Psuedo-code for how to get a list of posts & one or multiple comments

meteor-post-comments-flow.js

<template name="posts">
 <ul>
    {{each post in posts}}
      <li>
        Post: {{post._id}} {{post.title}}
        {{#if showMore}}
          {{> commentList postId=post._id}}
        {{else}}
          First comment: {{> commentSingle postId=post._id}}
        {{/if}}
      </li>
    {{/each}}
  </ul>
</template>

<template name="commentList">
  <ul>
    {{#each comment in comments}}
      <li>{{comment}}</li>
    {{/each}}
  </ul>
</template>

<template name="commentSingle">
  {{comment}}
</template>

Posts = new Meteor.Collection('posts');
Comments = new Meteor.Collection('comments');

if (Meteor.isClient) {
  Template.posts.onCreated(function () {
    this.subscribe('posts');
  });
  Template.posts.helpers({
    posts: () => {
      return Posts.find().fetch();
    },
  });
  Template.commentList.onCreated(function () {
    this.subscribe('comments', postId);
  });
  Template.commentList.helpers({
    comments: () => {
      return Comments.find().fetch();
    },
  });
  Template.commentSingle.onCreated(function () {
    // postId is passed when called from parent template
    this.subscribe('commentSingle', postId);
  });
  Template.commentSingle.helpers({
    comment: () => {
      return Comments.find().fetch();
    },
  });
}

if (Meteor.isServer) {
  Meteor.publish('posts', () = {
    Posts.find({});
  });
  Meteor.publish('comments', (pid) = {
    Comments.find({pid: pid});
  });
  Meteor.publish('commentSingle', (pid) = {
    Comments.find({pid: pid}, {limit: 1});
  });
}