@trailstash/ultra/lib/queryProviders/sparql.js

A web based tool for making MapLibre GL maps with data from sources such as Overpass, GeoJSON, GPX, KML, TCX, etc

import { layers } from "./osm.js";

import sparql2geojson from "../sparql2geojson.js";

export const popupTemplate = `
  <h3>columns</h3>
  {%- for prop in properties %}
    {%- if prop[0] startswith "https://" %}
      <code>{{ prop[0] }} = <a href="{{ prop[1] }}" target="_blank">{{ prop[1] }}</a></code>
    {%- else %}
      <code>{{ prop[0] }} = {{ prop[1] }}</code>
    {%- endif %}
    <br>
  {%- endfor %}
`;

const SOPHOX = "https://sophox.org/sparql";
const QLEVER_ROOT = "https://qlever.cs.uni-freiburg.de/api/";

const OSM_SERVERS = new Set([
  new URL("osm-planet", QLEVER_ROOT).toString(),
  SOPHOX,
]);

const source = async function (query, controller, { server, bounds }) {
  if (!server) {
    throw new Error("No SPARQL server endpoint specified");
  }
  const resp = await fetch(server, {
    method: "POST",
    body: new URLSearchParams([["query", query]]),
    signal: controller.signal,
    headers: {
      "Content-Type": "application/x-www-form-urlencoded",
      Accept: "application/sparql-results+json",
    },
  });
  if (!resp.ok) {
    throw new Error(`SPARQL API returned ${resp.status}: ${await resp.text()}`);
  }
  const data = sparql2geojson(await resp.json());
  let attribution = "";
  if (OSM_SERVERS.has(server)) {
    attribution =
      '\u003Ca href="https://www.openstreetmap.org/copyright" target="_blank"\u003E© OpenStreetMap contributors\u003C/a\u003E';
  }
  return {
    type: "geojson",
    data,
    attribution,
    generateId: true,
  };
};

export const sparql = {
  source,
  layers,
  popupTemplate,
};
export default sparql;

export const sophox = {
  ...sparql,
  source: (query, controller, { server, bounds }) =>
    source(query, controller, { server: server || SOPHOX, bounds }),
};

export const qlever = {
  ...sparql,
  source: (query, controller, { server, bounds }) =>
    source(query, controller, {
      server: new URL(server || "osm-planet", QLEVER_ROOT).toString(),
      bounds,
    }),
};