trifid-handler-fetch/lib/query.js

Fetch handler for Trifid

// @ts-check

/**
 * Perform a SPARQL query using Oxigraph.
 *
 * @param {import('oxigraph').Store} store Oxigraph store
 * @param {string} query The query to perform
 * @returns {Promise<{
 *   response: string;
 *   contentType: 'application/sparql-results+json' | 'application/n-quads' | 'text/plain' | string & Record<never, never>;
 * }>} SPARQL response.
 */
export const performOxigraphQuery = async (store, query) => {
  let contentType = 'text/plain'
  let results = 'Something went wrong.'

  const queryUpper = query.toUpperCase()
  const isConstructQuery = queryUpper.includes('CONSTRUCT') || queryUpper.includes('DESCRIBE')

  try {
    if (isConstructQuery) {
      const queryResults = store.query(query, {
        use_default_graph_as_union: true,
      })
      if (Array.isArray(queryResults)) {
        contentType = 'application/n-quads'
        results = queryResults.map((quad) => quad.toString()).join('.\n')
        if (results) {
          results = `${results}.\n`
        }
      } else {
        contentType = 'text/plain'
        results = 'Something went wrong while getting the query results (expected array).'
      }
    } else {
      const queryResults = store.query(query, {
        use_default_graph_as_union: true,
        results_format: 'json',
      })
      if (typeof queryResults === 'string') {
        contentType = 'application/sparql-results+json'
        results = queryResults
      } else {
        contentType = 'text/plain'
        results = 'Something went wrong while getting the query results (expected string).'
      }
    }
  } catch (error) {
    contentType = 'text/plain'
    if (error instanceof Error) {
      results = error.message
    } else {
      results = 'An error occurred while executing the query.'
    }
  }

  return {
    response: results,
    contentType,
  }
}