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

const longestFirst = (a: string, b: string): number => b.length - a.length;

/**
 * The kind of page a Titles & meta template is for, as the server keys its
 * variable sets: home, search, not_found, author, date, post:{type},
 * archive:{type}, term:{taxonomy}. Empty for a field of no template.
 */
export const templateContext = (
  key: string,
  postTypes: string[],
  taxonomies: string[]
): string => {
  const postType = [...postTypes]
    .sort(longestFirst)
    .find(slug => key.startsWith(`pt_${slug}_`));
  if (postType) {
    return key.startsWith(`pt_${postType}_archive_`)
      ? `archive:${postType}`
      : `post:${postType}`;
  }
  const taxonomy = [...taxonomies]
    .sort(longestFirst)
    .find(slug => key.startsWith(`tax_${slug}_`));
  if (taxonomy) {
    return `term:${taxonomy}`;
  }
  const prefixes: Array<[string, string]> = [
    ['home_', 'home'],
    ['author_', 'author'],
    ['date_archive_', 'date'],
    ['search_', 'search'],
    ['not_found_', 'not_found'],
  ];
  return prefixes.find(([prefix]) => key.startsWith(prefix))?.[1] ?? '';
};

/**
 * The variables of one template: the ones its kind of page can use, each
 * with what it prints there. Every variable when the server sent no set.
 */
export const contextVariables = (
  variables: ISeoVariable[],
  set: Record<string, string> | undefined
): ISeoVariable[] =>
  set
    ? variables
        .filter(variable => variable.name in set)
        .map(variable => ({ ...variable, example: set[variable.name] }))
    : variables;