HttpTriplestoreConnector.scala

/*
 * Copyright © 2021 - 2022 Swiss National Data and Service Center for the Humanities and/or DaSCH Service Platform contributors.
 * SPDX-License-Identifier: Apache-2.0
 */

package org.knora.webapi.store.triplestore.http

import akka.actor.Actor
import akka.actor.ActorLogging
import akka.actor.ActorSystem
import akka.actor.Status
import akka.event.LoggingAdapter
import org.apache.commons.lang3.StringUtils
import org.apache.http.Consts
import org.apache.http.HttpEntity
import org.apache.http.HttpHost
import org.apache.http.HttpRequest
import org.apache.http.NameValuePair
import org.apache.http.auth.AuthScope
import org.apache.http.auth.UsernamePasswordCredentials
import org.apache.http.client.AuthCache
import org.apache.http.client.config.RequestConfig
import org.apache.http.client.entity.UrlEncodedFormEntity
import org.apache.http.client.methods.CloseableHttpResponse
import org.apache.http.client.methods.HttpGet
import org.apache.http.client.methods.HttpPost
import org.apache.http.client.methods.HttpPut
import org.apache.http.client.protocol.HttpClientContext
import org.apache.http.client.utils.URIBuilder
import org.apache.http.entity.ContentType
import org.apache.http.entity.FileEntity
import org.apache.http.entity.StringEntity
import org.apache.http.impl.auth.BasicScheme
import org.apache.http.impl.client.BasicAuthCache
import org.apache.http.impl.client.BasicCredentialsProvider
import org.apache.http.impl.client.CloseableHttpClient
import org.apache.http.impl.client.HttpClients
import org.apache.http.message.BasicNameValuePair
import org.apache.http.util.EntityUtils
import org.knora.webapi._
import org.knora.webapi.exceptions._
import org.knora.webapi.feature.FeatureFactoryConfig
import org.knora.webapi.instrumentation.InstrumentationSupport
import org.knora.webapi.messages.store.triplestoremessages.SparqlResultProtocol._
import org.knora.webapi.messages.store.triplestoremessages._
import org.knora.webapi.messages.util.FakeTriplestore
import org.knora.webapi.messages.util.rdf._
import org.knora.webapi.settings.KnoraDispatchers
import org.knora.webapi.settings.KnoraSettings
import org.knora.webapi.store.triplestore.RdfDataObjectFactory
import org.knora.webapi.util.ActorUtil._
import org.knora.webapi.util.FileUtil
import spray.json._

import java.io.BufferedInputStream
import java.net.URI
import java.nio.charset.StandardCharsets
import java.nio.file.Files
import java.nio.file.Path
import java.nio.file.Paths
import java.nio.file.StandardCopyOption
import java.util
import scala.collection.mutable
import scala.concurrent.ExecutionContext
import scala.jdk.CollectionConverters._
import scala.util.Failure
import scala.util.Success
import scala.util.Try

/**
 * Submits SPARQL queries and updates to a triplestore over HTTP. Supports different triplestores, which can be configured in
 * `application.conf`.
 */
class HttpTriplestoreConnector extends Actor with ActorLogging with InstrumentationSupport {

  // MIME type constants.
  private val mimeTypeApplicationJson = "application/json"
  private val mimeTypeApplicationSparqlResultsJson = "application/sparql-results+json"
  private val mimeTypeTextTurtle = "text/turtle"
  private val mimeTypeApplicationSparqlUpdate = "application/sparql-update"
  private val mimeTypeApplicationNQuads = "application/n-quads"

  private implicit val system: ActorSystem = context.system
  private val settings = KnoraSettings(system)
  implicit val executionContext: ExecutionContext = system.dispatchers.lookup(KnoraDispatchers.KnoraBlockingDispatcher)
  override val log: LoggingAdapter = akka.event.Logging(system, this.getClass.getName)

  private val targetHost: HttpHost = new HttpHost(settings.triplestoreHost, settings.triplestorePort, "http")

  private val credsProvider: BasicCredentialsProvider = new BasicCredentialsProvider
  credsProvider.setCredentials(
    new AuthScope(targetHost.getHostName, targetHost.getPort),
    new UsernamePasswordCredentials(settings.triplestoreUsername, settings.triplestorePassword)
  )

  // Reading data should be quick, except when it is not ;-)
  private val queryTimeoutMillis = settings.triplestoreQueryTimeout.toMillis.toInt

  private val queryRequestConfig = RequestConfig
    .custom()
    .setConnectTimeout(queryTimeoutMillis)
    .setConnectionRequestTimeout(queryTimeoutMillis)
    .setSocketTimeout(queryTimeoutMillis)
    .build

  private val queryHttpClient: CloseableHttpClient = HttpClients.custom
    .setDefaultCredentialsProvider(credsProvider)
    .setDefaultRequestConfig(queryRequestConfig)
    .build

