package packer import ( "bytes" "cgl.tideland.biz/identifier" "encoding/hex" "fmt" "strconv" "text/template" "time" ) // ConfigTemplate processes string data as a text/template with some common // elements and functions available. Plugin creators should process as // many fields as possible through this. type ConfigTemplate struct { UserVars map[string]string root *template.Template i int } // NewConfigTemplate creates a new configuration template processor. func NewConfigTemplate() (*ConfigTemplate, error) { result := &ConfigTemplate{ UserVars: make(map[string]string), } result.root = template.New("configTemplateRoot") result.root.Funcs(template.FuncMap{ "timestamp": templateTimestamp, "user": result.templateUser, "uuid": templateUuid, }) return result, nil } // Process processes a single string, compiling and executing the template. func (t *ConfigTemplate) Process(s string, data interface{}) (string, error) { tpl, err := t.root.New(t.nextTemplateName()).Parse(s) if err != nil { return "", err } buf := new(bytes.Buffer) if err := tpl.Execute(buf, data); err != nil { return "", err } return buf.String(), nil } // Validate the template. func (t *ConfigTemplate) Validate(s string) error { root, err := t.root.Clone() if err != nil { return err } _, err = root.New("template").Parse(s) return err } func (t *ConfigTemplate) nextTemplateName() string { name := fmt.Sprintf("tpl%d", t.i) t.i++ return name } // User is the function exposed as "user" within the templates and // looks up user variables. func (t *ConfigTemplate) templateUser(n string) (string, error) { result, ok := t.UserVars[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) } func templateUuid() string { return hex.EncodeToString(identifier.NewUUID().Raw()) }