Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/app/slack.go

@@ -0,0 +1,116 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package app
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"image"
+	"mime/multipart"
+	"regexp"
+	"strings"
+	"time"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/server/channels/app/request"
+	"github.com/mattermost/mattermost-server/v6/server/channels/store"
+	"github.com/mattermost/mattermost-server/v6/server/platform/services/slackimport"
+)
+
+func (a *App) SlackImport(c *request.Context, fileData multipart.File, fileSize int64, teamID string) (*model.AppError, *bytes.Buffer) {
+	actions := slackimport.Actions{
+		UpdateActive: func(user *model.User, active bool) (*model.User, *model.AppError) {
+			return a.UpdateActive(c, user, active)
+		},
+		AddUserToChannel: a.AddUserToChannel,
+		JoinUserToTeam: func(team *model.Team, user *model.User, userRequestorId string) (*model.TeamMember, *model.AppError) {
+			return a.JoinUserToTeam(c, team, user, userRequestorId)
+		},
+		CreateDirectChannel: a.createDirectChannel,
+		CreateGroupChannel:  a.createGroupChannel,
+		CreateChannel: func(channel *model.Channel, addMember bool) (*model.Channel, *model.AppError) {
+			return a.CreateChannel(c, channel, addMember)
+		},
+		DoUploadFile: func(now time.Time, rawTeamId string, rawChannelId string, rawUserId string, rawFilename string, data []byte) (*model.FileInfo, *model.AppError) {
+			return a.DoUploadFile(c, now, rawTeamId, rawChannelId, rawUserId, rawFilename, data)
+		},
+		GenerateThumbnailImage: a.generateThumbnailImage,
+		GeneratePreviewImage:   a.generatePreviewImage,
+		InvalidateAllCaches:    func() { a.ch.srv.InvalidateAllCaches() },
+		MaxPostSize:            func() int { return a.ch.srv.platform.MaxPostSize() },
+		PrepareImage: func(fileData []byte) (image.Image, string, func(), error) {
+			img, imgType, release, err := prepareImage(a.ch.imgDecoder, bytes.NewReader(fileData))
+			if err != nil {
+				return nil, "", nil, err
+			}
+			return img, imgType, release, err
+		},
+	}
+
+	importer := slackimport.New(a.Srv().Store(), actions, a.Config())
+	return importer.SlackImport(c, fileData, fileSize, teamID)
+}
+
+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 (a *App) ProcessSlackAttachments(attachments []*model.SlackAttachment) []*model.SlackAttachment {
+	var nonNilAttachments = model.StringifySlackFieldValue(attachments)
+	for _, attachment := range attachments {
+		attachment.Pretext = a.ProcessSlackText(attachment.Pretext)
+		attachment.Text = a.ProcessSlackText(attachment.Text)
+		attachment.Title = a.ProcessSlackText(attachment.Title)
+
+		for _, field := range attachment.Fields {
+			if field != nil && field.Value != nil {
+				// Ensure the value is set to a string if it is set
+				field.Value = a.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 users, err := userStore.GetProfileByIds(context.Background(), userIDs, nil, true); err == nil {
+			for _, user := range users {
+				text = strings.Replace(text, "<@"+user.Id+">", "@"+user.Username, -1)
+			}
+		}
+	}
+	return text
+}