jsonld/lib/nodeMap.js

A JSON-LD Processor and API implementation in JavaScript.

/*
 * Copyright (c) 2017 Digital Bazaar, Inc. All rights reserved.
 */
'use strict';

const {isKeyword} = require('./context');
const graphTypes = require('./graphTypes');
const types = require('./types');
const util = require('./util');
const JsonLdError = require('./JsonLdError');

const api = {};
module.exports = api;

/**
 * Creates a merged JSON-LD node map (node ID => node).
 *
 * @param input the expanded JSON-LD to create a node map of.
 * @param [options] the options to use:
 *          [issuer] a jsonld.IdentifierIssuer to use to label blank nodes.
 *
 * @return the node map.
 */
api.createMergedNodeMap = (input, options) => {
  options = options || {};

  // produce a map of all subjects and name each bnode
  const issuer = options.issuer || new util.IdentifierIssuer('_:b');
  const graphs = {'@default': {}};
  api.createNodeMap(input, graphs, '@default', issuer);

  // add all non-default graphs to default graph
  return api.mergeNodeMaps(graphs);
};

/**
 * Recursively flattens the subjects in the given JSON-LD expanded input
 * into a node map.
 *
 * @param input the JSON-LD expanded input.
 * @param graphs a map of graph name to subject map.
 * @param graph the name of the current graph.
 * @param issuer the blank node identifier issuer.
 * @param name the name assigned to the current input if it is a bnode.
 * @param list the list to append to, null for none.
 */
api.createNodeMap = (input, graphs, graph, issuer, name, list) => {
  // recurse through array
  if(types.isArray(input)) {
    for(const node of input) {
      api.createNodeMap(node, graphs, graph, issuer, undefined, list);
    }
    return;
  }

  // add non-object to list
  if(!types.isObject(input)) {
    if(list) {
      list.push(input);
    }
    return;
  }

  // add values to list
  if(graphTypes.isValue(input)) {
    if('@type' in input) {
      let type = input['@type'];
      // rename @type blank node
      if(type.indexOf('_:') === 0) {
        input['@type'] = type = issuer.getId(type);
      }
    }
    if(list) {
      list.push(input);
    }
    return;
  } else if(list && graphTypes.isList(input)) {
    const _list = [];
    api.createNodeMap(input['@list'], graphs, graph, issuer, name, _list);
    list.push({'@list': _list});
    return;
  }

  // Note: At this point, input must be a subject.

  // spec requires @type to be named first, so assign names early
  if('@type' in input) {
    const types = input['@type'];
    for(const type of types) {
      if(type.indexOf('_:') === 0) {
        issuer.getId(type);
      }
    }
  }

  // get name for subject
  if(types.isUndefined(name)) {
    name = graphTypes.isBlankNode(input) ?
      issuer.getId(input['@id']) : input['@id'];
  }

  // add subject reference to list
  if(list) {
    list.push({'@id': name});
  }

  // create new subject or merge into existing one
  const subjects = graphs[graph];
  const subject = subjects[name] = subjects[name] || {};
  subject['@id'] = name;
  const properties = Object.keys(input).sort();
  for(let property of properties) {
    // skip @id
    if(property === '@id') {
      continue;
    }

    // handle reverse properties
    if(property === '@reverse') {
      const referencedNode = {'@id': name};
      const reverseMap = input['@reverse'];
      for(const reverseProperty in reverseMap) {
        const items = reverseMap[reverseProperty];
        for(const item of items) {
          let itemName = item['@id'];
          if(graphTypes.isBlankNode(item)) {
            itemName = issuer.getId(itemName);
          }
          api.createNodeMap(item, graphs, graph, issuer, itemName);
          util.addValue(
            subjects[itemName], reverseProperty, referencedNode,
            {propertyIsArray: true, allowDuplicate: false});
        }
      }
      continue;
    }

    // recurse into graph
    if(property === '@graph') {
      // add graph subjects map entry
      if(!(name in graphs)) {
        graphs[name] = {};
      }
      api.createNodeMap(input[property], graphs, name, issuer);
      continue;
    }

