certificates/templates/templates.go
2020-01-28 13:28:16 -08:00

181 lines
4.1 KiB
Go

package templates
import (
"bytes"
"io/ioutil"
"text/template"
"github.com/Masterminds/sprig"
"github.com/pkg/errors"
)
// TemplateType defines how a template will be written in disk.
type TemplateType string
const (
// Snippet will mark a template as a part of a file.
Snippet TemplateType = "snippet"
// File will mark a templates as a full file.
File TemplateType = "file"
)
// Output represents the text representation of a rendered template.
type Output struct {
Name string `json:"name"`
Type TemplateType `json:"type"`
Comment string `json:"comment"`
Path string `json:"path"`
Content []byte `json:"content"`
}
// Templates is a collection of templates and variables.
type Templates struct {
SSH *SSHTemplates `json:"ssh,omitempty"`
Data map[string]interface{} `json:"data,omitempty"`
}
// Validate returns an error if a template is not valid.
func (t *Templates) Validate() (err error) {
if t == nil {
return nil
}
// Validate members
if err = t.SSH.Validate(); err != nil {
return
}
// Do not allow "Step" and "User"
if t.Data != nil {
if _, ok := t.Data["Step"]; ok {
return errors.New("templates variables cannot contain 'Step' as a property")
}
if _, ok := t.Data["User"]; ok {
return errors.New("templates variables cannot contain 'User' as a property")
}
}
return nil
}
// LoadAll preloads all templates in memory. It returns an error if an error is
// found parsing at least one template.
func LoadAll(t *Templates) (err error) {
if t.SSH != nil {
for _, tt := range t.SSH.User {
if err = tt.Load(); err != nil {
return err
}
}
for _, tt := range t.SSH.Host {
if err = tt.Load(); err != nil {
return err
}
}
}
return nil
}
// SSHTemplates contains the templates defining ssh configuration files.
type SSHTemplates struct {
User []Template `json:"user"`
Host []Template `json:"host"`
}
// Validate returns an error if a template is not valid.
func (t *SSHTemplates) Validate() (err error) {
if t == nil {
return nil
}
for _, tt := range t.User {
if err = tt.Validate(); err != nil {
return
}
}
for _, tt := range t.Host {
if err = tt.Validate(); err != nil {
return
}
}
return
}
// Template represents on template file.
type Template struct {
*template.Template
Name string `json:"name"`
Type TemplateType `json:"type"`
TemplatePath string `json:"template"`
Path string `json:"path"`
Comment string `json:"comment"`
}
// Validate returns an error if the template is not valid.
func (t *Template) Validate() error {
switch {
case t == nil:
return nil
case t.Name == "":
return errors.New("template name cannot be empty")
case t.TemplatePath == "":
return errors.New("template template cannot be empty")
case t.Path == "":
return errors.New("template path cannot be empty")
}
// Defaults
if t.Type == "" {
t.Type = Snippet
}
if t.Comment == "" {
t.Comment = "#"
}
return nil
}
// Load loads the template in memory, returns an error if the parsing of the
// template fails.
func (t *Template) Load() error {
if t.Template == nil {
b, err := ioutil.ReadFile(t.TemplatePath)
if err != nil {
return errors.Wrapf(err, "error reading %s", t.TemplatePath)
}
tmpl, err := template.New(t.Name).Funcs(sprig.TxtFuncMap()).Parse(string(b))
if err != nil {
return errors.Wrapf(err, "error parsing %s", t.TemplatePath)
}
t.Template = tmpl
}
return nil
}
// Render executes the template with the given data and returns the rendered
// version.
func (t *Template) Render(data interface{}) ([]byte, error) {
if err := t.Load(); err != nil {
return nil, err
}
buf := new(bytes.Buffer)
if err := t.Execute(buf, data); err != nil {
return nil, errors.Wrapf(err, "error executing %s", t.TemplatePath)
}
return buf.Bytes(), nil
}
// Output renders the template and returns a template.Output struct or an error.
func (t *Template) Output(data interface{}) (Output, error) {
b, err := t.Render(data)
if err != nil {
return Output{}, err
}
return Output{
Name: t.Name,
Type: t.Type,
Comment: t.Comment,
Path: t.Path,
Content: b,
}, nil
}