Improve mail service

mail-service/cmd/api/handlers.go

@@ -5,10 +5,8 @@ import (
 	"fmt"
 	"log"
 	"net/http"
-	"time"
 
 	"github.com/tsawler/toolbox"
-	mail "github.com/xhit/go-simple-mail/v2"
 )
 
 type MailData struct {
@@ -35,7 +33,13 @@ func (app *Config) SendMail(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	err = app.SendMsg(mailData)
+	msg := Message{
+		From:    mailData.From,
+		To:      mailData.To,
+		Subject: mailData.Subject,
+		Data:    mailData.Content,
+	}
+	err = app.Mailer.SendSMTPMessage(msg)
 	if err != nil {
 		log.Println(err)
 		app.Tools.ErrorJSON(w, err)
@@ -48,37 +52,3 @@ func (app *Config) SendMail(w http.ResponseWriter, r *http.Request) {
 
 	app.Tools.WriteJSON(w, http.StatusAccepted, payload)
 }
-
-func (app *Config) SendMsg(m MailData) error {
-	server := mail.NewSMTPClient()
-	server.Host = app.Host
-	server.Port = app.Port
-
-	server.KeepAlive = false
-	server.ConnectTimeout = 10 * time.Second
-	server.SendTimeout = 10 * time.Second
-
-	smtpClient, err := server.Connect()
-	if err != nil {
-		log.Println(err)
-		return err
-	}
-
-	// Maybe add a template
-
-	email := mail.NewMSG()
-	email.SetFrom(m.From).
-		AddTo(m.To).
-		SetSubject(m.Subject).
-		SetBody(mail.TextHTML, m.Content)
-
-	err = email.Send(smtpClient)
-	if err != nil {
-		log.Println(err)
-		return err
-	}
-
-	log.Printf("Email sent to %s", m.To)
-
-	return nil
-}

