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import { merge } from "../core/utils.ts";
import type { Data, Page, Site } from "../core.ts";
export interface Options {  /** The list of extensions this plugin applies to */  extensions: string[];
  /** The field name used to save the page id */  idKey: string;
  /** The field name used to save the page type */  typeKey: string;
  /** The foreign keys per type (type => foreign_key) */  foreignKeys: Record<string, string | [string, string]>;}
// Default optionsexport const defaults: Options = {  extensions: [".html"],  idKey: "id",  typeKey: "type",  foreignKeys: {},};
export default function (userOptions?: Partial<Options>) {  const options = merge(defaults, userOptions);
  return (site: Site) => {    site.preprocess(options.extensions, index);
    function index(page1: Page, pages: Page[]) {      const data1 = page1.data;      const [type1, foreignKey1, id1] = getForeignKey(data1);
      // Index the current page with the other pages      pages.forEach(indexPage);
      // Index the current page with previously generated pages (if any)      site.pages.forEach(indexPage);
      function indexPage(page2: Page) {        if (page1 === page2) {          return;        }
        const data2 = page2.data;        const [type2, foreignKey2, id2] = getForeignKey(data2);
        // Page2 has a foreign key to page1        const directRelation = relate(          data1,          data2,          foreignKey1,          id1,          type1,        );
        // If it was related, do the opposite relation        if (directRelation && type2) {          saveMultipleRelation(            data2,            data1,            type2,          );          return;        }
        // Page1 has a foreign key to page2        const reverseRelation = relate(          data2,          data1,          foreignKey2,          id2,          type2,        );
        // If it was related, do the opposite relation        if (reverseRelation && type1) {          saveMultipleRelation(            data1,            data2,            type1,          );        }      }
      function relate(        rel: Data,        data: Data,        foreignKey?: string,        id?: string,        type?: string,      ): boolean {        if (foreignKey && type && id && data[foreignKey]) {          const relId = data[foreignKey] as string | string[];
          // The foreign key contain an array          if (Array.isArray(relId)) {            if (relId.includes(id)) {              saveMultipleRelation(rel, data, type);              return true;            }            return false;          }
          // The foreign key is a single value          if (relId == id) {            data[type] = rel;            return true;          }        }
        return false;      }
      function saveMultipleRelation(rel: Data, data: Data, type: string) {        const relData = (data[type] || []) as Data[];
        if (!relData.includes(rel)) {          relData.push(rel);          data[type] = relData;          // Sort by id          relData.sort((a, b) => {            const idA = a[options.idKey] as string;            const idB = b[options.idKey] as string;            return idA < idB ? -1 : 1;          });        }      }    }  };
  function getForeignKey(data: Data): [string?, string?, string?] {    const type = data[options.typeKey];    if (!type) {      return [undefined, undefined, undefined];    }
    const foreignKey = options.foreignKeys[type];    if (!foreignKey) {      return [type, undefined, undefined];    }
    if (Array.isArray(foreignKey)) {      const [fk, id] = foreignKey;
      return [type, fk, data[id]];    }
    return [type, foreignKey, data[options.idKey]];  }}