CLDRPluralRuleParser.js

/* eslint-disable camelcase */
/**
 * cldrpluralparser.js
 * A parser engine for CLDR plural rules.
 *
 * Copyright 2012-2014 Santhosh Thottingal and other contributors
 * Released under the MIT license
 * http://opensource.org/licenses/MIT
 *
 * @source https://github.com/santhoshtr/CLDRPluralRuleParser
 * @author Santhosh Thottingal <santhosh.thottingal@gmail.com>
 * @author Timo Tijhof
 * @author Amir Aharoni
 */

/**
 * Evaluates a plural rule in CLDR syntax for a number
 * @param {string} rule
 * @param {integer} number
 * @return {boolean} true if evaluation passed, false if evaluation failed.
 */
function pluralRuleParser (rule, number) {
  'use strict'

  /*
    Syntax: see http://unicode.org/reports/tr35/#Language_Plural_Rules
    -----------------------------------------------------------------
    condition     = and_condition ('or' and_condition)*
        ('@integer' samples)?
        ('@decimal' samples)?
    and_condition = relation ('and' relation)*
    relation      = is_relation | in_relation | within_relation
    is_relation   = expr 'is' ('not')? value
    in_relation   = expr (('not')? 'in' | '=' | '!=') range_list
    within_relation = expr ('not')? 'within' range_list
    expr          = operand (('mod' | '%') value)?
    operand       = 'n' | 'i' | 'f' | 't' | 'v' | 'w'
    range_list    = (range | value) (',' range_list)*
    value         = digit+
    digit         = 0|1|2|3|4|5|6|7|8|9
    range         = value'..'value
    samples       = sampleRange (',' sampleRange)* (',' ('…'|'...'))?
    sampleRange   = decimalValue '~' decimalValue
    decimalValue  = value ('.' value)?
    */

  // We don't evaluate the samples section of the rule. Ignore it.
  rule = rule.split('@')[0].replace(/^\s*/, '').replace(/\s*$/, '')

  if (!rule.length) {
    // Empty rule or 'other' rule.
    return true
  }

  // Indicates the current position in the rule as we parse through it.
  // Shared among all parsing functions below.
  let pos = 0

  const whitespace = makeRegexParser(/^\s+/)
  const value = makeRegexParser(/^\d+/)
  const _n_ = makeStringParser('n')
  const _i_ = makeStringParser('i')
  const _f_ = makeStringParser('f')
  const _t_ = makeStringParser('t')
  const _v_ = makeStringParser('v')
  const _w_ = makeStringParser('w')
  const _is_ = makeStringParser('is')
  const _isnot_ = makeStringParser('is not')
  const _isnot_sign_ = makeStringParser('!=')
  const _equal_ = makeStringParser('=')
  const _mod_ = makeStringParser('mod')
  const _percent_ = makeStringParser('%')
  const _not_ = makeStringParser('not')
  const _in_ = makeStringParser('in')
  const _within_ = makeStringParser('within')
  const _range_ = makeStringParser('..')
  const _comma_ = makeStringParser(',')
  const _or_ = makeStringParser('or')
  const _and_ = makeStringParser('and')

  function debug () {
    // console.log.apply(console, arguments);
  }

  debug('pluralRuleParser', rule, number)

  // Try parsers until one works, if none work return null
  function choice (parserSyntax) {
    return function () {
      let i, result

      for (i = 0; i < parserSyntax.length; i++) {
        result = parserSyntax[i]()

        if (result !== null) {
          return result
        }
      }

      return null
    }
  }

  // Try several parserSyntax-es in a row.
  // All must succeed; otherwise, return null.
  // This is the only eager one.
  function sequence (parserSyntax) {
    let i; let parserRes
    const originalPos = pos
    const result = []

    for (i = 0; i < parserSyntax.length; i++) {
      parserRes = parserSyntax[i]()

      if (parserRes === null) {
        pos = originalPos

        return null
      }

      result.push(parserRes)
    }

    return result
  }

  // Run the same parser over and over until it fails.
  // Must succeed a minimum of n times; otherwise, return null.
  function nOrMore (n, p) {
    return function () {
      const originalPos = pos
      const result = []
      let parsed = p()

      while (parsed !== null) {
        result.push(parsed)
        parsed = p()
      }

