comment endpoints

//...

// comment on an article
router.post('/:article/comments', auth.required, function(req, res, next) {
  // our auth middleware validates the user and puts the data in req.payload
  // find requesting user
  User.findById(req.payload.id).then(function(user){
    // DNE => 401 forbidden
    if (!user) { return res.sendStatus(401); }

    // comment obj
    var comment = new Comment(req.body.comment);
    comment.article = req.article;
    comment.author = user;

    // save comment to db and add to article comments list
    return comment.save().then(function() {
      req.article.comments = req.article.comments.concat([comment]);
      // save article update and return comment
      return req.article.save().then(function(article) {
        res.json({comment: comment.toJSONFor(user)});
      });
    });
  }).catch(next);
});

// list comments on an article
router.get('/:article/comments', auth.optional, function(req, res, next){
  // grab user if logged in
  Promise.resolve(req.payload ? User.findById(req.payload.id) : null).then(function(user){
    // populate the comments and author of each comment (lookup data of an id) and return array
    // sorted by newest to oldest comment.
    return req.article.populate({
      path: 'comments',
      populate: {
        path: 'author'
      },
      options: {
        sort: {
          createdAt: 'desc'
        }
      }
    }).execPopulate().then(function(article) {
      // return JSON of each comment
      return res.json({comments: req.article.comments.map(function(comment){
        return comment.toJSONFor(user);
      })});
    });
  }).catch(next);
});

// middleware to resolve :comment path variable
router.param('comment', function(req, res, next, id) {
  // grab comment by id and put it into the request
  Comment.findById(id).then(function(comment){
    if(!comment) { return res.sendStatus(404); }
    req.comment = comment;

    return next();
  }).catch(next);
});

router.delete('/:article/comments/:comment', auth.required, function(req, res, next) {
  // if requester=author remove comment from article, save schema, remove comment from db
  if (req.comment.author.toString() === req.payload.id.toString()) {
    req.article.comments.remove(req.comment._id);
    req.article.save()
      .then(Comment.find({_id: req.comment._id}).remove().exec())
      .then(function(){
        res.sendStatus(204);
      });
  } else {
    res.sendStatus(403);
  }
});

module.exports = router;