graph-explorer/src/graph-explorer/data/sparql/sparqlDataProvider.ts

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

import {
  objectValues,
  getOrCreateArrayInMap,
} from "../../viewUtils/collections";
import { DataProvider, LinkElementsParams, FilterParams } from "../provider";
import {
  Dictionary,
  ClassModel,
  LinkType,
  ElementModel,
  LinkModel,
  LinkCount,
  PropertyModel,
  ElementIri,
  ElementTypeIri,
  LinkTypeIri,
  PropertyTypeIri,
  LocalizedString,
} from "../model";
import {
  prependAdditionalBindings,
  enrichElementsWithImages,
  flattenClassTree,
  getClassTree,
  getClassInfo,
  getPropertyInfo,
  getLinkTypes,
  getElementsInfo,
  getElementTypes,
  getLinksInfo,
  getLinksTypeIds,
  getFilteredData,
  getLinksTypesOf,
  getLinkStatistics,
  triplesToElementBinding,
  isDirectLink,
  isDirectProperty,
} from "./responseHandler";
import {
  ClassBinding,
  ElementBinding,
  LinkBinding,
  PropertyBinding,
  BlankBinding,
  FilterBinding,
  LinkCountBinding,
  LinkTypeBinding,
  ElementImageBinding,
  ElementTypeBinding,
  SparqlResponse,
  Triple,
} from "./sparqlModels";
import {
  SparqlDataProviderSettings,
  OWLStatsSettings,
  LinkConfiguration,
  PropertyConfiguration,
} from "./sparqlDataProviderSettings";
import * as BlankNodes from "./blankNodes";
import { parseTurtleText } from "./turtle";

export enum SparqlQueryMethod {
  GET = 1,
  POST,
}

export type QueryFunction = (params: {
  url: string;
  body?: string;
  headers: Record<string, string>;
  method: string;
}) => Promise<Response>;

/**
 * Runtime settings of SPARQL data provider
 */
export interface SparqlDataProviderOptions {
  /**
   * If it's true then blank nodes will be present on the paper
   * By default blank nodes wont be shown
   */
  acceptBlankNodes?: boolean;

  /**
   *  sparql endpoint URL to use
   */
  endpointUrl: string;

  // there are two options for fetching images: specify imagePropertyUris
  // to use as image properties or specify a function to fetch image URLs

  /**
   * properties to use as image URLs
   */
  imagePropertyUris?: string[];

  /**
   * Allows to extract/fetch image URLs externally instead of using `imagePropertyUris` option.
   */
  prepareImages?: (
    elementInfo: Dictionary<ElementModel>
  ) => Promise<Dictionary<string>>;

  /**
   * Allows to extract/fetch labels separately from SPARQL query as an alternative or
   * in addition to `label` output binding.
   */
  prepareLabels?: (
    resources: Set<string>
  ) => Promise<Map<string, LocalizedString[]>>;

  /**
   * wether to use GET (more compatible (Virtuozo), more error-prone due to large request URLs)
   * or POST(less compatible, better on large data sets)
   */
  queryMethod?: SparqlQueryMethod;

  /*
   * function to send sparql requests
   */
  queryFunction?: QueryFunction;
}

export class SparqlDataProvider implements DataProvider {
  readonly options: SparqlDataProviderOptions;
  readonly settings: SparqlDataProviderSettings;

  private linkByPredicate = new Map<string, LinkConfiguration[]>();
  private linkById = new Map<LinkTypeIri, LinkConfiguration>();
  private openWorldLinks: boolean;

  private propertyByPredicate = new Map<string, PropertyConfiguration[]>();
  private openWorldProperties: boolean;

  constructor(
    options: SparqlDataProviderOptions,
    settings: SparqlDataProviderSettings = OWLStatsSettings
  ) {
    const { queryFunction = queryInternal } = options;
    this.options = { ...options, queryFunction };
    this.settings = settings;

    for (const link of settings.linkConfigurations) {
      this.linkById.set(link.id as LinkTypeIri, link);
      const predicate = isDirectLink(link) ? link.path : link.id;
      getOrCreateArrayInMap(this.linkByPredicate, predicate).push(link);
    }
    this.openWorldLinks =
      settings.linkConfigurations.length === 0 ||
      Boolean(settings.openWorldLinks);

