Two requests at same time Mongoose decreases value twice-CodePudding

I'm making a Node.js Blog API with Mongoose. I'm currently implementing a comments system in which you can up/downvote comments. However If a user hits the like/dislike route twice at a time it doesn't work like planned.

If a user spams the like button there is eg. this check: If a vote exists & liked, remove like and decrease liked count on comment. But if two requests at the same time are incomming it decreases the liked count twice.

Upvote Code:

exports.upvoteComment = async (req, res, next) => {
    const { id } = req.params

    const comment = await Comment.findById(id)
    if (!comment) {
        return next(new AppError("Comment not found", 404))
    }

    const vote = await Vote.findOneAndUpdate({
        type: 'comment', 
        refId: comment.id,
        authorId: req.user.id
    }, { 
        type: 'comment', 
        refId: comment.id,
        upvoted: true,
        authorId: req.user.id
    }, { upsert: true })

    if (!vote || !vote.upvoted) {
        comment.upvotes = comment.upvotes   1;
    }

    if (vote && vote.upvoted) {
        comment.upvotes = comment.upvotes - 1;
        await comment.save()
        await vote.remove()

        return res.status(200).json({ 
            ok: true, 
            voted: false, 
            upvoted: false, 
            upvotes: comment.upvotes, 
            downvotes: comment.downvotes 
        })
    }

    if (vote && !vote.upvoted) {
        comment.downvotes = comment.downvotes - 1;
    }

    await comment.save()

    return res.status(200).json({ 
        ok: true, 
        voted: true, 
        upvoted: true, 
        upvotes: comment.upvotes, 
        downvotes: comment.downvotes
    })
}

Vote Model:

    type: {
        type: String,
        required: true,
        enum: ["blog", "comment"]
    },
    upvoted: {
        type: Boolean,
        required: true,
    },
    refId: {
        type: mongoose.Schema.Types.ObjectId,
        required: true,
        index: true
    },
    authorId: {
        type: mongoose.Schema.Types.ObjectId,
        ref: "User",
        required: true
    }

How could I fix this problem?

CodePudding user response：

As I almost gave up I wanted to know how Youtube handles likes. So I looked at the network tab, and saw If I unvote the video, a request to /removelike was made. So I implemented a /unvote route and It worked!