Add FUNCTION placeholder

Author: imDaniX

reactions/src/main/java/fun/reactions/module/basic/BasicModule.java

@@ -230,7 +230,8 @@ public void onDisable(@NotNull ReActions.Platform platform) {
                 new ActivatorNamePlaceholder(),
                 new PersistentVarPlaceholders(),
                 new LocalVarPlaceholder(),
-                new EnderChestPlaceholder()
+                new EnderChestPlaceholder(),
+                new FunctionPlaceholder()
         );
     }
 

reactions/src/main/java/fun/reactions/module/basic/actions/RunFunctionAction.java

@@ -38,7 +38,8 @@ public boolean proceed(@NotNull Environment env, @NotNull String paramsStr) {
         } catch (StackOverflowError error) {
             env.getPlatform().logger().error(
                     "RUN_FUNCTION action failed in '" + env.getActivatorName() + "' due to stack overflow. " +
-                    "Consider limiting the usage of looped FUNCTION actions or try using EXECUTE actions when possible."
+                    "Consider limiting the usage of looped RUN_FUNCTION actions and FUNCTION placeholders " +
+                    "or try using EXECUTE actions."
             );
             return false;
         }

reactions/src/main/java/fun/reactions/module/basic/placeholders/FunctionPlaceholder.java

@@ -0,0 +1,43 @@
+package fun.reactions.module.basic.placeholders;
+
+import fun.reactions.model.activators.Activator;
+import fun.reactions.model.environment.Environment;
+import fun.reactions.model.environment.Variables;
+import fun.reactions.module.basic.activators.FunctionActivator;
+import fun.reactions.placeholders.Placeholder;
+import fun.reactions.util.naming.Aliased;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+@Aliased.Names("funct")
+public class FunctionPlaceholder implements Placeholder {
+    @Override
+    public @Nullable String resolve(@NotNull Environment env, @NotNull String key, @NotNull String params) {
+        Activator activator = env.getPlatform().getActivators().getActivator(params);
+        if (activator == null || activator.getClass() != FunctionActivator.class) {
+            return null;
+        }
+        String id = activator.getLogic().getName();
+        Variables vars = new Variables();
+        try {
+            activator.getLogic().execute(new Environment(
+                    env.getPlatform(),
+                    id,
+                    vars,
+                    env.getPlayer(),
+                    env.isAsync()
+            ));
+        } catch (StackOverflowError error) {
+            env.getPlatform().logger().error(
+                    "FUNCTION placeholder (" + params + ") failed in '" + env.getActivatorName() + "' due to stack overflow. " +
+                    "Consider limiting the usage of looped FUNCTION placeholders and RUN_FUNCTION actions."
+            );
+        }
+        return vars.getStringUnsafe("return");
+    }
+
+    @Override
+    public @NotNull String getName() {
+        return "function";
+    }
+}