PLT-3647 Email Batching (#3718)

* PLT-3647 Added config settings for email batching

* PLT-3647 Refactored generation of email notification

* PLT-3647 Added serverside code for email batching

* PLT-3647 Updated settings UI to enable email batching

* PLT-3647 Removed debug code

* PLT-3647 Fixed 0-padding of minutes in batched notification

* PLT-3647 Updated clientside UI for when email batching is disabled

* Go fmt

* PLT-3647 Changed email batching to be disabled by default

* Updated batched email message

* Added email batching toggle to system console

* Changed Email Notifications > Immediate setting to a 30 second batch interval

* Go fmt

* Fixed link to Mattermost icon in batched email notification

* Updated users to use 30 second email batching by default

* Fully disabled email batching when clustering is enabled

* Fixed email batching setting in the system console

* Fixed casing of 'Send Email notifications' -> 'Send email notifications'

* Updating UI Improvements for email batching (#3736)

* Updated text for notification settings and SiteURL.

* Prevented enabling email batching when SiteURL isn't set in the system console

* Re-added a couple debug messages

* Added warning text when clustering is enabled

6 files changed, 527 insertions, 28 deletions

diff --git a/api/admin.go b/api/admin.go
index cab55e7d3..3b324c75f 100644
--- a/api/admin.go
+++ b/api/admin.go
@@ -156,6 +156,10 @@ func reloadConfig(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 
 	utils.LoadConfig(utils.CfgFileName)
+
+	// start/restart email batching job if necessary
+	InitEmailBatching()
+
 	w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
 	ReturnStatusOK(w)
 }
@@ -204,6 +208,9 @@ func saveConfig(c *Context, w http.ResponseWriter, r *http.Request) {
 	// 	}
 	// }
 
+	// start/restart email batching job if necessary
+	InitEmailBatching()
+
 	rdata := map[string]string{}
 	rdata["status"] = "OK"
 	w.Write([]byte(model.MapToJson(rdata)))
diff --git a/api/api.go b/api/api.go
index 9e73bd125..5373565de 100644
--- a/api/api.go
+++ b/api/api.go
@@ -100,6 +100,8 @@ func InitApi() {
 	Srv.Router.Handle("/api/{anything:.*}", http.HandlerFunc(Handle404))
 
