@sap/eslint-plugin-cds/lib/utils/findFuzzy.js

ESLint plugin including recommended SAP Cloud Application Programming model and environment rules

'use strict'

const cache = new Map()

/**
 * Levenshtein distance algorithm using recursive calls and cache
 *
 * @param input search the list for a best match for this string
 * @param list a list of strings to match input against
 * @param {Function} [log] logging method to use, might be null if no logging is wanted
 * @param {boolean} [keepCase]
 * @param {Number} [threshold]
 * @returns {string[]} array with best matches, is never null but might be empty in case no search was possible
 *
 * @todo: Describe in which range the threshold should be.
 */
module.exports = function findFuzzy(input, list, log = null, keepCase = false, threshold = Number.MAX_SAFE_INTEGER) {
  if (typeof input !== 'string')
    return []

  let minDistWords = []

  if (input.length > 50 || list.length > 50) {
    return minDistWords
  }

  let minDist = Number.MAX_SAFE_INTEGER

  log && log('\nword\t\tlevDist\t\ttime(ms)')

  let runtime = 0

  for (const word of list) {
    const start = log && Date.now()
    let levDist
    if (word === word.toUpperCase() && !keepCase) {
      levDist = levDistance(input.toUpperCase(), word)
    } else {
      levDist = levDistance(input, word)
    }

    if (log) {
      const duration = Date.now() - start
      runtime = runtime + duration
      log(`${word}\t\t${levDist}\t\t${duration}`)
    }

    if (levDist === minDist) {
      if (!threshold || (threshold && levDist < threshold)) {
        minDistWords.push(word)
      }
    }

    if (levDist < minDist) {
      if (!threshold || (threshold && levDist < threshold)) {
        minDist = levDist
        minDistWords = [word]
      }
    }
  }

  log && log(`runtime: ${runtime}ms`)

  return minDistWords.sort()
}

function levDistance(a, b) {
  const cachedObj = cache.get(a)?.get(b)
  if (cachedObj)
    return cachedObj

  if (a.length === 0) {
    return addToCache(a, b, b.length)
  }

  if (b.length === 0) {
    return addToCache(a, b, a.length)
  }

  const tailA = a.substring(1)
  const tailB = b.substring(1)

  if (a[0] === b[0]) {
    return levDistance(tailA, tailB)
  }

  const lev1 = levDistance(tailA, b)
  const lev2 = levDistance(a, tailB)
  const lev3 = levDistance(tailA, tailB)

  const levDist = Math.min(lev1, lev2, lev3) + 1
  return addToCache(a, b, levDist)
}

function addToCache(a, b, value) {
  if (!cache.has(a))
    cache.set(a, new Map())
  cache.get(a).set(b, value)
  return value
}