decouple email content from sender to ensure thread safety

If two emails fired off at once, they would previously replace each
other's content and possibly send the wrong email to the wrong person.
construct* methods now return the email content, which is sent
separately.

api.go

@@ -92,10 +92,13 @@ func (app *appContext) checkInvites() {
 				for address, settings := range notify {
 					if settings["notify-expiry"] {
 						go func() {
-							if app.email.constructExpiry(code, data, app) != nil {
+							msg, err := app.email.constructExpiry(code, data, app)
+							if err != nil {
 								app.err.Printf("%s: Failed to construct expiry notification", code)
-							} else if app.email.send(address, app) != nil {
+								app.debug.Printf("Error: %s", err)
+							} else if err := app.email.send(address, msg); err != nil {
 								app.err.Printf("%s: Failed to send expiry notification", code)
+								app.debug.Printf("Error: %s", err)
 							} else {
 								app.info.Printf("Sent expiry notification to %s", address)
 							}
@@ -126,10 +129,13 @@ func (app *appContext) checkInvite(code string, used bool, username string) bool
 				for address, settings := range notify {
 					if settings["notify-expiry"] {
 						go func() {
-							if app.email.constructExpiry(code, inv, app) != nil {
+							msg, err := app.email.constructExpiry(code, inv, app)
+							if err != nil {
 								app.err.Printf("%s: Failed to construct expiry notification", code)
-							} else if app.email.send(address, app) != nil {
+								app.debug.Printf("Error: %s", err)
+							} else if err := app.email.send(address, msg); err != nil {
 								app.err.Printf("%s: Failed to send expiry notification", code)
+								app.debug.Printf("Error: %s", err)
 							} else {
 								app.info.Printf("Sent expiry notification to %s", address)
 							}
@@ -216,10 +222,11 @@ func (app *appContext) NewUser(gc *gin.Context) {
 		for address, settings := range invite.Notify {
 			if settings["notify-creation"] {
 				go func() {
-					if app.email.constructCreated(req.Code, req.Username, req.Email, invite, app) != nil {
+					msg, err := app.email.constructCreated(req.Code, req.Username, req.Email, invite, app)
+					if err != nil {
 						app.err.Printf("%s: Failed to construct user creation notification", req.Code)
 						app.debug.Printf("%s: Error: %s", req.Code, err)
-					} else if app.email.send(address, app) != nil {
+					} else if err := app.email.send(address, msg); err != nil {
 						app.err.Printf("%s: Failed to send user creation notification", req.Code)
 						app.debug.Printf("%s: Error: %s", req.Code, err)
 					} else {
@@ -300,11 +307,12 @@ func (app *appContext) GenerateInvite(gc *gin.Context) {
 	if req.Email != "" && app.config.Section("invite_emails").Key("enabled").MustBool(false) {
 		app.debug.Printf("%s: Sending invite email", invite_code)
 		invite.Email = req.Email
-		if err := app.email.constructInvite(invite_code, invite, app); err != nil {
+		msg, err := app.email.constructInvite(invite_code, invite, app)
+		if err != nil {
 			invite.Email = fmt.Sprintf("Failed to send to %s", req.Email)
 			app.err.Printf("%s: Failed to construct invite email", invite_code)
 			app.debug.Printf("%s: Error: %s", invite_code, err)
-		} else if err := app.email.send(req.Email, app); err != nil {
+		} else if err := app.email.send(req.Email, msg); err != nil {
 			invite.Email = fmt.Sprintf("Failed to send to %s", req.Email)
 			app.err.Printf("%s: %s", invite_code, invite.Email)
 			app.debug.Printf("%s: Error: %s", invite_code, err)
@@ -353,9 +361,9 @@ func (app *appContext) GetInvites(gc *gin.Context) {
 				address = app.config.Section("ui").Key("email").String()
 			}
 			if _, ok := inv.Notify[address]; ok {
-				for _, notify_type := range []string{"notify-expiry", "notify-creation"} {
-					if _, ok = inv.Notify[notify_type]; ok {
-						invite[notify_type] = inv.Notify[address][notify_type]
+				for _, notifyType := range []string{"notify-expiry", "notify-creation"} {
+					if _, ok = inv.Notify[notifyType]; ok {
+						invite[notifyType] = inv.Notify[address][notifyType]
 					}
 				}
 			}
@@ -557,7 +565,7 @@ func (app *appContext) SetDefaults(gc *gin.Context) {
 		respond(500, "Couldn't get user", gc)
 		return
 	}
-	userId := user["Id"].(string)
+	userID := user["Id"].(string)
 	policy := user["Policy"].(map[string]interface{})
 	app.storage.policy = policy
 	app.storage.storePolicy()
@@ -565,7 +573,7 @@ func (app *appContext) SetDefaults(gc *gin.Context) {
 	if req.Homescreen {
 		configuration := user["Configuration"].(map[string]interface{})
 		var displayprefs map[string]interface{}
-		displayprefs, status, err = app.jf.getDisplayPreferences(userId)
+		displayprefs, status, err = app.jf.getDisplayPreferences(userID)
 		if !(status == 200 || status == 204) || err != nil {
 			app.err.Printf("Failed to get DisplayPrefs: Code %d", status)
 			app.debug.Printf("Error: %s", err)

