fix media_type for media submission comments

fix the response media_type to be either video or audio instead of the
specific mime type when the below api endpoint is called
api/v1/courses/courseId:/assignments/assignmentId:/submissions

fixes MBL-17110
flag=assignments_2_student

test plan:
- have a course with an assignment and the Assignment Enhancements fla
  on
- add a media comment as a student to the assignment
- send a GET request to the following endpoint:
    api/v1/courses/:course_id/assignments/:assignment_id/submissions
    ?include%5B%5D=submission_comments
- find the submission with the media comment
- find the specific comment under the field "submission_comments"
- the comment will have a "media_comment" field in the comment
- confirm that the media_comment object has a field "media_type" that
  has just video or audio instead of the specific MIME type such as
  video/quicktime

Change-Id: I32da86c9934ca8955561b3e57262e8b81500c0bc
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/330653
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Derek Williams <derek.williams@instructure.com>
Reviewed-by: Christopher Soto <christopher.soto@instructure.com>
QA-Review: Kai Bjorkman <kbjorkman@instructure.com>
Product-Review: Ravi Koll <ravi.koll@instructure.com>

lib/api.rb

@@ -541,11 +541,12 @@ module Api
 
   def media_comment_json(media_object_or_hash)
     media_object_or_hash = OpenStruct.new(media_object_or_hash) if media_object_or_hash.is_a?(Hash)
+    convert_media_type = Attachment.mime_class(media_object_or_hash.media_type)
     {
-      "content-type" => "#{media_object_or_hash.media_type}/mp4",
+      "content-type" => "#{convert_media_type}/mp4",
       "display_name" => media_object_or_hash.title.presence || media_object_or_hash.user_entered_title,
       "media_id" => media_object_or_hash.media_id,
-      "media_type" => media_object_or_hash.media_type,
+      "media_type" => convert_media_type,
       "url" => user_media_download_url(user_id: @current_user.id,
                                        entryId: media_object_or_hash.media_id,
                                        type: "mp4",

spec/lib/api/v1/submission_comment_spec.rb

@@ -21,6 +21,23 @@
 require "spec_helper"
 
 describe Api::V1::SubmissionComment do
+  subject(:fake_controller) do
+    Class.new do
+      include Api
+      include Api::V1::Submission
+      include Api::V1::SubmissionComment
+      include Rails.application.routes.url_helpers
+
+      attr_writer :current_user
+
+      private
+
+      def default_url_options
+        { host: :localhost }
+      end
+    end.new
+  end
+
   before(:once) do
     course = Course.create!
     @student = User.create!
@@ -47,6 +64,22 @@ describe Api::V1::SubmissionComment do
     it "'edited_at' is nil if the submission comment has not been edited" do
       expect(comment_json[:edited_at]).to be_nil
     end
+
+    it "media_type in submission comment json has video instead of the specific mime type" do
+      @submission_comment.media_comment_id = 1
+      @submission_comment.media_comment_type = "video/mp4"
+      fake_controller.current_user = @student
+      submission_comment_json = fake_controller.submission_comment_json(@submission_comment, @student)
+      expect(submission_comment_json["media_comment"]["media_type"]).to eq("video")
+    end
+
+    it "media_type in submission comment json has audio instead of the specific mime type" do
+      @submission_comment.media_comment_id = 1
+      @submission_comment.media_comment_type = "audio/mp4"
+      fake_controller.current_user = @student
+      submission_comment_json = fake_controller.submission_comment_json(@submission_comment, @student)
+      expect(submission_comment_json["media_comment"]["media_type"]).to eq("audio")
+    end
   end
 
   describe "#anonymous_moderated_submission_comments_json" do

spec/lib/api/v1/submission_spec.rb

@@ -575,6 +575,15 @@ describe Api::V1::Submission do
         expect(submission).to be_read(user)
       end
     end
+
+    it "submission json returns video when media comment type is a specific video mime type" do
+      submission = assignment.submission_for_student(user)
+      submission.media_comment_id = 1
+      submission.media_comment_type = "video/mp4"
+      fake_controller.current_user = user
+      submission_json = fake_controller.submission_json(submission, assignment, user, session, context)
+      expect(submission_json.fetch("media_comment")["media_type"]).to eq "video"
+    end
   end
 
   describe "#submission_zip" do