Fix Chapa verify JSON parsing when amount is numeric.

Accept string or number for amount in verify and webhook payloads so GET /payments/verify can complete successfully.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/domain/chapa.go

@@ -1,5 +1,41 @@
 package domain
 
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// ChapaFlexibleString unmarshals JSON string or number (Chapa verify/webhook payloads vary).
+type ChapaFlexibleString string
+
+func (s *ChapaFlexibleString) UnmarshalJSON(data []byte) error {
+	if len(data) == 0 || string(data) == "null" {
+		*s = ""
+		return nil
+	}
+	switch data[0] {
+	case '"':
+		var v string
+		if err := json.Unmarshal(data, &v); err != nil {
+			return err
+		}
+		*s = ChapaFlexibleString(v)
+	case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-':
+		var n json.Number
+		if err := json.Unmarshal(data, &n); err != nil {
+			return err
+		}
+		*s = ChapaFlexibleString(n.String())
+	default:
+		return fmt.Errorf("chapa flexible string: unsupported json type %q", data[0])
+	}
+	return nil
+}
+
+func (s ChapaFlexibleString) String() string {
+	return string(s)
+}
+
 // ChapaInitializeRequest is sent to POST /transaction/initialize.
 type ChapaInitializeRequest struct {
 	Amount      string `json:"amount"`
@@ -32,13 +68,13 @@ type ChapaVerifyResponse struct {
 }
 
 type ChapaTransactionData struct {
-	TxRef         string `json:"tx_ref"`
-	Reference     string `json:"reference"`
-	Amount        string `json:"amount"`
-	Currency      string `json:"currency"`
-	Status        string `json:"status"`
-	PaymentMethod string `json:"payment_method"`
-	Mode          string `json:"mode"`
+	TxRef         string             `json:"tx_ref"`
+	Reference     string             `json:"reference"`
+	Amount        ChapaFlexibleString `json:"amount"`
+	Currency      string             `json:"currency"`
+	Status        string             `json:"status"`
+	PaymentMethod string             `json:"payment_method"`
+	Mode          string             `json:"mode"`
 }
 
 // ChapaWebhookPayload is the body POSTed to the webhook URL.
@@ -48,7 +84,7 @@ type ChapaWebhookPayload struct {
 	TxRef         string  `json:"tx_ref"`
 	Reference     string  `json:"reference"`
 	Status        string  `json:"status"`
-	Amount        string  `json:"amount"`
+	Amount        ChapaFlexibleString `json:"amount"`
 	Currency      string  `json:"currency"`
 	PaymentMethod string  `json:"payment_method"`
 	Mode          string  `json:"mode"`

internal/domain/chapa_test.go

@@ -0,0 +1,44 @@
+package domain
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestChapaFlexibleString_UnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name    string
+		raw     string
+		want    string
+		wantErr bool
+	}{
+		{name: "string amount", raw: `"500.00"`, want: "500.00"},
+		{name: "number amount", raw: `500`, want: "500"},
+		{name: "float amount", raw: `499.99`, want: "499.99"},
+		{name: "null", raw: `null`, want: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var s ChapaFlexibleString
+			err := json.Unmarshal([]byte(tt.raw), &s)
+			if (err != nil) != tt.wantErr {
+				t.Fatalf("err=%v wantErr=%v", err, tt.wantErr)
+			}
+			if s.String() != tt.want {
+				t.Fatalf("got %q want %q", s.String(), tt.want)
+			}
+		})
+	}
+}
+
+func TestChapaVerifyResponse_UnmarshalNumberAmount(t *testing.T) {
+	raw := `{"status":"success","message":"ok","data":{"tx_ref":"tx-1","reference":"ref-1","amount":500,"currency":"ETB","status":"success","payment_method":"telebirr"}}`
+	var resp ChapaVerifyResponse
+	if err := json.Unmarshal([]byte(raw), &resp); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if resp.Data.Amount.String() != "500" {
+		t.Fatalf("amount=%q want 500", resp.Data.Amount.String())
+	}
+}