 	utils.InitHTML()
+
+	InitEmailBatching()
 }
 
 func HandleEtag(etag string, w http.ResponseWriter, r *http.Request) bool {
diff --git a/api/email_batching.go b/api/email_batching.go
new file mode 100644
index 000000000..aa2836570
--- /dev/null
+++ b/api/email_batching.go
@@ -0,0 +1,252 @@
+// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package api
+
+import (
+	"database/sql"
+	"fmt"
+	"html/template"
+	"strconv"
+	"time"
+
+	"github.com/mattermost/platform/model"
+	"github.com/mattermost/platform/utils"
+
+	l4g "github.com/alecthomas/log4go"
+	"github.com/nicksnyder/go-i18n/i18n"
+)
+
+const (
+	EMAIL_BATCHING_TASK_NAME = "Email Batching"
+)
+
+var emailBatchingJob *EmailBatchingJob
+
+func InitEmailBatching() {
+	if *utils.Cfg.EmailSettings.EnableEmailBatching {
+		if emailBatchingJob == nil {
+			emailBatchingJob = MakeEmailBatchingJob(*utils.Cfg.EmailSettings.EmailBatchingBufferSize)
+		}
+
+		// note that we don't support changing EmailBatchingBufferSize without restarting the server
+
+		emailBatchingJob.Start()
+	}
+}
+
+func AddNotificationEmailToBatch(user *model.User, post *model.Post, team *model.Team) *model.AppError {
+	if !*utils.Cfg.EmailSettings.EnableEmailBatching {
+		return model.NewLocAppError("AddNotificationEmailToBatch", "api.email_batching.add_notification_email_to_batch.disabled.app_error", nil, "")
+	}
+
+	if !emailBatchingJob.Add(user, post, team) {
+		l4g.Error(utils.T("api.email_batching.add_notification_email_to_batch.channel_full.app_error"))
+		return model.NewLocAppError("AddNotificationEmailToBatch", "api.email_batching.add_notification_email_to_batch.channel_full.app_error", nil, "")
+	}
+
+	return nil
+}
+
+type batchedNotification struct {
+	userId   string
+	post     *model.Post
+	teamName string
+}
+
+type EmailBatchingJob struct {
+	newNotifications     chan *batchedNotification
+	pendingNotifications map[string][]*batchedNotification
+}
+
+func MakeEmailBatchingJob(bufferSize int) *EmailBatchingJob {
+	return &EmailBatchingJob{
+		newNotifications:     make(chan *batchedNotification, bufferSize),
+		pendingNotifications: make(map[string][]*batchedNotification),
+	}
+}
+
+func (job *EmailBatchingJob) Start() {
+	if task := model.GetTaskByName(EMAIL_BATCHING_TASK_NAME); task != nil {
+		task.Cancel()
+	}
+
+	l4g.Debug(utils.T("api.email_batching.start.starting"), *utils.Cfg.EmailSettings.EmailBatchingInterval)
+	model.CreateRecurringTask(EMAIL_BATCHING_TASK_NAME, job.CheckPendingEmails, time.Duration(*utils.Cfg.EmailSettings.EmailBatchingInterval)*time.Second)
+}
+
+func (job *EmailBatchingJob) Add(user *model.User, post *model.Post, team *model.Team) bool {
+	notification := &batchedNotification{
+		userId:   user.Id,
+		post:     post,
+		teamName: team.Name,
+	}
+
+	select {
+	case job.newNotifications <- notification:
+		return true
+	default:
+		// return false if we couldn't queue the email notification so that we can send an immediate email
+		return false
+	}
+}
+
+func (job *EmailBatchingJob) CheckPendingEmails() {
+	job.handleNewNotifications()
+
+	// it's a bit weird to pass the send email function through here, but it makes it so that we can test
+	// without actually sending emails
+	job.checkPendingNotifications(time.Now(), sendBatchedEmailNotification)
+
+	l4g.Debug(utils.T("api.email_batching.check_pending_emails.finished_running"), len(job.pendingNotifications))
+}
+
+func (job *EmailBatchingJob) handleNewNotifications() {
+	receiving := true
+
+	// read in new notifications to send
+	for receiving {
+		select {
+		case notification := <-job.newNotifications:
+			userId := notification.userId
+
+			if _, ok := job.pendingNotifications[userId]; !ok {
+				job.pendingNotifications[userId] = []*batchedNotification{notification}
+			} else {
+				job.pendingNotifications[userId] = append(job.pendingNotifications[userId], notification)
+			}
+		default:
+			receiving = false
+		}
+	}
+}
+
+func (job *EmailBatchingJob) checkPendingNotifications(now time.Time, handler func(string, []*batchedNotification)) {
+	// look for users who've acted since pending posts were received
