From 29240b9c6f4626fdccbc7ca5fed2bcbbfa21e48a Mon Sep 17 00:00:00 2001
From: Elias Nahum <nahumhbl@gmail.com>
Date: Thu, 6 Jun 2019 15:15:40 -0400
Subject: [PATCH] MM-16061 Keep unread channels in place on Tablets (#2865)

---
 app/actions/views/channel.js                  |  1 +
 .../sidebars/main/channels_list/list/index.js |  9 +++--
 app/constants/view.js                         |  9 +++++
 app/reducers/views/channel.js                 | 40 +++++++++++++++++++
 4 files changed, 55 insertions(+), 4 deletions(-)

diff --git a/app/actions/views/channel.js b/app/actions/views/channel.js
index c6903ad6b..511f5a8b6 100644
--- a/app/actions/views/channel.js
+++ b/app/actions/views/channel.js
@@ -394,6 +394,7 @@ export function handleSelectChannel(channelId, fromPushNotification = false) {
             {
                 type: ViewTypes.SELECT_CHANNEL_WITH_MEMBER,
                 data: channelId,
+                channel,
                 member,
             },
         ]));
diff --git a/app/components/sidebars/main/channels_list/list/index.js b/app/components/sidebars/main/channels_list/list/index.js
index 5e1ddb673..adb6f31a7 100644
--- a/app/components/sidebars/main/channels_list/list/index.js
+++ b/app/components/sidebars/main/channels_list/list/index.js
@@ -17,13 +17,13 @@ import {memoizeResult} from 'mattermost-redux/utils/helpers';
 import {isAdmin as checkIsAdmin, isSystemAdmin as checkIsSystemAdmin} from 'mattermost-redux/utils/user_utils';
 import {getConfig, getLicense} from 'mattermost-redux/selectors/entities/general';
 
-import {SidebarSectionTypes} from 'app/constants/view';
+import {DeviceTypes, ViewTypes} from 'app/constants';
 
 import List from './list';
 
 const filterZeroUnreads = memoizeResult((sections) => {
     return sections.filter((s) => {
-        if (s.type === SidebarSectionTypes.UNREADS) {
+        if (s.type === ViewTypes.SidebarSectionTypes.UNREADS) {
             return s.items.length > 0;
         }
         return true;
@@ -38,11 +38,12 @@ function mapStateToProps(state) {
     const isAdmin = checkIsAdmin(roles);
     const isSystemAdmin = checkIsSystemAdmin(roles);
     const sidebarPrefs = getSidebarPreferences(state);
-    const unreadChannelIds = getSortedUnreadChannelIds(state, null);
+    const lastUnreadChannel = DeviceTypes.IS_TABLET ? state.views.channel.keepChannelIdAsUnread : null;
+    const unreadChannelIds = getSortedUnreadChannelIds(state, lastUnreadChannel);
     const favoriteChannelIds = getSortedFavoriteChannelIds(state);
     const orderedChannelIds = filterZeroUnreads(getOrderedChannelIds(
         state,
-        null,
+        lastUnreadChannel,
         sidebarPrefs.grouping,
         sidebarPrefs.sorting,
         true, // The mobile app should always display the Unreads section regardless of user settings (MM-13420)
diff --git a/app/constants/view.js b/app/constants/view.js
index b885a87e9..42563da24 100644
--- a/app/constants/view.js
+++ b/app/constants/view.js
@@ -20,6 +20,13 @@ export const SidebarSectionTypes = {
     ALPHA: 'alpha',
 };
 
+export const NotificationLevels = {
+    DEFAULT: 'default',
+    ALL: 'all',
+    MENTION: 'mention',
+    NONE: 'none',
+};
+
 const ViewTypes = keyMirror({
     DATA_CLEANUP: null,
     SERVER_URL_CHANGED: null,
@@ -109,4 +116,6 @@ export default {
     PROFILE_PICTURE_SIZE: 32,
     DATA_SOURCE_USERS: 'users',
     DATA_SOURCE_CHANNELS: 'channels',
+    NotificationLevels,
+    SidebarSectionTypes,
 };
diff --git a/app/reducers/views/channel.js b/app/reducers/views/channel.js
index 8fd862ee3..87fd7f930 100644
--- a/app/reducers/views/channel.js
+++ b/app/reducers/views/channel.js
@@ -6,6 +6,7 @@ import {
     ChannelTypes,
     FileTypes,
     PostTypes,
+    UserTypes,
 } from 'mattermost-redux/action_types';
 
 import {ViewTypes} from 'app/constants';
@@ -348,6 +349,44 @@ function lastChannelViewTime(state = {}, action) {
     }
 }
 
+function keepChannelIdAsUnread(state = null, action) {
+    switch (action.type) {
+    case ViewTypes.SELECT_CHANNEL_WITH_MEMBER: {
+        const member = action.member;
+        const channel = action.channel;
+
+        if (!member || !channel) {
+            return state;
+        }
+
+        const msgCount = channel.total_msg_count - member.msg_count;
+        const hadMentions = member.mention_count > 0;
+        const hadUnreads = member.notify_props.mark_unread !== ViewTypes.NotificationLevels.MENTION && msgCount > 0;
+
+        if (hadMentions || hadUnreads) {
+            return {
+                id: member.channel_id,
+                hadMentions,
+            };
+        }
+
+        return null;
+    }
+
+    case ViewTypes.RECEIVED_FOCUSED_POST: {
+        if (state && action.channelId !== state.id) {
+            return null;
+        }
+        return state;
+    }
+
+    case UserTypes.LOGOUT_SUCCESS:
+        return null;
+    default:
+        return state;
+    }
+}
+
 export default combineReducers({
     displayName,
     drafts,
@@ -360,4 +399,5 @@ export default combineReducers({
     retryFailed,
     loadMorePostsVisible,
     lastChannelViewTime,
+    keepChannelIdAsUnread,
 });