config.go

@@ -69,5 +69,7 @@ func (app *appContext) loadConfig() error {
 	app.config.Section("notifications").Key("created_html").SetValue(app.config.Section("notifications").Key("created_html").MustString(filepath.Join(app.local_path, "created.html")))
 	app.config.Section("notifications").Key("created_text").SetValue(app.config.Section("notifications").Key("created_text").MustString(filepath.Join(app.local_path, "created.txt")))
 
+	app.email = NewEmailer(app)
+
 	return nil
 }

email.go

@@ -15,15 +15,64 @@ import (
 	"github.com/mailgun/mailgun-go/v4"
 )
 
-type Emailer struct {
-	smtpAuth                                 smtp.Auth
-	sendType, sendMethod, fromAddr, fromName string
-	content                                  Email
-	mg                                       *mailgun.MailgunImpl
-	mime                                     string
-	host                                     string
+// implements email sending, right now via smtp or mailgun.
+type emailClient interface {
+	send(address, fromName, fromAddr string, email *Email) error
 }
 
+type Mailgun struct {
+	client *mailgun.MailgunImpl
+}
+
+func (mg *Mailgun) send(address, fromName, fromAddr string, email *Email) error {
+	message := mg.client.NewMessage(
+		fmt.Sprintf("%s <%s>", fromName, fromAddr),
+		email.subject,
+		email.text,
+		address,
+	)
+	message.SetHtml(email.html)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+	defer cancel()
+	_, _, err := mg.client.Send(ctx, message)
+	return err
+}
+
+type Smtp struct {
+	sslTls       bool
+	host, server string
+	port         int
+	auth         smtp.Auth
+}
+
+func (sm *Smtp) send(address, fromName, fromAddr string, email *Email) error {
+	e := jEmail.NewEmail()
+	e.Subject = email.subject
+	e.From = fmt.Sprintf("%s <%s>", fromName, fromAddr)
+	e.To = []string{address}
+	e.Text = []byte(email.text)
+	e.HTML = []byte(email.html)
+	tlsConfig := &tls.Config{
+		InsecureSkipVerify: false,
+		ServerName:         sm.host,
+	}
+	server := fmt.Sprintf("%s:%d", sm.server, sm.port)
+	var err error
+	if sm.sslTls {
+		err = e.SendWithTLS(server, sm.auth, tlsConfig)
+	} else {
+		err = e.SendWithStartTLS(server, sm.auth, tlsConfig)
+	}
+	return err
+}
+
+// Emailer contains the email sender, email content, and methods to construct message content.
+type Emailer struct {
+	fromAddr, fromName string
+	sender             emailClient
+}
+
+// Email stores content.
 type Email struct {
 	subject    string
 	html, text string
@@ -50,29 +99,53 @@ func (email *Emailer) formatExpiry(expiry time.Time, tzaware bool, datePattern,
 	return
 }
 
