PLT-5012 Combine updateLastViewedAt, setLastViewedAt and setActiveChannel into a single API (#4840)

* Combine updateLastViewedAt, setLastViewedAt and setActiveChannel into a single API

* Remove preference DB writes

model/client.go

@@ -48,6 +48,13 @@ type Result struct {
 	Data      interface{}
 }
 
+type ResponseMetadata struct {
+	StatusCode int
+	Error      *AppError
+	RequestId  string
+	Etag       string
+}
+
 type Client struct {
 	Url           string       // The location of the server like "http://localhost:8065"
 	ApiUrl        string       // The api location of the server like "http://localhost:8065/api/v3"
@@ -1329,6 +1336,7 @@ func (c *Client) RemoveChannelMember(id, user_id string) (*Result, *AppError) {
 // UpdateLastViewedAt will mark a channel as read.
 // The channelId indicates the channel to mark as read. If active is true, push notifications
 // will be cleared if there are unread messages. The default for active is true.
+// SCHEDULED FOR DEPRECATION IN 3.8 - use ViewChannel instead
 func (c *Client) UpdateLastViewedAt(channelId string, active bool) (*Result, *AppError) {
 	data := make(map[string]interface{})
 	data["active"] = active
@@ -1341,6 +1349,24 @@ func (c *Client) UpdateLastViewedAt(channelId string, active bool) (*Result, *Ap
 	}
 }
 
+// ViewChannel performs all the actions related to viewing a channel. This includes marking
+// the channel and the previous one as read, marking the channel as being actively viewed.
+// ChannelId is required but may be blank to indicate no channel is being viewed.
+// PrevChannelId is optional, populate to indicate a channel switch occurred. Optionally
+// provide a non-zero Time, in Unix milliseconds, to manually set the viewing time.
+func (c *Client) ViewChannel(params ChannelView) (bool, *ResponseMetadata) {
+	if r, err := c.DoApiPost(c.GetTeamRoute()+"/channels/view", params.ToJson()); err != nil {
+		return false, &ResponseMetadata{StatusCode: r.StatusCode, Error: err}
+	} else {
+		return c.CheckStatusOK(r),
+			&ResponseMetadata{
+				StatusCode: r.StatusCode,
+				RequestId:  r.Header.Get(HEADER_REQUEST_ID),
+				Etag:       r.Header.Get(HEADER_ETAG_SERVER),
+			}
+	}
+}
+
 func (c *Client) GetChannelStats(id string, etag string) (*Result, *AppError) {
 	if r, err := c.DoApiGet(c.GetChannelRoute(id)+"/stats", "", etag); err != nil {
 		return nil, err
@@ -1718,6 +1744,7 @@ func (c *Client) GetStatusesByIds(userIds []string) (*Result, *AppError) {
 // SetActiveChannel sets the the channel id the user is currently viewing.
 // The channelId key is required but the value can be blank. Returns standard
 // response.
+// SCHEDULED FOR DEPRECATION IN 3.8 - use ViewChannel instead
 func (c *Client) SetActiveChannel(channelId string) (*Result, *AppError) {
 	data := map[string]string{}
 	data["channel_id"] = channelId