common: support user data

common/template.go

@@ -2,25 +2,29 @@ package common
 
 import (
 	"bytes"
+	"fmt"
 	"strconv"
 	"text/template"
 	"time"
 )
 
 type Template struct {
+	UserData map[string]string
+
 	root *template.Template
 }
 
 func NewTemplate() (*Template, error) {
-	root := template.New("configTemplateRoot")
-	root.Funcs(template.FuncMap{
-		"timestamp": templateTimestamp,
-	})
-
 	result := &Template{
-		root: root,
+		UserData: make(map[string]string),
 	}
 
+	result.root = template.New("configTemplateRoot")
+	result.root.Funcs(template.FuncMap{
+		"timestamp": templateTimestamp,
+		"user":      result.templateUser,
+	})
+
 	return result, nil
 }
 
@@ -38,6 +42,17 @@ func (t *Template) Process(s string, data interface{}) (string, error) {
 	return buf.String(), nil
 }
 
+// User is the function exposed as "user" within the templates and
+// looks up user variables.
+func (t *Template) templateUser(n string) (string, error) {
+	result, ok := t.UserData[n]
+	if !ok {
+		return "", fmt.Errorf("uknown user var: %s", n)
+	}
+
+	return result, nil
+}
+
 func templateTimestamp() string {
 	return strconv.FormatInt(time.Now().UTC().Unix(), 10)
 }

common/template_test.go

@@ -7,7 +7,7 @@ import (
 	"time"
 )
 
-func TestTemplateProcess(t *testing.T) {
+func TestTemplateProcess_timestamp(t *testing.T) {
 	tpl, err := NewTemplate()
 	if err != nil {
 		t.Fatalf("err: %s", err)
@@ -28,3 +28,21 @@ func TestTemplateProcess(t *testing.T) {
 		t.Fatalf("val: %d (current: %d)", val, currentTime)
 	}
 }
+
+func TestTemplateProcess_user(t *testing.T) {
+	tpl, err := NewTemplate()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	tpl.UserData["foo"] = "bar"
+
+	result, err := tpl.Process(`{{user "foo"}}`, nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if result != "bar" {
+		t.Fatalf("bad: %s", result)
+	}
+}