const GENERIC_FAMILIES = new Set([
  "cursive",
  "emoji",
  "fangsong",
  "fantasy",
  "inherit",
  "initial",
  "math",
  "monospace",
  "revert",
  "revert-layer",
  "sans-serif",
  "serif",
  "system-ui",
  "ui-monospace",
  "ui-rounded",
  "ui-sans-serif",
  "ui-serif",
  "unset",
]);

const isQuotedFamily = (family: string): boolean =>
  /^(?:"(?:\\.|[^"\\])*"|'(?:\\.|[^'\\])*')$/u.test(family);

const quoteFamily = (family: string): string => {
  const trimmed = family.trim();
  const normalized = trimmed.toLowerCase();
  if (!trimmed) return "inherit";
  if (GENERIC_FAMILIES.has(normalized)) return normalized;
  if (isQuotedFamily(trimmed)) return trimmed;
  return `"${trimmed
    .replace(/\\/gu, "\\\\")
    .replace(/"/gu, '\\"')
    .replace(/[\n\r\f]/gu, " ")}"`;
};

/** Quote reviewed font-family values before they enter CSS text or variables. */
export const cssFontFamily = (value: unknown): string => {
  const source = typeof value === "string" ? value.trim() : "";
  if (!source) return "inherit";
  return source.split(",").map(quoteFamily).join(", ");
};