mail-service/cmd/api/mailer.go

@@ -0,0 +1,168 @@
+package main
+
+import (
+	"bytes"
+	"embed"
+	"html/template"
+	"log"
+	"time"
+
+	"github.com/vanng822/go-premailer/premailer"
+	mail "github.com/xhit/go-simple-mail/v2"
+)
+
+//go:embed templates
+var emailTemplateFS embed.FS
+
+type Mail struct {
+	Domain     string
+	Host       string
+	Port       int
+	Username   string
+	Password   string
+	Encryption string
+	FromAddr   string
+	FromName   string
+}
+
+type Message struct {
+	From        string
+	FromName    string
+	To          string
+	Subject     string
+	Attachments []string
+	Data        any
+	DataMap     map[string]any
+}
+
+func (m *Mail) SendSMTPMessage(msg Message) error {
+	if msg.From == "" {
+		msg.From = m.FromAddr
+	}
+
+	if msg.FromName == "" {
+		msg.FromName = m.FromName
+	}
+
+	data := map[string]any{
+		"message": msg.Data,
+	}
+
+	msg.DataMap = data
+
+	formattedMessage, err := m.buildHTMLMessage(msg)
+	if err != nil {
+		return err
+	}
+	plainMessage, err := m.buildPlainTextMessage(msg)
+	if err != nil {
+		return err
+	}
+
+	server := mail.NewSMTPClient()
+	server.Host = m.Host
+	server.Port = m.Port
+	server.Username = m.Username
+	server.Password = m.Password
+	server.Encryption = m.getEncryption(m.Encryption)
+	server.KeepAlive = false
+	server.ConnectTimeout = 10 * time.Second
+	server.SendTimeout = 10 * time.Second
+
+	log.Println(server.Host, server.Port)
+
+	smtpClient, err := server.Connect()
+	if err != nil {
+		return err
+	}
+
+	email := mail.NewMSG()
+	email.SetFrom(msg.From).AddTo(msg.To).SetSubject(msg.Subject)
+
+	email.SetBody(mail.TextPlain, plainMessage)
+	email.AddAlternative(mail.TextHTML, formattedMessage)
+
+	if len(msg.Attachments) > 0 {
+		for _, x := range msg.Attachments {
+			email.AddAttachment(x)
+		}
+	}
+
+	err = email.Send(smtpClient)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (m *Mail) buildPlainTextMessage(msg Message) (string, error) {
+	templateToRender := "templates/mail.plain.gohtml"
+
+	t, err := template.New("email-plain").ParseFS(emailTemplateFS, templateToRender)
+	if err != nil {
+		return "", err
+	}
+
+	var tpl bytes.Buffer
+	if err = t.ExecuteTemplate(&tpl, "body", msg.DataMap); err != nil {
+		return "", err
+	}
+
+	formattedMessage := tpl.String()
+
+	return formattedMessage, nil
+}
+
+func (m *Mail) buildHTMLMessage(msg Message) (string, error) {
+	templateToRender := "templates/mail.html.gohtml"
+
+	t, err := template.New("email-html").ParseFS(emailTemplateFS, templateToRender)
+	if err != nil {
+		return "", err
+	}
+
+	var tpl bytes.Buffer
+	if err = t.ExecuteTemplate(&tpl, "body", msg.DataMap); err != nil {
+		return "", err
+	}
+
+	formattedMessage := tpl.String()
+	formattedMessage, err = m.inlineCSS(formattedMessage)
+	if err != nil {
+		return "", err
+	}
+
+	return formattedMessage, nil
+}
+
+func (m *Mail) inlineCSS(s string) (string, error) {
+	options := premailer.Options{
+		RemoveClasses:     false,
+		CssToAttributes:   false,
+		KeepBangImportant: true,
+	}
+
+	prem, err := premailer.NewPremailerFromString(s, &options)
+	if err != nil {
+		return "", err
+	}
+	html, err := prem.Transform()
+	if err != nil {
+		return "", err
+	}
+	return html, nil
+}
+
+func (m *Mail) getEncryption(s string) mail.Encryption {
+	switch s {
+	case "tls":
+		return mail.EncryptionSTARTTLS
+	case "ssl":
+		return mail.EncryptionSSLTLS
+	case "none":
+		return mail.EncryptionNone
+	default:
+		return mail.EncryptionNone
+	}
+}

mail-service/cmd/api/main.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"os"
+	"strconv"
 
 	"github.com/tsawler/toolbox"
 )
@@ -17,12 +19,12 @@ type Config struct {
 	Password   string
 	Encryption string
 	Tools      toolbox.Tools
+	Mailer     Mail
 }
 
 func main() {
 	app := Config{
-		Host: "mailhog",
-		Port: 1025,
+		Mailer: createMail(),
 	}
 
 	log.Printf("Starting mail service on port %s\n", webPort)
@@ -38,3 +40,17 @@ func main() {
 		log.Panic(err)
 	}
 }
+
+func createMail() Mail {
+	port, _ := strconv.Atoi(os.Getenv("MAIL_PORT"))
+	return Mail{
+		Domain:     os.Getenv("MAIL_DOMAIN"),
+		Host:       os.Getenv("MAIL_HOST"),
+		Port:       port,
+		Username:   os.Getenv("MAIL_USERNAME"),
+		Password:   os.Getenv("MAIL_PASSWORD"),
+		Encryption: os.Getenv("MAIL_ENCRYPTION"),
+		FromName:   os.Getenv("FROM_NAME"),
+		FromAddr:   os.Getenv("FROM_ADDR"),
+	}
+}

mail-service/cmd/api/templates/mail.html.gohtml

@@ -0,0 +1,13 @@
+{{ define "body" }}
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta name="viewport" content="width=device-width">
+        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
+        <title></title>
+    </head>
+    <body>
+        <p>{{.message}}</p>
+    </body>
+</html>
+{{ end }}

mail-service/cmd/api/templates/mail.plain.gohtml

@@ -0,0 +1,3 @@
+{{ define "body" }}
+{{.message}}
+{{ end }}