make-plural-compiler/lib/compile-range.js

Translates Unicode CLDR pluralization rules to executable JavaScript

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.compileRange = compileRange;
const CAT = ['zero', 'one', 'two', 'few', 'many', 'other'];

function parseKey(key) {
  const match = key.match(/^pluralRange-start-(\w+)-end-(\w+)$/);
  if (!match) throw new Error(`Plural range key does not match expected form: ${key}`);
  const [, start, end] = match;
  if (!CAT.includes(start) || !CAT.includes(end)) throw new Error(`Unsupported plural category in plural range key: ${key}`);
  return [start, end];
}

function buildResult(data) {
  let allOther = true;
  let allStart = true;
  let allEnd = true;
  const tests = [];

  if (data) {
    for (const [key, result] of Object.entries(data)) {
      const [start, end] = parseKey(key);
      if (!CAT.includes(result)) throw new Error(`Unsupported plural category as plural range result: ${result}`);
      if (allOther && result !== 'other') allOther = false;
      if (allStart && result !== start) allStart = false;
      if (allEnd && result !== end) allEnd = false;
      tests.push({
        start,
        end,
        result
      });
    }
  }

  if (allOther) return '"other"';
  if (allStart) return 'start || "other"';
  if (allEnd) return 'end || "other"';
  const lines = [];
  const done = [];

  for (const {
    start,
    end,
    result
  } of tests) {
    if (result === 'other' || done.includes(end)) continue;

    if (tests.filter(t => t.end === end).every(t => t.result === result)) {
      lines.push(`end === "${end}" ? "${result}"`);
      done.push(end);
    } else {
      lines.push(`(start === "${start}" && end === "${end}") ? "${result}"`);
    }
  }

  lines.push('"other"');
  return lines.length < 4 ? lines.join(' : ') : '(\n  ' + lines.join('\n  : ') + '\n)';
}
/**
 * Compiles Unicode CLDR plural range data into a corresponding JavaScript function
 *
 * @typedef {'zero'|'one'|'two'|'few'|'many'|'other'} Category - One of the valid
 *   CLDR plural cateogries: `'zero' | 'one' | 'two' | 'few' | 'many' | 'other'`
 * @param {Record<string, Category>} [data] - Plural range data, with keys matching
 *   the regular expression `^pluralRange-start-(\w+)-end-(\w+)$`.
 * @returns {(start: Category, end: Category) => Category} A function, which when
 *   given a `start` and an `end` category, determines the plural category of the
 *   entire range.
 */


function compileRange(data) {
  const args = 'start, end';
  const res = buildResult(data);
  const fn = new Function(args, `return ${res};`);

  fn.toString = () => `(${args}) => ${res}`;

  return fn;
}