natural/lib/natural/stemmers/porter_stemmer_it.js

General natural language (tokenizing, stemming (English, Russian, Spanish), part-of-speech tagging, sentiment analysis, classification, inflection, phonetics, tfidf, WordNet, jaro-winkler, Levenshtein distance, Dice's Coefficient) facilities for node.

/*
Copyright (c) 2012, Leonardo Fenu, Chris Umbel

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/


'use strict'

const Stemmer = require('./stemmer_it')

const PorterStemmer = new Stemmer()
module.exports = PorterStemmer

function isVowel (letter) {
  return (letter === 'a' || letter === 'e' || letter === 'i' || letter === 'o' || letter === 'u' || letter === 'à' ||
    letter === 'è' || letter === 'ì' || letter === 'ò' || letter === 'ù')
}

function getNextVowelPos (token, start) {
  start = start + 1
  const length = token.length
  for (let i = start; i < length; i++) {
    if (isVowel(token[i])) {
      return i
    }
  }
  return length
}

function getNextConsonantPos (token, start) {
  const length = token.length
  for (let i = start; i < length; i++) { if (!isVowel(token[i])) return i }
  return length
}

function endsin (token, suffix) {
  if (token.length < suffix.length) return false
  return (token.slice(-suffix.length) === suffix)
}

function endsinArr (token, suffixes) {
  for (let i = 0; i < suffixes.length; i++) {
    if (endsin(token, suffixes[i])) return suffixes[i]
  }
  return ''
}

function replaceAcute (token) {
  let str = token.replace(/á/gi, 'à')
  str = str.replace(/é/gi, 'è')
  str = str.replace(/í/gi, 'ì')
  str = str.replace(/ó/gi, 'ò')
  str = str.replace(/ú/gi, 'ù')
  return str
}

function vowelMarking (token) {
  function replacer (match, p1, p2, p3) {
    return p1 + p2.toUpperCase() + p3
  }
  const str = token.replace(/([aeiou])(i|u)([aeiou])/g, replacer)
  return str
}

// perform full stemming algorithm on a single word
PorterStemmer.stem = function (token) {
  token = token.toLowerCase()
  token = replaceAcute(token)
  token = token.replace(/qu/g, 'qU')
  token = vowelMarking(token)

  if (token.length < 3) {
    return token
  }

  let r1 = token.length
  let r2 = token.length
  let rv = token.length
  const len = token.length
  // R1 is the region after the first non-vowel following a vowel,
  for (let i = 0; i < token.length - 1 && r1 === len; i++) {
    if (isVowel(token[i]) && !isVowel(token[i + 1])) {
      r1 = i + 2
    }
  }
  // Or is the null region at the end of the word if there is no such non-vowel.

  // R2 is the region after the first non-vowel following a vowel in R1
  for (let i = r1; i < token.length - 1 && r2 === len; i++) {
    if (isVowel(token[i]) && !isVowel(token[i + 1])) {
      r2 = i + 2
    }
  }

  // Or is the null region at the end of the word if there is no such non-vowel.

  // If the second letter is a consonant, RV is the region after the next following vowel,

  // RV as follow

  if (len > 3) {
    if (!isVowel(token[1])) {
      // If the second letter is a consonant, RV is the region after the next following vowel
      rv = getNextVowelPos(token, 1) + 1
    } else if (isVowel(token[0]) && isVowel(token[1])) {
      // or if the first two letters are vowels, RV is the region after the next consonant
      rv = getNextConsonantPos(token, 2) + 1
    } else {
      // otherwise (consonant-vowel case) RV is the region after the third letter. But RV is the end of the word if these positions cannot be found.
      rv = 3
    }
  }

  let r1txt = token.substring(r1)
  let r2txt = token.substring(r2)
  let rvtxt = token.substring(rv)

  const tokenOrig = token

  // Step 0: Attached pronoun

  const pronounSuf = ['glieli', 'glielo', 'gliene', 'gliela', 'gliele', 'sene', 'tene', 'cela', 'cele', 'celi', 'celo', 'cene', 'vela', 'vele', 'veli', 'velo', 'vene', 'mela', 'mele', 'meli', 'melo', 'mene', 'tela', 'tele', 'teli', 'telo', 'gli', 'ci', 'la', 'le', 'li', 'lo', 'mi', 'ne', 'si', 'ti', 'vi']
  const pronounSufPre1 = ['ando', 'endo']
  const pronounSufPre2 = ['ar', 'er', 'ir']
  let suf = endsinArr(token, pronounSuf)

  if (suf !== '') {
    const preSuff1 = endsinArr(rvtxt.slice(0, -suf.length), pronounSufPre1)
    const preSuff2 = endsinArr(rvtxt.slice(0, -suf.length), pronounSufPre2)

    if (preSuff1 !== '') {
      token = token.slice(0, -suf.length)
    }
    if (preSuff2 !== '') {
      token = token.slice(0, -suf.length) + 'e'
    }
  }