    for (const property of settings.propertyConfigurations) {
      const predicate = isDirectProperty(property)
        ? property.path
        : property.id;
      getOrCreateArrayInMap(this.propertyByPredicate, predicate).push(property);
    }
    this.openWorldProperties =
      settings.propertyConfigurations.length === 0 ||
      Boolean(settings.openWorldProperties);
  }

  async classTree(): Promise<ClassModel[]> {
    const { defaultPrefix, schemaLabelProperty, classTreeQuery } =
      this.settings;
    if (!classTreeQuery) {
      return [];
    }

    const query =
      defaultPrefix +
      resolveTemplate(classTreeQuery, {
        schemaLabelProperty,
      });
    const result = await this.executeSparqlQuery<ClassBinding>(query);
    const classTree = getClassTree(result);

    if (this.options.prepareLabels) {
      await attachLabels(
        flattenClassTree(classTree),
        this.options.prepareLabels
      );
    }

    return classTree;
  }

  async propertyInfo(params: {
    propertyIds: PropertyTypeIri[];
  }): Promise<Dictionary<PropertyModel>> {
    const { defaultPrefix, schemaLabelProperty, propertyInfoQuery } =
      this.settings;

    let properties: Dictionary<PropertyModel>;
    if (propertyInfoQuery) {
      const ids = params.propertyIds
        .map(escapeIri)
        .map((id) => ` ( ${id} )`)
        .join(" ");
      const query =
        defaultPrefix +
        resolveTemplate(propertyInfoQuery, {
          ids,
          schemaLabelProperty,
        });
      const result = await this.executeSparqlQuery<PropertyBinding>(query);
      properties = getPropertyInfo(result);
    } else {
      properties = {};
      for (const id of params.propertyIds) {
        properties[id] = { id, label: { values: [] } };
      }
    }

    if (this.options.prepareLabels) {
      await attachLabels(objectValues(properties), this.options.prepareLabels);
    }

    return properties;
  }

  async classInfo(params: {
    classIds: ElementTypeIri[];
  }): Promise<ClassModel[]> {
    const { defaultPrefix, schemaLabelProperty, classInfoQuery } =
      this.settings;

    let classes: ClassModel[];
    if (classInfoQuery) {
      const ids = params.classIds
        .map(escapeIri)
        .map((id) => ` ( ${id} )`)
        .join(" ");
      const query =
        defaultPrefix +
        resolveTemplate(classInfoQuery, {
          ids,
          schemaLabelProperty,
        });
      const result = await this.executeSparqlQuery<ClassBinding>(query);
      classes = getClassInfo(result);
    } else {
      classes = params.classIds.map(
        (id): ClassModel => ({ id, label: { values: [] }, children: [] })
      );
    }

    if (this.options.prepareLabels) {
      await attachLabels(classes, this.options.prepareLabels);
    }

    return classes;
  }

  async linkTypesInfo(params: {
    linkTypeIds: LinkTypeIri[];
  }): Promise<LinkType[]> {
    const { defaultPrefix, schemaLabelProperty, linkTypesInfoQuery } =
      this.settings;

    let linkTypes: LinkType[];
    if (linkTypesInfoQuery) {
      const ids = params.linkTypeIds
        .map(escapeIri)
        .map((id) => ` ( ${id} )`)
        .join(" ");
      const query =
        defaultPrefix +
        resolveTemplate(linkTypesInfoQuery, {
          ids,
          schemaLabelProperty,
        });
      const result = await this.executeSparqlQuery<LinkTypeBinding>(query);
      linkTypes = getLinkTypes(result);
    } else {
      linkTypes = params.linkTypeIds.map(
        (id): LinkType => ({ id, label: { values: [] } })
      );
    }

    if (this.options.prepareLabels) {
      await attachLabels(linkTypes, this.options.prepareLabels);
    }

    return linkTypes;
  }

  async linkTypes(): Promise<LinkType[]> {
    const {
      defaultPrefix,
      schemaLabelProperty,
      linkTypesQuery,
      linkTypesPattern,
    } = this.settings;
    if (!linkTypesQuery) {
      return [];
    }

