PLT-7824 Added support for mentions with <@userid> and <!here> (#7615) (#7737)

app/slack.go

@@ -0,0 +1,76 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"regexp"
+
+	"fmt"
+	"strings"
+
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/store"
+)
+
+func (a *App) ProcessSlackText(text string) string {
+	text = expandAnnouncement(text)
+	text = replaceUserIds(a.Srv.Store.User(), text)
+
+	return text
+}
+
+// Expand announcements in incoming webhooks from Slack. Those announcements
+// can be found in the text attribute, or in the pretext, text, title and value
+// attributes of the attachment structure. The Slack attachment structure is
+// documented here: https://api.slack.com/docs/attachments
+func (app *App) ProcessSlackAttachments(a []*model.SlackAttachment) []*model.SlackAttachment {
+	var nonNilAttachments = model.StringifySlackFieldValue(a)
+	for _, attachment := range a {
+		attachment.Pretext = app.ProcessSlackText(attachment.Pretext)
+		attachment.Text = app.ProcessSlackText(attachment.Text)
+		attachment.Title = app.ProcessSlackText(attachment.Title)
+
+		for _, field := range attachment.Fields {
+			if field.Value != nil {
+				// Ensure the value is set to a string if it is set
+				field.Value = app.ProcessSlackText(fmt.Sprintf("%v", field.Value))
+			}
+		}
+	}
+	return nonNilAttachments
+}
+
+// To mention @channel or @here via a webhook in Slack, the message should contain
+// <!channel> or <!here>, as explained at the bottom of this article:
+// https://get.slack.help/hc/en-us/articles/202009646-Making-announcements
+func expandAnnouncement(text string) string {
+	a1 := [3]string{"<!channel>", "<!here>", "<!all>"}
+	a2 := [3]string{"@channel", "@here", "@all"}
+
+	for i, a := range a1 {
+		text = strings.Replace(text, a, a2[i], -1)
+	}
+	return text
+}
+
+// Replaces user IDs mentioned like this <@userID> to a normal username (eg. @bob)
+// This is required so that Mattermost maintains Slack compatibility
+// Refer to: https://api.slack.com/changelog/2017-09-the-one-about-usernames
+func replaceUserIds(userStore store.UserStore, text string) string {
+	rgx, err := regexp.Compile("<@([a-zA-Z0-9]+)>")
+	if err == nil {
+		userIds := make([]string, 0)
+		matches := rgx.FindAllStringSubmatch(text, -1)
+		for _, match := range matches {
+			userIds = append(userIds, match[1])
+		}
+
+		if res := <-userStore.GetProfileByIds(userIds, true); res.Err == nil {
+			for _, user := range res.Data.([]*model.User) {
+				text = strings.Replace(text, "<@"+user.Id+">", "@"+user.Username, -1)
+			}
+		}
+	}
+	return text
+}