  if (token !== tokenOrig) {
    r1txt = token.substring(r1)
    r2txt = token.substring(r2)
    rvtxt = token.substring(rv)
  }

  const tokenAfter0 = token

  // Step 1:  Standard suffix removal

  if ((suf = endsinArr(r2txt, ['ativamente', 'abilamente', 'ivamente', 'osamente', 'icamente'])) !== '') {
    token = token.slice(0, -suf.length) // delete
  } else if ((suf = endsinArr(r2txt, ['icazione', 'icazioni', 'icatore', 'icatori', 'azione', 'azioni', 'atore', 'atori'])) !== '') {
    token = token.slice(0, -suf.length) // delete
  } else if ((suf = endsinArr(r2txt, ['logia', 'logie'])) !== '') {
    token = token.slice(0, -suf.length) + 'log' // replace with log
  } else if ((suf = endsinArr(r2txt, ['uzione', 'uzioni', 'usione', 'usioni'])) !== '') {
    token = token.slice(0, -suf.length) + 'u' // replace with u
  } else if ((suf = endsinArr(r2txt, ['enza', 'enze'])) !== '') {
    token = token.slice(0, -suf.length) + 'ente' // replace with ente
  } else if ((suf = endsinArr(rvtxt, ['amento', 'amenti', 'imento', 'imenti'])) !== '') {
    token = token.slice(0, -suf.length) // delete
  } else if ((suf = endsinArr(r1txt, ['amente'])) !== '') {
    token = token.slice(0, -suf.length) // delete
  } else if ((suf = endsinArr(r2txt, ['atrice', 'atrici', 'abile', 'abili', 'ibile', 'ibili', 'mente', 'ante', 'anti', 'anza', 'anze', 'iche', 'ichi', 'ismo', 'ismi', 'ista', 'iste', 'isti', 'istà', 'istè', 'istì', 'ico', 'ici', 'ica', 'ice', 'oso', 'osi', 'osa', 'ose'])) !== '') {
    token = token.slice(0, -suf.length) // delete
  } else if ((suf = endsinArr(r2txt, ['abilità', 'icità', 'ività', 'ità'])) !== '') {
    token = token.slice(0, -suf.length) // delete
  } else if ((suf = endsinArr(r2txt, ['icativa', 'icativo', 'icativi', 'icative', 'ativa', 'ativo', 'ativi', 'ative', 'iva', 'ivo', 'ivi', 'ive'])) !== '') {
    token = token.slice(0, -suf.length)
  }

  if (token !== tokenAfter0) {
    r1txt = token.substring(r1)
    r2txt = token.substring(r2)
    rvtxt = token.substring(rv)
  }

  const tokenAfter1 = token

  // Step 2:  Verb suffixes

  if (tokenAfter0 === tokenAfter1) {
    if ((suf = endsinArr(rvtxt, ['erebbero', 'irebbero', 'assero', 'assimo', 'eranno', 'erebbe', 'eremmo', 'ereste', 'eresti', 'essero', 'iranno', 'irebbe', 'iremmo', 'ireste', 'iresti', 'iscano', 'iscono', 'issero', 'arono', 'avamo', 'avano', 'avate', 'eremo', 'erete', 'erono', 'evamo', 'evano', 'evate', 'iremo', 'irete', 'irono', 'ivamo', 'ivano', 'ivate', 'ammo', 'ando', 'asse', 'assi', 'emmo', 'enda', 'ende', 'endi', 'endo', 'erai', 'Yamo', 'iamo', 'immo', 'irai', 'irei', 'isca', 'isce', 'isci', 'isco', 'erei', 'uti', 'uto', 'ita', 'ite', 'iti', 'ito', 'iva', 'ivi', 'ivo', 'ono', 'uta', 'ute', 'ano', 'are', 'ata', 'ate', 'ati', 'ato', 'ava', 'avi', 'avo', 'erà', 'ere', 'erò', 'ete', 'eva', 'evi', 'evo', 'irà', 'ire', 'irò', 'ar', 'ir'])) !== '') {
      token = token.slice(0, -suf.length)
    }
  }

  r1txt = token.substring(r1)
  r2txt = token.substring(r2)
  rvtxt = token.substring(rv)

  // Always do step 3.

  if ((suf = endsinArr(rvtxt, ['ia', 'ie', 'ii', 'io', 'ià', 'iè', 'iì', 'iò', 'a', 'e', 'i', 'o', 'à', 'è', 'ì', 'ò'])) !== '') {
    token = token.slice(0, -suf.length)
  }

  r1txt = token.substring(r1)
  r2txt = token.substring(r2)
  rvtxt = token.substring(rv)

  if ((suf = endsinArr(rvtxt, ['ch'])) !== '') {
    token = token.slice(0, -suf.length) + 'c' // replace with c
  } else if ((suf = endsinArr(rvtxt, ['gh'])) !== '') {
    token = token.slice(0, -suf.length) + 'g' // replace with g
  }

  r1txt = token.substring(r1)
  r2txt = token.substring(r2)
  rvtxt = token.substring(rv)

  return token.toLowerCase()
}