import { readFile } from 'node:fs/promises';
import path from 'node:path';

import type { Font } from 'satori';

import { SANS, SERIF } from './layout';

/**
 * Font binaries for the panel renderer, read from `public/fonts` rather than
 * from `node_modules`.
 *
 * The rendered pixels feed a content hash that decides whether the e-ink panel
 * redraws, so they have to be reproducible. Vendored files make that true; an
 * install tree or a CDN would not.
 */
/**
 * The sans families the panel can be set in.
 *
 * More than one exists because choosing a typeface for a 1-bit panel is done
 * by looking at it thresholded, not by reading its specimen: anti-aliasing is
 * what most screen faces rely on, and there is none here.
 */
export const SANS_FAMILIES = {
  inter: ['inter-400.woff', 'inter-600.woff', 'inter-700.woff'],
  atkinson: ['atkinson-400.woff', 'atkinson-700.woff', 'atkinson-700.woff'],
  plex: ['plex-400.woff', 'plex-600.woff', 'plex-700.woff'],
} as const;

export type SansFamily = keyof typeof SANS_FAMILIES;

const WEIGHTS: Font['weight'][] = [400, 600, 700];

const cache = new Map<SansFamily, Font[]>();

export async function loadScreenFonts(family: SansFamily = 'inter'): Promise<Font[]> {
  const hit = cache.get(family);
  if (hit) {
    return hit;
  }

  const directory = path.join(process.cwd(), 'public', 'fonts');
  const files = SANS_FAMILIES[family];

  const fonts = await Promise.all([
    ...files.map(async (file, index) => ({
      name: SANS,
      data: await readFile(path.join(directory, file)),
      weight: WEIGHTS[index] ?? 400,
      style: 'normal' as const,
    })),
    (async () => ({
      name: SERIF,
      data: await readFile(path.join(directory, 'source-serif-600.woff')),
      weight: 600 as Font['weight'],
      style: 'normal' as const,
    }))(),
  ]);

  cache.set(family, fonts);
  return fonts;
}