deletePost(parent,args,{db,pubsub},info){
       const isPostExists = db.posts.findIndex((post)=> post.id === args.id)
        if(isPostExists === -1){
            throw new Error('Post does not exist!')
        }
        //splice will return the index of the removed items from the array object
        const [post] = db.posts.splice(isPostExists, 1)

        db.comments = db.comments.filter((comment) => comment.post !== args.id)

        if(post.published){
            pubsub.publish('post', {
                post:{
                    mutation: 'DELETED',
                    data: post
                }
            })
        }
        return post
    }