    const query =
      defaultPrefix +
      resolveTemplate(linkTypesQuery, {
        linkTypesPattern,
        schemaLabelProperty,
      });
    const result = await this.executeSparqlQuery<LinkTypeBinding>(query);
    const linkTypes = getLinkTypes(result);

    if (this.options.prepareLabels) {
      await attachLabels(linkTypes, this.options.prepareLabels);
    }

    return linkTypes;
  }

  async elementInfo(params: {
    elementIds: ElementIri[];
  }): Promise<Dictionary<ElementModel>> {
    const nonBlankResources = params.elementIds.filter(
      (id) => !BlankNodes.isEncodedBlank(id)
    );
    const blankNodeResponse = this.options.acceptBlankNodes
      ? BlankNodes.elementInfo(params.elementIds)
      : undefined;

    let triples: Triple[];
    if (nonBlankResources.length > 0) {
      const ids = nonBlankResources
        .map(escapeIri)
        .map((id) => ` (${id})`)
        .join(" ");
      const { defaultPrefix, dataLabelProperty, elementInfoQuery } =
        this.settings;
      const query =
        defaultPrefix +
        resolveTemplate(elementInfoQuery, {
          ids,
          dataLabelProperty,
          propertyConfigurations: this.formatPropertyInfo(),
        });
      triples = await this.executeSparqlConstruct(query);
    } else {
      triples = [];
    }

    const types = this.queryManyElementTypes(
      this.settings.propertyConfigurations.length > 0 ? params.elementIds : []
    );

    const bindings = triplesToElementBinding(triples);
    const bindingsWithBlanks = prependAdditionalBindings(
      bindings,
      blankNodeResponse
    );
    const elementModels = getElementsInfo(
      bindingsWithBlanks,
      await types,
      this.propertyByPredicate,
      this.openWorldProperties
    );

    if (this.options.prepareLabels) {
      await attachLabels(
        objectValues(elementModels),
        this.options.prepareLabels
      );
    }

    if (this.options.prepareImages) {
      await prepareElementImages(this.options.prepareImages, elementModels);
    } else if (
      this.options.imagePropertyUris &&
      this.options.imagePropertyUris.length
    ) {
      await this.attachImages(elementModels, this.options.imagePropertyUris);
    }

    return elementModels;
  }

  private async attachImages(
    elementsInfo: Dictionary<ElementModel>,
    types: string[]
  ): Promise<void> {
    const ids = Object.keys(elementsInfo)
      .filter((id) => !BlankNodes.isEncodedBlank(id))
      .map(escapeIri)
      .map((id) => ` ( ${id} )`)
      .join(" ");
    const typesString = types
      .map(escapeIri)
      .map((id) => ` ( ${id} )`)
      .join(" ");

    const query =
      this.settings.defaultPrefix +
      `
            SELECT ?inst ?linkType ?image
            WHERE {{
                VALUES (?inst) {${ids}}
                VALUES (?linkType) {${typesString}}
                ${this.settings.imageQueryPattern}
            }}
        `;
    try {
      const bindings = await this.executeSparqlQuery<ElementImageBinding>(
        query
      );
      enrichElementsWithImages(bindings, elementsInfo);
    } catch (err) {
      console.error(err);
    }
  }

  async linksInfo(params: {
    elementIds: ElementIri[];
    linkTypeIds: LinkTypeIri[];
  }): Promise<LinkModel[]> {
    const nonBlankResources = params.elementIds.filter(
      (id) => !BlankNodes.isEncodedBlank(id)
    );
    const blankNodeResponse = this.options.acceptBlankNodes
      ? BlankNodes.linksInfo(params.elementIds)
      : undefined;

    const linkConfigurations = this.formatLinkLinks();

    let bindings: Promise<SparqlResponse<LinkBinding>>;
    let types: Promise<Map<ElementIri, Set<ElementTypeIri>>>;
    if (nonBlankResources.length > 0) {
      const ids = nonBlankResources
        .map(escapeIri)
        .map((id) => ` ( ${id} )`)
        .join(" ");
      const linksInfoQuery =
        this.settings.defaultPrefix +
        resolveTemplate(this.settings.linksInfoQuery, {
          ids,
          linkConfigurations,
        });
      bindings = this.executeSparqlQuery<LinkBinding>(linksInfoQuery);
      types = this.queryManyElementTypes(params.elementIds);
    } else {
      bindings = Promise.resolve({
        head: { vars: [] },
        results: { bindings: [] },
      });
      types = this.queryManyElementTypes([]);
    }

