chore: use go-kit for sending emails (#1565)

backend/go.mod

@@ -14,8 +14,6 @@ require (
 	github.com/disintegration/imageorient v0.0.0-20180920195336-8147d86e83ec
 	github.com/disintegration/imaging v1.6.2
 	github.com/dunglas/go-urlpattern v0.0.0-20241020164140-716dfa1c80b1
-	github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6
-	github.com/emersion/go-smtp v0.24.0
 	github.com/fsnotify/fsnotify v1.10.1
 	github.com/gin-contrib/slog v1.2.1
 	github.com/gin-gonic/gin v1.12.0
@@ -28,7 +26,7 @@ require (
 	github.com/google/uuid v1.6.0
 	github.com/hashicorp/go-uuid v1.0.3
 	github.com/italypaleale/francis v0.1.0-beta.6
-	github.com/italypaleale/go-kit v0.0.0-20260703002252-b413738a463f
+	github.com/italypaleale/go-kit v0.0.0-20260705144331-cc6661f9a8cf
 	github.com/jackc/pgx/v5 v5.10.0
 	github.com/jinzhu/copier v0.4.0
 	github.com/joho/godotenv v1.5.1

backend/go.sum

@@ -133,10 +133,6 @@ github.com/dunglas/httpsfv v1.1.0 h1:Jw76nAyKWKZKFrpMMcL76y35tOpYHqQPzHQiwDvpe54
 github.com/dunglas/httpsfv v1.1.0/go.mod h1:zID2mqw9mFsnt7YC3vYQ9/cjq30q41W+1AnDwH8TiMg=
 github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
 github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
-github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6 h1:oP4q0fw+fOSWn3DfFi4EXdT+B+gTtzx8GC9xsc26Znk=
-github.com/emersion/go-sasl v0.0.0-20241020182733-b788ff22d5a6/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
-github.com/emersion/go-smtp v0.24.0 h1:g6AfoF140mvW0vLNPD/LuCBLEAdlxOjIXqbIkJIS6Wk=
-github.com/emersion/go-smtp v0.24.0/go.mod h1:ZtRRkbTyp2XTHCA+BmyTFTrj8xY4I+b4McvHxCU2gsQ=
 github.com/fatih/color v1.19.0 h1:Zp3PiM21/9Ld6FzSKyL5c/BULoe/ONr9KlbYVOfG8+w=
 github.com/fatih/color v1.19.0/go.mod h1:zNk67I0ZUT1bEGsSGyCZYZNrHuTkJJB+r6Q9VuMi0LE=
 github.com/felixge/httpsnoop v1.1.0 h1:3YtUj32ZZkqZtt3sZZsClsymw/QDuVfpNhoA31zeORc=
@@ -249,8 +245,8 @@ github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/italypaleale/francis v0.1.0-beta.6 h1:88XGnFMwQEMsGSJvI9vrGGvp//WKipXH8YPnfNHDStQ=
 github.com/italypaleale/francis v0.1.0-beta.6/go.mod h1:3QQ1iSRGzvxJZ5gfVlVR1RyPDUAgzyN+m2vHeeR7OVs=
-github.com/italypaleale/go-kit v0.0.0-20260703002252-b413738a463f h1:cyvaGWNg9AisrfG2guQspCawM6HhLaqbpHAppsePyH4=
-github.com/italypaleale/go-kit v0.0.0-20260703002252-b413738a463f/go.mod h1:pl0r3F+thZIyDsyDo8aOUsAIVcsRuAeP1bB4GuAHLoY=
+github.com/italypaleale/go-kit v0.0.0-20260705144331-cc6661f9a8cf h1:8tk4010URtPgVqwZb7CDiNsuQI71qc8t7VSS4IaxoTY=
+github.com/italypaleale/go-kit v0.0.0-20260705144331-cc6661f9a8cf/go.mod h1:pl0r3F+thZIyDsyDo8aOUsAIVcsRuAeP1bB4GuAHLoY=
 github.com/italypaleale/go-sql-utils v0.2.4-0.20260702021114-e1dfdfb67d0e h1:HDhmMkWAlLy/Elr/+T7diAZgAI+sDY2hYAyIAyefUYk=
 github.com/italypaleale/go-sql-utils v0.2.4-0.20260702021114-e1dfdfb67d0e/go.mod h1:BJStxMfB6fzYVcOe0oZQCjGIPZQu76UBmg1Wuy6Z/7I=
 github.com/jackc/pgerrcode v0.0.0-20250907135507-afb5586c32a6 h1:D/V0gu4zQ3cL2WKeVNVM4r2gLxGGf6McLwgXzRTo2RQ=

