Fix course instance generation for classrooms

app/templates/courses/classroom-view.jade

@@ -53,7 +53,7 @@ block content
             .progress
               .progress-bar(style='width:'+stats.levels.pctDone)
           else if paidFor
-            button.enable-btn.btn.btn-info.btn-sm(data-user-id=user.id, data-course-instance-id=courseInstance.id) Enable
+            button.enable-btn.btn.btn-info.btn-sm(data-user-id=user.id, data-course-instance-cid=courseInstance.cid) Enable
             
     if !paidFor
       .text-center

app/views/courses/ClassroomView.coffee

@@ -50,10 +50,22 @@ module.exports = class ClassroomView extends RootView
       @supermodel.loadCollection(sessions, 'sessions')
       courseInstance.sessions = sessions
       sessions.courseInstance = courseInstance
+      courseInstance.sessionsByUser = {}
       @listenToOnce sessions, 'sync', (sessions) ->
         @sessions.add(sessions.slice())
         sessions.courseInstance.sessionsByUser = sessions.groupBy('creator')
-      
+    
+    # generate course instance JIT, in the meantime have models w/out equivalents in the db
+    for course in @courses.models
+      query = {courseID: course.id, classroomID: @classroom.id}
+      courseInstance = @courseInstances.findWhere(query)
+      if not courseInstance
+        courseInstance = new CourseInstance(query)
+        @courseInstances.add(courseInstance)
+        courseInstance.sessions = new CocoCollection([], {model: LevelSession})
+        sessions.courseInstance = courseInstance
+        courseInstance.sessionsByUser = {}
+
   onLoaded: ->
     userSessions = @sessions.groupBy('creator')
     for user in @users.models
@@ -105,11 +117,20 @@ module.exports = class ClassroomView extends RootView
     @openModalView(modal)
 
   onClickEnableButton: (e) ->
-    courseInstance = @courseInstances.get($(e.target).data('course-instance-id'))
+    courseInstance = @courseInstances.get($(e.target).data('course-instance-cid'))
     userID = $(e.target).data('user-id')
-    courseInstance.addMember(userID)
     $(e.target).attr('disabled', true)
-    @listenToOnce courseInstance, 'sync', @render
+
+    onCourseInstanceCreated = =>
+      courseInstance.addMember(userID)
+      @listenToOnce courseInstance, 'sync', @render
+      
+    if courseInstance.isNew()
+      # adding the first student to this course, so generate the course instance for it
+      courseInstance.save(null, {validate: false})
+      courseInstance.once 'sync', onCourseInstanceCreated
+    else
+      onCourseInstanceCreated()
 
   onClickRemoveStudentLink: (e) ->
     user = @users.get($(e.target).closest('a').data('user-id'))

app/views/courses/TeacherCoursesView.coffee

@@ -60,7 +60,9 @@ module.exports = class TeacherCoursesView extends RootView
       # TODO: how to get new classroom from modal?
       @classrooms.add(modal.classroom)
       # TODO: will this definitely fire after modal saves new classroom?
-      @listenToOnce modal.classroom, 'sync', @render
+      @listenToOnce modal.classroom, 'sync', ->
+        @addFreeCourseInstances()
+        @render()
 
   onClickEditClassroomSmall: (e) ->
     classroomID = $(e.target).data('classroom-id')
@@ -68,3 +70,26 @@ module.exports = class TeacherCoursesView extends RootView
     modal = new ClassroomSettingsModal({classroom: classroom})
     @openModalView(modal)
     @listenToOnce modal, 'hide', @render
+    
+  onLoaded: ->
+    super()
+    @addFreeCourseInstances()
+
+  addFreeCourseInstances: ->
+    # so that when students join the classroom, they can automatically get free courses
+    # non-free courses are generated when the teacher first adds a student to them
+    for classroom in @classrooms.models
+      for course in @courses.models
+        continue if not course.get('free')
+        courseInstance = @courseInstances.findWhere({classroomID: classroom.id, courseID: course.id})
+        if not courseInstance
+          courseInstance = new CourseInstance({
+            classroomID: classroom.id
+            courseID: course.id
+          })
+          # TODO: figure out a better way to get around triggering validation errors for properties
+          # that the server will end up filling in, like an empty members array, ownerID
+          courseInstance.save(null, {validate: false})
+          @courseInstances.add(courseInstance)
+          @listenToOnce courseInstance, 'sync', @addFreeCourseInstances
+          return