      if (result.length < n) {
        pos = originalPos

        return null
      }

      return result
    }
  }

  // Helpers - just make parserSyntax out of simpler JS builtin types
  function makeStringParser (s) {
    const len = s.length

    return function () {
      let result = null

      if (rule.substr(pos, len) === s) {
        result = s
        pos += len
      }

      return result
    }
  }

  function makeRegexParser (regex) {
    return function () {
      const matches = rule.substr(pos).match(regex)

      if (matches === null) {
        return null
      }

      pos += matches[0].length

      return matches[0]
    }
  }

  /**
     * Integer digits of n.
     */
  function i () {
    let result = _i_()

    if (result === null) {
      debug(' -- failed i', parseInt(number, 10))

      return result
    }

    result = parseInt(number, 10)
    debug(' -- passed i ', result)

    return result
  }

  /**
     * Absolute value of the source number (integer and decimals).
     */
  function n () {
    let result = _n_()

    if (result === null) {
      debug(' -- failed n ', number)

      return result
    }

    result = parseFloat(number, 10)
    debug(' -- passed n ', result)

    return result
  }

  /**
     * Visible fractional digits in n, with trailing zeros.
     */
  function f () {
    let result = _f_()

    if (result === null) {
      debug(' -- failed f ', number)

      return result
    }

    result = (number + '.').split('.')[1] || 0
    debug(' -- passed f ', result)

    return result
  }

  /**
     * Visible fractional digits in n, without trailing zeros.
     */
  function t () {
    let result = _t_()

    if (result === null) {
      debug(' -- failed t ', number)

      return result
    }

    result = (number + '.').split('.')[1].replace(/0$/, '') || 0
    debug(' -- passed t ', result)

    return result
  }

  /**
     * Number of visible fraction digits in n, with trailing zeros.
     */
  function v () {
    let result = _v_()

    if (result === null) {
      debug(' -- failed v ', number)

      return result
    }

    result = (number + '.').split('.')[1].length || 0
    debug(' -- passed v ', result)

    return result
  }

  /**
     * Number of visible fraction digits in n, without trailing zeros.
     */
  function w () {
    let result = _w_()

    if (result === null) {
      debug(' -- failed w ', number)

      return result
    }

    result = (number + '.').split('.')[1].replace(/0$/, '').length || 0
    debug(' -- passed w ', result)

    return result
  }

  // operand       = 'n' | 'i' | 'f' | 't' | 'v' | 'w'
  const operand = choice([n, i, f, t, v, w])

  // expr          = operand (('mod' | '%') value)?
  const expression = choice([mod, operand])

  function mod () {
    const result = sequence(
      [operand, whitespace, choice([_mod_, _percent_]), whitespace, value]
    )

    if (result === null) {
      debug(' -- failed mod')

      return null
    }

    debug(' -- passed ', parseInt(result[0], 10), result[2], parseInt(result[4], 10))

    return parseFloat(result[0]) % parseInt(result[4], 10)
  }

  function not () {
    const result = sequence([whitespace, _not_])

    if (result === null) {
      debug(' -- failed not')

      return null
    }

    return result[1]
  }

  // is_relation   = expr 'is' ('not')? value
  function is () {
    const result = sequence([expression, whitespace, choice([_is_]), whitespace, value])

    if (result !== null) {
      debug(' -- passed is :', result[0], ' == ', parseInt(result[4], 10))

      return result[0] === parseInt(result[4], 10)
    }

    debug(' -- failed is')

    return null
  }

  // is_relation   = expr 'is' ('not')? value
  function isnot () {
    const result = sequence(
      [expression, whitespace, choice([_isnot_, _isnot_sign_]), whitespace, value]
    )

    if (result !== null) {
      debug(' -- passed isnot: ', result[0], ' != ', parseInt(result[4], 10))

      return result[0] !== parseInt(result[4], 10)
    }

    debug(' -- failed isnot')

    return null
  }

  function not_in () {
    let i; let range_list
    const result = sequence([expression, whitespace, _isnot_sign_, whitespace, rangeList])

    if (result !== null) {
      debug(' -- passed not_in: ', result[0], ' != ', result[4])
      range_list = result[4]

      for (i = 0; i < range_list.length; i++) {
        if (parseInt(range_list[i], 10) === parseInt(result[0], 10)) {
          return false
        }
      }