+	for userId, notifications := range job.pendingNotifications {
+		schan := Srv.Store.Status().Get(userId)
+		pchan := Srv.Store.Preference().Get(userId, model.PREFERENCE_CATEGORY_NOTIFICATIONS, model.PREFERENCE_NAME_EMAIL_INTERVAL)
+		batchStartTime := notifications[0].post.CreateAt
+
+		// check if the user has been active and would've seen any new posts
+		if result := <-schan; result.Err != nil {
+			l4g.Error(utils.T("api.email_batching.check_pending_emails.status.app_error"), result.Err)
+			delete(job.pendingNotifications, userId)
+			continue
+		} else if status := result.Data.(*model.Status); status.LastActivityAt >= batchStartTime {
+			delete(job.pendingNotifications, userId)
+			continue
+		}
+
+		// get how long we need to wait to send notifications to the user
+		var interval int64
+		if result := <-pchan; result.Err != nil {
+			// default to 30 seconds to match the send "immediate" setting
+			interval, _ = strconv.ParseInt(model.PREFERENCE_DEFAULT_EMAIL_INTERVAL, 10, 64)
+		} else {
+			preference := result.Data.(model.Preference)
+
+			if value, err := strconv.ParseInt(preference.Value, 10, 64); err != nil {
+				interval, _ = strconv.ParseInt(model.PREFERENCE_DEFAULT_EMAIL_INTERVAL, 10, 64)
+			} else {
+				interval = value
+			}
+		}
+
+		// send the email notification if it's been long enough
+		if now.Sub(time.Unix(batchStartTime/1000, 0)) > time.Duration(interval)*time.Second {
+			go handler(userId, notifications)
+			delete(job.pendingNotifications, userId)
+		}
+	}
+}
+
+func sendBatchedEmailNotification(userId string, notifications []*batchedNotification) {
+	uchan := Srv.Store.User().Get(userId)
+	pchan := Srv.Store.Preference().Get(userId, model.PREFERENCE_CATEGORY_DISPLAY_SETTINGS, model.PREFERENCE_NAME_DISPLAY_NAME_FORMAT)
+
+	var user *model.User
+	if result := <-uchan; result.Err != nil {
+		l4g.Warn("api.email_batching.send_batched_email_notification.user.app_error")
+		return
+	} else {
+		user = result.Data.(*model.User)
+	}
+
+	translateFunc := utils.GetUserTranslations(user.Locale)
+
+	var displayNameFormat string
+	if result := <-pchan; result.Err != nil && result.Err.DetailedError != sql.ErrNoRows.Error() {
+		l4g.Warn("api.email_batching.send_batched_email_notification.preferences.app_error")
+		return
+	} else if result.Err != nil {
+		// no display name format saved, so fall back to default
+		displayNameFormat = model.PREFERENCE_DEFAULT_DISPLAY_NAME_FORMAT
+	} else {
+		displayNameFormat = result.Data.(model.Preference).Value
+	}
+
+	var contents string
+	for _, notification := range notifications {
+		template := utils.NewHTMLTemplate("post_batched_post", user.Locale)
+
+		contents += renderBatchedPost(template, notification.post, notification.teamName, displayNameFormat, translateFunc)
+	}
+
+	tm := time.Unix(notifications[0].post.CreateAt/1000, 0)
+
+	subject := translateFunc("api.email_batching.send_batched_email_notification.subject", len(notifications), map[string]interface{}{
+		"SiteName": utils.Cfg.TeamSettings.SiteName,
+		"Year":     tm.Year(),
+		"Month":    translateFunc(tm.Month().String()),
+		"Day":      tm.Day(),
+	})
+
+	body := utils.NewHTMLTemplate("post_batched_body", user.Locale)
+	body.Props["SiteURL"] = *utils.Cfg.ServiceSettings.SiteURL
+	body.Props["Posts"] = template.HTML(contents)
+	body.Props["BodyText"] = translateFunc("api.email_batching.send_batched_email_notification.body_text", len(notifications))
+
+	if err := utils.SendMail(user.Email, subject, body.Render()); err != nil {
+		l4g.Warn(utils.T("api.email_batchings.send_batched_email_notification.send.app_error"), user.Email, err)
+	}
+}
+
+func renderBatchedPost(template *utils.HTMLTemplate, post *model.Post, teamName string, displayNameFormat string, translateFunc i18n.TranslateFunc) string {
+	schan := Srv.Store.User().Get(post.UserId)
+	cchan := Srv.Store.Channel().Get(post.ChannelId)
+
+	template.Props["Button"] = translateFunc("api.email_batching.render_batched_post.go_to_post")
+	template.Props["PostMessage"] = getMessageForNotification(post, translateFunc)