    // recurse into included
    if(property === '@included') {
      api.createNodeMap(input[property], graphs, graph, issuer);
      continue;
    }

    // copy non-@type keywords
    if(property !== '@type' && isKeyword(property)) {
      if(property === '@index' && property in subject &&
        (input[property] !== subject[property] ||
        input[property]['@id'] !== subject[property]['@id'])) {
        throw new JsonLdError(
          'Invalid JSON-LD syntax; conflicting @index property detected.',
          'jsonld.SyntaxError',
          {code: 'conflicting indexes', subject});
      }
      subject[property] = input[property];
      continue;
    }

    // iterate over objects
    const objects = input[property];

    // if property is a bnode, assign it a new id
    if(property.indexOf('_:') === 0) {
      property = issuer.getId(property);
    }

    // ensure property is added for empty arrays
    if(objects.length === 0) {
      util.addValue(subject, property, [], {propertyIsArray: true});
      continue;
    }
    for(let o of objects) {
      if(property === '@type') {
        // rename @type blank nodes
        o = (o.indexOf('_:') === 0) ? issuer.getId(o) : o;
      }

      // handle embedded subject or subject reference
      if(graphTypes.isSubject(o) || graphTypes.isSubjectReference(o)) {
        // skip null @id
        if('@id' in o && !o['@id']) {
          continue;
        }

        // relabel blank node @id
        const id = graphTypes.isBlankNode(o) ?
          issuer.getId(o['@id']) : o['@id'];

        // add reference and recurse
        util.addValue(
          subject, property, {'@id': id},
          {propertyIsArray: true, allowDuplicate: false});
        api.createNodeMap(o, graphs, graph, issuer, id);
      } else if(graphTypes.isValue(o)) {
        util.addValue(
          subject, property, o,
          {propertyIsArray: true, allowDuplicate: false});
      } else if(graphTypes.isList(o)) {
        // handle @list
        const _list = [];
        api.createNodeMap(o['@list'], graphs, graph, issuer, name, _list);
        o = {'@list': _list};
        util.addValue(
          subject, property, o,
          {propertyIsArray: true, allowDuplicate: false});
      } else {
        // handle @value
        api.createNodeMap(o, graphs, graph, issuer, name);
        util.addValue(
          subject, property, o, {propertyIsArray: true, allowDuplicate: false});
      }
    }
  }
};

/**
 * Merge separate named graphs into a single merged graph including
 * all nodes from the default graph and named graphs.
 *
 * @param graphs a map of graph name to subject map.
 *
 * @return the merged graph map.
 */
api.mergeNodeMapGraphs = graphs => {
  const merged = {};
  for(const name of Object.keys(graphs).sort()) {
    for(const id of Object.keys(graphs[name]).sort()) {
      const node = graphs[name][id];
      if(!(id in merged)) {
        merged[id] = {'@id': id};
      }
      const mergedNode = merged[id];

      for(const property of Object.keys(node).sort()) {
        if(isKeyword(property) && property !== '@type') {
          // copy keywords
          mergedNode[property] = util.clone(node[property]);
        } else {
          // merge objects
          for(const value of node[property]) {
            util.addValue(
              mergedNode, property, util.clone(value),
              {propertyIsArray: true, allowDuplicate: false});
          }
        }
      }
    }
  }

  return merged;
};

api.mergeNodeMaps = graphs => {
  // add all non-default graphs to default graph
  const defaultGraph = graphs['@default'];
  const graphNames = Object.keys(graphs).sort();
  for(const graphName of graphNames) {
    if(graphName === '@default') {
      continue;
    }
    const nodeMap = graphs[graphName];
    let subject = defaultGraph[graphName];
    if(!subject) {
      defaultGraph[graphName] = subject = {
        '@id': graphName,
        '@graph': []
      };
    } else if(!('@graph' in subject)) {
      subject['@graph'] = [];
    }
    const graph = subject['@graph'];
    for(const id of Object.keys(nodeMap).sort()) {
      const node = nodeMap[id];
      // only add full subjects
      if(!graphTypes.isSubjectReference(node)) {
        graph.push(node);
      }
    }
  }
  return defaultGraph;
};