rdflib/esm/jsonldparser.js

an RDF library for node.js. Suitable for client and server side.

import { arrayToStatements } from './utils';

/**
 * Parses json-ld formatted JS objects to a rdf Term.
 * @param kb - The DataFactory to use.
 * @param obj - The json-ld object to process.
 * @return {Literal|NamedNode|BlankNode|Collection}
 */
export function jsonldObjectToTerm(kb, obj) {
  if (typeof obj === 'string') {
    return kb.rdfFactory.literal(obj);
  }
  if (Object.prototype.hasOwnProperty.call(obj, '@list')) {
    if (kb.rdfFactory.supports["COLLECTIONS"] === true) {
      return listToCollection(kb, obj['@list']);
    }
    return listToStatements(kb, obj);
  }
  if (Object.prototype.hasOwnProperty.call(obj, '@id')) {
    return nodeType(kb, obj);
  }
  if (Object.prototype.hasOwnProperty.call(obj, '@language')) {
    return kb.rdfFactory.literal(obj['@value'], obj['@language']);
  }
  if (Object.prototype.hasOwnProperty.call(obj, '@type')) {
    return kb.rdfFactory.literal(obj['@value'], kb.rdfFactory.namedNode(obj['@type']));
  }
  if (Object.prototype.hasOwnProperty.call(obj, '@value')) {
    return kb.rdfFactory.literal(obj['@value']);
  }
  return kb.rdfFactory.literal(obj);
}

/**
 * Adds the statements in a json-ld list object to {kb}.
 */
function listToStatements(kb, obj) {
  const listId = obj['@id'] ? nodeType(kb, obj) : kb.rdfFactory.blankNode();
  const items = obj['@list'].map(listItem => jsonldObjectToTerm(kb, listItem));
  const statements = arrayToStatements(kb.rdfFactory, listId, items);
  kb.addAll(statements);
  return listId;
}
function listToCollection(kb, obj) {
  if (!Array.isArray(obj)) {
    throw new TypeError("Object must be an array");
  }
  return kb.rdfFactory.collection(obj.map(o => jsonldObjectToTerm(kb, o)));
}

/**
 * Takes a json-ld formatted string {str} and adds its statements to {kb}.
 *
 * Ensure that {kb.rdfFactory} is a DataFactory.
 */
export default function jsonldParser(str, kb, base, callback) {
  const baseString = base && Object.prototype.hasOwnProperty.call(base, 'termType') ? base.value : base;
  return import('jsonld').then(jsonld => {
    return jsonld.flatten(JSON.parse(str), null, {
      base: baseString
    });
  }).then(flattened => flattened.reduce((store, flatResource) => {
    kb = processResource(kb, base, flatResource);
    return kb;
  }, kb)).then(callback).catch(callback);
}
function nodeType(kb, obj) {
  if (obj['@id'].startsWith('_:')) {
    // This object is a Blank Node. Pass the id without the `_:` prefix
    return kb.rdfFactory.blankNode(obj['@id'].substring(2));
  } else {
    // This object is a Named Node
    return kb.rdfFactory.namedNode(obj['@id']);
  }
}
function processResource(kb, base, flatResource) {
  const id = flatResource['@id'] ? nodeType(kb, flatResource) : kb.rdfFactory.blankNode();
  for (const property of Object.keys(flatResource)) {
    if (property === '@id') {
      continue;
    } else if (property == '@graph') {
      // the JSON-LD flattened structure may contain nested graphs
      // the id value for this object is the new base (named graph id) for all nested flat resources
      const graphId = id;
      // this is an array of resources
      const nestedFlatResources = flatResource[property];

      // recursively process all flat resources in the array, but with the graphId as base.
      for (let i = 0; i < nestedFlatResources.length; i++) {
        kb = processResource(kb, graphId, nestedFlatResources[i]);
      }
    }
    const value = flatResource[property];
    if (Array.isArray(value)) {
      for (let i = 0; i < value.length; i++) {
        kb.addStatement(createStatement(kb, id, property, value[i], base));
      }
    } else {
      kb.addStatement(createStatement(kb, id, property, value, base));
    }
  }
  return kb;
}

/**
 * Create statement quad depending on @type being a type node
 * @param kb
 * @param subject id
 * @param property
 * @param value
 * @return quad statement
 */
function createStatement(kb, id, property, value, base) {
  let predicate, object;
  if (property === "@type") {
    predicate = kb.rdfFactory.namedNode("http://www.w3.org/1999/02/22-rdf-syntax-ns#type");
    object = kb.rdfFactory.namedNode(value);
  } else {
    predicate = kb.rdfFactory.namedNode(property);
    object = jsonldObjectToTerm(kb, value);
  }
  return kb.rdfFactory.quad(id, predicate, object, kb.rdfFactory.namedNode(base));
}