import type { ISeoVariable } from '../../service/seo/seo.interface';

const escapeRegExp = (text: string): string =>
  text.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');

/**
 * What a title or description template renders to, with every variable
 * replaced by the example the server lists for it. Mirrors the PHP engine:
 * unknown variables disappear and separators left without a side are
 * dropped.
 */
export const previewTemplate = (
  template: string,
  variables: ISeoVariable[],
  separator: string
): string => {
  const examples = new Map(
    variables.map(variable => [variable.name, variable.example])
  );
  const sep = separator.trim() || '-';
  const rendered = template.replace(/%[a-z_]+(?:\([^)]*\))?%/gi, token =>
    token === '%sep%' ? sep : (examples.get(token) ?? '')
  );
  const edge = new RegExp(
    `^(?:\\s*${escapeRegExp(sep)}\\s*)+|(?:\\s*${escapeRegExp(sep)}\\s*)+$`,
    'g'
  );
  const repeated = new RegExp(`(?:\\s*${escapeRegExp(sep)}\\s*){2,}`, 'g');
  return rendered
    .replace(/\s+/g, ' ')
    .replace(repeated, ` ${sep} `)
    .replace(edge, '')
    .trim();
};