From 2f44c9f5c9bf72927313d35e4dfaa478711943fb Mon Sep 17 00:00:00 2001
From: Pavel Gabriel <alovak@gmail.com>
Date: Mon, 11 Sep 2023 16:05:48 +0200
Subject: [PATCH] implement unmarshal

---
 exp_test.go             | 39 +++++++++++++++++++++++++++++++++++++++
 field/composite_test.go |  2 +-
 field/string.go         | 37 +++++++++++++++++++++++++++----------
 message.go              | 16 ++++++++++++----
 4 files changed, 79 insertions(+), 15 deletions(-)

diff --git a/exp_test.go b/exp_test.go
index 970358c..4e88c61 100644
--- a/exp_test.go
+++ b/exp_test.go
@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/moov-io/iso8583"
+	"github.com/moov-io/iso8583/field"
 	"github.com/moov-io/iso8583/specs"
 	"github.com/stretchr/testify/require"
 )
@@ -164,4 +165,42 @@ func TestStructWithTypes(t *testing.T) {
 			})
 		}
 	})
+
+	t.Run("unpack", func(t *testing.T) {
+		type authRequest struct {
+			MTI                  string `index:"0"`
+			PrimaryAccountNumber string `index:"2"`
+		}
+
+		packed := []byte("011040000000000000000000000000000000164242424242424242")
+
+		message := iso8583.NewMessage(specs.Spec87ASCII)
+		err := message.Unpack(packed)
+		require.NoError(t, err)
+
+		data := authRequest{}
+		err = message.Unmarshal(&data)
+		require.NoError(t, err)
+		require.Equal(t, "0110", data.MTI)
+		require.Equal(t, "4242424242424242", data.PrimaryAccountNumber)
+	})
+
+	t.Run("unpack2", func(t *testing.T) {
+		type authRequest struct {
+			MTI                  *string       `index:"0"`
+			PrimaryAccountNumber *field.String `index:"2"`
+		}
+
+		packed := []byte("011040000000000000000000000000000000164242424242424242")
+
+		message := iso8583.NewMessage(specs.Spec87ASCII)
+		err := message.Unpack(packed)
+		require.NoError(t, err)
+
+		data := authRequest{}
+		err = message.Unmarshal(&data)
+		require.NoError(t, err)
+		require.Equal(t, "0110", *data.MTI)
+		require.Equal(t, "4242424242424242", data.PrimaryAccountNumber.Value())
+	})
 }
diff --git a/field/composite_test.go b/field/composite_test.go
index 83e0ea7..f789adb 100644
--- a/field/composite_test.go
+++ b/field/composite_test.go
@@ -745,7 +745,7 @@ func TestCompositePacking(t *testing.T) {
 		err = composite.Unmarshal(data)
 
 		require.Error(t, err)
-		require.EqualError(t, err, "failed to get data from field 1: data does not match required *String type")
+		require.Contains(t, err.Error(), "failed to get data from field 1: data does not match required *String")
 	})
 
 	t.Run("Unpack returns an error on failure of subfield to unpack bytes", func(t *testing.T) {
diff --git a/field/string.go b/field/string.go
index 0640390..598712d 100644
--- a/field/string.go
+++ b/field/string.go
@@ -2,8 +2,8 @@ package field
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
+	"reflect"
 	"strconv"
 
 	"github.com/moov-io/iso8583/utils"
@@ -111,17 +111,34 @@ func (f *String) Unpack(data []byte) (int, error) {
 }
 
 func (f *String) Unmarshal(v interface{}) error {
-	if v == nil {
-		return nil
-	}
-
-	str, ok := v.(*String)
-	if !ok {
-		return errors.New("data does not match required *String type")
+	switch val := v.(type) {
+	case reflect.Value:
+		switch val.Kind() {
+		case reflect.String:
+			val.SetString(f.value)
+		case reflect.Int:
+			i, err := strconv.Atoi(f.value)
+			if err != nil {
+				return fmt.Errorf("failed to convert string to int: %w", err)
+			}
+			val.SetInt(int64(i))
+		default:
+			return fmt.Errorf("data does not match required reflect.Value type")
+		}
+	case *string:
+		*val = f.value
+	case *int:
+		i, err := strconv.Atoi(f.value)
+		if err != nil {
+			return fmt.Errorf("failed to convert string to int: %w", err)
+		}
+		*val = i
+	case *String:
+		val.value = f.value
+	default:
+		return fmt.Errorf("data does not match required *String or *string type")
 	}
 
-	str.value = f.value
-
 	return nil
 }
 
diff --git a/message.go b/message.go
index 7cd406c..59bb884 100644
--- a/message.go
+++ b/message.go
@@ -433,11 +433,19 @@ func (m *Message) Unmarshal(v interface{}) error {
 		}
 
 		dataField := dataStruct.Field(i)
-		if dataField.IsNil() {
-			dataField.Set(reflect.New(dataField.Type().Elem()))
-		}
 
-		err = messageField.Unmarshal(dataField.Interface())
+		// if field is pointer we will pass pointer to the field
+		if dataField.Kind() == reflect.Ptr {
+			if dataField.IsZero() {
+				fmt.Println("is zero")
+				dataField.Set(reflect.New(dataField.Type().Elem()))
+			}
+
+			err = messageField.Unmarshal(dataField.Interface())
+		} else {
+			// if field is not pointer we will pass the field as reflect.Value
+			err = messageField.Unmarshal(dataField)
+		}
 		if err != nil {
 			return fmt.Errorf("failed to get value from field %d: %w", fieldIndex, err)
 		}