copy template helper (#10)

template.go

@@ -1,24 +1,37 @@
 package junocfg
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
+	"regexp"
+	"strings"
 	"text/template"
-	//	"gopkg.in/yaml.v2"
+
+	"gopkg.in/yaml.v2"
 )
 
 func CheckTemplate(tmpl []byte) (*template.Template, error) {
-	t, err := template.New("template").Parse(string(tmpl))
+	helpers := template.FuncMap{
+		"copy": copyFunc(bytes.NewBuffer([]byte{})),
+	}
+
+	t, err := template.New("template").Funcs(helpers).Parse(string(tmpl))
 	return t, err
 }
 
 func RenderAndCheckTemplate(tmpl []byte, settingsMap map[string]interface{}) (string, error) {
-	t, err := CheckTemplate(tmpl)
+	buffer := bytes.NewBuffer([]byte{})
+
+	helpers := template.FuncMap{
+		"copy": copyFunc(buffer),
+	}
+
+	t, err := template.New("template").Funcs(helpers).Parse(string(tmpl))
 	if err != nil {
 		return "", fmt.Errorf("check template failed [%s]\n", err)
 	}
 
-	buffer := bytes.NewBuffer([]byte{})
 	if err := t.Execute(buffer, settingsMap); err != nil {
 		return "", fmt.Errorf("failed to render template [%s]\n", err)
 	}
@@ -31,3 +44,47 @@ func RenderAndCheckTemplate(tmpl []byte, settingsMap map[string]interface{}) (st
 	}
 	return buffer.String(), nil
 }
+
+//copy returns a template helper that is aware of it's current indent
+//and copies given data to the result YAML according to this indent
+func copyFunc(buf *bytes.Buffer) func(interface{}) (string, error) {
+	return func(in interface{}) (result string, err error) {
+		b, err := yaml.Marshal(in)
+		if err != nil {
+			return "", err
+		}
+
+		indent, err := indent(buf)
+		if err != nil {
+			return "", err
+		}
+
+		rr := []string{}
+		scanner := bufio.NewScanner(bytes.NewBuffer(b))
+		for scanner.Scan() {
+			rr = append(rr, scanner.Text()+"\n")
+		}
+
+		return strings.Join(rr, indent), scanner.Err()
+	}
+}
+
+var rxSpaces = regexp.MustCompile("^\\s*$")
+
+func indent(b *bytes.Buffer) (string, error) {
+	var line string
+	scanner := bufio.NewScanner(bytes.NewBuffer(b.Bytes()))
+	for scanner.Scan() {
+		line = scanner.Text()
+	}
+
+	if err := scanner.Err(); err != nil {
+		return "", err
+	}
+
+	if rxSpaces.MatchString(line) {
+		return line, nil
+	}
+
+	return "", nil
+}