Provide basic string manupilation functions for template executions.

This change centralizes the template manipulation in a single package
and adds basic string functions to their execution.

Signed-off-by: David Calavera <david.calavera@gmail.com>

utils/templates/templates.go

@@ -0,0 +1,33 @@
+package templates
+
+import (
+	"encoding/json"
+	"strings"
+	"text/template"
+)
+
+// basicFunctions are the set of initial
+// functions provided to every template.
+var basicFunctions = template.FuncMap{
+	"json": func(v interface{}) string {
+		a, _ := json.Marshal(v)
+		return string(a)
+	},
+	"split": strings.Split,
+	"join":  strings.Join,
+	"title": strings.Title,
+	"lower": strings.ToLower,
+	"upper": strings.ToUpper,
+}
+
+// Parse creates a new annonymous template with the basic functions
+// and parses the given format.
+func Parse(format string) (*template.Template, error) {
+	return NewParse("", format)
+}
+
+// NewParse creates a new tagged template with the basic functions
+// and parses the given format.
+func NewParse(tag, format string) (*template.Template, error) {
+	return template.New(tag).Funcs(basicFunctions).Parse(format)
+}

utils/templates/templates_test.go

@@ -0,0 +1,38 @@
+package templates
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestParseStringFunctions(t *testing.T) {
+	tm, err := Parse(`{{join (split . ":") "/"}}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var b bytes.Buffer
+	if err := tm.Execute(&b, "text:with:colon"); err != nil {
+		t.Fatal(err)
+	}
+	want := "text/with/colon"
+	if b.String() != want {
+		t.Fatalf("expected %s, got %s", want, b.String())
+	}
+}
+
+func TestNewParse(t *testing.T) {
+	tm, err := NewParse("foo", "this is a {{ . }}")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var b bytes.Buffer
+	if err := tm.Execute(&b, "string"); err != nil {
+		t.Fatal(err)
+	}
+	want := "this is a string"
+	if b.String() != want {
+		t.Fatalf("expected %s, got %s", want, b.String())
+	}
+}