packer-cn/packer/config_template.go

89 lines
1.9 KiB
Go

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())
}