@bahulneel/rdflib/src/factories/canonical-data-factory.ts

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

import BlankNode from '../blank-node'
import Literal from '../literal'
import NamedNode from '../named-node'
import Statement from '../statement'
import Variable from '../variable'
import {
  SubjectType,
  PredicateType,
  ObjectType,
  GraphType,
  EmptyTermType,
  DefaultGraphTermType,
  VariableTermType,
  BlankNodeTermType,
  LiteralTermType,
  NamedNodeTermType,
} from '../types'
import { defaultGraphNode } from '../utils/default-graph-uri'
import {
  Comparable,
  DataFactory,
  DefaultFactoryTypes,
  Feature,
} from './factory-types'
import { isQuad, isTerm } from '../utils/terms'
import { NamedNode as TFNamedNode, Quad, Term } from '../tf-types'

export { defaultGraphURI } from '../utils/default-graph-uri'

/**
 * Gets the default graph
 */
export function defaultGraph(): NamedNode {
  return defaultGraphNode
}

/** A basic internal RDFlib datafactory, which does not support Collections  */
const CanonicalDataFactory: DataFactory = {

  supports: {
    [Feature.collections]: false,
    [Feature.defaultGraphType]: false,
    [Feature.equalsMethod]: true,
    [Feature.identity]: false,
    [Feature.id]: true,
    [Feature.reversibleId]: false,
    [Feature.variableType]: true,
  },

  /**
   * Creates a new blank node
   * @param value - The blank node's identifier
   */
  blankNode(value?: string): BlankNode {
    return new BlankNode(value)
  },

  defaultGraph,

  /**
   * Compares to (rdf) objects for equality.
   */
  equals(a: Comparable, b: Comparable): boolean {
    if (a === b || !a || !b) {
      return true
    }

    if (isQuad(a) || isQuad(b)) {
      if (isQuad(a) && isQuad(b)) {
        return (
          this.equals(a.subject, b.subject) &&
          this.equals(a.predicate, b.predicate) &&
          this.equals(a.object, b.object) &&
          this.equals(a.graph, b.graph)
        )
      }

      return false
    }

    if (isTerm(a) && isTerm(b)) {
      return this.id(a) === this.id(b)
    }

    return false
  },

  /**
   * Generates a uniquely identifiably *idempotent* string for the given {term}.
   *
   * Equivalent to [[Term.hashString]]
   *
   * @example Use this to associate data with a term in an object
   *   { obj[id(term)] = "myData" }
   */
  id (term: Term | Statement | undefined): string {
    if (!term) {
      return 'undefined'
    }

    if (isQuad(term)) {
      return this.quadToNQ(term)
    }

    switch (term.termType) {
      case DefaultGraphTermType:
        return 'defaultGraph'
      case VariableTermType:
        return Variable.toString(term)
      default:
        const nq = this.termToNQ(term)
        if (nq) {
          return nq
        }

        throw new Error(`Can't id term with type '${term.termType}'`)
    }
  },

  isQuad (obj: any): obj is Statement {
    return obj instanceof Statement
  },

  /**
   * Creates a new literal node. Does some JS literal parsing for ease of use.
   * @param value - The lexical value
   * @param languageOrDatatype - Either the language or the datatype
   */
  literal(
    value: string | number | boolean | Date,
    languageOrDatatype?: string | TFNamedNode
  ): Literal {
    if (typeof value !== "string" && !languageOrDatatype) {
      return Literal.fromValue(value)
    }

    const strValue = typeof value === 'string' ? value : '' + value
    if (typeof languageOrDatatype === 'string') {
      if (languageOrDatatype.indexOf(':') === -1) {
        return new Literal(strValue, languageOrDatatype)
      } else {
        return new Literal(strValue, null, this.namedNode(languageOrDatatype))
      }
    } else {
      return new Literal(strValue, null, languageOrDatatype)
    }
  },

  /**
   * Creates a new named node
   * @param value - The new named node
   */
  namedNode(value: string): NamedNode {
    return new NamedNode(value)
  },

  /**
   * Creates a new statement
   * @param subject - The subject
   * @param predicate - The predicate
   * @param object - The object
   * @param graph - The containing graph
   */
  quad(
    subject: Term | SubjectType,
    predicate: Term | PredicateType,
    object: Term | ObjectType,
    graph?: Term | GraphType
  ): Statement {
    graph = graph || defaultGraph()
    return new Statement(subject, predicate, object, graph)
  },

  quadToNQ(q: Statement | Quad): string {
    return `${this.termToNQ(q.subject)} ${this.termToNQ(q.predicate)} ${this.termToNQ(q.object)} ${this.termToNQ(q.graph)} .`;
  },

  /** Stringify a {term} to n-quads serialization. */
  termToNQ(term: Term): string {
    switch (term.termType) {
      case BlankNodeTermType:
        return '_:' + term.value
      case DefaultGraphTermType:
        return ''
      case EmptyTermType:
        return '<http://www.w3.org/1999/02/22-rdf-syntax-ns#nil>'
      case LiteralTermType:
        return Literal.toNT(term as Literal)
      case NamedNodeTermType:
        return '<' + term.value + '>'
      default:
        throw new Error(`Can't serialize nonstandard term type (was '${term.termType}')`)
    }
  },

  /** Convert an rdf object (term or quad) to n-quads serialization. */
  toNQ (term: Term | (DefaultFactoryTypes & Variable)): string {
    if (this.isQuad(term)) {
      return this.quadToNQ(term);
    }

    return this.termToNQ(term);
  },

  /**
   * Creates a new variable
   * @param name - The name for the variable
   */
  variable(name?: string): Variable {
    return new Variable(name)
  },
}

/** Contains the factory methods as defined in the spec, plus id */
export default CanonicalDataFactory