align smartcsv output with other formats

make api call universal, so CSV can be saved anywhere
by the client
make CLI print the smart CSV to stdout as with other formats

api.go

@@ -9,7 +9,6 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
-	"os"
 
 	"golang.org/x/oauth2"
 )
@@ -371,20 +370,12 @@ func (auth *Client) GetTransactions(from, to TimeStamp, limit string) (*Transact
 }
 
 // Get transactions for the given time window as N26 CSV file. Stored as 'smrt_statement.csv'
-func (auth *Client) GetSmartStatementCsv(from, to TimeStamp) error {
+func (auth *Client) GetSmartStatementCsv(from, to TimeStamp, reader func (io.Reader) error) error {
 	//Filter is applied only if both values are set
 	if from.IsZero() || to.IsZero() {
 		return errors.New("Start and end time must be set")
 	}
-	return auth.n26RawRequest(http.MethodGet, fmt.Sprintf("/api/smrt/reports/%v/%v/statements", from.AsMillis(), to.AsMillis()), nil, func(r io.Reader) error {
-		file, err := os.Create("smrt_statement.csv")
-		if err != nil {
-			return err
-		}
-		defer file.Close()
-		_, err = io.Copy(file, r)
-		return err
-	})
+	return auth.n26RawRequest(http.MethodGet, fmt.Sprintf("/api/smrt/reports/%v/%v/statements", from.AsMillis(), to.AsMillis()), nil, reader)
 }
 
 func (auth *Client) GetStatements(retType string) (string, *Statements) {

cmd/n26/n26.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"sort"
 	"strconv"
@@ -256,8 +257,10 @@ func main() {
 						fmt.Println("Start and end time must be set for smart CSV!")
 						return nil
 					}
-					err = API.GetSmartStatementCsv(from, to)
-					fmt.Println("Report saved as smrt_statement.csv.")
+					err = API.GetSmartStatementCsv(from, to, func(r io.Reader) error {
+						_, err := io.Copy(os.Stdout, r)
+						return err
+					})
 					return
 				}
 				writer, err := getTransactionWriter(c.Args().First())