    const bindingsWithBlanks = prependAdditionalBindings(
      await bindings,
      blankNodeResponse
    );
    const linksInfo = getLinksInfo(
      bindingsWithBlanks,
      await types,
      this.linkByPredicate,
      this.openWorldLinks
    );
    return linksInfo;
  }

  async linkTypesOf(params: { elementId: ElementIri }): Promise<LinkCount[]> {
    if (
      this.options.acceptBlankNodes &&
      BlankNodes.isEncodedBlank(params.elementId)
    ) {
      return Promise.resolve(getLinksTypesOf(BlankNodes.linkTypesOf(params)));
    }
    const {
      defaultPrefix,
      linkTypesOfQuery,
      linkTypesStatisticsQuery,
      filterTypePattern,
    } = this.settings;

    const elementIri = escapeIri(params.elementId);
    const forAll = this.formatLinkUnion(
      params.elementId,
      undefined,
      undefined,
      "?outObject",
      "?inObject",
      false
    );
    if (forAll.usePredicatePart) {
      forAll.unionParts.push(`{ ${elementIri} ?link ?outObject }`);
      forAll.unionParts.push(`{ ?inObject ?link ${elementIri} }`);
    }

    const query =
      defaultPrefix +
      resolveTemplate(linkTypesOfQuery, {
        elementIri,
        linkConfigurations: forAll.unionParts.join("\nUNION\n"),
      });

    const linkTypeBindings = await this.executeSparqlQuery<LinkTypeBinding>(
      query
    );
    const linkTypeIds = getLinksTypeIds(
      linkTypeBindings,
      this.linkByPredicate,
      this.openWorldLinks
    );

    const navigateElementFilterOut = this.options.acceptBlankNodes
      ? `FILTER (IsIri(?outObject) || IsBlank(?outObject))`
      : `FILTER IsIri(?outObject)`;
    const navigateElementFilterIn = this.options.acceptBlankNodes
      ? `FILTER (IsIri(?inObject) || IsBlank(?inObject))`
      : `FILTER IsIri(?inObject)`;

    const foundLinkStats: LinkCount[] = [];
    await Promise.all(
      linkTypeIds.map(async (linkId) => {
        const linkConfig = this.linkById.get(linkId);
        let linkConfigurationOut: string;
        let linkConfigurationIn: string;

        if (!linkConfig || isDirectLink(linkConfig)) {
          const predicate = escapeIri(
            linkConfig && isDirectLink(linkConfig) ? linkConfig.path : linkId
          );
          linkConfigurationOut = `${elementIri} ${predicate} ?outObject`;
          linkConfigurationIn = `?inObject ${predicate} ${elementIri}`;
        } else {
          linkConfigurationOut = this.formatLinkPath(
            linkConfig.path,
            elementIri,
            "?outObject"
          );
          linkConfigurationIn = this.formatLinkPath(
            linkConfig.path,
            "?inObject",
            elementIri
          );
        }

        if (linkConfig && linkConfig.domain?.length > 0) {
          const commaSeparatedDomains = linkConfig.domain
            .map(escapeIri)
            .join(", ");
          const restrictionOut = filterTypePattern.replace(
            /[?$]inst\b/g,
            elementIri
          );
          const restrictionIn = filterTypePattern.replace(
            /[?$]inst\b/g,
            "?inObject"
          );
          linkConfigurationOut += ` { ${restrictionOut} FILTER(?class IN (${commaSeparatedDomains})) }`;
          linkConfigurationIn += ` { ${restrictionIn} FILTER(?class IN (${commaSeparatedDomains})) }`;
        }

        const statsQuery =
          defaultPrefix +
          resolveTemplate(linkTypesStatisticsQuery, {
            linkId: escapeIri(linkId),
            elementIri,
            linkConfigurationOut,
            linkConfigurationIn,
            navigateElementFilterOut,
            navigateElementFilterIn,
          });

