Adds encoding and decoding of cast in trasnformer#trasnform

commands/speed.go

@@ -69,33 +69,27 @@ func (t *SpeedTransformation) Transform(c *cast.Cast) (err error) {
 
 func speedAction(c *cli.Context) (err error) {
 	var (
-		input  = c.Args().First()
-		output = c.String("out")
+		input          = c.Args().First()
+		output         = c.String("out")
+		transformation = &SpeedTransformation{
+			factor: c.Float64("factor"),
+			from:   c.Float64("start"),
+			to:     c.Float64("end"),
+		}
 	)
 
-	transformation := &SpeedTransformation{
-		factor: c.Float64("factor"),
-		from:   c.Float64("start"),
-		to:     c.Float64("end"),
-	}
-
 	t, err := transformer.New(transformation, input, output)
 	if err != nil {
-		err = cli.NewExitError(
-			"failed to create transformation: " +
-				err.Error(), 1)
+		err = cli.NewExitError(err, 1)
 		return
 	}
 
-	err = t.Apply()
+	err = t.Transform()
 	if err != nil {
-		err = cli.NewExitError(
-			"failed to apply transformation: " +
-				err.Error(), 1)
+		err = cli.NewExitError(err, 1)
 		return
 	}
 
 	t.Close()
-
 	return
 }

commands/transformer/transformer.go

@@ -14,8 +14,7 @@ type Transformation interface {
 type Transformer struct {
 	input          *os.File
 	output         *os.File
-	cast           *cast.Cast
-	Transformation Transformation
+	transformation Transformation
 }
 
 func New(t Transformation, input, output string) (m *Transformer, err error) {
@@ -27,7 +26,7 @@ func New(t Transformation, input, output string) (m *Transformer, err error) {
 	m = &Transformer{
 		input:          os.Stdin,
 		output:         os.Stdout,
-		Transformation: t,
+		transformation: t,
 	}
 
 	if input != "" {
@@ -66,8 +65,30 @@ func New(t Transformation, input, output string) (m *Transformer, err error) {
 	return
 }
 
-func (m *Transformer) Apply() (err error) {
-	err = m.Transformation.Transform(m.cast)
+func (m *Transformer) Transform() (err error) {
+	var decodedCast *cast.Cast
+
+	decodedCast, err = cast.Decode(m.input)
+	if err != nil {
+		err = errors.Wrapf(err,
+			"failed to decode cast from input")
+		return
+	}
+
+	err = m.transformation.Transform(decodedCast)
+	if err != nil {
+		err = errors.Wrapf(err,
+			"failed to transform cast")
+		return
+	}
+
+	err = cast.Encode(m.output, decodedCast)
+	if err != nil {
+		err = errors.Wrapf(err,
+			"failed to save modified cast")
+		return
+	}
+
 	return
 }