allow messaging more than 100 students from quizzes

fixes CNVS-39904

conversation create api has a limit of 100 recipients for private
messages, so we need to batch them client side

test plan:
- test using "Message students who" in quizzes with > 100 people
- also test from a group category (other place where this code is
reused)

Change-Id: I387105ca3a9d9245a795cad07c9fb3c576c78478
Reviewed-on: https://gerrit.instructure.com/131385
Tested-by: Jenkins
Reviewed-by: Felix Milea-Ciobanu <fmileaciobanu@instructure.com>
QA-Review: KC Naegle <knaegle@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>

app/coffeescripts/models/Conversation.coffee

@@ -18,9 +18,8 @@
 define [
   'i18n!conversations'
   'Backbone'
-  'underscore'
   'jquery'
-], (I18n,{Model},_,$) ->
+], (I18n, {Model}, $) ->
 
   class Conversation extends Model
 
@@ -37,13 +36,13 @@ define [
     NO_RECIPIENTS_ERR = I18n.t('no_recipients_choose_another_group',
       'No recipients are in this group. Please choose another group.')
 
-    validate: (attrs,options) ->
+    validate: (attrs, options) ->
       errors = {}
       if !attrs.body or !$.trim(attrs.body.toString())
         errors.body = [ message: BLANK_BODY_ERR ]
       if !attrs.recipients || !attrs.recipients.length
         errors.recipients = [ message: NO_RECIPIENTS_ERR ]
-      if _.keys(errors).length
+      if Object.keys(errors).length
         errors
       else
         undefined

app/coffeescripts/models/ConversationCreator.coffee

@@ -0,0 +1,36 @@
+#
+# Copyright (C) 2017 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+
+define [
+  'jquery'
+  'lodash'
+  'compiled/models/Conversation'
+], ($, _, Conversation) ->
+
+  class ConversationCreator
+    constructor: (opts) ->
+      @chunkSize = opts.chunkSize || 100
+
+    save: (data, saveOpts) ->
+      xhrs = _.chunk(data.recipients, @chunkSize).map (chunk) ->
+        chunkData = Object.assign({}, data, { recipients: chunk })
+        (new Conversation).save(chunkData, saveOpts)
+      $.when.apply($, xhrs)
+
+    # we can validate the full data set in one go
+    validate: (attrs, options) ->
+      (new Conversation).validate(attrs, options)

app/coffeescripts/views/MessageStudentsDialog.coffee

@@ -21,11 +21,11 @@ define [
   'compiled/views/DialogFormView'
   'jst/messageStudentsDialog'
   'jst/EmptyDialogFormWrapper'
-  'compiled/models/Conversation'
+  'compiled/models/ConversationCreator'
   'jst/_messageStudentsWhoRecipientList'
   'underscore'
   'compiled/jquery/serializeForm'
-], (I18n, $, DialogFormView, template, wrapperTemplate, Conversation, recipientListTemplate, _) ->
+], (I18n, $, DialogFormView, template, wrapperTemplate, ConversationCreator, recipientListTemplate, _) ->
 
   class MessageStudentsDialog extends DialogFormView
 
@@ -68,7 +68,7 @@ define [
         I18n.t('message_students', 'Message students')
 
       @recipients = @recipientGroups[0].recipients
-      @model or= new Conversation
+      @model or= new ConversationCreator(chunkSize: ENV.MAX_GROUP_CONVERSATION_SIZE)
 
     toJSON: =>
       json = {}

app/controllers/quizzes/quizzes_controller.rb

@@ -239,7 +239,8 @@ class Quizzes::QuizzesController < ApplicationController
         COURSE_ID: @context.id,
         LOCKDOWN_BROWSER: @quiz.require_lockdown_browser?,
         QUIZ: quiz_json(@quiz,@context,@current_user,session),
-        QUIZZES_URL: course_quizzes_url(@context)
+        QUIZZES_URL: course_quizzes_url(@context),
+        MAX_GROUP_CONVERSATION_SIZE: Conversation.max_group_conversation_size
       }
       append_sis_data(hash)
       js_env(hash)

spec/coffeescripts/models/ConversationCreatorSpec.coffee

@@ -0,0 +1,47 @@
+#
+# Copyright (C) 2013 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+
+define [
+  'compiled/models/ConversationCreator'
+], (ConversationCreator) ->
+
+  QUnit.module "ConversationCreator",
+    setup: ->
+      @cc = new ConversationCreator(chunkSize: 2)
+      @server = sinon.fakeServer.create()
+
+    teardown: ->
+      @server.restore()
+
+  respond = (data) ->
+
+  test "#validate passes through to Conversation", ->
+    ok @cc.validate(body: '')
+    ok @cc.validate(body: null).body
+    ok @cc.validate(body: 'body', recipients: [{}]) == undefined
+
+  test "#save calls save in batches", ->
+    spy = @spy()
+    @server.respondWith("POST", '/api/v1/conversations', (xhr) ->
+      spy()
+      xhr.respond([200, { "Content-Type": "application/json"}, JSON.stringify({})])
+    )
+    dfd = @cc.save(body: 'body', recipients: [1, 2, 3, 4])
+    equal dfd.state(), "pending"
+    @server.respond()
+    equal dfd.state(), "resolved"
+    ok spy.calledTwice