backend/internal/service/email_service.go

@@ -1,24 +1,16 @@
 package service
 
 import (
-	"bytes"
 	"context"
-	"crypto/tls"
 	"errors"
 	"fmt"
 	htemplate "html/template"
-	"io"
-	"mime/multipart"
-	"mime/quotedprintable"
-	"net/textproto"
-	"os"
+	"net"
+	"net/url"
 	"strings"
 	ttemplate "text/template"
-	"time"
 
-	"github.com/emersion/go-sasl"
-	"github.com/emersion/go-smtp"
-	"github.com/google/uuid"
+	"github.com/italypaleale/go-kit/emailer"
 	"gorm.io/gorm"
 
 	"github.com/pocket-id/pocket-id/backend/internal/common"
@@ -82,224 +74,103 @@ func SendEmail[V any](ctx context.Context, srv *EmailService, toEmail email.Addr
 		Data:    tData,
 	}
 
-	body, boundary, err := prepareBody(srv, template, data)
+	// Render the text and HTML bodies
+	text, html, err := renderBody(srv, template, data)
 	if err != nil {
 		return fmt.Errorf("prepare email body for '%s': %w", template.Path, err)
 	}
 
-	// Construct the email message
-	c := email.NewComposer()
-	c.AddHeader("Subject", template.Title(data))
-	c.AddAddressHeader("From", []email.Address{
-		{
-			Email: dbConfig.SmtpFrom.Value,
-			Name:  dbConfig.AppName.Value,
-		},
-	})
-	c.AddAddressHeader("To", []email.Address{toEmail})
-	c.AddHeaderRaw("Content-Type",
-		fmt.Sprintf("multipart/alternative;\n boundary=%s;\n charset=UTF-8", boundary),
-	)
-
-	c.AddHeader("MIME-Version", "1.0")
-	c.AddHeader("Date", time.Now().Format(time.RFC1123Z))
-
-	// to create a message-id, we need the FQDN of the sending server, but that may be a docker hostname or localhost
-	// so we use the domain of the from address instead (the same as Thunderbird does)
-	// if the address does not have an @ (which would be unusual), we use hostname
-
-	fromAddress := dbConfig.SmtpFrom.Value
-	domain := ""
-	if strings.Contains(fromAddress, "@") {
-		domain = strings.Split(fromAddress, "@")[1]
-	} else {
-		hostname, err := os.Hostname()
-		if err != nil {
-			// can that happen? we just give up
-			return fmt.Errorf("failed to get own hostname: %w", err)
-		} else {
-			domain = hostname
-		}
-	}
-	c.AddHeader("Message-ID", "<"+uuid.New().String()+"@"+domain+">")
-
-	c.Body(body)
-
-	// Check if the context is still valid before attemtping to connect
-	// We need to do this because the smtp library doesn't have context support
-	select {
-	case <-ctx.Done():
-		return ctx.Err()
-	default:
-		// All good
-	}
-
-	// Connect to the SMTP server
-	client, err := srv.getSmtpClient()
+	// Configure the emailer from the current app config
+	e, err := srv.getEmailer(ctx, dbConfig)
 	if err != nil {
-		return fmt.Errorf("failed to connect to SMTP server: %w", err)
-	}
-	defer client.Close()
-
-	// Check if the context is still valid before sending the email
-	select {
-	case <-ctx.Done():
-		return ctx.Err()
-	default:
-		// All good
+		return fmt.Errorf("failed to configure emailer: %w", err)
 	}
 