+	template.Props["PostLink"] = *utils.Cfg.ServiceSettings.SiteURL + "/" + teamName + "/pl/" + post.Id
+
+	tm := time.Unix(post.CreateAt/1000, 0)
+	timezone, _ := tm.Zone()
+
+	template.Props["Date"] = translateFunc("api.email_batching.render_batched_post.date", map[string]interface{}{
+		"Year":     tm.Year(),
+		"Month":    translateFunc(tm.Month().String()),
+		"Day":      tm.Day(),
+		"Hour":     tm.Hour(),
+		"Minute":   fmt.Sprintf("%02d", tm.Minute()),
+		"Timezone": timezone,
+	})
+
+	if result := <-schan; result.Err != nil {
+		l4g.Warn(utils.T("api.email_batching.render_batched_post.sender.app_error"))
+		return ""
+	} else {
+		template.Props["SenderName"] = result.Data.(*model.User).GetDisplayNameForPreference(displayNameFormat)
+	}
+
+	if result := <-cchan; result.Err != nil {
+		l4g.Warn(utils.T("api.email_batching.render_batched_post.channel.app_error"))
+		return ""
+	} else if channel := result.Data.(*model.Channel); channel.Type == model.CHANNEL_DIRECT {
+		template.Props["ChannelName"] = translateFunc("api.email_batching.render_batched_post.direct_message")
+	} else {
+		template.Props["ChannelName"] = channel.DisplayName
+	}
+
+	return template.Render()
+}
diff --git a/api/email_batching_test.go b/api/email_batching_test.go
new file mode 100644
index 000000000..d1619f912
--- /dev/null
+++ b/api/email_batching_test.go
@@ -0,0 +1,193 @@
+// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package api
+
+import (
+	"testing"
+	"time"
+
+	"github.com/mattermost/platform/model"
+	"github.com/mattermost/platform/store"
+)
+
+func TestHandleNewNotifications(t *testing.T) {
+	Setup()
+
+	id1 := model.NewId()
+	id2 := model.NewId()
+	id3 := model.NewId()
+
+	// test queueing of received posts by user
+	job := MakeEmailBatchingJob(128)
+
+	job.handleNewNotifications()
+
+	if len(job.pendingNotifications) != 0 {
+		t.Fatal("shouldn't have added any pending notifications")
+	}
+
+	job.Add(&model.User{Id: id1}, &model.Post{UserId: id1, Message: "test"}, &model.Team{Name: "team"})
+	if len(job.pendingNotifications) != 0 {
+		t.Fatal("shouldn't have added any pending notifications")
+	}
+
+	job.handleNewNotifications()
+	if len(job.pendingNotifications) != 1 {
+		t.Fatal("should have received posts for 1 user")
+	} else if len(job.pendingNotifications[id1]) != 1 {
+		t.Fatal("should have received 1 post for user")
+	}
+
+	job.Add(&model.User{Id: id1}, &model.Post{UserId: id1, Message: "test"}, &model.Team{Name: "team"})
+	job.handleNewNotifications()
+	if len(job.pendingNotifications) != 1 {
+		t.Fatal("should have received posts for 1 user")
+	} else if len(job.pendingNotifications[id1]) != 2 {
+		t.Fatal("should have received 2 posts for user1", job.pendingNotifications[id1])
+	}
+
+	job.Add(&model.User{Id: id2}, &model.Post{UserId: id1, Message: "test"}, &model.Team{Name: "team"})
+	job.handleNewNotifications()
+	if len(job.pendingNotifications) != 2 {
+		t.Fatal("should have received posts for 2 users")
+	} else if len(job.pendingNotifications[id1]) != 2 {
+		t.Fatal("should have received 2 posts for user1")
+	} else if len(job.pendingNotifications[id2]) != 1 {
+		t.Fatal("should have received 1 post for user2")
+	}
+
+	job.Add(&model.User{Id: id2}, &model.Post{UserId: id2, Message: "test"}, &model.Team{Name: "team"})
+	job.Add(&model.User{Id: id1}, &model.Post{UserId: id3, Message: "test"}, &model.Team{Name: "team"})
+	job.Add(&model.User{Id: id3}, &model.Post{UserId: id3, Message: "test"}, &model.Team{Name: "team"})
+	job.Add(&model.User{Id: id2}, &model.Post{UserId: id2, Message: "test"}, &model.Team{Name: "team"})
+	job.handleNewNotifications()
+	if len(job.pendingNotifications) != 3 {
+		t.Fatal("should have received posts for 3 users")
+	} else if len(job.pendingNotifications[id1]) != 3 {
+		t.Fatal("should have received 3 posts for user1")
+	} else if len(job.pendingNotifications[id2]) != 3 {
+		t.Fatal("should have received 3 posts for user2")
+	} else if len(job.pendingNotifications[id3]) != 1 {
+		t.Fatal("should have received 1 post for user3")
+	}
+
