to_infinitive.js

'use strict';
const irregular_verbs = require('../../../data/irregular_verbs');
let known_verbs = Object.keys(irregular_verbs).reduce(function(h, k) {
  Object.keys(irregular_verbs[k]).forEach(function(k2) {
    h[irregular_verbs[k][k2]] = k;
  });
  return h;
}, {});


let rules = {
  participle: [
    {
      reg: /own$/i,
      to: 'ow'
    },
    {
      reg: /(.)un([g|k])$/i,
      to: '$1in$2'
    },
    {
      reg: /(..)en$/i,
      to: '$1e'
    },
  ],
  actor: [
    {
      reg: /(er)er$/i,
      to: '$1'
    }
  ],
  present: [
    {
      reg: /(ies)$/i,
      to: 'y'
    }, {
      reg: /(tch|sh)es$/i,
      to: '$1'
    }, {
      reg: /(ss)es$/i,
      to: '$1'
    }, {
      reg: /([tzlshicgrvdnkmu])es$/i,
      to: '$1e'
    }, {
      reg: /(n[dtk]|c[kt]|[eo]n|i[nl]|er|a[ytrl])s$/i,
      to: '$1'
    }, {
      reg: /(ow)s$/i,
      to: '$1'
    }, {
      reg: /(op)s$/i,
      to: '$1'
    }, {
      reg: /([eirs])ts$/i,
      to: '$1t'
    }, {
      reg: /(ll)s$/i,
      to: '$1'
    }, {
      reg: /(el)s$/i,
      to: '$1'
    }, {
      reg: /(ip)es$/i,
      to: '$1e'
    }, {
      reg: /ss$/i,
      to: 'ss'
    }, {
      reg: /s$/i,
      to: ''
    }],
  gerund: [
    {
      reg: /pping$/i,
      to: 'p'
    }, {
      reg: /lling$/i,
      to: 'll'
    }, {
      reg: /tting$/i,
      to: 't'
    }, {
      reg: /ssing$/i,
      to: 'ss'
    }, {
      reg: /gging$/i,
      to: 'g'
    }, {
      reg: /([^aeiou])ying$/i,
      to: '$1y'
    }, {
      reg: /(i.)ing$/i,
      to: '$1e'
    }, {
      reg: /(u[rtcb]|[bdtpkg]l|n[cg]|a[gdkvtc]|[ua]s|[dr]g|yz|o[rlsp]|cre)ing$/i,
      to: '$1e'
    }, {
      reg: /(ch|sh)ing$/i,
      to: '$1'
    }, {
      reg: /(..)ing$/i,
      to: '$1'
    }],
  past: [
    {
      reg: /(ued)$/i,
      to: 'ue'
    }, {
      reg: /(e|i)lled$/i,
      to: '$1ll'
    }, {
      reg: /(sh|ch)ed$/i,
      to: '$1'
    }, {
      reg: /(tl|gl)ed$/i,
      to: '$1e'
    }, {
      reg: /(ss)ed$/i,
      to: '$1'
    }, {
      reg: /pped$/i,
      to: 'p'
    }, {
      reg: /tted$/i,
      to: 't'
    }, {
      reg: /gged$/i,
      to: 'g'
    }, {
      reg: /(h|ion|n[dt]|ai.|[cs]t|pp|all|ss|tt|int|ail|ld|en|oo.|er|k|pp|w|ou.|rt|ght|rm)ed$/i,
      to: '$1'
    }, {
      reg: /(..[^aeiou])ed$/i,
      to: '$1e'
    }, {
      reg: /ied$/i,
      to: 'y'
    }, {
      reg: /(.o)ed$/i,
      to: '$1o'
    }, {
      reg: /(.i)ed$/i,
      to: '$1'
    }, {
      reg: /([rl])ew$/i,
      to: '$1ow'
    }, {
      reg: /([pl])t$/i,
      to: '$1t'
    }]
};

const to_infinitive = function (str, from_tense) {
  if (known_verbs[str]) {
    return known_verbs[str];
  }
  if (from_tense === 'infinitive') {
    return str;
  }
  let regs = rules[from_tense] || [];
  for(let i = 0; i < regs.length; i++) {
    if (str.match(regs[i].reg)) {
      return str.replace(regs[i].reg, regs[i].to);
    }
  }
  return str;
};