 	// Send the email
-	err = srv.sendEmailContent(client, toEmail, c)
+	err = e.SendEmail(ctx, emailer.EmailAddress{
+		Name:    toEmail.Name,
+		Address: toEmail.Email,
+	}, template.Title(data), emailer.SendEmailMessage{
+		Text: text,
+		HTML: html,
+	})
 	if err != nil {
-		return fmt.Errorf("send email content: %w", err)
+		return fmt.Errorf("failed to send email: %w", err)
 	}
 
 	return nil
 }
 
-func (srv *EmailService) getSmtpClient() (client *smtp.Client, err error) {
-	dbConfig := srv.appConfigService.GetDbConfig()
-
-	port := dbConfig.SmtpPort.Value
-	smtpAddress := dbConfig.SmtpHost.Value + ":" + port
-
-	tlsConfig := &tls.Config{
-		InsecureSkipVerify: dbConfig.SmtpSkipCertVerify.IsTrue(), //nolint:gosec
-		ServerName:         dbConfig.SmtpHost.Value,
-	}
-
-	// Connect to the SMTP server based on TLS setting
-	switch dbConfig.SmtpTls.Value {
-	case "none":
-		client, err = smtp.Dial(smtpAddress)
-	case "tls":
-		client, err = smtp.DialTLS(smtpAddress, tlsConfig)
-	case "starttls":
-		client, err = smtp.DialStartTLS(
-			smtpAddress,
-			tlsConfig,
-		)
-	default:
-		return nil, fmt.Errorf("invalid SMTP TLS setting: %s", dbConfig.SmtpTls.Value)
-	}
+// getEmailer builds an emailer.Emailer from the current app config.
+func (srv *EmailService) getEmailer(ctx context.Context, dbConfig *model.AppConfig) (emailer.Emailer, error) {
+	// We support SMTP only (for now)
+	connString, err := smtpConnString(dbConfig)
 	if err != nil {
-		return nil, fmt.Errorf("failed to connect to SMTP server: %w", err)
+		return nil, err
 	}
 
-	client.CommandTimeout = 10 * time.Second
+	return emailer.NewEmailer(ctx, emailer.NewEmailerOpts{
+		ConnString: connString,
+	})
+}
 
-	// Send the HELO command
-	if err := srv.sendHelloCommand(client); err != nil {
-		return nil, fmt.Errorf("failed to send HELO command: %w", err)
+// smtpConnString builds the SMTP connection string that go-kit's emailer expects:
+// smtp://<username>:<password>@<host>:<port>?fromAddress=<address>&fromName=<name>&tls=<none|starttls|tls>&insecureSkipVerify=<true|false>
+func smtpConnString(dbConfig *model.AppConfig) (string, error) {
+	host := dbConfig.SmtpHost.Value
+	if host == "" {
+		return "", errors.New("SMTP host is not configured")
 	}
 
-	// Set up the authentication if user or password are set
+	u := &url.URL{
+		Scheme: "smtp",
+		Host:   host,
+	}
+	port := dbConfig.SmtpPort.Value
+	if port != "" {
+		u.Host = net.JoinHostPort(host, port)
+	}
+
+	// Include credentials when set
 	smtpUser := dbConfig.SmtpUser.Value
 	smtpPassword := dbConfig.SmtpPassword.Value
-
 	if smtpUser != "" || smtpPassword != "" {
-		// Authenticate with plain auth
-		auth := sasl.NewPlainClient("", smtpUser, smtpPassword)
-		if err := client.Auth(auth); err != nil {
-			// If the server does not support plain auth, try login auth
-			var smtpErr *smtp.SMTPError
-			ok := errors.As(err, &smtpErr)
-			if ok && smtpErr.Code == smtp.ErrAuthUnknownMechanism.Code {
-				auth = sasl.NewLoginClient(smtpUser, smtpPassword)
-				err = client.Auth(auth)
-			}
-			// Both plain and login auth failed
-			if err != nil {
-				return nil, fmt.Errorf("failed to authenticate: %w", err)
-			}
-
-		}
+		u.User = url.UserPassword(smtpUser, smtpPassword)
 	}
 