+	// test ordering of received posts
+	job = MakeEmailBatchingJob(128)
+
+	job.Add(&model.User{Id: id1}, &model.Post{UserId: id1, Message: "test1"}, &model.Team{Name: "team"})
+	job.Add(&model.User{Id: id1}, &model.Post{UserId: id1, Message: "test2"}, &model.Team{Name: "team"})
+	job.Add(&model.User{Id: id2}, &model.Post{UserId: id1, Message: "test3"}, &model.Team{Name: "team"})
+	job.Add(&model.User{Id: id1}, &model.Post{UserId: id1, Message: "test4"}, &model.Team{Name: "team"})
+	job.Add(&model.User{Id: id2}, &model.Post{UserId: id1, Message: "test5"}, &model.Team{Name: "team"})
+	job.handleNewNotifications()
+	if job.pendingNotifications[id1][0].post.Message != "test1" ||
+		job.pendingNotifications[id1][1].post.Message != "test2" ||
+		job.pendingNotifications[id1][2].post.Message != "test4" {
+		t.Fatal("incorrect order of received posts for user1")
+	} else if job.pendingNotifications[id2][0].post.Message != "test3" ||
+		job.pendingNotifications[id2][1].post.Message != "test5" {
+		t.Fatal("incorrect order of received posts for user2")
+	}
+}
+
+func TestCheckPendingNotifications(t *testing.T) {
+	Setup()
+
+	id1 := model.NewId()
+
+	job := MakeEmailBatchingJob(128)
+	job.pendingNotifications[id1] = []*batchedNotification{
+		{
+			post: &model.Post{
+				UserId:   id1,
+				CreateAt: 10000000,
+			},
+		},
+	}
+
+	store.Must(Srv.Store.Status().SaveOrUpdate(&model.Status{
+		UserId:         id1,
+		LastActivityAt: 9999000,
+	}))
+	store.Must(Srv.Store.Preference().Save(&model.Preferences{{
+		UserId:   id1,
+		Category: model.PREFERENCE_CATEGORY_NOTIFICATIONS,
+		Name:     model.PREFERENCE_NAME_EMAIL_INTERVAL,
+		Value:    "60",
+	}}))
+
+	// test that notifications aren't sent before interval
+	job.checkPendingNotifications(time.Unix(10001, 0), func(string, []*batchedNotification) {})
+
+	if job.pendingNotifications[id1] == nil || len(job.pendingNotifications[id1]) != 1 {
+		t.Fatal("should'nt have sent queued post")
+	}
+
+	// test that notifications are cleared if the user has acted
+	store.Must(Srv.Store.Status().SaveOrUpdate(&model.Status{
+		UserId:         id1,
+		LastActivityAt: 10001000,
+	}))
+
+	job.checkPendingNotifications(time.Unix(10002, 0), func(string, []*batchedNotification) {})
+
+	if job.pendingNotifications[id1] != nil && len(job.pendingNotifications[id1]) != 0 {
+		t.Fatal("should've remove queued post since user acted")
+	}
+
+	// test that notifications are sent if enough time passes since the first message
+	job.pendingNotifications[id1] = []*batchedNotification{
+		{
+			post: &model.Post{
+				UserId:   id1,
+				CreateAt: 10060000,
+				Message:  "post1",
+			},
+		},
+		{
+			post: &model.Post{
+				UserId:   id1,
+				CreateAt: 10090000,
+				Message:  "post2",
+			},
+		},
+	}
+
+	received := make(chan *model.Post, 2)
+	timeout := make(chan bool)
+
+	job.checkPendingNotifications(time.Unix(10130, 0), func(s string, notifications []*batchedNotification) {
+		for _, notification := range notifications {
+			received <- notification.post
+		}
+	})
+
+	go func() {
+		// start a timeout to make sure that we don't get stuck here on a failed test
+		time.Sleep(5 * time.Second)
+		timeout <- true
+	}()
+
+	if job.pendingNotifications[id1] != nil && len(job.pendingNotifications[id1]) != 0 {
+		t.Fatal("should've remove queued posts when sending messages")
+	}
+
+	select {
+	case post := <-received:
+		if post.Message != "post1" {
+			t.Fatal("should've received post1 first")
+		}
+	case _ = <-timeout:
+		t.Fatal("timed out waiting for first post notification")
+	}
+
+	select {
+	case post := <-received:
+		if post.Message != "post2" {
+			t.Fatal("should've received post2 second")
+		}
+	case _ = <-timeout:
+		t.Fatal("timed out waiting for second post notification")
+	}
+}
diff --git a/api/post.go b/api/post.go
index a873e16a8..93b88a432 100644
--- a/api/post.go
+++ b/api/post.go
@@ -23,6 +23,7 @@ import (
 	"github.com/mattermost/platform/model"
 	"github.com/mattermost/platform/store"
 	"github.com/mattermost/platform/utils"
+	"github.com/nicksnyder/go-i18n/i18n"
 )
 
