Split main into functions

main.go

@@ -12,29 +12,65 @@ import (
 
 func main() {
 	filename := "./main.tf"
-	src, err := ioutil.ReadFile(filename)
+
+	err := updateFile(filename)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "failed to open file: %s, err = %+v\n", filename, err)
+		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
+}
+
+func updateFile(filename string) error {
+	f, err := parseConfig(filename)
+	if err != nil {
+		return err
+	}
+
+	err = updateTerraform(f)
+	if err != nil {
+		return err
+	}
+
+	err = updateProvider(f)
+	if err != nil {
+		return err
+	}
+
+	tokens := f.BuildTokens(nil)
+	buf := hclwrite.Format(tokens.Bytes())
+
+	fmt.Printf("%s\n", buf)
+	return nil
+}
+
+func parseConfig(filename string) (*hclwrite.File, error) {
+	src, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open file: %s, err = %+v", filename, err)
+	}
 
 	f, diags := hclwrite.ParseConfig(src, filename, hcl.Pos{Line: 1, Column: 1})
 	if diags.HasErrors() {
-		fmt.Fprintf(os.Stderr, "failed to parse file: %s", diags)
-		os.Exit(1)
+		return nil, fmt.Errorf("failed to parse file: %s", diags)
 	}
 
+	return f, nil
+}
+
+func updateTerraform(f *hclwrite.File) error {
 	tf := f.Body().FirstMatchingBlock("terraform", []string{})
 	tf.Body().SetAttributeValue("required_version", cty.StringVal("0.12.6"))
 
+	return nil
+}
+
+func updateProvider(f *hclwrite.File) error {
+	tf := f.Body().FirstMatchingBlock("terraform", []string{})
 	providers := tf.Body().FirstMatchingBlock("required_providers", []string{})
 	providers.Body().SetAttributeValue("null", cty.StringVal("2.1.2"))
 
 	aws := f.Body().FirstMatchingBlock("provider", []string{"aws"})
 	aws.Body().SetAttributeValue("version", cty.StringVal("2.23.0"))
 
-	tokens := f.BuildTokens(nil)
-	buf := hclwrite.Format(tokens.Bytes())
-
-	fmt.Printf("%s\n", buf)
+	return nil
 }