      return true
    }

    debug(' -- failed not_in')

    return null
  }

  // range_list    = (range | value) (',' range_list)*
  function rangeList () {
    const result = sequence([choice([range, value]), nOrMore(0, rangeTail)])
    let resultList = []

    if (result !== null) {
      resultList = resultList.concat(result[0])

      if (result[1][0]) {
        resultList = resultList.concat(result[1][0])
      }

      return resultList
    }

    debug(' -- failed rangeList')

    return null
  }

  function rangeTail () {
    // ',' range_list
    const result = sequence([_comma_, rangeList])

    if (result !== null) {
      return result[1]
    }

    debug(' -- failed rangeTail')

    return null
  }

  // range         = value'..'value
  function range () {
    let i; let array; let left; let right
    const result = sequence([value, _range_, value])

    if (result !== null) {
      debug(' -- passed range')

      array = []
      left = parseInt(result[0], 10)
      right = parseInt(result[2], 10)

      for (i = left; i <= right; i++) {
        array.push(i)
      }

      return array
    }

    debug(' -- failed range')

    return null
  }

  function _in () {
    // in_relation   = expr ('not')? 'in' range_list
    const result = sequence(
      [expression, nOrMore(0, not), whitespace, choice([_in_, _equal_]), whitespace, rangeList]
    )

    if (result !== null) {
      debug(' -- passed _in:', result)

      const rangeList = result[5]

      for (let i = 0; i < rangeList.length; i++) {
        if (parseInt(rangeList[i], 10) === parseFloat(result[0])) {
          return (result[1][0] !== 'not')
        }
      }

      return (result[1][0] === 'not')
    }

    debug(' -- failed _in ')

    return null
  }

  /**
     * The difference between "in" and "within" is that
     * "in" only includes integers in the specified range,
     * while "within" includes all values.
     */
  function within () {
    // within_relation = expr ('not')? 'within' range_list
    const result = sequence(
      [expression, nOrMore(0, not), whitespace, _within_, whitespace, rangeList]
    )

    if (result !== null) {
      debug(' -- passed within')

      const range_list = result[5]

      if ((result[0] >= parseInt(range_list[0], 10)) &&
                (result[0] < parseInt(range_list[range_list.length - 1], 10))) {
        return (result[1][0] !== 'not')
      }

      return (result[1][0] === 'not')
    }

    debug(' -- failed within ')

    return null
  }

  // relation      = is_relation | in_relation | within_relation
  const relation = choice([is, not_in, isnot, _in, within])

  // and_condition = relation ('and' relation)*
  function and () {
    let i
    const result = sequence([relation, nOrMore(0, andTail)])

    if (result) {
      if (!result[0]) {
        return false
      }

      for (i = 0; i < result[1].length; i++) {
        if (!result[1][i]) {
          return false
        }
      }

      return true
    }

    debug(' -- failed and')

    return null
  }

  // ('and' relation)*
  function andTail () {
    const result = sequence([whitespace, _and_, whitespace, relation])

    if (result !== null) {
      debug(' -- passed andTail', result)

      return result[3]
    }

    debug(' -- failed andTail')

    return null
  }
  //  ('or' and_condition)*
  function orTail () {
    const result = sequence([whitespace, _or_, whitespace, and])

    if (result !== null) {
      debug(' -- passed orTail: ', result[3])

      return result[3]
    }

    debug(' -- failed orTail')

    return null
  }

  // condition     = and_condition ('or' and_condition)*
  function condition () {
    let i
    const result = sequence([and, nOrMore(0, orTail)])

    if (result) {
      for (i = 0; i < result[1].length; i++) {
        if (result[1][i]) {
          return true
        }
      }

      return result[0]
    }

    return false
  }

  const result = condition()

  /**
     * For success, the pos must have gotten to the end of the rule
     * and returned a non-null.
     * n.b. This is part of language infrastructure,
     * so we do not throw an internationalizable message.
     */
  if (result === null) {
    throw new Error('Parse error at position ' + pos.toString() + ' for rule: ' + rule)
  }

  if (pos !== rule.length) {
    debug('Warning: Rule not parsed completely. Parser stopped at ', rule.substr(0, pos), ' for rule: ', rule)
  }

  return result
}

export default pluralRuleParser