,8 +61,16 @@ public class Action {
         /// </summary>
         private readonly Dictionary<string, string> parameterPostconditions = new();
 
+        /// <summary>
+        /// State mutator for modifying state programmatically after action execution or evaluation.
+        /// </summary>
         private readonly StateMutatorCallback? stateMutator;
 
+        /// <summary>
+        /// State checker for checking state programmatically before action execution or evaluation.
+        /// </summary>
+        private readonly StateCheckerCallback? stateChecker;
+
         /// <summary>
         /// Parameters to be passed to the action.
         /// </summary>
@@ -82,7 +90,8 @@ public class Action {
         /// <param name="arithmeticPostconditions">Arithmetic postconditions added to state after the action is successfully executed.</param>
         /// <param name="parameterPostconditions">Parameter postconditions copied to state after the action is successfully executed.</param>
         /// <param name="stateMutator">Callback for modifying state after action execution or evaluation.</param>
-        public Action(string? name = null, Dictionary<string, PermutationSelectorCallback>? permutationSelectors = null, ExecutorCallback? executor = null, float cost = 1f, CostCallback? costCallback = null, Dictionary<string, object?>? preconditions = null, Dictionary<string, ComparisonValuePair>? comparativePreconditions = null, Dictionary<string, object?>? postconditions = null, Dictionary<string, object>? arithmeticPostconditions = null, Dictionary<string, string>? parameterPostconditions = null, StateMutatorCallback? stateMutator = null) {
+        /// <param name="stateChecker">Callback for checking state before action execution or evaluation.</param>
+        public Action(string? name = null, Dictionary<string, PermutationSelectorCallback>? permutationSelectors = null, ExecutorCallback? executor = null, float cost = 1f, CostCallback? costCallback = null, Dictionary<string, object?>? preconditions = null, Dictionary<string, ComparisonValuePair>? comparativePreconditions = null, Dictionary<string, object?>? postconditions = null, Dictionary<string, object>? arithmeticPostconditions = null, Dictionary<string, string>? parameterPostconditions = null, StateMutatorCallback? stateMutator = null, StateCheckerCallback? stateChecker = null) {
             if (permutationSelectors == null) this.permutationSelectors = new();
             else this.permutationSelectors = permutationSelectors;
             if (executor == null) this.executor = DefaultExecutorCallback;
@@ -96,6 +105,7 @@ public Action(string? name = null, Dictionary<string, PermutationSelectorCallbac
             if (arithmeticPostconditions != null) this.arithmeticPostconditions = arithmeticPostconditions;
             if (parameterPostconditions != null) this.parameterPostconditions = parameterPostconditions;
             if (stateMutator != null) this.stateMutator = stateMutator;
+            if (stateChecker != null) this.stateChecker = stateChecker;
         }
 
         /// <summary>
@@ -118,7 +128,7 @@ public Action(string? name = null, Dictionary<string, PermutationSelectorCallbac
         /// </summary>
         /// <returns>A copy of the action.</returns>
         public Action Copy() {
-            var newAction = new Action(Name, permutationSelectors, executor, cost, costCallback, preconditions.Copy(), comparativePreconditions.Copy(), postconditions.Copy(), arithmeticPostconditions.CopyNonNullable(), parameterPostconditions.Copy(), stateMutator) {
+            var newAction = new Action(Name, permutationSelectors, executor, cost, costCallback, preconditions.Copy(), comparativePreconditions.Copy(), postconditions.Copy(), arithmeticPostconditions.CopyNonNullable(), parameterPostconditions.Copy(), stateMutator, stateChecker) {
                 parameters = parameters.Copy()
             };
             return newAction;
@@ -200,6 +210,7 @@ internal bool IsPossible(Dictionary<string, object?> state) {
                 }
                 else return false;
             }
+            if (stateChecker?.Invoke(this, state) == false) return false;
             return true;
         }
 

MountainGoap/CallbackDelegates/StateCheckerCallback.cs

@@ -0,0 +1,13 @@
+// <copyright file="StateCheckerCallback.cs" company="Chris Muller">
+// Copyright (c) Chris Muller. All rights reserved.
+// </copyright>
+
+namespace MountainGoap {
+    /// <summary>
+    /// Delegate type for a callback that checks state before action execution or evaluation (the latter during planning).
+    /// </summary>
+    /// <param name="action">Action being executed or evaluated.</param>
+    /// <param name="currentState">State as it will be when the action is executed or evaluated.</param>
+    /// <returns>True if the state is okay for executing the action, otherwise false.</returns>
+    public delegate bool StateCheckerCallback(Action action, Dictionary<string, object?> currentState);
+}

MountainGoap/CallbackDelegates/StateMutatorCallback.cs

@@ -6,7 +6,7 @@ namespace MountainGoap {
     /// <summary>
     /// Delegate type for a callback that mutates state following action execution or evaluation (the latter during planning).
     /// </summary>
-    /// <param name="action">Action being executed.</param>
+    /// <param name="action">Action being executed or evaluated.</param>
     /// <param name="currentState">State as it will be when the action is executed or evaluated.</param>
     public delegate void StateMutatorCallback(Action action, Dictionary<string, object?> currentState);
 }

MountainGoap/MountainGoap.csproj

@@ -6,7 +6,7 @@
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <GenerateDocumentationFile>True</GenerateDocumentationFile>
-	<VersionPrefix>0.12.0</VersionPrefix>
+	<VersionPrefix>0.13.0</VersionPrefix>
 	<GeneratePackageOnBuild>True</GeneratePackageOnBuild>
 	<Description>A simple GOAP (Goal Oriented Action Planning) library.</Description>
 	<Copyright>MIT licensed 2022</Copyright>