/**
 * Copyright (c) 2018 The xterm.js authors. All rights reserved.
 * @license MIT
 */

import * as fontFinder from 'font-finder';
import * as fontLigatures from 'font-ligatures';

import parse from './parse';

let fontsPromise: Promise<fontFinder.FontList> | undefined = undefined;

/**
 * Loads the font ligature wrapper for the specified font family if it could be
 * resolved, throwing if it is unable to find a suitable match.
 * @param fontFamily The CSS font family definition to resolve
 * @param cacheSize The size of the ligature cache to maintain if the font is resolved
 */
export default async function load(fontFamily: string, cacheSize: number): Promise<fontLigatures.Font | undefined> {
  if (!fontsPromise) {
    fontsPromise = fontFinder.list();
  }

  const fonts = await fontsPromise;
  for (const family of parse(fontFamily)) {
    // If we reach one of the generic font families, the font resolution
    // will end for the browser and we can't determine the specific font
    // used. Throw.
    if (genericFontFamilies.includes(family)) {
      return undefined;
    }

    if (fonts.hasOwnProperty(family) && fonts[family].length > 0) {
      return await fontLigatures.loadFile(fonts[family][0].path, { cacheSize });
    }
  }

  // If none of the fonts could resolve, throw an error
  return undefined;
}

// https://drafts.csswg.org/css-fonts-4/#generic-font-families
const genericFontFamilies = [
  'serif',
  'sans-serif',
  'cursive',
  'fantasy',
  'monospace',
  'system-ui',
  'emoji',
  'math',
  'fangsong'
];