refactor stdin check

cmd/root.go

@@ -18,7 +18,6 @@ package cmd
 
 import (
 	"errors"
-	"log"
 	"os"
 
 	"github.com/spf13/cobra"
@@ -28,6 +27,21 @@ import (
 var presets []string
 var transition bool
 
+/*
+ * checkStdin checks if any data has been passed in through stdin and returns
+ * an error if we don't believe so.
+ */
+func checkStdin() error {
+	stat, err := os.Stdin.Stat()
+	if err != nil {
+		return err
+	} else if (stat.Mode() & os.ModeCharDevice) != 0 {
+		return errors.New("nothing to read from stdin")
+	}
+
+	return nil
+}
+
 /*
  * validatePresets performs some basic checks on the presets passed in and
  * returns an error if it finds a problem.
@@ -108,11 +122,9 @@ func update(m *milkDropWindow) (bool, error) {
  * milkbucket sets up the program and starts a rendering loop.
  */
 func milkbucket(cmd *cobra.Command, args []string) {
-	stat, err := os.Stdin.Stat()
+	err := checkStdin()
 	if err != nil {
 		panic(err)
-	} else if (stat.Mode() & os.ModeCharDevice) != 0 {
-		log.Fatal("nothing to read from stdin")
 	}
 
 	err = sdl.Init(sdl.INIT_VIDEO)