similar-context-plugin.js

const stringSimilarity = require('string-similarity')
const keywordExtractor = require('keyword-extractor')
const utils = require('../utils.js')

/**
 * Param 'extractKeywords' by default false:
 * Returns a comparing score of two strings based on Dice's Coefficient using the stringSimilarity module.
 *
 * If param 'extractKeywords' is true: first uses the keyword-extractor to get the keywords, then compares the keywords with stringSimilarity to get a context score
 *
 * @param sString1 - first string for comparison
 * @param sString2 - second string for comparison
 * @param params - object with attribute:
 *  'extractKeywords' as parameter for extracting the keywords (true - extract keyword before calculating similarity score, false - whithout extraction)
 */
function similarityPlugin (sString1, sString2, params) {
  let extractKeywords = (params && params['extractKeywords']) || false

  if ((typeof sString1 === 'undefined') || (typeof sString2 === 'undefined')) {
    throw new Error(`Two Strings as input are needed.`)
  }

  utils.isValidString(sString1)
  utils.isValidString(sString2)

  if (typeof extractKeywords !== 'boolean') {
    throw new Error(`Boolean expected, found ${extractKeywords}`)
  }

  if (extractKeywords) {
    sString1 = getKeywords(sString1)
    sString2 = getKeywords(sString2)
  }
  return stringSimilarity.compareTwoStrings(sString1, sString2)
}

/**
* Uses the keyword-extractor module to get the keywords from the description and then joins the array to a string
*
* @param description - as string
*/
function getKeywords (description) {
  return keywordExtractor.extract(description, {
    language: 'english',
    remove_digits: true,
    return_changed_case: true,
    remove_duplicates: false
  }).join(' ')
}

module.exports = similarityPlugin