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email.go
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email.go
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package formailer
import (
"bytes"
"crypto/rand"
"encoding/base32"
"fmt"
"html/template"
"os"
"strconv"
"strings"
"time"
// embed is used to embed the default template file
_ "embed"
"github.com/aymerick/douceur/inliner"
mail "github.com/xhit/go-simple-mail/v2"
)
//go:embed template.html
var defaultTemplate string
// Email contains all the setting to send an email
type Email struct {
// ID is used when looking up SMTP settings.
// It is case-insensitive but will be matched as UPPERCASE. ex: SMTP_FORM-ID_HOST.
ID string
To string
From string
Cc []string
Bcc []string
ReplyTo string
Subject string
// Template is a go html template to be used when generating the email.
Template string
}
func or(a, b string) string {
if len(a) < 1 {
return b
}
return a
}
// template allows for fallback on the default template when no template has beeen provided
func (e *Email) template() string {
return or(e.Template, defaultTemplate)
}
// server returns a sever using the ENV for auth falling back on the default for each missing param
func (e *Email) server() (*mail.SMTPServer, error) {
prefix := fmt.Sprintf("SMTP_%s_", strings.ToUpper(e.ID))
host := or(os.Getenv(prefix+"HOST"), os.Getenv("SMTP_HOST"))
user := or(os.Getenv(prefix+"USER"), os.Getenv("SMTP_USER"))
pass := or(os.Getenv(prefix+"PASS"), os.Getenv("SMTP_PASS"))
defaultPort := os.Getenv("SMTP_PORT")
emailPort := os.Getenv(prefix + "PORT")
stringPort := or(emailPort, defaultPort)
if len(host) < 1 {
return nil, fmt.Errorf("incomplete SMTP configuration missing %sHOST or SMTP_HOST for %s", prefix, e.ID)
}
if len(stringPort) < 1 {
return nil, fmt.Errorf("incomplete SMTP configuration missing %sPORT or SMTP_PORT for %s", prefix, e.ID)
}
if len(user) < 1 {
return nil, fmt.Errorf("incomplete SMTP configuration missing %sUSER or SMTP_USER for %s", prefix, e.ID)
}
if len(pass) < 1 {
return nil, fmt.Errorf("incomplete SMTP configuration missing %sPASS or SMTP_PASS for %s", prefix, e.ID)
}
port, err := strconv.Atoi(stringPort)
if err != nil {
if len(emailPort) < 1 {
prefix = "SMTP_"
}
return nil, fmt.Errorf("could not parse %sPORT: %w", prefix, err)
}
server := mail.NewSMTPClient()
server.Host = host
server.Port = port
server.Username = user
server.Password = pass
server.Encryption = mail.EncryptionTLS
server.Authentication = mail.AuthLogin
server.KeepAlive = false
server.ConnectTimeout = 10 * time.Second
server.SendTimeout = 10 * time.Minute
return server, nil
}
func (e *Email) generate(s *Submission) (string, error) {
t := template.New("email").Funcs(templateFuncMap)
_, err := t.Parse(e.template())
if err != nil {
return "", err
}
var email bytes.Buffer
err = t.Execute(&email, s)
if err != nil {
return "", err
}
return inliner.Inline(email.String())
}
// Email returns a *mail.Email generating the message with the provided submission
func (e *Email) Email(submission *Submission) (*mail.Email, error) {
message, err := e.generate(submission)
if err != nil {
return nil, fmt.Errorf("failed to generate message: %w", err)
}
token := make([]byte, 32)
if _, err := rand.Read(token); err != nil {
return nil, fmt.Errorf("failed to generate message-id: %w", err)
}
email := mail.NewMSG()
email.AddTo(e.To)
email.SetFrom(e.From)
email.SetSubject(e.Subject)
email.SetBody(mail.TextHTML, message)
email.AddHeader("Message-Id", base32.StdEncoding.EncodeToString(token))
if len(e.ReplyTo) > 0 {
email.SetReplyTo(e.ReplyTo)
}
for _, a := range e.Cc {
email.AddCc(a)
}
for _, a := range e.Bcc {
email.AddBcc(a)
}
for _, attachment := range submission.Attachments {
email.AddAttachmentData(attachment.Data, attachment.Filename, attachment.MimeType)
}
return email, nil
}
// Send sends the provided email
func (e *Email) Send(email *mail.Email) error {
server, err := e.server()
if err != nil {
return err
}
client, err := server.Connect()
if err != nil {
return err
}
defer client.Close()
return email.Send(client)
}