From 119a1d0059c6781548f38554b78c85e1e9d17cbe Mon Sep 17 00:00:00 2001
From: gessnerfl <flo.gessner@gamil.com>
Date: Fri, 29 Sep 2023 10:14:18 +0200
Subject: [PATCH] #195: add support for logical ANDs used as wrappers.

---
 .../instana-api-model-to-tag-filter.go        |  8 +++++--
 .../instana-api-model-to-tag-filter_test.go   | 23 +++++++++++++++----
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/instana/tagfilter/instana-api-model-to-tag-filter.go b/instana/tagfilter/instana-api-model-to-tag-filter.go
index 88d8cda..d088a49 100644
--- a/instana/tagfilter/instana-api-model-to-tag-filter.go
+++ b/instana/tagfilter/instana-api-model-to-tag-filter.go
@@ -125,8 +125,8 @@ func (m *tagFilterMapper) mapRightOfLogicalOr(right *expressionHandle) *LogicalO
 
 func (m *tagFilterMapper) mapLogicalAnd(elements []*expressionHandle) (*expressionHandle, error) {
 	total := len(elements)
-	if total < 2 {
-		return nil, fmt.Errorf("at least two elements are expected for logical and")
+	if total < 1 {
+		return nil, fmt.Errorf("at least one element is expected for logical and")
 	}
 	if elements[0].and != nil {
 		return nil, fmt.Errorf("invalid logical and expression: logical and is not allowed for first element")
@@ -135,6 +135,10 @@ func (m *tagFilterMapper) mapLogicalAnd(elements []*expressionHandle) (*expressi
 	operator := Operator(restapi.LogicalAnd)
 	var expression *LogicalAndExpression
 
+	if total == 1 {
+		return elements[0], nil
+	}
+
 	for i := total - 2; i >= 0; i-- {
 		if expression == nil {
 			expression = &LogicalAndExpression{
diff --git a/instana/tagfilter/instana-api-model-to-tag-filter_test.go b/instana/tagfilter/instana-api-model-to-tag-filter_test.go
index 4f9b783..d4eab8c 100644
--- a/instana/tagfilter/instana-api-model-to-tag-filter_test.go
+++ b/instana/tagfilter/instana-api-model-to-tag-filter_test.go
@@ -446,15 +446,30 @@ func TestShouldFailToMapLogicalAndFromInstanaAPIWhenFirstElementIsAnAndExpressio
 	require.Contains(t, err.Error(), "logical and is not allowed for first element")
 }
 
-func TestShouldFailToMapLogicalAndFromInstanaAPIWhenOnlyOneElementIsProvided(t *testing.T) {
+func TestShouldUnwrapLogicalAndFromInstanaAPIWhenOnlyOneElementIsProvided(t *testing.T) {
 	primaryExpression := restapi.NewUnaryTagFilter(restapi.TagFilterEntityDestination, tagFilterName, restapi.IsEmptyOperator)
 	input := restapi.NewLogicalAndTagFilter([]restapi.TagFilterExpressionElement{primaryExpression})
 
+	expectedResult := &FilterExpression{
+		Expression: &LogicalOrExpression{
+			Left: &LogicalAndExpression{
+				Left: &BracketExpression{
+					Primary: &PrimaryExpression{
+						UnaryOperation: &UnaryOperationExpression{
+							Entity:   &EntitySpec{Identifier: tagFilterName, Origin: utils.StringPtr(EntityOriginDestination.Key())},
+							Operator: Operator(restapi.IsEmptyOperator),
+						},
+					},
+				},
+			},
+		},
+	}
+
 	mapper := NewMapper()
-	_, err := mapper.FromAPIModel(input)
+	result, err := mapper.FromAPIModel(input)
 
-	require.NotNil(t, err)
-	require.Contains(t, err.Error(), "at least two elements are expected for logical and")
+	require.NoError(t, err)
+	require.Equal(t, expectedResult, result)
 }
 
 func TestShouldMapLogicalOrWithTwoPrimaryExpressionsFromInstanaAPI(t *testing.T) {