121 lines
4.7 KiB
Go
121 lines
4.7 KiB
Go
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// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: MIT
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//go:build linux || freebsd
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package email
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import (
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"bytes"
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"fmt"
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"html/template"
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"net/smtp"
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"time"
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"sourcedock.dev/petrbalvin/nuntius/internal/config"
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)
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// emailTemplateAcknowledgement is the HTML body of the automated receipt
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// a form with auto_reply enabled sends to the submitter.
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var emailTemplateAcknowledgement = template.Must(template.New("acknowledgement").Parse(`<!DOCTYPE html>
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<html lang="en">
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<head><meta charset="UTF-8"></head>
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<body style="margin:0;padding:0;background:#f3f4f6;font-family:Inter,ui-sans-serif,system-ui,sans-serif">
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<table width="100%" cellpadding="0" cellspacing="0" style="background:#f3f4f6;padding:32px 0">
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<tr><td align="center">
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<table width="460" cellpadding="0" cellspacing="0" style="background:#fff;border-radius:12px;overflow:hidden;box-shadow:0 2px 16px rgba(0,0,0,.06)">
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<tr><td style="background:#1e40af;padding:20px 24px">
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<p style="margin:0;font-size:18px;font-weight:700;color:#fff">Message received</p>
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</td></tr>
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<tr><td style="padding:24px">
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<p style="font-size:14px;line-height:1.6;color:#1f2937;margin:0 0 12px">Hello,</p>
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<p style="font-size:14px;line-height:1.6;color:#1f2937;margin:0 0 12px">your message to <strong>{{.FormName}}</strong> was received. A reply will follow as soon as possible.</p>
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<p style="font-size:14px;line-height:1.6;color:#1f2937;margin:0">Please do not respond to this automated receipt.</p>
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{{if .Brand}}
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<p style="font-size:11px;color:#9ca3af;margin:16px 0 0;border-top:1px solid #e5e7eb;padding-top:16px">Delivered by <strong style="color:#6b7280">{{.Brand}}</strong></p>
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{{end}}
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</td></tr>
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</table>
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</td></tr>
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</table>
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</body>
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</html>`))
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// SendAcknowledgement mails the submitter a short receipt. It uses the
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// form's SMTP identity, and the Reply-To points at the owner, so a reply
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// to the receipt lands in the human's inbox and not into the void.
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func (s *FormSender) SendAcknowledgement(to string) error {
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auth := smtp.PlainAuth("", s.form.SMTP.User, s.form.SMTP.Password, s.form.SMTP.Host)
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msg, err := composeAcknowledgement(s.form, to)
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if err != nil {
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return fmt.Errorf("compose acknowledgement: %w", err)
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}
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return sendMail(s.form.SMTP, auth, s.form.From, []string{to}, msg, s.form.SMTP.Timeout(), s.TLSConfig)
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}
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// composeAcknowledgement builds the multipart receipt. The submitted
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// values are deliberately not echoed back: the receipt confirms arrival,
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// it does not mirror a message's content into the submitter's inbox,
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// where any third party who could fill the form would read it.
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func composeAcknowledgement(form *config.Form, to string) ([]byte, error) {
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// --- HTML part ---
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var htmlBuf bytes.Buffer
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if err := emailTemplateAcknowledgement.Execute(&htmlBuf, map[string]string{
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"FormName": form.Name,
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"Brand": form.Brand(),
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}); err != nil {
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// template.Must guarantees valid templates; unreachable in
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// normal operation.
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htmlBuf.Reset()
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fmt.Fprintf(&htmlBuf, "<p>Email generation error: %v</p>", err)
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}
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// --- Subject + plain-text body ---
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subject := "Message received"
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if tag := subjectTag(form, ""); tag != "" {
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subject = tag + " " + subject
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}
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footer := ""
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if brand := form.Brand(); brand != "" {
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footer = "--\r\nDelivered by " + brand + "\r\n"
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}
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text := fmt.Sprintf(
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"Hello,\r\n\r\n"+
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"your message to %s was received. A reply will follow as soon as possible.\r\n"+
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"Please do not respond to this automated receipt.\r\n\r\n%s",
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form.Name, footer,
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)
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// Assemble multipart/alternative. The boundary comes first so that
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// randomness failure aborts the message before anything is built.
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boundary, err := randomBoundary()
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if err != nil {
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return nil, err
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}
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var msg bytes.Buffer
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msg.WriteString(fmt.Sprintf("From: %s\r\n", sanitizeHeaderValue(form.From)))
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msg.WriteString(fmt.Sprintf("To: %s\r\n", sanitizeHeaderValue(to)))
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msg.WriteString(fmt.Sprintf("Subject: %s\r\n", sanitizeHeaderValue(subject)))
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msg.WriteString(fmt.Sprintf("Date: %s\r\n", time.Now().UTC().Format(time.RFC1123Z)))
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msg.WriteString(fmt.Sprintf("Reply-To: %s\r\n", sanitizeHeaderValue(form.To)))
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msg.WriteString("MIME-Version: 1.0\r\n")
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msg.WriteString(fmt.Sprintf("Content-Type: multipart/alternative; boundary=%s\r\n", boundary))
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msg.WriteString("\r\n")
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msg.WriteString(fmt.Sprintf("--%s\r\n", boundary))
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msg.WriteString("Content-Type: text/plain; charset=UTF-8\r\n")
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msg.WriteString("\r\n")
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msg.WriteString(text)
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msg.WriteString("\r\n")
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msg.WriteString(fmt.Sprintf("--%s\r\n", boundary))
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msg.WriteString("Content-Type: text/html; charset=UTF-8\r\n")
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msg.WriteString("\r\n")
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msg.WriteString(htmlBuf.String())
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msg.WriteString("\r\n")
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msg.WriteString(fmt.Sprintf("--%s--\r\n", boundary))
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return msg.Bytes(), nil
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}
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