//go:build linux || freebsd
// Package email handles SMTP message composition and delivery.
package email
import (
"bytes"
"fmt"
"html/template"
"net/smtp"
"time"
"sourcedock.dev/petrbalvin/nuntius/internal/config"
"sourcedock.dev/petrbalvin/nuntius/pkg/contactform"
)
// FormSender delivers contact form submissions for a single form
// using its own SMTP credentials. Each form has its own FormSender
// so credentials are isolated per tenant.
type FormSender struct {
form *config.Form
}
// NewFormSender returns a new FormSender bound to the given form.
func NewFormSender(form *config.Form) *FormSender {
return &FormSender{form: form}
}
// Send composes and sends a multi-part email (plain text + HTML)
// for the given request. Returns an error if the SMTP round-trip fails.
func (s *FormSender) Send(req contactform.Request) error {
auth := smtp.PlainAuth("", s.form.SMTP.User, s.form.SMTP.Password, s.form.SMTP.Host)
msg := compose(s.form.From, s.form.To, req, s.form.Name, s.form.Type)
return smtp.SendMail(s.form.SMTP.AddrFor(), auth, s.form.From, []string{s.form.To}, msg)
}
// emailTemplateContact is the HTML body template for contact-type forms.
var emailTemplateContact = template.Must(template.New("contact").Parse(`
Contact Form Submission
{{.FormName}}
From {{.Name}}{{.Email}}
{{if .Service}}
Service Interest {{.Service}}
{{end}}
Received {{.Received}}
Message
{{.Message}}
Delivered by nuntius — a contact form backend for Linux servers.
`))
// emailTemplateFeedback is the HTML body template for feedback-type forms.
var emailTemplateFeedback = template.Must(template.New("feedback").Parse(`
New Feedback
{{.FormName}}
From
{{.Name}} {{.Email}}
Feedback
{{.Message}}
Delivered by nuntius
`))
// emailTemplateNewsletter is the HTML body template for newsletter-signup forms.
var emailTemplateNewsletter = template.Must(template.New("newsletter").Parse(`
{{.FormName}} — new subscriber
Email
{{.Email}}
Delivered by nuntius
`))
// emailTemplateGeneric is the HTML body template for generic forms.
var emailTemplateGeneric = template.Must(template.New("generic").Parse(`
Form Submission
{{.FormName}}
From
{{.Name}} {{.Email}}
Message
{{.Message}}
Delivered by nuntius
`))
func compose(from, to string, req contactform.Request, formName, formType string) []byte {
received := time.Now().UTC().Format("January 2, 2006 at 15:04 UTC")
// --- HTML part ---
var htmlBuf bytes.Buffer
tmpl := emailTemplateContact
switch formType {
case "newsletter":
tmpl = emailTemplateNewsletter
case "feedback":
tmpl = emailTemplateFeedback
case "generic":
tmpl = emailTemplateGeneric
}
_ = tmpl.Execute(&htmlBuf, map[string]string{
"FormName": formName,
"Name": req.Name,
"Email": req.Email,
"Service": req.Service,
"Message": req.Message,
"Received": received,
})
// --- Subject + plain-text body per form type ---
var subject, text string
switch formType {
case "newsletter":
subject = fmt.Sprintf("[nuntius/%s] New newsletter subscriber", formName)
text = fmt.Sprintf(
"New Newsletter Subscriber: %s\r\n"+
"---\r\n"+
"Email: %s\r\n"+
"Received: %s\r\n"+
"\r\n"+
"Delivered by nuntius\r\n",
formName, req.Email, received,
)
case "feedback":
subject = fmt.Sprintf("[nuntius/%s] New feedback", formName)
text = fmt.Sprintf(
"New Feedback: %s\r\n"+
"---\r\n"+
"From: %s <%s>\r\n"+
"Received: %s\r\n"+
"\r\n"+
"%s\r\n\r\n"+
"Delivered by nuntius\r\n",
formName, req.Name, req.Email, received, req.Message,
)
case "generic":
subject = fmt.Sprintf("[nuntius/%s] New submission", formName)
text = fmt.Sprintf(
"New Submission: %s\r\n"+
"---\r\n"+
"From: %s <%s>\r\n"+
"Received: %s\r\n"+
"\r\n"+
"%s\r\n\r\n"+
"Delivered by nuntius\r\n",
formName, req.Name, req.Email, received, req.Message,
)
default: // contact
subject = fmt.Sprintf("[nuntius/%s] Contact form submission", formName)
if req.Service != "" {
subject = fmt.Sprintf("[nuntius/%s][%s] Contact form submission", formName, req.Service)
}
text = fmt.Sprintf(
"Contact Form Submission: %s\r\n"+
"---\r\n"+
"From: %s <%s>\r\n"+
"Service interest: %s\r\n"+
"Received: %s\r\n"+
"\r\n"+
"%s\r\n\r\n"+
"Delivered by nuntius\r\n",
formName, req.Name, req.Email, req.Service, received, req.Message,
)
}
// Assemble multipart/alternative message.
boundary := "nuntius-boundary"
var msg bytes.Buffer
msg.WriteString(fmt.Sprintf("From: %s\r\n", from))
msg.WriteString(fmt.Sprintf("To: %s\r\n", to))
msg.WriteString(fmt.Sprintf("Subject: %s\r\n", subject))
msg.WriteString(fmt.Sprintf("Date: %s\r\n", time.Now().UTC().Format(time.RFC1123Z)))
msg.WriteString(fmt.Sprintf("Reply-To: %s\r\n", req.Email))
msg.WriteString("MIME-Version: 1.0\r\n")
msg.WriteString(fmt.Sprintf("Content-Type: multipart/alternative; boundary=%s\r\n", boundary))
msg.WriteString("\r\n")
msg.WriteString(fmt.Sprintf("--%s\r\n", boundary))
msg.WriteString("Content-Type: text/plain; charset=UTF-8\r\n")
msg.WriteString("\r\n")
msg.WriteString(text)
msg.WriteString("\r\n")
msg.WriteString(fmt.Sprintf("--%s\r\n", boundary))
msg.WriteString("Content-Type: text/html; charset=UTF-8\r\n")
msg.WriteString("\r\n")
msg.WriteString(htmlBuf.String())
msg.WriteString("\r\n")
msg.WriteString(fmt.Sprintf("--%s--\r\n", boundary))
return msg.Bytes()
}