sssom-js/lib/valid-uri.js

Simple Standard for Sharing Ontology Mappings (SSOM) JavaScript library

/**
 * Code adopted from npm package <https://npmjs.org/package/validate.io-uri>
 * Copyright (c) 2015 by Athan Reines, licensed under MIT.
 */

// REGEXP //

let URI,
  ILLEGALS,
  HEX1,
  HEX2,
  PATH,
  SCHEME

// RFC 3986:
URI = /(?:([^:/?#]+):)?(?:\/\/([^/?#]*))?([^?#]*)(?:\?[^#]*)?(?:#.*)?/
/**
	<scheme name> : <hierarchical part > [ ? <query> ] [ # <fragment> ]

	(?:([^:\/?#]+):)
		-	match the scheme, including the ':', but only capture the scheme name

	?
		-	match the scheme 0 or 1 times

	(?:\/\/([^\/?#]*))
		-	match the hierarchical part which is everything which is not a '/', '#', or '?', but only capture whatever comes after the '//'

	?
		-	match the hierarchical part 0 or 1 times

	([^?#]*)
		-	capture everything (the path) until meeting a '?' or '#'

	(?:\?[^#]*)
		-	match, but don't capture, an optional query

	(?:#.*)?
		-	match, but don't capture, an optional fragment
*/

// Illegal characters (anything which is not in between the square brackets):
ILLEGALS = /[^a-z0-9:/?#[\]@!$&'()*+,;=._~%-]/i

// Incomplete HEX escapes:
HEX1 = /%[^0-9a-f]/i
HEX2 = /%[0-9a-f](:?[^0-9a-f]|$)/i

// If authority is not present, path must not begin with '//'
PATH = /^\/\//

// Scheme must begin with a letter, then consist of letters, digits, '+', '.', or '-' => e.g., 'http', 'https', 'ftp'
SCHEME = /^[a-z][a-z0-9+.-]*$/

export function isURI( val ) {
  let parts,
    scheme,
    authority,
    path
  if ( typeof val !== "string" ) {
    return false
  }
  // [1] Check for illegal characters:
  if ( ILLEGALS.test( val ) ) {
    return false
  }
  // [2] Check for incomplete HEX escapes:
  if ( HEX1.test( val ) || HEX2.test( val ) ) {
    return false
  }
  // [3] Split the string into various URI components:
  parts = val.match( URI )
  scheme = parts[ 1 ]
  authority = parts[ 2 ]
  path = parts[ 3 ]
  // [4] Scheme is required and must be valid:
  if ( !scheme || !scheme.length || !SCHEME.test( scheme.toLowerCase() ) ) {
    return false
  }
  // [5] If authority is not present, path must not begin with a '//':
  if ( !authority && PATH.test( path ) ) {
    return false
  }
  return true
}