-func (email *Emailer) init(app *appContext) {
-	email.fromAddr = app.config.Section("email").Key("address").String()
-	email.fromName = app.config.Section("email").Key("from").String()
-	email.sendMethod = app.config.Section("email").Key("method").String()
-	if email.sendMethod == "mailgun" {
-		email.mg = mailgun.NewMailgun(strings.Split(email.fromAddr, "@")[1], app.config.Section("mailgun").Key("api_key").String())
-		api_url := app.config.Section("mailgun").Key("api_url").String()
-		// Mailgun client takes the base url, so we need to trim off the end (e.g 'v3/messages'
-		if strings.Contains(api_url, "messages") {
-			api_url = api_url[0:strings.LastIndex(api_url, "/")]
-			api_url = api_url[0:strings.LastIndex(api_url, "/")]
+func NewEmailer(app *appContext) *Emailer {
+	emailer := &Emailer{
+		fromAddr: app.config.Section("email").Key("address").String(),
+		fromName: app.config.Section("email").Key("from").String(),
 	}
-		email.mg.SetAPIBase(api_url)
-	} else if email.sendMethod == "smtp" {
-		app.host = app.config.Section("smtp").Key("server").String()
-		email.smtpAuth = smtp.PlainAuth("", email.fromAddr, app.config.Section("smtp").Key("password").String(), app.host)
+	method := app.config.Section("email").Key("method").String()
+	if method == "smtp" {
+		sslTls := false
+		if app.config.Section("smtp").Key("encryption").String() == "ssl_tls" {
+			sslTls = true
+		}
+		emailer.NewSMTP(app.config.Section("smtp").Key("server").String(), app.config.Section("smtp").Key("port").MustInt(465), app.config.Section("smtp").Key("password").String(), app.host, sslTls)
+	} else if method == "mailgun" {
+		emailer.NewMailgun(app.config.Section("mailgun").Key("api_url").String(), app.config.Section("mailgun").Key("api_key").String())
+	}
+	return emailer
+}
+
+func (emailer *Emailer) NewMailgun(url, key string) {
+	sender := &Mailgun{
+		client: mailgun.NewMailgun(strings.Split(emailer.fromAddr, "@")[1], key),
+	}
+	// Mailgun client takes the base url, so we need to trim off the end (e.g 'v3/messages'
+	if strings.Contains(url, "messages") {
+		url = url[0:strings.LastIndex(url, "/")]
+		url = url[0:strings.LastIndex(url, "/")]
+	}
+	sender.client.SetAPIBase(url)
+	emailer.sender = sender
+}
+
+func (emailer *Emailer) NewSMTP(server string, port int, password, host string, sslTls bool) {
+	emailer.sender = &Smtp{
+		auth:   smtp.PlainAuth("", emailer.fromAddr, password, host),
+		server: server,
+		host:   host,
+		port:   port,
+		sslTls: sslTls,
 	}
 }
 
-func (email *Emailer) constructInvite(code string, invite Invite, app *appContext) error {
-	email.content.subject = app.config.Section("invite_emails").Key("subject").String()
+func (emailer *Emailer) constructInvite(code string, invite Invite, app *appContext) (*Email, error) {
+	email := &Email{
+		subject: app.config.Section("invite_emails").Key("subject").String(),
+	}
 	expiry := invite.ValidTill
-	d, t, expires_in := email.formatExpiry(expiry, false, app.datePattern, app.timePattern)
+	d, t, expires_in := emailer.formatExpiry(expiry, false, app.datePattern, app.timePattern)
 	message := app.config.Section("email").Key("message").String()
 	invite_link := app.config.Section("invite_emails").Key("url_base").String()
 	invite_link = fmt.Sprintf("%s/%s", invite_link, code)
@@ -81,7 +154,7 @@ func (email *Emailer) constructInvite(code string, invite Invite, app *appContex
 		fpath := app.config.Section("invite_emails").Key("email_" + key).String()
 		tpl, err := template.ParseFiles(fpath)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		var tplData bytes.Buffer
 		err = tpl.Execute(&tplData, map[string]string{
@@ -92,26 +165,27 @@ func (email *Emailer) constructInvite(code string, invite Invite, app *appContex
 			"message":     message,
 		})
 		if err != nil {
-			return err
+			return nil, err
 		}
 		if key == "html" {
-			email.content.html = tplData.String()
+			email.html = tplData.String()
 		} else {
-			email.content.text = tplData.String()
+			email.text = tplData.String()
 		}
 	}
-	email.sendType = "invite"
-	return nil
+	return email, nil
 }
 
