From d246fc07da3d5cd2ba3b49f54ff1f9abe1a78557 Mon Sep 17 00:00:00 2001
From: Krisztian Gacsal <chrisgacsal@users.noreply.github.com>
Date: Wed, 13 Nov 2024 16:21:46 +0100
Subject: [PATCH] fix: Plan discount JSON serialization

---
 openmeter/productcatalog/plan/discount.go     | 40 +++++++++--------
 .../productcatalog/plan/discount_test.go      | 44 +++++++++++++++++++
 .../productcatalog/plan/httpdriver/mapping.go |  3 --
 3 files changed, 66 insertions(+), 21 deletions(-)
 create mode 100644 openmeter/productcatalog/plan/discount_test.go

diff --git a/openmeter/productcatalog/plan/discount.go b/openmeter/productcatalog/plan/discount.go
index e85393141..97068fbbc 100644
--- a/openmeter/productcatalog/plan/discount.go
+++ b/openmeter/productcatalog/plan/discount.go
@@ -56,38 +56,49 @@ func (d *Discount) RateCardKeys() []string {
 func (d *Discount) MarshalJSON() ([]byte, error) {
 	var b []byte
 	var err error
+	var serde interface{}
 
 	switch d.t {
 	case PercentageDiscountType:
-		b, err = json.Marshal(d.percentage)
-		if err != nil {
-			return nil, fmt.Errorf("failed to json marshal percentage discount: %w", err)
+		serde = struct {
+			Type DiscountType `json:"type"`
+			*PercentageDiscount
+		}{
+			Type:               PercentageDiscountType,
+			PercentageDiscount: d.percentage,
 		}
 	default:
-		return nil, fmt.Errorf("invalid discount type: %s", d.t)
+		return nil, fmt.Errorf("invalid Discount type: %s", d.t)
+	}
+
+	b, err = json.Marshal(serde)
+	if err != nil {
+		return nil, fmt.Errorf("failed to JSON serialize Discount: %w", err)
 	}
 
 	return b, nil
 }
 
 func (d *Discount) UnmarshalJSON(bytes []byte) error {
-	meta := &DiscountMeta{}
+	serde := &struct {
+		Type DiscountType `json:"type"`
+	}{}
 
-	if err := json.Unmarshal(bytes, meta); err != nil {
-		return fmt.Errorf("failed to json unmarshal discount type: %w", err)
+	if err := json.Unmarshal(bytes, serde); err != nil {
+		return fmt.Errorf("failed to JSON deserialize Discount type: %w", err)
 	}
 
-	switch meta.Type {
+	switch serde.Type {
 	case PercentageDiscountType:
 		v := &PercentageDiscount{}
 		if err := json.Unmarshal(bytes, v); err != nil {
-			return fmt.Errorf("failed to json unmarshal percentage discount: %w", err)
+			return fmt.Errorf("failed to JSON deserialize Discount: %w", err)
 		}
 
 		d.percentage = v
 		d.t = PercentageDiscountType
 	default:
-		return fmt.Errorf("invalid discount type: %s", meta.Type)
+		return fmt.Errorf("invalid Discount type: %s", serde.Type)
 	}
 
 	return nil
@@ -127,7 +138,7 @@ func NewDiscountFrom[T PercentageDiscount](v T) Discount {
 	d := Discount{}
 
 	switch any(v).(type) {
-	case FlatPrice:
+	case PercentageDiscount:
 		percentage := any(v).(PercentageDiscount)
 		d.FromPercentage(percentage)
 	}
@@ -135,16 +146,9 @@ func NewDiscountFrom[T PercentageDiscount](v T) Discount {
 	return d
 }
 
-type DiscountMeta struct {
-	// Type of the Discount.
-	Type DiscountType `json:"type"`
-}
-
 var _ Validator = (*PercentageDiscount)(nil)
 
 type PercentageDiscount struct {
-	DiscountMeta
-
 	// Percentage defines percentage of the discount.
 	Percentage decimal.Decimal `json:"percentage"`
 
diff --git a/openmeter/productcatalog/plan/discount_test.go b/openmeter/productcatalog/plan/discount_test.go
new file mode 100644
index 000000000..58f233c55
--- /dev/null
+++ b/openmeter/productcatalog/plan/discount_test.go
@@ -0,0 +1,44 @@
+package plan
+
+import (
+	"testing"
+
+	decimal "github.com/alpacahq/alpacadecimal"
+	json "github.com/json-iterator/go"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDiscount_JSON(t *testing.T) {
+	tests := []struct {
+		Name          string
+		Discount      Discount
+		ExpectedError bool
+	}{
+		{
+			Name: "Valid",
+			Discount: NewDiscountFrom(PercentageDiscount{
+				Percentage: decimal.NewFromFloat(99.9),
+				RateCards: []string{
+					"ratecard-1",
+					"ratecard-2",
+				},
+			}),
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.Name, func(t *testing.T) {
+			b, err := json.Marshal(&test.Discount)
+			require.NoError(t, err)
+
+			t.Logf("Serialized Discount: %s", string(b))
+
+			d := Discount{}
+			err = json.Unmarshal(b, &d)
+			require.NoError(t, err)
+
+			assert.Equal(t, test.Discount, d)
+		})
+	}
+}
diff --git a/openmeter/productcatalog/plan/httpdriver/mapping.go b/openmeter/productcatalog/plan/httpdriver/mapping.go
index 32a3217ef..613a8a556 100644
--- a/openmeter/productcatalog/plan/httpdriver/mapping.go
+++ b/openmeter/productcatalog/plan/httpdriver/mapping.go
@@ -322,9 +322,6 @@ func AsPlanPhase(a api.PlanPhase, namespace, phaseID string) (plan.Phase, error)
 			switch discount.Type {
 			case api.DiscountPercentageTypePercentage:
 				percentageDiscount := plan.PercentageDiscount{
-					DiscountMeta: plan.DiscountMeta{
-						Type: plan.PercentageDiscountType,
-					},
 					Percentage: decimal.NewFromFloat(float64(discount.Percentage)),
 					RateCards:  lo.FromPtrOr(discount.RateCards, nil),
 				}