prompt 4

internal/mailer/smtp.go

@@ -0,0 +1,102 @@
+package mailer
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/mail"
+	"net/smtp"
+	"strconv"
+	"strings"
+	"time"
+
+	"trustcontact/internal/config"
+)
+
+type SMTPMailer struct {
+	host     string
+	port     int
+	username string
+	password string
+	from     string
+	fromName string
+}
+
+func NewSMTPMailer(cfg *config.Config) (*SMTPMailer, error) {
+	if strings.TrimSpace(cfg.SMTP.Host) == "" {
+		return nil, fmt.Errorf("smtp host is required")
+	}
+	if cfg.SMTP.Port <= 0 {
+		return nil, fmt.Errorf("smtp port must be > 0")
+	}
+	if strings.TrimSpace(cfg.SMTP.From) == "" {
+		return nil, fmt.Errorf("smtp from is required")
+	}
+
+	return &SMTPMailer{
+		host:     cfg.SMTP.Host,
+		port:     cfg.SMTP.Port,
+		username: cfg.SMTP.Username,
+		password: cfg.SMTP.Password,
+		from:     cfg.SMTP.From,
+		fromName: cfg.SMTP.FromName,
+	}, nil
+}
+
+func (m *SMTPMailer) Send(ctx context.Context, to, subject, htmlBody, textBody string) error {
+	if ctx != nil {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+	}
+
+	addr := net.JoinHostPort(m.host, strconv.Itoa(m.port))
+	msg := m.buildMessage(to, subject, htmlBody, textBody)
+
+	var auth smtp.Auth
+	if m.username != "" {
+		auth = smtp.PlainAuth("", m.username, m.password, m.host)
+	}
+
+	if err := smtp.SendMail(addr, auth, m.from, []string{to}, []byte(msg)); err != nil {
+		return err
+	}
+
+	if ctx != nil {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (m *SMTPMailer) buildMessage(to, subject, htmlBody, textBody string) string {
+	boundary := fmt.Sprintf("mixed-%d", time.Now().UTC().UnixNano())
+	fromAddr := (&mail.Address{Name: m.fromName, Address: m.from}).String()
+	toAddr := (&mail.Address{Address: to}).String()
+
+	headers := []string{
+		fmt.Sprintf("From: %s", fromAddr),
+		fmt.Sprintf("To: %s", toAddr),
+		fmt.Sprintf("Subject: %s", subject),
+		"MIME-Version: 1.0",
+		fmt.Sprintf("Content-Type: multipart/alternative; boundary=%q", boundary),
+		"",
+	}
+
+	parts := []string{
+		fmt.Sprintf("--%s", boundary),
+		"Content-Type: text/plain; charset=UTF-8",
+		"",
+		textBody,
+		fmt.Sprintf("--%s", boundary),
+		"Content-Type: text/html; charset=UTF-8",
+		"",
+		htmlBody,
+		fmt.Sprintf("--%s--", boundary),
+		"",
+	}
+
+	return strings.Join(append(headers, parts...), "\r\n")
+}