get_posts.js

// user_id -> int ; post_ids -> []
function get_posts(user_id, post_ids) {
  //usually we will just use an ORM here
  let post_ids_str = "(";
  //serialize the post_ids for the query
  post_ids.map(val => {
    post_ids_str += `${val.toString()}, `;
  })
  post_ids_str += ")";
  
  let posts = await getFromDB("SELECT * FROM post WHERE id IN " + post_ids_str);
  let posts_obj = {};
  //we have the posts now
  
  //get the user_id list
  let user_ids = posts.map(val => {
    posts_obj[val.id] = {
        ...val
    };
    return val.user_id;
  });
  
  //serialize the user_ids for the query
  let user_ids_str = "(";
  user_ids.map(val => {
    user_ids_str += `${val.toString()}, `;
  })
  user_ids_str += ")";

  let users = await getFromDB("SELECT * FROM user WHERE id IN " + user_ids_str);
  let users_obj = {};
  users.map(val => {
      let follows = await getFromDB(`SELECT * FROM follow WHERE follower_id=${user_id} AND following_id=${val.user_id}`);
          users_obj[val.id] = {
              id: val.id,
              username: val.username,
              full_name: val.full_name,
              profile_picture: val.profile_picture,
              followed: follows ? true : false,
          }
  })
  //we have the users now

  //build up the return object
  let response = post_ids.map(val => {
      if(!posts_obj[val]) {
          //Procedure should place null values for non-existing posts in the resulting list.
          return null;
      } else {
          let liked = await getFromDB(`SELECT * FROM like WHERE post_id=${val} AND user_id=${posts_obj[val].user_id}`);
          return {
              id: val,
              description: posts_obj[val].description,
              owner: users_obj[posts_obj[val].user_id],
              image: posts_obj[val].image,
              created_at: posts_obj[val].created_at,
              liked: liked ? true : false,
          }
      }
  });
  
  return response;
}