 const (
@@ -770,6 +771,14 @@ func sendNotificationEmail(c *Context, post *model.Post, user *model.User, chann
 		return
 	}
 
+	if *utils.Cfg.EmailSettings.EnableEmailBatching {
+		if err := AddNotificationEmailToBatch(user, post, team); err == nil {
+			return
+		}
+
+		// fall back to sending a single email if we can't batch it for some reason
+	}
+
 	var channelName string
 	var bodyText string
 	var subjectText string
@@ -802,7 +811,7 @@ func sendNotificationEmail(c *Context, post *model.Post, user *model.User, chann
 
 	bodyPage := utils.NewHTMLTemplate("post_body", user.Locale)
 	bodyPage.Props["SiteURL"] = c.GetSiteURL()
-	bodyPage.Props["PostMessage"] = model.ClearMentionTags(post.Message)
+	bodyPage.Props["PostMessage"] = getMessageForNotification(post, userLocale)
 	bodyPage.Props["TeamLink"] = teamURL + "/pl/" + post.Id
 	bodyPage.Props["BodyText"] = bodyText
 	bodyPage.Props["Button"] = userLocale("api.templates.post_body.button")
@@ -811,39 +820,36 @@ func sendNotificationEmail(c *Context, post *model.Post, user *model.User, chann
 			"Hour": fmt.Sprintf("%02d", tm.Hour()), "Minute": fmt.Sprintf("%02d", tm.Minute()),
 			"TimeZone": zone, "Month": month, "Day": day}))
 
-	// attempt to fill in a message body if the post doesn't have any text
-	if len(strings.TrimSpace(bodyPage.Props["PostMessage"])) == 0 && len(post.Filenames) > 0 {
-		// extract the filenames from their paths and determine what type of files are attached
-		filenames := make([]string, len(post.Filenames))
-		onlyImages := true
-		for i, filename := range post.Filenames {
-			var err error
-			if filenames[i], err = url.QueryUnescape(filepath.Base(filename)); err != nil {
-				// this should never error since filepath was escaped using url.QueryEscape
-				filenames[i] = filepath.Base(filename)
-			}
+	if err := utils.SendMail(user.Email, subjectPage.Render(), bodyPage.Render()); err != nil {
+		l4g.Error(utils.T("api.post.send_notifications_and_forget.send.error"), user.Email, err)
+	}
+}
 