  // Some updates could take a while.
  private val updateTimeoutMillis = settings.triplestoreUpdateTimeout.toMillis.toInt

  private val updateTimeoutConfig = RequestConfig
    .custom()
    .setConnectTimeout(updateTimeoutMillis)
    .setConnectionRequestTimeout(updateTimeoutMillis)
    .setSocketTimeout(updateTimeoutMillis)
    .build

  private val updateHttpClient: CloseableHttpClient = HttpClients.custom
    .setDefaultCredentialsProvider(credsProvider)
    .setDefaultRequestConfig(updateTimeoutConfig)
    .build

  // For updates that could take a very long time.
  private val longTimeoutMillis = settings.triplestoreUpdateTimeout.toMillis.toInt * 10

  private val longRequestConfig = RequestConfig
    .custom()
    .setConnectTimeout(longTimeoutMillis)
    .setConnectionRequestTimeout(longTimeoutMillis)
    .setSocketTimeout(longTimeoutMillis)
    .build

  private val longRequestClient: CloseableHttpClient = HttpClients.custom
    .setDefaultCredentialsProvider(credsProvider)
    .setDefaultRequestConfig(longRequestConfig)
    .build

  private val queryPath: String = s"/${settings.triplestoreDatabaseName}/query"

  private val sparqlUpdatePath: String = s"/${settings.triplestoreDatabaseName}/update"

  private val checkRepositoryPath: String = "/$/server"

  private val graphPath: String = s"/${settings.triplestoreDatabaseName}/get"

  private val repositoryDownloadPath = s"/${settings.triplestoreDatabaseName}"

  private val repositoryUploadPath = repositoryDownloadPath

  private val logDelimiter = "\n" + StringUtils.repeat('=', 80) + "\n"

  private val dataInsertPath = s"/${settings.triplestoreDatabaseName}/data"

  /**
   * Receives a message requesting a SPARQL select or update, and returns an appropriate response message or
   * [[Status.Failure]]. If a serious error occurs (i.e. an error that isn't the client's fault), this
   * method first returns `Failure` to the sender, then throws an exception.
   */
  def receive: PartialFunction[Any, Unit] = {
    case SparqlSelectRequest(sparql: String) => try2Message(sender(), sparqlHttpSelect(sparql), log)
    case sparqlConstructRequest: SparqlConstructRequest =>
      try2Message(sender(), sparqlHttpConstruct(sparqlConstructRequest), log)
    case sparqlExtendedConstructRequest: SparqlExtendedConstructRequest =>
      try2Message(sender(), sparqlHttpExtendedConstruct(sparqlExtendedConstructRequest), log)
    case SparqlConstructFileRequest(
          sparql: String,
          graphIri: IRI,
          outputFile: Path,
          outputFormat: QuadFormat,
          featureFactoryConfig: FeatureFactoryConfig
        ) =>
      try2Message(
        sender(),
        sparqlHttpConstructFile(sparql, graphIri, outputFile, outputFormat, featureFactoryConfig),
        log
      )
    case NamedGraphFileRequest(
          graphIri: IRI,
          outputFile: Path,
          outputFormat: QuadFormat,
          featureFactoryConfig: FeatureFactoryConfig
        ) =>
      try2Message(sender(), sparqlHttpGraphFile(graphIri, outputFile, outputFormat, featureFactoryConfig), log)
    case NamedGraphDataRequest(graphIri: IRI) => try2Message(sender(), sparqlHttpGraphData(graphIri), log)
    case SparqlUpdateRequest(sparql: String)  => try2Message(sender(), sparqlHttpUpdate(sparql), log)
    case SparqlAskRequest(sparql: String)     => try2Message(sender(), sparqlHttpAsk(sparql), log)
    case ResetRepositoryContent(rdfDataObjects: Seq[RdfDataObject], prependDefaults: Boolean) =>
      try2Message(sender(), resetTripleStoreContent(rdfDataObjects, prependDefaults), log)
    case DropAllTRepositoryContent() => try2Message(sender(), dropAllTriplestoreContent(), log)
    case InsertRepositoryContent(rdfDataObjects: Seq[RdfDataObject]) =>
      try2Message(sender(), insertDataIntoTriplestore(rdfDataObjects), log)
    case HelloTriplestore(msg: String) if msg == settings.triplestoreType => sender() ! HelloTriplestore(settings.triplestoreType)
    case CheckTriplestoreRequest()                               => try2Message(sender(), checkTriplestore(), log)
    case SearchIndexUpdateRequest(subjectIri: Option[String]) =>
      try2Message(sender(), Success(SparqlUpdateResponse()), log)
    case DownloadRepositoryRequest(outputFile: Path, featureFactoryConfig: FeatureFactoryConfig) =>
      try2Message(sender(), downloadRepository(outputFile, featureFactoryConfig), log)
    case UploadRepositoryRequest(inputFile: Path) => try2Message(sender(), uploadRepository(inputFile), log)
    case InsertGraphDataContentRequest(graphContent: String, graphName: String) =>
      try2Message(sender(), insertDataGraphRequest(graphContent, graphName), log)
    case SimulateTimeoutRequest() => try2Message(sender(), doSimulateTimeout(), log)
    case other =>
      sender() ! Status.Failure(
        UnexpectedMessageException(s"Unexpected message $other of type ${other.getClass.getCanonicalName}")
      )
  }

