feat: Document presence indicator (#1114)

* Update websockets to allow joining document-based rooms

* dynamic websocket joining

* emit user.join/leave events when entering and exiting document rooms

* presence storage

* feat: frontend presence store

* lint

* UI updates

* First pass editing state

* refactoring

* Timeout per user/doc
lint

* Document data loading refactor to keep Socket mounted

* restore: Mark as viewed functionality
Add display of 'you' to collaborators

* fix: Socket/document remount when document slug changes due to title change

* Revert unneccessary package update

* Move editing ping interval to a shared constant

* fix: Flash of sidebar when loading page directly on editing mode

* separate document and revision loading

* add comments for socket events

* fix: Socket events getting bound multiple times on reconnect

* fix: Clear client side presence state on disconnect

* fix: Don't ignore server side error
Improved documentation

* More comments / why comments

* rename Socket -> SocketPresence

* fix: Handle redis is down
remove unneccessary join

* fix: PR feedback

server/models/View.js

@@ -1,5 +1,8 @@
 // @flow
-import { DataTypes, sequelize } from '../sequelize';
+import subMilliseconds from 'date-fns/sub_milliseconds';
+import { Op, DataTypes, sequelize } from '../sequelize';
+import { User } from '../models';
+import { USER_PRESENCE_INTERVAL } from '../../shared/constants';
 
 const View = sequelize.define(
   'view',
@@ -9,6 +12,9 @@ const View = sequelize.define(
       defaultValue: DataTypes.UUIDV4,
       primaryKey: true,
     },
+    lastEditingAt: {
+      type: DataTypes.DATE,
+    },
     count: {
       type: DataTypes.INTEGER,
       defaultValue: 1,
@@ -33,4 +39,46 @@ View.increment = async where => {
   return model;
 };
 
+View.findByDocument = async documentId => {
+  return View.findAll({
+    where: { documentId },
+    order: [['updatedAt', 'DESC']],
+    include: [
+      {
+        model: User,
+        paranoid: false,
+      },
+    ],
+  });
+};
+
+View.findRecentlyEditingByDocument = async documentId => {
+  return View.findAll({
+    where: {
+      documentId,
+      lastEditingAt: {
+        [Op.gt]: subMilliseconds(new Date(), USER_PRESENCE_INTERVAL * 2),
+      },
+    },
+    order: [['lastEditingAt', 'DESC']],
+  });
+};
+
+View.touch = async (documentId: string, userId: string, isEditing: boolean) => {
+  const [view] = await View.findOrCreate({
+    where: {
+      userId,
+      documentId,
+    },
+  });
+
+  if (isEditing) {
+    const lastEditingAt = new Date();
+    view.lastEditingAt = lastEditingAt;
+    await view.save();
+  }
+
+  return view;
+};
+
 export default View;