code refactoring

field/composite.go

@@ -6,14 +6,12 @@ import (
 	"fmt"
 	"math"
 	"reflect"
-	"regexp"
 	"strconv"
 	"sync"
 
 	"github.com/moov-io/iso8583/encoding"
 	"github.com/moov-io/iso8583/prefix"
 	"github.com/moov-io/iso8583/sort"
-
 	"github.com/moov-io/iso8583/utils"
 )
 
@@ -676,21 +674,9 @@ func orderedKeys(kvs map[string]Field, sorter sort.StringSlice) []string {
 	return keys
 }
 
-var fieldNameTagRe = regexp.MustCompile(`^F.+$`)
-
 // getFieldIndexOrTag returns index or tag of the field. First, it checks the
 // field name. If it does not match F.+ pattern, it checks value of `index`
 // tag.  If empty string, then index/tag was not found for the field.
 func getFieldIndexOrTag(field reflect.StructField) (string, error) {
-	dataFieldName := field.Name
-
-	if fieldIndex := field.Tag.Get("index"); fieldIndex != "" {
-		return fieldIndex, nil
-	}
-
-	if len(dataFieldName) > 0 && fieldNameTagRe.MatchString(dataFieldName) {
-		return dataFieldName[1:], nil
-	}
-
-	return "", nil
+	return NewIndexTag(field).Tag, nil
 }

index_tag.go → field/index_tag.go

@@ -1,11 +1,14 @@
-package iso8583
+package field
 
 import (
 	"reflect"
+	"regexp"
 	"strconv"
 	"strings"
 )
 
+var fieldNameIndexRe = regexp.MustCompile(`^F.+$`)
+
 type IndexTag struct {
 	Id int // is -1 if index is not a number
 

message.go

@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
-	"regexp"
 	"sort"
 	"strconv"
 	"sync"
@@ -427,7 +426,7 @@ func (m *Message) Marshal(v interface{}) error {
 
 	// iterate over struct fields
 	for i := 0; i < dataStruct.NumField(); i++ {
-		indexTag := NewIndexTag(dataStruct.Type().Field(i))
+		indexTag := field.NewIndexTag(dataStruct.Type().Field(i))
 
 		// skip field without index or if index in tag is not defined
 		if indexTag.Id < 0 {
@@ -486,23 +485,19 @@ func (m *Message) Unmarshal(v interface{}) error {
 
 	// iterate over struct fields
 	for i := 0; i < dataStruct.NumField(); i++ {
-		fieldIndex, err := getFieldIndex(dataStruct.Type().Field(i))
-		if err != nil {
-			return fmt.Errorf("getting field %d index: %w", i, err)
-		}
-
-		// skip field without index
-		if fieldIndex < 0 {
-			continue
+		indexTag := field.NewIndexTag(dataStruct.Type().Field(i))
+		// skip field without index or if index in tag is not defined
+		if indexTag.Id < 0 {
+			return fmt.Errorf("getting field %d index error", i)
 		}
 
 		// we can get data only if field value is set
-		messageField := m.GetField(fieldIndex)
+		messageField := m.GetField(indexTag.Id)
 		if messageField == nil {
 			continue
 		}
 
-		if _, set := m.fieldsMap[fieldIndex]; !set {
+		if _, set := m.fieldsMap[indexTag.Id]; !set {
 			continue
 		}
 
@@ -512,47 +507,17 @@ func (m *Message) Unmarshal(v interface{}) error {
 			if dataField.IsNil() || dataField.IsZero() {
 				dataField.Set(reflect.New(dataField.Type().Elem()))
 			}
-			err = messageField.Unmarshal(dataField.Interface())
+			err := messageField.Unmarshal(dataField.Interface())
 			if err != nil {
-				return fmt.Errorf("failed to get value from field %d: %w", fieldIndex, err)
+				return fmt.Errorf("failed to get value from field %d: %w", indexTag.Id, err)
 			}
 		default: // Native types
-			err = messageField.Unmarshal(dataField)
+			err := messageField.Unmarshal(dataField)
 			if err != nil {
-				return fmt.Errorf("failed to get value from field %d: %w", fieldIndex, err)
+				return fmt.Errorf("failed to get value from field %d: %w", indexTag.Id, err)
 			}
 		}
 	}
 
