/**
 * Self-hosted Inter (variable, upright) from @fontsource-variable/inter.
 *
 * src/index.css declares one @font-face per unicode-range subset with a
 * relative `url(fonts/<file>)`, which resolves to src/fonts/ — a generated,
 * gitignored copy of the package's files (`ensureFonts()`; Bun's CSS bundler
 * must be able to resolve every url()).
 *
 * - Dev (`bun dev`): the HTML-import bundler inlines them as base64. Fine
 *   locally.
 * - Production (scripts/build.ts): `external: ["*.woff2"]` keeps them out of
 *   the bundle — Bun inlines every resolvable CSS url() asset, which would put
 *   ~220 KB into the render-blocking stylesheet and defeat unicode-range lazy
 *   loading. The build copies them to dist/fonts/ and precaches them instead.
 *
 * Same-origin either way, so COEP `require-corp` (D-023) allows them.
 */

import { copyFile, mkdir } from "node:fs/promises";
import { join } from "node:path";

const PACKAGE_FILES = join(import.meta.dir, "../node_modules/@fontsource-variable/inter/files");
const CSS_PATH = join(import.meta.dir, "../src/index.css");
export const FONTS_DIR = join(import.meta.dir, "../src/fonts");

/** The font files a stylesheet references via `url(fonts/<file>)`. */
export function fontFilesInCss(css: string): string[] {
  const files = [...css.matchAll(/url\(["']?fonts\/([^"')]+)["']?\)/g)].map((match) => match[1]!);
  return [...new Set(files)];
}

/**
 * Copy every font src/index.css references into src/fonts/ (idempotent).
 * Always overwrites (~220 KB), so a package upgrade can't leave stale copies.
 */
export async function ensureFonts(): Promise<string[]> {
  const files = fontFilesInCss(await Bun.file(CSS_PATH).text());
  await mkdir(FONTS_DIR, { recursive: true });
  for (const name of files) {
    await copyFile(join(PACKAGE_FILES, name), join(FONTS_DIR, name));
  }
  return files;
}