From 6b0a58afd7fb58f6709d42440e07c7ccec1dc3d7 Mon Sep 17 00:00:00 2001
From: Alysson Ribeiro <15274059+sonalys@users.noreply.github.com>
Date: Fri, 15 Nov 2024 19:21:07 +0100
Subject: [PATCH] Feature(engine): allow developer to set their own default
 functions

---
 ast/DataContext.go    |  6 +++++-
 engine/GruleEngine.go | 19 +++++++++++--------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/ast/DataContext.go b/ast/DataContext.go
index b809d1c..75a90b1 100755
--- a/ast/DataContext.go
+++ b/ast/DataContext.go
@@ -17,10 +17,14 @@ package ast
 //go:generate mockgen -destination=../mocks/ast/DataContext.go -package=mocksAst . IDataContext
 
 import (
-	"github.com/hyperjumptech/grule-rule-engine/model"
 	"reflect"
+
+	"github.com/hyperjumptech/grule-rule-engine/model"
 )
 
+// DefaultFuncKey defines the key used for default functions.
+const DefaultFuncKey = "DEFUNC"
+
 // NewDataContext will create a new DataContext instance
 func NewDataContext() IDataContext {
 
diff --git a/engine/GruleEngine.go b/engine/GruleEngine.go
index 1c62f62..6f9f4eb 100755
--- a/engine/GruleEngine.go
+++ b/engine/GruleEngine.go
@@ -17,11 +17,12 @@ package engine
 import (
 	"context"
 	"fmt"
-	"github.com/sirupsen/logrus"
-	"go.uber.org/zap"
 	"sort"
 	"time"
 
+	"github.com/sirupsen/logrus"
+	"go.uber.org/zap"
+
 	"github.com/hyperjumptech/grule-rule-engine/ast"
 	"github.com/hyperjumptech/grule-rule-engine/logger"
 )
@@ -130,13 +131,15 @@ func (g *GruleEngine) ExecuteWithContext(ctx context.Context, dataCtx ast.IDataC
 	// Prepare the timer, we need to measure the processing time in debug mode.
 	startTime := time.Now()
 
-	// Prepare the build-in function and add to datacontext.
-	defunc := &ast.BuiltInFunctions{
-		Knowledge:     knowledge,
-		WorkingMemory: knowledge.WorkingMemory,
-		DataContext:   dataCtx,
+	if dataCtx.Get(ast.DefaultFuncKey) == nil {
+		// Prepare the build-in function and add to datacontext.
+		defunc := &ast.BuiltInFunctions{
+			Knowledge:     knowledge,
+			WorkingMemory: knowledge.WorkingMemory,
+			DataContext:   dataCtx,
+		}
+		dataCtx.Add(ast.DefaultFuncKey, defunc)
 	}
-	dataCtx.Add("DEFUNC", defunc)
 
 	// Working memory need to be resetted. all Expression will be set as not evaluated.
 	log.Debugf("Resetting Working memory")