        const bindings = await this.executeSparqlQuery<LinkCountBinding>(
          statsQuery
        );
        const linkStats = getLinkStatistics(bindings);
        if (linkStats) {
          foundLinkStats.push(linkStats);
        }
      })
    );
    return foundLinkStats;
  }

  linkElements(params: LinkElementsParams): Promise<Dictionary<ElementModel>> {
    // for sparql we have rich filtering features and we just reuse filter.
    return this.filter({
      refElementId: params.elementId,
      refElementLinkId: params.linkId,
      linkDirection: params.direction,
      limit: params.limit,
      offset: params.offset,
      languageCode: "",
    });
  }

  async filter(baseParams: FilterParams): Promise<Dictionary<ElementModel>> {
    const params: FilterParams = { ...baseParams };
    if (params.limit === undefined) {
      params.limit = 100;
    }

    // query types to match link configuration domains
    const types = this.querySingleElementTypes(
      params.refElementId && this.settings.linkConfigurations.length > 0
        ? params.refElementId
        : undefined
    );

    const blankFiltration = this.options.acceptBlankNodes
      ? BlankNodes.filter(params)
      : undefined;
    if (blankFiltration && blankFiltration.results.bindings.length > 0) {
      return getFilteredData(
        blankFiltration,
        await types,
        this.linkByPredicate,
        this.openWorldLinks
      );
    }

    const filterQuery = this.createFilterQuery(params);
    const bindings = await this.executeSparqlQuery<
      ElementBinding & FilterBinding
    >(filterQuery);

    let bindingsWithBlanks: SparqlResponse<ElementBinding & FilterBinding>;
    if (this.options.acceptBlankNodes) {
      bindingsWithBlanks = await BlankNodes.updateFilterResults(
        bindings,
        (blankQuery) => this.executeSparqlQuery<BlankBinding>(blankQuery),
        this.settings
      );
    } else {
      bindingsWithBlanks = bindings as SparqlResponse<
        ElementBinding & FilterBinding
      >;
    }

    const elementModels = getFilteredData(
      bindingsWithBlanks,
      await types,
      this.linkByPredicate,
      this.openWorldLinks
    );

    if (this.options.prepareLabels) {
      await attachLabels(
        objectValues(elementModels),
        this.options.prepareLabels
      );
    }

    return elementModels;
  }

  private createFilterQuery(params: FilterParams): string {
    if (!params.refElementId && params.refElementLinkId) {
      throw new Error(
        "Cannot execute refElementLink filter without refElement"
      );
    }

    let outerProjection = "?inst ?class ?label ?blankType";
    let innerProjection = "?inst";

    let refQueryPart = "";
    let refQueryTypes = "";
    if (params.refElementId) {
      outerProjection += " ?link ?direction";
      innerProjection += " ?link ?direction";
      refQueryPart = this.createRefQueryPart({
        elementId: params.refElementId,
        linkId: params.refElementLinkId,
        direction: params.linkDirection,
      });

      if (this.settings.linkConfigurations.length > 0) {
        outerProjection += " ?classAll";
        refQueryTypes = this.settings.filterTypePattern.replace(
          /[?$]class\b/g,
          "?classAll"
        );
      }
    }

    let elementTypePart = "";
    if (params.elementTypeId) {
      const elementTypeIri = escapeIri(params.elementTypeId);
      elementTypePart = this.settings.filterTypePattern.replace(
        /[?$]class\b/g,
        elementTypeIri
      );
      elementTypePart += " .";
    }

    const { defaultPrefix, fullTextSearch, dataLabelProperty } = this.settings;

    let textSearchPart = "";
    if (params.text) {
      innerProjection += " ?score";
      if (this.settings.fullTextSearch.extractLabel) {
        textSearchPart += sparqlExtractLabel("?inst", "?extractedLabel");
      }
      textSearchPart = resolveTemplate(fullTextSearch.queryPattern, {
        text: params.text,
        dataLabelProperty,
      });
    }

    const blankNodes = this.options.acceptBlankNodes;
    if (blankNodes) {
      outerProjection += ` ${BlankNodes.BLANK_NODE_QUERY_PARAMETERS}`;
    }

