support changing tags order when editing transaction

pkg/api/transactions.go

@@ -320,8 +320,6 @@ func (a *TransactionsApi) TransactionModifyHandler(c *core.Context) (interface{}
 	}
 
 	transactionTagIds := allTransactionTagIds[transaction.TransactionId]
-	addTransactionTagIds := utils.Int64SliceMinus(tagIds, transactionTagIds)
-	removeTransactionTagIds := utils.Int64SliceMinus(transactionTagIds, tagIds)
 
 	newTransaction := &models.Transaction{
 		TransactionId:   transaction.TransactionId,
@@ -345,11 +343,18 @@ func (a *TransactionsApi) TransactionModifyHandler(c *core.Context) (interface{}
 		(transaction.Type != models.TRANSACTION_DB_TYPE_TRANSFER_OUT || newTransaction.RelatedAccountId == transaction.RelatedAccountId) &&
 		(transaction.Type != models.TRANSACTION_DB_TYPE_TRANSFER_OUT || newTransaction.RelatedAccountAmount == transaction.RelatedAccountAmount) &&
 		newTransaction.Comment == transaction.Comment &&
-		len(addTransactionTagIds) < 1 &&
-		len(removeTransactionTagIds) < 1 {
+		utils.Int64SliceEquals(tagIds, transactionTagIds) {
 		return nil, errs.ErrNothingWillBeUpdated
 	}
 
+	var addTransactionTagIds []int64
+	var removeTransactionTagIds []int64
+
+	if !utils.Int64SliceEquals(tagIds, transactionTagIds) {
+		removeTransactionTagIds = transactionTagIds
+		addTransactionTagIds = tagIds
+	}
+
 	err = a.transactions.ModifyTransaction(newTransaction, addTransactionTagIds, removeTransactionTagIds)
 
 	if err != nil {

pkg/utils/slices.go

@@ -1,5 +1,24 @@
 package utils
 
+// Int64SliceEquals returns whether specific two int64 arrays equal
+func Int64SliceEquals(s1, s2 []int64) bool {
+	if (s1 == nil) != (s2 == nil) {
+		return false
+	}
+
+	if len(s1) != len(s2) {
+		return false
+	}
+
+	for i := 0; i < len(s1); i++ {
+		if s1[i] != s2[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
 // Int64SliceMinus returns a int64 array which contains items in s1 but not in s2
 func Int64SliceMinus(s1, s2 []int64) []int64 {
 	if s1 == nil {