// Vite inlines the file's text at build time. This is deliberately NOT a `readFileSync`
// against `import.meta.url`: that works in dev and then throws ENOENT during prerender,
// because the bundled chunk sits in `dist/server/.prerender/` and the CSS does not follow
// it there. `?raw` puts the bytes in the bundle, where they are needed.
import tokensCss from '../styles/tokens.css?raw';

/**
 * Reads `tokens.css` at build time and exposes its custom properties to JavaScript.
 *
 * This exists because a few values have to leave CSS: `<meta name="theme-color">`, the OG
 * card's background, an SVG diagram's stroke. Copying them into a template would be
 * exactly the drift §7 warns about — "one CSS file changes most of the appearance, and
 * then there is a hardcoded #0e1318 in the footer" — and `checkTokens.mjs` would fail the
 * build for it, correctly.
 *
 * So the token file stays the single source and this reads it, rather than the other way
 * round. Deliberately a plain regex over `--name: value;` and not a CSS parser: the file
 * it reads is one we own and keep flat, and a dependency here would be a dependency in the
 * build of every page.
 *
 * Note that this resolves the STOCK values. A bind-mounted `theme.css` overrides tokens in
 * the browser, at runtime, which is the whole point — anything derived through this module
 * is therefore build-time and will not follow a mounted theme. Keep that list short.
 */
function readTokens() {
  const withoutComments = tokensCss.replace(/\/\*[\s\S]*?\*\//g, '');
  const out = {};
  for (const match of withoutComments.matchAll(/(--[a-z0-9-]+)\s*:\s*([^;]+);/gi)) {
    out[match[1]] = match[2].trim();
  }
  return Object.freeze(out);
}

export const tokens = readTokens();

/** Throws rather than emitting `undefined` into a template. */
export function token(name) {
  const value = tokens[name];
  if (!value) {
    throw new Error(
      `Unknown design token "${name}". Every token is defined in src/styles/tokens.css; ` +
        `add it there rather than inlining a value at the call site.`
    );
  }
  return value;
}