    return `${defaultPrefix}
            ${fullTextSearch.prefix}

        SELECT ${outerProjection}
        WHERE {
            {
                SELECT DISTINCT ${innerProjection} WHERE {
                    ${fullTextSearch.elementFirst ? "" : textSearchPart}
                    ${elementTypePart}
                    ${refQueryPart}
                    ${fullTextSearch.elementFirst ? textSearchPart : ""}
                    ${this.settings.filterAdditionalRestriction}
                }
                ${textSearchPart ? "ORDER BY DESC(?score)" : ""}
                LIMIT ${params.limit} OFFSET ${params.offset}
            }
            ${refQueryTypes}
            ${resolveTemplate(this.settings.filterElementInfoPattern, {
              dataLabelProperty,
            })}
            ${blankNodes ? BlankNodes.BLANK_NODE_QUERY : ""}
        } ${textSearchPart ? "ORDER BY DESC(?score)" : ""}
        `;
  }

  executeSparqlQuery<Binding>(query: string) {
    const method = this.options.queryMethod
      ? this.options.queryMethod
      : SparqlQueryMethod.GET;
    return executeSparqlQuery<Binding>(
      this.options.endpointUrl,
      query,
      method,
      this.options.queryFunction
    );
  }

  executeSparqlConstruct(query: string): Promise<Triple[]> {
    const method = this.options.queryMethod
      ? this.options.queryMethod
      : SparqlQueryMethod.GET;
    return executeSparqlConstruct(
      this.options.endpointUrl,
      query,
      method,
      this.options.queryFunction
    );
  }

  protected createRefQueryPart(params: {
    elementId: ElementIri;
    linkId?: LinkTypeIri;
    direction?: "in" | "out";
  }) {
    const { elementId, linkId, direction } = params;

    const { unionParts, usePredicatePart } = this.formatLinkUnion(
      elementId,
      linkId,
      direction,
      "?inst",
      "?inst",
      true
    );

    if (usePredicatePart) {
      const refElementIRI = escapeIri(params.elementId);
      let refLinkType: string | undefined;
      if (linkId) {
        const link = this.linkById.get(linkId);
        refLinkType =
          link && isDirectLink(link) ? escapeIri(link.path) : escapeIri(linkId);
      }

      const linkPattern = refLinkType || "?link";
      const bindType = refLinkType ? `BIND(${refLinkType} as ?link)` : "";
      // FILTER ISIRI is used to prevent blank nodes appearing in results
      const blankFilter = this.options.acceptBlankNodes
        ? "FILTER(isIri(?inst) || isBlank(?inst))"
        : "FILTER(isIri(?inst))";

      if (!direction || direction === "out") {
        unionParts.push(
          `{ ${refElementIRI} ${linkPattern} ?inst BIND("out" as ?direction) ${bindType} ${blankFilter} }`
        );
      }
      if (!direction || direction === "in") {
        unionParts.push(
          `{ ?inst ${linkPattern} ${refElementIRI} BIND("in" as ?direction) ${bindType} ${blankFilter} }`
        );
      }
    }

    let resultPattern =
      unionParts.length === 0 ? "FILTER(false)" : unionParts.join(`\nUNION\n`);

    const useAllLinksPattern =
      !linkId && this.settings.filterRefElementLinkPattern.length > 0;
    if (useAllLinksPattern) {
      resultPattern += `\n${this.settings.filterRefElementLinkPattern}`;
    }

    return resultPattern;
  }

  private formatLinkUnion(
    refElementIri: ElementIri,
    linkIri: LinkTypeIri | undefined,
    direction: "in" | "out" | undefined,
    outElementVar: string,
    inElementVar: string,
    bindDirection: boolean
  ) {
    const { linkConfigurations } = this.settings;
    const fixedIri = escapeIri(refElementIri);

    const unionParts: string[] = [];
    let hasDirectLink = false;

    for (const link of linkConfigurations) {
      if (linkIri && link.id !== linkIri) {
        continue;
      }
      if (isDirectLink(link)) {
        hasDirectLink = true;
      } else {
        const linkType = escapeIri(link.id);
        if (!direction || direction === "out") {
          const path = this.formatLinkPath(link.path, fixedIri, outElementVar);
          const boundedDirection = bindDirection
            ? `BIND("out" as ?direction) `
            : "";
          unionParts.push(
            `{ ${path} BIND(${linkType} as ?link) ${boundedDirection}}`
          );
        }
        if (!direction || direction === "in") {
          const path = this.formatLinkPath(link.path, inElementVar, fixedIri);
          const boundedDirection = bindDirection
            ? `BIND("in" as ?direction) `
            : "";
          unionParts.push(
            `{ ${path} BIND(${linkType} as ?link) ${boundedDirection}}`
          );
        }
      }
    }

