/*
Copyright 2018 Google LLC
Use of this source code is governed by an MIT-style
license that can be found in the LICENSE file or at
https://opensource.org/licenses/MIT.
*/
const errors = require('./errors');
/**
* Escaping user input to be treated as a literal string within a regular
* expression can be accomplished by simple replacement.
*
* From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
*
* @private
* @param {string} string The string to be used as part of a regular
* expression
* @return {string} A string that is safe to use in a regular
* expression.
*
* @private
*/
const escapeRegExp = (string) => {
return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
};
module.exports = (modifyURLPrefix) => {
if (!modifyURLPrefix ||
typeof modifyURLPrefix !== 'object' ||
Array.isArray(modifyURLPrefix)) {
throw new Error(errors['modify-url-prefix-bad-prefixes']);
}
// If there are no entries in modifyURLPrefix, just return an identity
// function as a shortcut.
if (Object.keys(modifyURLPrefix).length === 0) {
return (entry) => entry;
}
Object.keys(modifyURLPrefix).forEach((key) => {
if (typeof modifyURLPrefix[key] !== 'string') {
throw new Error(errors['modify-url-prefix-bad-prefixes']);
}
});
// Escape the user input so it's safe to use in a regex.
const safeModifyURLPrefixes = Object.keys(modifyURLPrefix).map(escapeRegExp);
// Join all the `modifyURLPrefix` keys so a single regex can be used.
const prefixMatchesStrings = safeModifyURLPrefixes.join('|');
// Add `^` to the front the prefix matches so it only matches the start of
// a string.
const modifyRegex = new RegExp(`^(${prefixMatchesStrings})`);
return (originalManifest) => {
const manifest = originalManifest.map((entry) => {
if (typeof entry.url !== 'string') {
throw new Error(errors['manifest-entry-bad-url']);
}
entry.url = entry.url.replace(modifyRegex, (match) => {
return modifyURLPrefix[match];
});
return entry;
});
return {manifest};
};
};