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JavaScript

'use strict';
const {
unassigned_code_points,
commonly_mapped_to_nothing,
non_ASCII_space_characters,
prohibited_characters,
bidirectional_r_al,
bidirectional_l,
} = require('./lib/memory-code-points');
module.exports = saslprep;
// 2.1. Mapping
/**
* non-ASCII space characters [StringPrep, C.1.2] that can be
* mapped to SPACE (U+0020)
*/
const mapping2space = non_ASCII_space_characters;
/**
* the "commonly mapped to nothing" characters [StringPrep, B.1]
* that can be mapped to nothing.
*/
const mapping2nothing = commonly_mapped_to_nothing;
// utils
const getCodePoint = character => character.codePointAt(0);
const first = x => x[0];
const last = x => x[x.length - 1];
/**
* Convert provided string into an array of Unicode Code Points.
* Based on https://stackoverflow.com/a/21409165/1556249
* and https://www.npmjs.com/package/code-point-at.
* @param {string} input
* @returns {number[]}
*/
function toCodePoints(input) {
const codepoints = [];
const size = input.length;
for (let i = 0; i < size; i += 1) {
const before = input.charCodeAt(i);
if (before >= 0xd800 && before <= 0xdbff && size > i + 1) {
const next = input.charCodeAt(i + 1);
if (next >= 0xdc00 && next <= 0xdfff) {
codepoints.push((before - 0xd800) * 0x400 + next - 0xdc00 + 0x10000);
i += 1;
continue;
}
}
codepoints.push(before);
}
return codepoints;
}
/**
* SASLprep.
* @param {string} input
* @param {Object} opts
* @param {boolean} opts.allowUnassigned
* @returns {string}
*/
function saslprep(input, opts = {}) {
if (typeof input !== 'string') {
throw new TypeError('Expected string.');
}
if (input.length === 0) {
return '';
}
// 1. Map
const mapped_input = toCodePoints(input)
// 1.1 mapping to space
.map(character => (mapping2space.get(character) ? 0x20 : character))
// 1.2 mapping to nothing
.filter(character => !mapping2nothing.get(character));
// 2. Normalize
const normalized_input = String.fromCodePoint
.apply(null, mapped_input)
.normalize('NFKC');
const normalized_map = toCodePoints(normalized_input);
// 3. Prohibit
const hasProhibited = normalized_map.some(character =>
prohibited_characters.get(character)
);
if (hasProhibited) {
throw new Error(
'Prohibited character, see https://tools.ietf.org/html/rfc4013#section-2.3'
);
}
// Unassigned Code Points
if (opts.allowUnassigned !== true) {
const hasUnassigned = normalized_map.some(character =>
unassigned_code_points.get(character)
);
if (hasUnassigned) {
throw new Error(
'Unassigned code point, see https://tools.ietf.org/html/rfc4013#section-2.5'
);
}
}
// 4. check bidi
const hasBidiRAL = normalized_map.some(character =>
bidirectional_r_al.get(character)
);
const hasBidiL = normalized_map.some(character =>
bidirectional_l.get(character)
);
// 4.1 If a string contains any RandALCat character, the string MUST NOT
// contain any LCat character.
if (hasBidiRAL && hasBidiL) {
throw new Error(
'String must not contain RandALCat and LCat at the same time,' +
' see https://tools.ietf.org/html/rfc3454#section-6'
);
}
/**
* 4.2 If a string contains any RandALCat character, a RandALCat
* character MUST be the first character of the string, and a
* RandALCat character MUST be the last character of the string.
*/
const isFirstBidiRAL = bidirectional_r_al.get(
getCodePoint(first(normalized_input))
);
const isLastBidiRAL = bidirectional_r_al.get(
getCodePoint(last(normalized_input))
);
if (hasBidiRAL && !(isFirstBidiRAL && isLastBidiRAL)) {
throw new Error(
'Bidirectional RandALCat character must be the first and the last' +
' character of the string, see https://tools.ietf.org/html/rfc3454#section-6'
);
}
return normalized_input;
}