    const usePredicatePart = this.openWorldLinks || hasDirectLink;
    return { unionParts, usePredicatePart };
  }

  formatLinkLinks(): string {
    const unionParts: string[] = [];
    let hasDirectLink = false;
    for (const link of this.settings.linkConfigurations) {
      if (isDirectLink(link)) {
        hasDirectLink = true;
      } else {
        const linkType = escapeIri(link.id);
        unionParts.push(
          `{ ${this.formatLinkPath(
            link.path,
            "?source",
            "?target"
          )} BIND(${linkType} as ?type) }`
        );
      }
    }

    const usePredicatePart = this.openWorldLinks || hasDirectLink;
    if (usePredicatePart) {
      unionParts.push(`{ ?source ?type ?target }`);
    }

    return unionParts.join("\nUNION\n");
  }

  formatLinkPath(path: string, source: string, target: string): string {
    return path
      .replace(/[?$]source\b/g, source)
      .replace(/[?$]target\b/g, target);
  }

  formatPropertyInfo(): string {
    const unionParts: string[] = [];
    let hasDirectProperty = false;
    for (const property of this.settings.propertyConfigurations) {
      if (isDirectProperty(property)) {
        hasDirectProperty = true;
      } else {
        const propType = escapeIri(property.id);
        const formatted = this.formatPropertyPath(
          property.path,
          "?inst",
          "?propValue"
        );
        unionParts.push(`{ ${formatted} BIND(${propType} as ?propType) }`);
      }
    }

    const usePredicatePart = this.openWorldProperties || hasDirectProperty;
    if (usePredicatePart) {
      unionParts.push(`{ ?inst ?propType ?propValue }`);
    }

    return unionParts.join("\nUNION\n");
  }

  formatPropertyPath(path: string, subject: string, value: string): string {
    return path.replace(/[?$]inst\b/g, subject).replace(/[?$]value\b/g, value);
  }

  private async querySingleElementTypes(
    element: ElementIri | undefined
  ): Promise<Set<ElementTypeIri> | undefined> {
    const types = await this.queryManyElementTypes(element ? [element] : []);
    return types.get(element);
  }

  private async queryManyElementTypes(
    elements: readonly ElementIri[]
  ): Promise<Map<ElementIri, Set<ElementTypeIri>>> {
    if (elements.length === 0) {
      return new Map();
    }
    const { filterTypePattern } = this.settings;
    const ids = elements
      .filter((iri) => !BlankNodes.isEncodedBlank(iri))
      .map((iri) => `(${escapeIri(iri)})`)
      .join(" ");

    const queryTemplate =
      this.settings.defaultPrefix +
      `SELECT ?inst ?class { VALUES(?inst) { \${ids} } \${filterTypePattern} }`;
    const query = resolveTemplate(queryTemplate, { ids, filterTypePattern });
    let response = await this.executeSparqlQuery<ElementTypeBinding>(query);

    if (
      this.options.acceptBlankNodes &&
      elements.find(BlankNodes.isEncodedBlank)
    ) {
      const blankResponse = BlankNodes.getElementTypes(elements);
      response = prependAdditionalBindings(response, blankResponse);
    }

    return getElementTypes(response);
  }
}

interface LabeledItem {
  id: string;
  label: { values: LocalizedString[] };
}

async function attachLabels(
  items: readonly LabeledItem[],
  fetchLabels: SparqlDataProviderOptions["prepareLabels"]
): Promise<void> {
  const resources = new Set<string>();
  for (const item of items) {
    if (BlankNodes.isEncodedBlank(item.id)) {
      continue;
    }
    resources.add(item.id);
  }
  const labels = await fetchLabels(resources);
  for (const item of items) {
    if (labels.has(item.id)) {
      item.label = { values: labels.get(item.id) };
    }
  }
}

