refac: removed 7 direct and 12 indirect go modules for custom code instead

internal/infrastructure/mailer/message.go

@@ -0,0 +1,90 @@
+package mailer
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"mime"
+	"mime/quotedprintable"
+	"net/mail"
+	"strings"
+	"time"
+)
+
+const (
+	senderDisplayName = "RenewCMS"
+	messageIDBytes    = 16
+	lineBreak         = "\r\n"
+)
+
+type message struct {
+	from    mail.Address
+	to      mail.Address
+	subject string
+	body    string
+	sentAt  time.Time
+}
+
+func newMessage(sender string, receiver string, subject string, body string, sentAt time.Time) (message, error) {
+	from, err := mail.ParseAddress(sender)
+	if err != nil {
+		return message{}, fmt.Errorf("invalid sender address: %w", err)
+	}
+	to, err := mail.ParseAddress(receiver)
+	if err != nil {
+		return message{}, fmt.Errorf("invalid receiver address: %w", err)
+	}
+	if strings.ContainsAny(subject, "\r\n") {
+		return message{}, errors.New("subject contains a line break")
+	}
+	return message{
+		from:    mail.Address{Name: senderDisplayName, Address: from.Address},
+		to:      *to,
+		subject: subject,
+		body:    body,
+		sentAt:  sentAt,
+	}, nil
+}
+
+func (m message) messageID() (string, error) {
+	_, domain, _ := strings.Cut(m.from.Address, "@")
+	random := make([]byte, messageIDBytes)
+	if _, err := rand.Read(random); err != nil {
+		return "", err
+	}
+	return "<" + hex.EncodeToString(random) + "@" + domain + ">", nil
+}
+
+func (m message) bytes() ([]byte, error) {
+	id, err := m.messageID()
+	if err != nil {
+		return nil, err
+	}
+
+	var out bytes.Buffer
+	headers := []struct{ name, value string }{
+		{"From", m.from.String()},
+		{"To", m.to.String()},
+		{"Subject", mime.QEncoding.Encode("utf-8", m.subject)},
+		{"Date", m.sentAt.Format(time.RFC1123Z)},
+		{"Message-ID", id},
+		{"MIME-Version", "1.0"},
+		{"Content-Type", "text/html; charset=UTF-8"},
+		{"Content-Transfer-Encoding", "quoted-printable"},
+	}
+	for _, h := range headers {
+		out.WriteString(h.name + ": " + h.value + lineBreak)
+	}
+	out.WriteString(lineBreak)
+
+	encoder := quotedprintable.NewWriter(&out)
+	if _, err := encoder.Write([]byte(m.body)); err != nil {
+		return nil, err
+	}
+	if err := encoder.Close(); err != nil {
+		return nil, err
+	}
+	return out.Bytes(), nil
+}