resolvers.js

const { AuthenticationError, PubSub } = require('apollo-server')
const Pin = require('./models/Pin')

const pubSub = new PubSub()
const PIN_ADDED = "PIN_ADDED"
const PIN_DELETED = "PIN_DELETED"
const PIN_UPDATED = "PIN_UPDATED"

const authenticated = next => (root, args, ctx, info) => {
    if (!ctx.currentUser) {
        throw new AuthenticationError('You must be logged in')
    }
    return next(root, args, ctx, info)
}

module.exports = {
    Query: {
        me: authenticated((root, args, ctx) => ctx.currentUser),
        getPins: async (root, args, ctx) => {
            const pins = await Pin.find({})
                .populate('author')
                .populate('comments.author')
            return pins
        }
    },
    Mutation: {
        createPin: authenticated(async (root, args, ctx) => {
            const newPin = await new Pin({
                ...args.input,
                author: ctx.currentUser._id
            }).save()
            const pinAdded = await Pin.populate(newPin, 'author')
            pubSub.publish(PIN_ADDED, {pinAdded})
            return pinAdded
        }),
        deletePin: authenticated(async (root, args, ctx) => {
           const pinDeleted =  await Pin.findOneAndDelete({ _id: args.pinId }).exec()
           pubSub.publish(PIN_DELETED, {pinDeleted})
           return pinDeleted
        }),
        createComment: authenticated(async (root, args, ctx) => {
            const newComment = {text: args.text, author:ctx.currentUser._id}
            const pinUpdated =  await Pin.findOneAndUpdate(
                { _id: args.pinId },
                { $push: {comments: newComment}},
                { new: true }
                ).populate("author")
                .populate("comments.author")
            pubSub.publish(PIN_UPDATED, {pinUpdated})
            return pinUpdated
         })
    },
    Subscription:{
        pinAdded: {
            subscribe: () => pubSub.asyncIterator(PIN_ADDED)
        },
        pinDeleted: {
            subscribe: () => pubSub.asyncIterator(PIN_DELETED)
        },
        pinUpdated: {
            subscribe: () => pubSub.asyncIterator(PIN_UPDATED)
        }
    }
}