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registry.go
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registry.go
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// Copyright © 2019 The Things Network Foundation, The Things Industries B.V.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package email
import (
"fmt"
"html/template"
"sync"
"go.thethings.network/lorawan-stack/v3/pkg/errors"
"go.thethings.network/lorawan-stack/v3/pkg/fetch"
)
// TemplateRegistry contains multiple email templates, identified by name.
type TemplateRegistry struct {
fetcher fetch.Interface
registry sync.Map
shared *template.Template
}
// NewTemplateRegistry returns a new template registry that uses the given fetcher.
func NewTemplateRegistry(fetcher fetch.Interface, includes ...string) (*TemplateRegistry, error) {
r := &TemplateRegistry{
fetcher: fetcher,
shared: template.New("").Funcs(defaultFuncs),
}
for _, include := range includes {
data, err := fetcher.File(include)
if err != nil {
return nil, err
}
shared, err := r.shared.New(include).Parse(string(data))
if err != nil {
return nil, err
}
r.shared = shared
}
return r, nil
}
type registeredTemplate struct {
m *MessageTemplate
err error
ready chan struct{}
}
func (r *TemplateRegistry) getTemplate(data MessageData) (m *MessageTemplate, err error) {
name := data.TemplateName()
registeredI, ok := r.registry.LoadOrStore(name, ®isteredTemplate{ready: make(chan struct{})})
registered := registeredI.(*registeredTemplate)
if ok {
<-registered.ready
return registered.m, registered.err
}
defer func() {
registered.m, registered.err = m, err
close(registered.ready)
}()
m = &MessageTemplate{Name: name}
subject, html, text := data.DefaultTemplates()
if r.fetcher != nil {
subjectBytes, err := r.fetcher.File(fmt.Sprintf("%s.subject.txt", name))
if err != nil && !errors.IsNotFound(err) {
return nil, err
}
if len(subjectBytes) > 0 {
subject = string(subjectBytes)
}
htmlBytes, err := r.fetcher.File(fmt.Sprintf("%s.html", name))
if err != nil && !errors.IsNotFound(err) {
return nil, err
}
if len(htmlBytes) > 0 {
html = string(htmlBytes)
}
textBytes, err := r.fetcher.File(fmt.Sprintf("%s.txt", name))
if err != nil && !errors.IsNotFound(err) {
return nil, err
}
if len(textBytes) > 0 {
text = string(textBytes)
}
}
template, err := r.shared.Clone()
if err != nil {
return nil, err
}
m.SubjectTemplate, err = template.New(name + "_subject").Parse(subject)
if err != nil {
return nil, err
}
m.HTMLTemplate, err = template.New(name + "_html_body").Parse(html)
if err != nil {
return nil, err
}
if text != "" {
m.TextTemplate, err = template.New(name + "_text_body").Parse(text)
if err != nil {
return nil, err
}
}
return m, nil
}
// Render message template data into a message.
func (r *TemplateRegistry) Render(data MessageData) (*Message, error) {
template, err := r.getTemplate(data)
if err != nil {
return nil, err
}
message, err := template.Execute(data)
if err != nil {
return nil, err
}
message.RecipientName, message.RecipientAddress = data.Recipient()
return message, nil
}
// MessageData interface contains everything we need to create an email.Message.
// The DefaultTemplates should be able to execute using the MessageData itself.
type MessageData interface {
TemplateName() string
Recipient() (name, address string)
DefaultTemplates() (subject, html, text string)
}