function prepareElementImages(
  fetchImages: SparqlDataProviderOptions["prepareImages"],
  elementsInfo: Dictionary<ElementModel>
): Promise<void> {
  return fetchImages(elementsInfo).then((images) => {
    for (const iri in images) {
      if (
        Object.prototype.hasOwnProperty.call(images, iri) &&
        elementsInfo[iri]
      ) {
        elementsInfo[iri].image = images[iri];
      }
    }
  });
}

function resolveTemplate(template: string, values: Dictionary<string>) {
  let result = template;
  for (const replaceKey in values) {
    if (!Object.prototype.hasOwnProperty.call(values, replaceKey)) {
      continue;
    }
    const replaceValue = values[replaceKey];
    if (replaceValue) {
      result = result.replace(
        new RegExp("\\${" + replaceKey + "}", "g"),
        replaceValue
      );
    }
  }
  return result;
}

export function executeSparqlQuery<Binding>(
  endpoint: string,
  query: string,
  method: SparqlQueryMethod,
  queryFunction: QueryFunction
): Promise<SparqlResponse<Binding>> {
  let internalQuery: Promise<Response>;
  if (method === SparqlQueryMethod.GET) {
    internalQuery = queryFunction({
      url: appendQueryParams(endpoint, { query }),
      headers: {
        Accept: "application/sparql-results+json",
      },
      method: "GET",
    });
  } else {
    internalQuery = queryFunction({
      url: endpoint,
      body: query,
      headers: {
        Accept: "application/sparql-results+json",
        "Content-Type": "application/sparql-query; charset=UTF-8",
      },
      method: "POST",
    });
  }
  return internalQuery.then((response): Promise<SparqlResponse<Binding>> => {
    if (response.ok) {
      return response.json();
    } else {
      const error = new Error(response.statusText);
      (error as any).response = response;
      throw error;
    }
  });
}

export function executeSparqlConstruct(
  endpoint: string,
  query: string,
  method: SparqlQueryMethod,
  queryFunction: QueryFunction
): Promise<Triple[]> {
  let internalQuery: Promise<Response>;
  if (method === SparqlQueryMethod.GET) {
    internalQuery = queryFunction({
      url: appendQueryParams(endpoint, { query }),
      headers: {
        Accept: "text/turtle",
      },
      method: "GET",
    });
  } else {
    internalQuery = queryFunction({
      url: endpoint,
      body: query,
      headers: {
        Accept: "text/turtle",
        "Content-Type": "application/sparql-query; charset=UTF-8",
      },
      method: "POST",
    });
  }
  return internalQuery
    .then((response) => {
      if (response.ok) {
        return response.text();
      } else {
        const error = new Error(response.statusText);
        (error as any).response = response;
        throw error;
      }
    })
    .then(parseTurtleText);
}

function appendQueryParams(
  endpoint: string,
  queryParams: Record<string, string> = {}
) {
  const initialSeparator = endpoint.indexOf("?") < 0 ? "?" : "&";
  const additionalParams =
    initialSeparator +
    Object.keys(queryParams)
      .map((key) => `${key}=${encodeURIComponent(queryParams[key])}`)
      .join("&");
  return endpoint + additionalParams;
}

function queryInternal(params: {
  url: string;
  body?: string;
  headers: any;
  method: string;
}) {
  return fetch(params.url, {
    method: params.method,
    body: params.body,
    credentials: "same-origin",
    mode: "cors",
    cache: "default",
    headers: params.headers,
  });
}

function sparqlExtractLabel(subject: string, label: string): string {
  return `
        BIND ( str( ${subject} ) as ?uriStr)
        BIND ( strafter(?uriStr, "#") as ?label3)
        BIND ( strafter(strafter(?uriStr, "//"), "/") as ?label6)
        BIND ( strafter(?label6, "/") as ?label5)
        BIND ( strafter(?label5, "/") as ?label4)
        BIND (if (?label3 != "", ?label3,
            if (?label4 != "", ?label4,
            if (?label5 != "", ?label5, ?label6))) as ${label})
    `;
}

function escapeIri(iri: string) {
  if (typeof iri !== "string") {
    throw new Error(`Cannot escape IRI of type "${typeof iri}"`);
  }
  return `<${iri}>`;
}