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import { merge } from "../core/utils/object.ts";
import type Site from "../core/site.ts";import type { Data, Page } from "../core/file.ts";
type RelationFilter = (data1: Data, data2: Data) => boolean;
interface ForeignKeyOptions {  foreignKey: string;  relationKey?: string;  pluralRelationKey?: string;  idKey?: string;  filter?: RelationFilter;}
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 | ForeignKeyOptions>;}
// Default optionsexport const defaults: Options = {  extensions: [".html"],  idKey: "id",  typeKey: "type",  foreignKeys: {},};
export default function (userOptions: Options) {  const options = merge(defaults, userOptions);
  return (site: Site) => {    site.preprocess(options.extensions, index);
    function index(pages1: Page[], pages: Page[]) {      pages1.forEach((page1) => {        const data1 = page1.data;        const [          type1,          foreignKey1,          id1,          relationType1,          pluralRelationKey1,          filter1,        ] = getRelationInfo(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;
          if (filter1 && !filter1(data1, page2.data)) {            return;          }
          const [            type2,            foreignKey2,            id2,            relationType2,            pluralRelationKey2,            filter2,          ] = getRelationInfo(data2);
          if (filter2 && !filter2(data2, page1.data)) {            return;          }
          // Page2 has a foreign key to page1          const directRelation = relate(            data1,            data2,            foreignKey1,            id1,            type1,            relationType1,            pluralRelationKey1,          );          // If it was related, do the opposite relation          if (directRelation && pluralRelationKey2) {            saveMultipleRelation(              data2,              data1,              pluralRelationKey2,            );            return;          }
          // Page1 has a foreign key to page2          const reverseRelation = relate(            data2,            data1,            foreignKey2,            id2,            type2,            relationType2,            pluralRelationKey2,          );
          // If it was related, do the opposite relation          if (reverseRelation && pluralRelationKey1) {            saveMultipleRelation(              data1,              data2,              pluralRelationKey1,            );          }        }
        function relate(          rel: Data,          data: Data,          foreignKey?: string,          id?: string,          type?: string,          relationKey?: string,          pluralRelationKey?: 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, pluralRelationKey || type);                return true;              }              return false;            }
            // The foreign key is a single value            if (relId == id) {              data[relationKey || 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 getRelationInfo(    data: Data,  ): [string?, string?, string?, string?, string?, RelationFilter?] {    const type = data[options.typeKey];    if (!type) {      return [];    }
    const foreignKey = options.foreignKeys[type];    if (!foreignKey) {      return [type, undefined, undefined, type, type];    }
    if (typeof foreignKey === "string") {      return [type, foreignKey, data[options.idKey], type, type];    }
    return [      type,      foreignKey.foreignKey,      data[foreignKey.idKey || options.idKey],      foreignKey.relationKey || type,      foreignKey.pluralRelationKey || foreignKey.relationKey || type,      foreignKey.filter,    ];  }}