-	return client, err
+	// TLS values from config: none, starttls, tls
+	tlsMode := dbConfig.SmtpTls.Value
+	if tlsMode == "" {
+		tlsMode = "none"
+	}
+
+	// Build the query string args
+	q := url.Values{}
+	q.Set("fromAddress", dbConfig.SmtpFrom.Value)
+	q.Set("fromName", dbConfig.AppName.Value)
+	q.Set("tls", tlsMode)
+	if dbConfig.SmtpSkipCertVerify.IsTrue() {
+		q.Set("insecureSkipVerify", "true")
+	}
+	u.RawQuery = q.Encode()
+
+	// Return the connection string
+	return u.String(), nil
 }
 
-func (srv *EmailService) sendHelloCommand(client *smtp.Client) error {
-	hostname, err := os.Hostname()
-	if err == nil {
-		if err := client.Hello(hostname); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-func (srv *EmailService) sendEmailContent(client *smtp.Client, toEmail email.Address, c *email.Composer) error {
-	// Set the sender
-	if err := client.Mail(srv.appConfigService.GetDbConfig().SmtpFrom.Value, nil); err != nil {
-		return fmt.Errorf("failed to set sender: %w", err)
-	}
-
-	// Set the recipient
-	if err := client.Rcpt(toEmail.Email, nil); err != nil {
-		return fmt.Errorf("failed to set recipient: %w", err)
-	}
-
-	// Get a writer to write the email data
-	w, err := client.Data()
-	if err != nil {
-		return fmt.Errorf("failed to start data: %w", err)
-	}
-
-	// Write the email content
-	_, err = io.Copy(w, strings.NewReader(c.String()))
-	if err != nil {
-		return fmt.Errorf("failed to write email data: %w", err)
-	}
-
-	// Close the writer
-	if err := w.Close(); err != nil {
-		return fmt.Errorf("failed to close data writer: %w", err)
-	}
-
-	return nil
-}
-
-func prepareBody[V any](srv *EmailService, template email.Template[V], data *email.TemplateData[V]) (string, string, error) {
-	body := bytes.NewBuffer(nil)
-	mpart := multipart.NewWriter(body)
-
-	// prepare text part
-	var textHeader = textproto.MIMEHeader{}
-	textHeader.Add("Content-Type", "text/plain; charset=UTF-8")
-	textHeader.Add("Content-Transfer-Encoding", "quoted-printable")
-	textPart, err := mpart.CreatePart(textHeader)
-	if err != nil {
-		return "", "", fmt.Errorf("create text part: %w", err)
-	}
-
-	textQp := quotedprintable.NewWriter(textPart)
-	err = email.GetTemplate(srv.textTemplates, template).ExecuteTemplate(textQp, "root", data)
+// renderBody renders the text and HTML templates for the message into strings
+func renderBody[V any](srv *EmailService, template email.Template[V], data *email.TemplateData[V]) (text string, html string, err error) {
+	textBuilder := &strings.Builder{}
+	err = email.GetTemplate(srv.textTemplates, template).ExecuteTemplate(textBuilder, "root", data)
 	if err != nil {
 		return "", "", fmt.Errorf("execute text template: %w", err)
 	}
-	textQp.Close()
 
-	var htmlHeader = textproto.MIMEHeader{}
-	htmlHeader.Add("Content-Type", "text/html; charset=UTF-8")
-	htmlHeader.Add("Content-Transfer-Encoding", "quoted-printable")
-	htmlPart, err := mpart.CreatePart(htmlHeader)
-	if err != nil {
-		return "", "", fmt.Errorf("create html part: %w", err)
-	}
-
-	htmlQp := quotedprintable.NewWriter(htmlPart)
-	err = email.GetTemplate(srv.htmlTemplates, template).ExecuteTemplate(htmlQp, "root", data)
+	htmlBuilder := &strings.Builder{}
+	err = email.GetTemplate(srv.htmlTemplates, template).ExecuteTemplate(htmlBuilder, "root", data)
 	if err != nil {
 		return "", "", fmt.Errorf("execute html template: %w", err)
 	}
-	htmlQp.Close()
 
-	err = mpart.Close()
-	if err != nil {
-		return "", "", fmt.Errorf("close multipart: %w", err)
-	}
-
-	return body.String(), mpart.Boundary(), nil
+	return textBuilder.String(), htmlBuilder.String(), nil
 }