graph-explorer/examples/resources/exampleMetadataApi.ts

Graph Explorer can be used to explore and RDF graphs in SPARQL endpoints or on the web.

import {
  ElementModel,
  LinkModel,
  ElementIri,
  ElementTypeIri,
  LinkTypeIri,
  PropertyTypeIri,
  LinkDirection,
  MetadataApi,
  ValidationApi,
  ValidationEvent,
  ElementError,
  LinkError,
  LiteralProperty,
  DirectedLinkType,
  CancellationToken,
} from "../../src/graph-explorer/index";

const OWL_PREFIX = "http://www.w3.org/2002/07/owl#";
const RDFS_PREFIX = "http://www.w3.org/2000/01/rdf-schema#";

const owl = {
  class: (OWL_PREFIX + "Class") as ElementTypeIri,
  objectProperty: (OWL_PREFIX + "ObjectProperty") as ElementTypeIri,
  domain: (OWL_PREFIX + "domain") as LinkTypeIri,
  range: (OWL_PREFIX + "range") as LinkTypeIri,
};
const rdfs = {
  subClassOf: (RDFS_PREFIX + "subClassOf") as LinkTypeIri,
  subPropertyOf: (RDFS_PREFIX + "subPropertyOf") as LinkTypeIri,
};

function hasType(model: ElementModel, type: ElementTypeIri) {
  return Boolean(model.types.find((t) => t === type));
}

const SIMULATED_DELAY = 500; /* ms */

export class ExampleMetadataApi implements MetadataApi {
  async canDropOnCanvas(
    source: ElementModel,
    ct: CancellationToken
  ): Promise<boolean> {
    await delay(SIMULATED_DELAY, ct);
    const elementTypes = await this.typesOfElementsDraggedFrom(source, ct);
    CancellationToken.throwIfAborted(ct);
    return elementTypes.length > 0;
  }

  async canDropOnElement(
    source: ElementModel,
    target: ElementModel,
    ct: CancellationToken
  ): Promise<boolean> {
    //await delay(SIMULATED_DELAY, ct);
    const linkTypes = await this.possibleLinkTypes(source, target, ct);
    CancellationToken.throwIfAborted(ct);
    return linkTypes.length > 0;
  }

  async possibleLinkTypes(
    source: ElementModel,
    target: ElementModel,
    ct: CancellationToken
  ): Promise<DirectedLinkType[]> {
    await delay(SIMULATED_DELAY, ct);
    return hasType(source, owl.class) && hasType(target, owl.class)
      ? mapLinkTypes([rdfs.subClassOf]).concat(
          mapLinkTypes([rdfs.subClassOf], LinkDirection.in)
        )
      : hasType(source, owl.objectProperty) && hasType(target, owl.class)
      ? mapLinkTypes([owl.domain, owl.range])
      : hasType(target, owl.objectProperty) && hasType(source, owl.class)
      ? mapLinkTypes([owl.domain, owl.range], LinkDirection.in)
      : hasType(source, owl.objectProperty) &&
        hasType(target, owl.objectProperty)
      ? mapLinkTypes([rdfs.subPropertyOf]).concat(
          mapLinkTypes([rdfs.subPropertyOf], LinkDirection.in)
        )
      : [];

    function mapLinkTypes(
      types: LinkTypeIri[],
      direction: LinkDirection = LinkDirection.out
    ): DirectedLinkType[] {
      return types.map((linkTypeIri) => ({ linkTypeIri, direction }));
    }
  }

  async typesOfElementsDraggedFrom(
    source: ElementModel,
    ct: CancellationToken
  ): Promise<ElementTypeIri[]> {
    await delay(SIMULATED_DELAY, ct);
    return hasType(source, owl.class)
      ? [owl.class]
      : hasType(source, owl.objectProperty)
      ? [owl.class, owl.objectProperty]
      : [];
  }

  async propertiesForType(
    _type: ElementTypeIri,
    _ct: CancellationToken
  ): Promise<PropertyTypeIri[]> {
    //await delay(SIMULATED_DELAY, ct);
    return [];
  }

  async canDeleteElement(
    element: ElementModel,
    ct: CancellationToken
  ): Promise<boolean> {
    await delay(SIMULATED_DELAY, ct);
    return true;
  }

  async filterConstructibleTypes(
    types: ReadonlySet<ElementTypeIri>,
    _ct: CancellationToken
  ): Promise<ReadonlySet<ElementTypeIri>> {
    //await delay(SIMULATED_DELAY, ct);
    const result = new Set<ElementTypeIri>();
    types.forEach((type) => {
      if (type === "http://xmlns.com/foaf/0.1/Person") {
        result.add(type);
      }
    });
    return result;
  }

  async canEditElement(
    element: ElementModel,
    ct: CancellationToken
  ): Promise<boolean> {
    await delay(SIMULATED_DELAY, ct);
    return true;
  }

  async canLinkElement(
    _element: ElementModel,
    _ct: CancellationToken
  ): Promise<boolean> {
    //await delay(SIMULATED_DELAY, ct);
    return true;
  }

  async canDeleteLink(
    _link: LinkModel,
    _source: ElementModel,
    _target: ElementModel,
    _ct: CancellationToken
  ): Promise<boolean> {
    //await delay(SIMULATED_DELAY, ct);
    return true;
  }

  async canEditLink(
    _link: LinkModel,
    _source: ElementModel,
    _target: ElementModel,
    _ct: CancellationToken
  ): Promise<boolean> {
    //await delay(SIMULATED_DELAY, ct);
    return true;
  }

  async generateNewElement(
    types: readonly ElementTypeIri[],
    ct: CancellationToken
  ): Promise<ElementModel> {
    await delay(SIMULATED_DELAY, ct);
    const random32BitDigits = Math.floor((1 + Math.random()) * 0x100000000)
      .toString(16)
      .substring(1);
    return {
      id: `${types[0]}_${random32BitDigits}` as ElementIri,
      types: [...types],
      label: { values: [{ value: "New Entity", language: "" }] },
      properties: {
        "http://xmlns.com/foaf/0.1/name": {
          type: "string",
          values: [{ language: "", value: "helo" }],
        } as LiteralProperty,
      },
    };
  }
}

export class ExampleValidationApi implements ValidationApi {
  async validate(
    event: ValidationEvent
  ): Promise<(ElementError | LinkError)[]> {
    const errors: (ElementError | LinkError)[] = [];
    if (event.target.types.indexOf(owl.class) >= 0) {
      event.state.links.forEach((e) => {
        if (!e.before && e.after.sourceId === event.target.id) {
          errors.push({
            type: "link",
            target: e.after,
            message: "Cannot add any new link from a Class",
          });
          const linkType = event.model.createLinkType(e.after.linkTypeId);
          errors.push({
            type: "element",
            target: event.target.id,
            message: `Cannot create <${linkType.id}> link from a Class`,
          });
        }
      });
    }

    await delay(SIMULATED_DELAY, event.cancellation);
    return errors;
  }
}

async function delay(amountMs: number, ct: CancellationToken) {
  CancellationToken.throwIfAborted(ct);
  await waitTimeout(amountMs);
  CancellationToken.throwIfAborted(ct);
}

function waitTimeout(amountMs: number): Promise<void> {
  if (amountMs === 0) {
    return Promise.resolve();
  }
  return new Promise((resolve) => setTimeout(resolve, amountMs));
}