-			ext := filepath.Ext(filename)
-			onlyImages = onlyImages && model.IsFileExtImage(ext)
-		}
-		filenamesString := strings.Join(filenames, ", ")
+func getMessageForNotification(post *model.Post, translateFunc i18n.TranslateFunc) string {
+	if len(strings.TrimSpace(post.Message)) != 0 || len(post.Filenames) == 0 {
+		return post.Message
+	}
 
-		var attachmentPrefix string
-		if onlyImages {
-			attachmentPrefix = "Image"
-		} else {
-			attachmentPrefix = "File"
-		}
-		if len(post.Filenames) > 1 {
-			attachmentPrefix += "s"
+	// extract the filenames from their paths and determine what type of files are attached
+	filenames := make([]string, len(post.Filenames))
+	onlyImages := true
+	for i, filename := range post.Filenames {
+		var err error
+		if filenames[i], err = url.QueryUnescape(filepath.Base(filename)); err != nil {
+			// this should never error since filepath was escaped using url.QueryEscape
+			filenames[i] = filepath.Base(filename)
 		}
 
-		bodyPage.Props["PostMessage"] = userLocale("api.post.send_notifications_and_forget.sent",
-			map[string]interface{}{"Prefix": attachmentPrefix, "Filenames": filenamesString})
+		ext := filepath.Ext(filename)
+		onlyImages = onlyImages && model.IsFileExtImage(ext)
 	}
 
-	if err := utils.SendMail(user.Email, subjectPage.Render(), bodyPage.Render()); err != nil {
-		l4g.Error(utils.T("api.post.send_notifications_and_forget.send.error"), user.Email, err)
+	props := map[string]interface{}{"Filenames": strings.Join(filenames, ", ")}
+
+	if onlyImages {
+		return translateFunc("api.post.get_message_for_notification.images_sent", len(filenames), props)
+	} else {
+		return translateFunc("api.post.get_message_for_notification.files_sent", len(filenames), props)
 	}
 }
 
diff --git a/api/post_test.go b/api/post_test.go
index f27e843da..2239e92cd 100644
--- a/api/post_test.go
+++ b/api/post_test.go
@@ -1147,3 +1147,42 @@ func TestGetFlaggedPosts(t *testing.T) {
 		t.Fatal("should not have gotten a flagged post")
 	}
 }
+
+func TestGetMessageForNotification(t *testing.T) {
+	Setup()
+	translateFunc := utils.GetUserTranslations("en")
+
+	post := &model.Post{
+		Message:   "test",
+		Filenames: model.StringArray{},
+	}
+
+	if getMessageForNotification(post, translateFunc) != "test" {
+		t.Fatal("should've returned message text")
+	}
+
+	post.Filenames = model.StringArray{"test1.png"}
+	if getMessageForNotification(post, translateFunc) != "test" {
+		t.Fatal("should've returned message text, even with attachments")
+	}
+
+	post.Message = ""
+	if message := getMessageForNotification(post, translateFunc); message != "1 image sent: test1.png" {
+		t.Fatal("should've returned number of images:", message)
+	}
+
+	post.Filenames = model.StringArray{"test1.png", "test2.jpg"}
+	if message := getMessageForNotification(post, translateFunc); message != "2 images sent: test1.png, test2.jpg" {
+		t.Fatal("should've returned number of images:", message)
+	}
+
+	post.Filenames = model.StringArray{"test1.go"}
+	if message := getMessageForNotification(post, translateFunc); message != "1 file sent: test1.go" {
+		t.Fatal("should've returned number of files:", message)
+	}
+
+	post.Filenames = model.StringArray{"test1.go", "test2.jpg"}
+	if message := getMessageForNotification(post, translateFunc); message != "2 files sent: test1.go, test2.jpg" {
+		t.Fatal("should've returned number of mixed files:", message)
+	}
+}