/**
 * Insert markup before the document's closing </body> or </head>, ignoring
 * occurrences inside inline scripts, styles, or string literals.
 */

function maskHtmlLiteralRegions(html) {
  return String(html ?? '').replace(/<script\b[^>]*>[\s\S]*?<\/script>/gi, (match) =>
    ' '.repeat(match.length),
  ).replace(/<style\b[^>]*>[\s\S]*?<\/style>/gi, (match) => ' '.repeat(match.length));
}

export function injectBeforeDocumentClosingBody(html, markup) {
  const source = String(html ?? '');
  const injection = String(markup ?? '');
  if (!injection) return source;
  const masked = maskHtmlLiteralRegions(source).toLowerCase();
  const lastIndex = masked.lastIndexOf('</body>');
  if (lastIndex < 0) return `${source}${injection}`;
  return `${source.slice(0, lastIndex)}${injection}${source.slice(lastIndex)}`;
}

export function injectBeforeDocumentClosingHead(html, markup) {
  const source = String(html ?? '');
  const injection = String(markup ?? '');
  if (!injection) return source;
  const masked = maskHtmlLiteralRegions(source).toLowerCase();
  const index = masked.indexOf('</head>');
  if (index < 0) return `${injection}${source}`;
  return `${source.slice(0, index)}${injection}${source.slice(index)}`;
}