libphonenumber-js/source/findNumbers/isValidCandidate.js

A simpler (and smaller) rewrite of Google Android's libphonenumber library in javascript

// Copy-pasted from `PhoneNumberMatcher.js`.

import { PLUS_CHARS } from '../constants.js'
import { limit } from './util.js'

import {
	isLatinLetter,
	isInvalidPunctuationSymbol
} from './utf-8.js'

const OPENING_PARENS = '(\\[\uFF08\uFF3B'
const CLOSING_PARENS = ')\\]\uFF09\uFF3D'
const NON_PARENS = `[^${OPENING_PARENS}${CLOSING_PARENS}]`

export const LEAD_CLASS = `[${OPENING_PARENS}${PLUS_CHARS}]`

// Punctuation that may be at the start of a phone number - brackets and plus signs.
const LEAD_CLASS_LEADING = new RegExp('^' + LEAD_CLASS)

// Limit on the number of pairs of brackets in a phone number.
const BRACKET_PAIR_LIMIT = limit(0, 3)

/**
 * Pattern to check that brackets match. Opening brackets should be closed within a phone number.
 * This also checks that there is something inside the brackets. Having no brackets at all is also
 * fine.
 *
 * An opening bracket at the beginning may not be closed, but subsequent ones should be.  It's
 * also possible that the leading bracket was dropped, so we shouldn't be surprised if we see a
 * closing bracket first. We limit the sets of brackets in a phone number to four.
 */
const MATCHING_BRACKETS_ENTIRE = new RegExp
(
	'^'
	+ "(?:[" + OPENING_PARENS + "])?" + "(?:" + NON_PARENS + "+" + "[" + CLOSING_PARENS + "])?"
	+ NON_PARENS + "+"
	+ "(?:[" + OPENING_PARENS + "]" + NON_PARENS + "+[" + CLOSING_PARENS + "])" + BRACKET_PAIR_LIMIT
	+ NON_PARENS + "*"
	+ '$'
)

/**
 * Matches strings that look like publication pages. Example:
 * <pre>Computing Complete Answers to Queries in the Presence of Limited Access Patterns.
 * Chen Li. VLDB J. 12(3): 211-227 (2003).</pre>
 *
 * The string "211-227 (2003)" is not a telephone number.
 */
const PUB_PAGES = /\d{1,5}-+\d{1,5}\s{0,4}\(\d{1,4}/

export default function isValidCandidate(candidate, offset, text, leniency)
{
	// Check the candidate doesn't contain any formatting
	// which would indicate that it really isn't a phone number.
	if (!MATCHING_BRACKETS_ENTIRE.test(candidate) || PUB_PAGES.test(candidate)) {
		return
	}

	// If leniency is set to VALID or stricter, we also want to skip numbers that are surrounded
	// by Latin alphabetic characters, to skip cases like abc8005001234 or 8005001234def.
	if (leniency !== 'POSSIBLE')
	{
		// If the candidate is not at the start of the text,
		// and does not start with phone-number punctuation,
		// check the previous character.
		if (offset > 0 && !LEAD_CLASS_LEADING.test(candidate))
		{
			const previousChar = text[offset - 1]
			// We return null if it is a latin letter or an invalid punctuation symbol.
			if (isInvalidPunctuationSymbol(previousChar) || isLatinLetter(previousChar)) {
				return false
			}
		}

		const lastCharIndex = offset + candidate.length
		if (lastCharIndex < text.length)
		{
			const nextChar = text[lastCharIndex]
			if (isInvalidPunctuationSymbol(nextChar) || isLatinLetter(nextChar)) {
				return false
			}
		}
	}

	return true
}