 	return nil
 }
-
-var fieldNameIndexRe = regexp.MustCompile(`^F\d+$`)
-
-// fieldIndex returns index of the field. First, it checks field name. If it
-// does not match FNN (when NN is digits), it checks value of `index` tag.  If
-// negative value returned (-1) then index was not found for the field.
-func getFieldIndex(field reflect.StructField) (int, error) {
-	dataFieldName := field.Name
-
-	if indexStr := field.Tag.Get("index"); indexStr != "" {
-		fieldIndex, err := strconv.Atoi(indexStr)
-		if err != nil {
-			return -1, fmt.Errorf("converting field index into int: %w", err)
-		}
-
-		return fieldIndex, nil
-	}
-
-	if len(dataFieldName) > 0 && fieldNameIndexRe.MatchString(dataFieldName) {
-		indexStr := dataFieldName[1:]
-		fieldIndex, err := strconv.Atoi(indexStr)
-		if err != nil {
-			return -1, fmt.Errorf("converting field index into int: %w", err)
-		}
-
-		return fieldIndex, nil
-	}
-
-	return -1, nil
-}

message_test.go

@@ -1415,21 +1415,17 @@ func Test_getFieldIndex(t *testing.T) {
 			F1 string
 		}{}).Elem()
 
-		index, err := getFieldIndex(st.Type().Field(0))
-
-		require.NoError(t, err)
-		require.Equal(t, 1, index)
+		indexTag := field.NewIndexTag(st.Type().Field(0))
+		require.Equal(t, 1, indexTag.Id)
 	})
 
 	t.Run("returns index from field tag instead of field name when both match", func(t *testing.T) {
 		st := reflect.ValueOf(&struct {
 			F1 string `index:"2"`
 		}{}).Elem()
 
-		index, err := getFieldIndex(st.Type().Field(0))
-
-		require.NoError(t, err)
-		require.Equal(t, 2, index)
+		indexTag := field.NewIndexTag(st.Type().Field(0))
+		require.Equal(t, 2, indexTag.Id)
 	})
 
 	t.Run("returns index from field tag", func(t *testing.T) {
@@ -1440,43 +1436,33 @@ func Test_getFieldIndex(t *testing.T) {
 		}{}).Elem()
 
 		// get index from field Name
-		_, err := getFieldIndex(st.Type().Field(0))
-
-		require.Error(t, err)
-		require.EqualError(t, err, "converting field index into int: strconv.Atoi: parsing \"abcd\": invalid syntax")
+		indexTag := field.NewIndexTag(st.Type().Field(0))
+		require.Equal(t, -1, indexTag.Id)
 
 		// get index from field F
-		index, err := getFieldIndex(st.Type().Field(1))
-
-		require.NoError(t, err)
-		require.Equal(t, 2, index)
+		indexTag = field.NewIndexTag(st.Type().Field(1))
+		require.Equal(t, 2, indexTag.Id)
 
 		// get index from field Amount
-		index, err = getFieldIndex(st.Type().Field(2))
-
-		require.NoError(t, err)
-		require.Equal(t, 3, index)
+		indexTag = field.NewIndexTag(st.Type().Field(2))
+		require.Equal(t, 3, indexTag.Id)
 	})
 
 	t.Run("returns empty string when no tag and field name does not match the pattern", func(t *testing.T) {
 		st := reflect.ValueOf(&struct {
 			Name string
 		}{}).Elem()
 
-		index, err := getFieldIndex(st.Type().Field(0))
-
-		require.NoError(t, err)
-		require.Equal(t, -1, index)
+		indexTag := field.NewIndexTag(st.Type().Field(0))
+		require.Equal(t, -1, indexTag.Id)
 
 		// single letter field without tag is ignored
 		st = reflect.ValueOf(&struct {
 			F string
 		}{}).Elem()
 
-		index, err = getFieldIndex(st.Type().Field(0))
-
-		require.NoError(t, err)
-		require.Equal(t, -1, index)
+		indexTag = field.NewIndexTag(st.Type().Field(0))
+		require.Equal(t, -1, indexTag.Id)
 	})
 }