PLT-3077 Add group messaging (#5489)

* Implement server changes for group messaging

* Majority of client-side implementation

* Some server updates

* Added new React multiselect component

* Fix style issues

* Add custom renderer for options

* Fix model test

* Update ENTER functionality for multiselect control

* Remove buttons from multiselect UI control

* Updating group messaging UI (#5524)

* Move filter controls up a component level

* Scroll with arrow keys

* Updating mobile layout for multiselect (#5534)

* Fix race condition when backspacing quickly

* Hidden or new GMs show up for regular messages

* Add overriding of number remaining text

* Add UI filtering for team if config setting set

* Add icon to channel switcher and class prop to status icon

* Minor updates per feedback

* Improving group messaging UI (#5563)

* UX changes per feedback

* Update email for group messages

* UI fixes for group messaging (#5587)

* Fix missing localization string

* Add maximum users message when adding members to GM

* Fix input clearing on Android

* Updating group messaging UI (#5603)

* Updating UI for group messaging (#5604)

2 files changed, 75 insertions, 2 deletions

diff --git a/api/channel.go b/api/channel.go
index 6eda72dd9..2604cc5ce 100644
--- a/api/channel.go
+++ b/api/channel.go
@@ -25,6 +25,7 @@ func InitChannel() {
 	BaseRoutes.Channels.Handle("/create", ApiUserRequired(createChannel)).Methods("POST")
 	BaseRoutes.Channels.Handle("/view", ApiUserRequired(viewChannel)).Methods("POST")
 	BaseRoutes.Channels.Handle("/create_direct", ApiUserRequired(createDirectChannel)).Methods("POST")
+	BaseRoutes.Channels.Handle("/create_group", ApiUserRequired(createGroupChannel)).Methods("POST")
 	BaseRoutes.Channels.Handle("/update", ApiUserRequired(updateChannel)).Methods("POST")
 	BaseRoutes.Channels.Handle("/update_header", ApiUserRequired(updateChannelHeader)).Methods("POST")
 	BaseRoutes.Channels.Handle("/update_purpose", ApiUserRequired(updateChannelPurpose)).Methods("POST")
@@ -98,6 +99,38 @@ func createDirectChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func createGroupChannel(c *Context, w http.ResponseWriter, r *http.Request) {
+	if !app.SessionHasPermissionTo(c.Session, model.PERMISSION_CREATE_GROUP_CHANNEL) {
+		c.SetPermissionError(model.PERMISSION_CREATE_GROUP_CHANNEL)
+		return
+	}
+
+	userIds := model.ArrayFromJson(r.Body)
+	if len(userIds) == 0 {
+		c.SetInvalidParam("createGroupChannel", "user_ids")
+		return
+	}
+
+	found := false
+	for _, id := range userIds {
+		if id == c.Session.UserId {
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		userIds = append(userIds, c.Session.UserId)
+	}
+
+	if sc, err := app.CreateGroupChannel(userIds); err != nil {
+		c.Err = err
+		return
+	} else {
+		w.Write([]byte(sc.ToJson()))
+	}
+}
+
 func CanManageChannel(c *Context, channel *model.Channel) bool {
 	if channel.Type == model.CHANNEL_OPEN && !app.SessionHasPermissionToChannel(c.Session, channel.Id, model.PERMISSION_MANAGE_PUBLIC_CHANNEL_PROPERTIES) {
 		c.SetPermissionError(model.PERMISSION_MANAGE_PUBLIC_CHANNEL_PROPERTIES)
@@ -457,7 +490,7 @@ func getChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if channel.TeamId != c.TeamId && channel.Type != model.CHANNEL_DIRECT {
+	if channel.TeamId != c.TeamId && !channel.IsGroupOrDirect() {
 		c.Err = model.NewLocAppError("getChannel", "api.channel.get_channel.wrong_team.app_error", map[string]interface{}{"ChannelId": id, "TeamId": c.TeamId}, "")
 		return
 	}
@@ -493,7 +526,7 @@ func getChannelByName(c *Context, w http.ResponseWriter, r *http.Request) {
 			return
 		}
 
-		if channel.TeamId != c.TeamId && channel.Type != model.CHANNEL_DIRECT {
+		if channel.TeamId != c.TeamId && !channel.IsGroupOrDirect() {
 			c.Err = model.NewLocAppError("getChannel", "api.channel.get_channel.wrong_team.app_error", map[string]interface{}{"ChannelName": channelName, "TeamId": c.TeamId}, "")
 			return
 		}
diff --git a/api/channel_test.go b/api/channel_test.go
index 2e6484dfa..d8da3374b 100644
--- a/api/channel_test.go
+++ b/api/channel_test.go
@@ -219,6 +219,46 @@ func TestCreateDirectChannel(t *testing.T) {
 	}
 }
 
+func TestCreateGroupChannel(t *testing.T) {
+	th := Setup().InitBasic()
+	Client := th.BasicClient
+	user := th.BasicUser
+	user2 := th.BasicUser2
+	user3 := th.CreateUser(Client)
+
+	userIds := []string{user.Id, user2.Id, user3.Id}
+
+	var channel *model.Channel
+	if result, err := Client.CreateGroupChannel(userIds); err != nil {
+		t.Fatal(err)
+	} else {
+		channel = result.Data.(*model.Channel)
+	}
+
+	if channel.Type != model.CHANNEL_GROUP {
+		t.Fatal("channel type was not group")
+	}
+
+	// Don't fail on group channels already existing and return the original channel again
+	if result, err := Client.CreateGroupChannel(userIds); err != nil {
+		t.Fatal(err)
+	} else if result.Data.(*model.Channel).Id != channel.Id {
+		t.Fatal("didn't return original group channel when saving a duplicate")
+	}
+
+	if _, err := Client.CreateGroupChannel([]string{user.Id}); err == nil {
+		t.Fatal("should have failed with not enough users")
+	}
+
+	if _, err := Client.CreateGroupChannel([]string{}); err == nil {
+		t.Fatal("should have failed with not enough users")
+	}
+
+	if _, err := Client.CreateGroupChannel([]string{user.Id, user2.Id, user3.Id, "junk"}); err == nil {
+		t.Fatal("should have failed with non-existent user")
+	}
+}
+
 func TestUpdateChannel(t *testing.T) {
 	th := Setup().InitBasic().InitSystemAdmin()
 	Client := th.SystemAdminClient