import {getDOM} from '../dom/dom_adapter';
import {assertionsEnabled} from '../facade/lang';

/**
 * A pattern that recognizes a commonly useful subset of URLs that are safe.
 *
 * This regular expression matches a subset of URLs that will not cause script
 * execution if used in URL context within a HTML document. Specifically, this
 * regular expression matches if (comment from here on and regex copied from
 * Soy's EscapingConventions):
 * (1) Either a protocol in a whitelist (http, https, mailto or ftp).
 * (2) or no protocol.  A protocol must be followed by a colon. The below
 *     allows that by allowing colons only after one of the characters [/?#].
 *     A colon after a hash (#) must be in the fragment.
 *     Otherwise, a colon after a (?) must be in a query.
 *     Otherwise, a colon after a single solidus (/) must be in a path.
 *     Otherwise, a colon after a double solidus (//) must be in the authority
 *     (before port).
 *
 * The pattern disallows &, used in HTML entity declarations before
 * one of the characters in [/?#]. This disallows HTML entities used in the
 * protocol name, which should never happen, e.g. "http" for "http".
 * It also disallows HTML entities in the first path part of a relative path,
 * e.g. "foo<bar/baz".  Our existing escaping functions should not produce
 * that. More importantly, it disallows masking of a colon,
 * e.g. "javascript:...".
 *
 * This regular expression was taken from the Closure sanitization library.
 */
const SAFE_URL_PATTERN = /^(?:(?:https?|mailto|ftp|tel|file):|[^&:/?#]*(?:[/?#]|$))/gi;

/** A pattern that matches safe data URLs. Only matches image and video types. */
const DATA_URL_PATTERN = /^data:(?:image\/(?:bmp|gif|jpeg|jpg|png|tiff|webp)|video\/(?:mpeg|mp4|ogg|webm));base64,[a-z0-9+\/]+=*$/i;

export function sanitizeUrl(url: string): string {
  url = String(url);
  if (url.match(SAFE_URL_PATTERN) || url.match(DATA_URL_PATTERN)) return url;

  if (assertionsEnabled()) getDOM().log('WARNING: sanitizing unsafe URL value ' + url);

  return 'unsafe:' + url;
}