/**
 * Twemoji glyphs, fetched from the jsDelivr CDN.
 *
 * @module
 */

/** The pinned Twemoji release. */
const TWEMOJI_VERSION = "16.0.1";

/** Fetched glyphs by codepoint, so repeated runs don't re-hit the network. */
const glyphCache = new Map<string, string>();

/**
 * Fetches Twemoji's plain vector-path SVG for `emoji`, whose file is named
 * `cp` (see `emojiToCodepoint` in lib/site-icons.ts).
 *
 * @throws {Error} When the glyph can't be fetched.
 */
export async function fetchTwemojiSvg(
  emoji: string,
  cp: string,
): Promise<string> {
  const cached = glyphCache.get(cp);
  if (cached) return cached;
  const url =
    `https://cdn.jsdelivr.net/gh/jdecked/twemoji@${TWEMOJI_VERSION}/assets/svg/${cp}.svg`;
  let res: Response;
  try {
    res = await fetch(url);
  } catch (cause) {
    throw new Error(
      `Failed to fetch Twemoji glyph for "${emoji}" (${cp}) from ${url}`,
      { cause },
    );
  }
  if (!res.ok) {
    throw new Error(
      `Failed to fetch Twemoji glyph for "${emoji}" (${cp}) from ${url}: ${res.status} ${res.statusText}`,
    );
  }
  const svg = await res.text();
  glyphCache.set(cp, svg);
  return svg;
}