compromise/src/terms/tagger/steps/08-date_step.js

natural language processing in the browser

'use strict';
const log = require('../paths').log;
const path = 'tagger/datePass';

const preDate = {
  on: true,
  in: true,
  before: true,
  by: true,
  after: true,
  during: true,
};

//ensure a year is approximately typical for common years
const isYear = (t) => {
  if (t.tag.Ordinal) {
    return false;
  }
  let num = t.value.cardinal;
  if (!num || num < 1000 || num > 3000) {
    return false;
  }
  return true;
};

//rules for two-term dates
const twoDates = [{
  condition: (a, b) => (preDate[a.normal] && b.tag.Date),
  reason: 'predate-date'
}, ];

//rules for three-term dates
const threeDates = [{
  condition: (a, b, c) => (a.tag.Month && b.tag.Value && c.tag.Cardinal && isYear(c)),
  reason: 'month-value-year'
}, {
  condition: (a, b, c) => (a.tag.Date && b.normal === 'and' && c.tag.Date),
  reason: 'date-and-date'
}, ];

//non-destructively tag values & prepositions as dates
const datePass = function (s) {
  log.here(path);
  //set verbs as auxillaries
  for (let i = 0; i < s.terms.length - 1; i++) {
    let a = s.terms[i];
    let b = s.terms[i + 1];
    let c = s.terms[i + 2];
    if (c) {
      for (let o = 0; o < threeDates.length; o++) {
        if (threeDates[o].condition(a, b, c)) {
          a.tagAs('Date', threeDates[o].reason);
          b.tagAs('Date', threeDates[o].reason);
          c.tagAs('Date', threeDates[o].reason);
        }
      }
    }
    for (let o = 0; o < twoDates.length; o++) {
      if (twoDates[o].condition(a, b)) {
        a.tagAs('Date', twoDates[o].reason);
        b.tagAs('Date', twoDates[o].reason);
      }
    }
    //in 2018
    if (a.tag.Date || (preDate[a.normal]) && b.tag.Value) {
      let year = parseInt(b.normal, 10);
      if (year && year > 1200 && year < 2090) {
        a.tagAs('Date', 'in-year');
        b.tagAs('Date', 'in-year');
      }
    }
  }
  return s;
};

module.exports = datePass;