-func (email *Emailer) constructExpiry(code string, invite Invite, app *appContext) error {
-	email.content.subject = "Notice: Invite expired"
+func (emailer *Emailer) constructExpiry(code string, invite Invite, app *appContext) (*Email, error) {
+	email := &Email{
+		subject: "Notice: Invite expired",
+	}
 	expiry := app.formatDatetime(invite.ValidTill)
 	for _, key := range []string{"html", "text"} {
 		fpath := app.config.Section("notifications").Key("expiry_" + key).String()
 		tpl, err := template.ParseFiles(fpath)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		var tplData bytes.Buffer
 		err = tpl.Execute(&tplData, map[string]string{
@@ -119,20 +193,21 @@ func (email *Emailer) constructExpiry(code string, invite Invite, app *appContex
 			"expiry": expiry,
 		})
 		if err != nil {
-			return err
+			return nil, err
 		}
 		if key == "html" {
-			email.content.html = tplData.String()
+			email.html = tplData.String()
 		} else {
-			email.content.text = tplData.String()
+			email.text = tplData.String()
 		}
 	}
-	email.sendType = "expiry"
-	return nil
+	return email, nil
 }
 
-func (email *Emailer) constructCreated(code, username, address string, invite Invite, app *appContext) error {
-	email.content.subject = "Notice: User created"
+func (emailer *Emailer) constructCreated(code, username, address string, invite Invite, app *appContext) (*Email, error) {
+	email := &Email{
+		subject: "Notice: User created",
+	}
 	created := app.formatDatetime(invite.Created)
 	var tplAddress string
 	if app.config.Section("email").Key("no_username").MustBool(false) {
@@ -144,7 +219,7 @@ func (email *Emailer) constructCreated(code, username, address string, invite In
 		fpath := app.config.Section("notifications").Key("created_" + key).String()
 		tpl, err := template.ParseFiles(fpath)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		var tplData bytes.Buffer
 		err = tpl.Execute(&tplData, map[string]string{
@@ -154,27 +229,28 @@ func (email *Emailer) constructCreated(code, username, address string, invite In
 			"time":     created,
 		})
 		if err != nil {
-			return err
+			return nil, err
 		}
 		if key == "html" {
-			email.content.html = tplData.String()
+			email.html = tplData.String()
 		} else {
-			email.content.text = tplData.String()
+			email.text = tplData.String()
 		}
 	}
-	email.sendType = "created"
-	return nil
+	return email, nil
 }
 
-func (email *Emailer) constructReset(pwr Pwr, app *appContext) error {
-	email.content.subject = app.config.Section("password_resets").Key("subject").MustString("Password reset - Jellyfin")
-	d, t, expires_in := email.formatExpiry(pwr.Expiry, true, app.datePattern, app.timePattern)
+func (emailer *Emailer) constructReset(pwr Pwr, app *appContext) (*Email, error) {
+	email := &Email{
+		subject: app.config.Section("password_resets").Key("subject").MustString("Password reset - Jellyfin"),
+	}
+	d, t, expires_in := emailer.formatExpiry(pwr.Expiry, true, app.datePattern, app.timePattern)
 	message := app.config.Section("email").Key("message").String()
 	for _, key := range []string{"html", "text"} {
 		fpath := app.config.Section("password_resets").Key("email_" + key).String()
 		tpl, err := template.ParseFiles(fpath)
 		if err != nil {
-			return err
+			return nil, err
 		}
 		var tplData bytes.Buffer
 		err = tpl.Execute(&tplData, map[string]string{
@@ -186,55 +262,17 @@ func (email *Emailer) constructReset(pwr Pwr, app *appContext) error {
 			"message":     message,
 		})
 		if err != nil {
-			return err
+			return nil, err
 		}
 		if key == "html" {
-			email.content.html = tplData.String()
+			email.html = tplData.String()
 		} else {
-			email.content.text = tplData.String()
+			email.text = tplData.String()
 		}
 	}
-	email.sendType = "reset"
-	return nil
+	return email, nil
 }
 
