refactor: project structure

pkg/email/email.go

@@ -0,0 +1,172 @@
+package email
+
+import (
+	"bytes"
+	"crypto/tls"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"net/smtp"
+)
+
+const (
+	mime      = "MIME-version: 1.0;\nContent-Type: text/html; charset=\"UTF-8\";\n\n"
+	delimeter = "**=myohmy689407924327"
+)
+
+type SMTPClientIface interface {
+	StartTLS(*tls.Config) error
+	Auth(a smtp.Auth) error
+	Close() error
+	Data() (io.WriteCloser, error)
+	Mail(from string) error
+	Quit() error
+	Rcpt(to string) error
+}
+
+type SmtpDialFn func(hostPort string) (SMTPClientIface, error)
+
+type EmailService struct {
+	auth      smtp.Auth
+	host      string
+	port      string
+	from      string
+	tlsconfig *tls.Config
+	dial      SmtpDialFn
+}
+
+func NewMailService(config MailServiceConfig) *EmailService {
+	return &EmailService{
+		auth: config.Auth,
+		host: config.Host,
+		port: config.Port,
+		from: config.From,
+		tlsconfig: &tls.Config{
+			InsecureSkipVerify: true,
+			ServerName:         config.Host,
+		},
+		dial: dial,
+	}
+}
+
+type MailServiceConfig struct {
+	Auth smtp.Auth
+	Host string
+	Port string
+	From string // Sender email address
+}
+
+func dial(hostPort string) (SMTPClientIface, error) {
+	client, err := smtp.Dial(hostPort)
+	if err != nil {
+		return nil, err
+	}
+	return client, nil
+}
+
+func (e *EmailService) SendEmail(emailData EmailMessage) error {
+	msg, err := newMessage(e.from, emailData.To, emailData.Subject).
+		withAttachments(emailData.Body, emailData.Attachments)
+
+	if err != nil {
+		return fmt.Errorf("error while preparing email: %w", err)
+	}
+
+	return e.send(emailData.To, msg)
+}
+
+func (e *EmailService) send(to string, msg []byte) error {
+	c, err := e.dial(e.host + ":" + e.port)
+	if err != nil {
+		return fmt.Errorf("DIAL: %s", err)
+	}
+
+	if err = c.StartTLS(e.tlsconfig); err != nil {
+		return fmt.Errorf("c.StartTLS: %s", err)
+	}
+
+	// Auth
+	if err = c.Auth(e.auth); err != nil {
+		return fmt.Errorf("c.Auth: %s", err)
+	}
+
+	// To && From
+	if err = c.Mail(e.from); err != nil {
+		return fmt.Errorf("c.Mail: %s", err)
+	}
+
+	if err = c.Rcpt(to); err != nil {
+		return fmt.Errorf("c.Rcpt: %s", err)
+	}
+
+	// Data
+	w, err := c.Data()
+	if err != nil {
+		return fmt.Errorf("c.Data: %s", err)
+	}
+
+	written, err := w.Write(msg)
+	if err != nil {
+		return fmt.Errorf("w.Write: %s", err)
+	}
+
+	if written <= 0 {
+		return fmt.Errorf("%d bytes written", written)
+	}
+
+	if err = w.Close(); err != nil {
+		return fmt.Errorf("w.Close: %s", err)
+	}
+
+	if err = c.Quit(); err != nil {
+		return fmt.Errorf("w.Quit: %s", err)
+	}
+	return nil
+}
+
+type message struct {
+	from    string
+	to      string
+	subject string
+}
+
+func newMessage(from, to, subject string) message {
+	return message{from: from, to: to, subject: subject}
+}
+
+func (m message) withAttachments(body string, attachments []EmailAttachment) ([]byte, error) {
+	headers := make(map[string]string)
+	headers["From"] = m.from
+	headers["To"] = m.to
+	headers["Subject"] = m.subject
+	headers["MIME-Version"] = "1.0"
+
+	var message bytes.Buffer
+
+	for k, v := range headers {
+		message.WriteString(k)
+		message.WriteString(": ")
+		message.WriteString(v)
+		message.WriteString("\r\n")
+	}
+
+	message.WriteString("Content-Type: " + fmt.Sprintf("multipart/mixed; boundary=\"%s\"\r\n", delimeter))
+	message.WriteString("--" + delimeter + "\r\n")
+	message.WriteString("Content-Type: text/html; charset=\"UTF-8\"\r\n\r\n")
+	message.WriteString(body + "\r\n\r\n")
+
+	for _, attachment := range attachments {
+		attachmentRawFile, err := attachment.ReadContent()
+		if err != nil {
+			return nil, err
+		}
+		message.WriteString("--" + delimeter + "\r\n")
+		message.WriteString("Content-Disposition: attachment; filename=\"" + attachment.Title + "\"\r\n")
+		message.WriteString("Content-Type: application/octet-stream\r\n")
+		message.WriteString("Content-Transfer-Encoding: base64\r\n\r\n")
+		message.WriteString(base64.StdEncoding.EncodeToString(attachmentRawFile) + "\r\n")
+	}
+
+	message.WriteString("--" + delimeter + "--") // End the message
+	return message.Bytes(), nil
+}