KnackSteem API Updates

Repository

https://github.com/knacksteem/knacksteem-api

Pull Request

https://github.com/knacksteem/knacksteem-api/pull/4

What is the KnackSteem?

As mentioned in the KnackSteem repository on Github, This project is meant for people with great skills to showcase them and earn reward while doing so.
When the frontend is completed as well, the KnackSteem platform will become clearer :)

New Features

Steem API
I used the light-rpc library for the Steem API because I used it before and it's really useful, fast and light :) We used it for backend of Steemia app before.
I created a route to query posts from blockchain. This route takes the author and permalink parameters, request queries the post from blockchain with controller and returns the response with post.

Single Post Route

const controller = require('../../controllers/posts.controller');

router.route('/:author/:permlink').get(controller.getSinglePost)

Post Controller
The Post Controller queries the post from the Steem API with the parameters. If one of the parameters is missing or incorrect, it returns an error. In addition, if an error is received while querying the post, the API returns an error indicating that the parameters are incorrect.

If the post is successfully queried, the API performs all parsing operations to make implemetation easier on the frontend.

json_metadata is parsed in JSON format.
exact author reputation is calculated.
vote values are calculated in SBD.
votes are sorted by SBD value.

/**
 * Method to get a single post from Steem Blockchain
 * @param {*} req 
 * @param {*} res 
 * @author Huseyin Terkir (hsynterkr)
 * @returns an object with the post from Steem Blockchain
 * @public
 */
exports.getSinglePost = (req, res, next) => {

  let author = req.params.author;
  let permlink = req.params.permlink;

  if (author === null || author === undefined || author === '') {
    return next(helper.ReturnError(500, 'Required parameter "author" is missing.', 'Internal'));
  } else if (permlink === null || permlink === undefined || permlink === '') {
    return next(helper.ReturnError(500, 'Required parameter "permlink" is missing.', 'Internal'));
  }

  client.sendAsync('get_content', [author, permlink]).then(post => {
    if (!post.author || !post.permlink) {
      return next(helper.ReturnError(404, 'Required parameter "permlink" or "author" is wrong!', 'Not Found'));
    }
    post.json_metadata = JSON.parse(post.json_metadata);

    // Get body image of the post.
    post.image = post.json_metadata.image[0];

    // Use steem formatter to format reputation 
    post.author_reputation = steem.formatter.reputation(post.author_reputation);

    // Calculate total payout for vote values
    let totalPayout =
    parseFloat(post.pending_payout_value) +
    parseFloat(post.total_payout_value) +
    parseFloat(post.curator_payout_value);

    for(i in post.beneficiaries) {
      post.beneficiaries[i].weight = (post.beneficiaries[i].weight)/100
    }

    // Calculate recent voteRshares and ratio values.
    let voteRshares = post.active_votes.reduce((a, b) => a + parseFloat(b.rshares), 0);
    let ratio = totalPayout / voteRshares;
    
    // Calculate exact values of votes
    for(i in post.active_votes) {
      post.active_votes[i].value = (post.active_votes[i].rshares * ratio).toFixed(2);
      post.active_votes[i].reputation = steem.formatter.reputation(post.active_votes[i].reputation);
      post.active_votes[i].percent = post.active_votes[i].percent / 100;
      post.active_votes[i].profile_image = 'https://steemitimages.com/u/' + post.active_votes[i].voter + '/avatar/small'
    }

    // Sort votes by vote value
    let active_votes = post.active_votes.slice(0);
    active_votes.sort((a,b) => {
      return b.value - a.value
    })

    return res.json(post);

  }).catch(err => console.log(err));
};

Helper Util Class
I've created a utility class to improve code usability, and keep code quality high. Currently there are only 2 functions: isVoted() and ReturnError()

isVoted() function is used to determine whether a user votes for a particular post. isVoted() function gets 2 parameters, vote array and username.
The for loop checks the array and determines whether the given user has voted the post.

/**
 * Method to validate vote. 
 * @param {Number} array 
 * @param {String} user 
 * @description It will return true if the user has voted, otherwise it will return false.
 * @returns boolean (is voted or not)
 */
exports.isVoted = (array, user) => {
  for (let vote of array) {
    if (vote.voter === user) {
      return true;
    }
  }
  return false;
}

ReturnError() is a function that will be called when an error occurs.
It takes 3 parameters. Error status, Error Message and Error Type

/**
 * Method to generate JSON for error
 * @param {Number} code 
 * @param {String} msg 
 * @param {String} type
 */
exports.ReturnError = (code, msg, type) => {
  return {
      status: code,
      message: msg,
      type: type
  }
}