-func (email *Emailer) send(address string, app *appContext) error {
-	if email.sendMethod == "mailgun" {
-		message := email.mg.NewMessage(
-			fmt.Sprintf("%s <%s>", email.fromName, email.fromAddr),
-			email.content.subject,
-			email.content.text,
-			address)
-		message.SetHtml(email.content.html)
-		mgapp, cancel := context.WithTimeout(context.Background(), time.Second*30)
-		defer cancel()
-		_, _, err := email.mg.Send(mgapp, message)
-		if err != nil {
-			return err
-		}
-	} else if email.sendMethod == "smtp" {
-		e := jEmail.NewEmail()
-		e.Subject = email.content.subject
-		e.From = fmt.Sprintf("%s <%s>", email.fromName, email.fromAddr)
-		e.To = []string{address}
-		e.Text = []byte(email.content.text)
-		e.HTML = []byte(email.content.html)
-		smtpType := app.config.Section("smtp").Key("encryption").String()
-		tlsConfig := &tls.Config{
-			InsecureSkipVerify: false,
-			ServerName:         app.host,
-		}
-		var err error
-		if smtpType == "ssl_tls" {
-			port := app.config.Section("smtp").Key("port").MustInt(465)
-			server := fmt.Sprintf("%s:%d", app.host, port)
-			err = e.SendWithTLS(server, email.smtpAuth, tlsConfig)
-		} else if smtpType == "starttls" {
-			port := app.config.Section("smtp").Key("port").MustInt(587)
-			server := fmt.Sprintf("%s:%d", app.host, port)
-			e.SendWithStartTLS(server, email.smtpAuth, tlsConfig)
-		}
-		return err
-	}
-	return nil
+func (emailer *Emailer) send(address string, email *Email) error {
+	return emailer.sender.send(address, emailer.fromName, emailer.fromAddr, email)
 }

main.go

@@ -53,7 +53,7 @@ type appContext struct {
 	timePattern      string
 	storage          Storage
 	validator        Validator
-	email            Emailer
+	email            *Emailer
 	info, debug, err *log.Logger
 	host             string
 	port             int
@@ -361,8 +361,6 @@ func start(asDaemon, firstCall bool) {
 		}
 		app.validator.init(validatorConf)
 
-		app.email.init(app)
-
 		inviteDaemon := NewRepeater(time.Duration(60*time.Second), app)
 		go inviteDaemon.Run()
 
@@ -476,7 +474,7 @@ func main() {
 		folder = os.Getenv("TEMP")
 	}
 	SOCK = filepath.Join(folder, SOCK)
-	fmt.Println(SOCK)
+	fmt.Println("Socket:", SOCK)
 	if flagPassed("start") {
 		args := []string{}
 		for i, f := range os.Args {

pwreset.go

@@ -71,10 +71,13 @@ func pwrMonitor(app *appContext, watcher *fsnotify.Watcher) {
 						app.err.Printf("Couldn't find email for user \"%s\". Make sure it's set", pwr.Username)
 						return
 					}
-					if app.email.constructReset(pwr, app) != nil {
+					msg, err := app.email.constructReset(pwr, app)
+					if err != nil {
 						app.err.Printf("Failed to construct password reset email for %s", pwr.Username)
-					} else if app.email.send(address, app) != nil {
+						app.debug.Printf("%s: Error: %s", pwr.Username, err)
+					} else if err := app.email.send(address, msg); err != nil {
 						app.err.Printf("Failed to send password reset email to \"%s\"", address)
+						app.debug.Printf("%s: Error: %s", pwr.Username, err)
 					} else {
 						app.info.Printf("Sent password reset email to \"%s\"", address)
 					}