  /**
   * Simulates a read timeout.
   */
  private def doSimulateTimeout(): Try[SparqlSelectResult] = {
    val sparql = """SELECT ?foo WHERE {
                   |    BIND("foo" AS ?foo)
                   |}""".stripMargin

    sparqlHttpSelect(sparql = sparql, simulateTimeout = true)
  }

  /**
   * Given a SPARQL SELECT query string, runs the query, returning the result as a [[SparqlSelectResult]].
   *
   * @param sparql the SPARQL SELECT query string.
   * @param simulateTimeout if `true`, simulate a read timeout.
   * @return a [[SparqlSelectResult]].
   */
  private def sparqlHttpSelect(sparql: String, simulateTimeout: Boolean = false): Try[SparqlSelectResult] = {
    def parseJsonResponse(sparql: String, resultStr: String): Try[SparqlSelectResult] = {
      val parseTry = Try {
        resultStr.parseJson.convertTo[SparqlSelectResult]
      }

      parseTry match {
        case Success(parsed) => Success(parsed)
        case Failure(e) =>
          if (resultStr.contains("##  Query cancelled due to timeout during execution")) {
            log.error(e, "Triplestore timed out while sending a response, after sending statuscode 200.")
            Failure(
              TriplestoreTimeoutException(
                "Triplestore timed out while sending a response, after sending statuscode 200.",
                e,
                log
              )
            )
          } else {
            log.error(
              e,
              s"Couldn't parse response from triplestore:$logDelimiter$resultStr${logDelimiter}in response to SPARQL query:$logDelimiter$sparql"
            )
            Failure(TriplestoreResponseException("Couldn't parse Turtle from triplestore", e, log))
          }
      }
    }

    for {
      // Are we using the fake triplestore?
      resultStr <-
        if (settings.useFakeTriplestore) {
          // Yes: get the response from it.
          Try(FakeTriplestore.data(sparql))
        } else {
          // No: get the response from the real triplestore over HTTP.
          getSparqlHttpResponse(sparql, isUpdate = false, simulateTimeout = simulateTimeout)
        }

      // Are we preparing a fake triplestore?
      _ = if (settings.prepareFakeTriplestore) {
        // Yes: add the query and the response to it.
        FakeTriplestore.add(sparql, resultStr, log)
      }

      // _ = println(s"SPARQL: $logDelimiter$sparql")
      // _ = println(s"Result: $logDelimiter$resultStr")

      // Parse the response as a JSON object and generate a response message.
      responseMessage <- parseJsonResponse(sparql, resultStr)
    } yield responseMessage
  }

  /**
   * Given a SPARQL CONSTRUCT query string, runs the query, returning the result as a [[SparqlConstructResponse]].
   *
   * @param sparqlConstructRequest the request message.
   * @return a [[SparqlConstructResponse]]
   */
  private def sparqlHttpConstruct(sparqlConstructRequest: SparqlConstructRequest): Try[SparqlConstructResponse] = {
    // println(logDelimiter + sparql)

    val rdfFormatUtil: RdfFormatUtil = RdfFeatureFactory.getRdfFormatUtil(sparqlConstructRequest.featureFactoryConfig)

    def parseTurtleResponse(
      sparql: String,
      turtleStr: String,
      rdfFormatUtil: RdfFormatUtil
    ): Try[SparqlConstructResponse] = {
      val parseTry = Try {
        val rdfModel: RdfModel = rdfFormatUtil.parseToRdfModel(rdfStr = turtleStr, rdfFormat = Turtle)
        val statementMap: mutable.Map[IRI, Seq[(IRI, String)]] = mutable.Map.empty

        for (st: Statement <- rdfModel) {
          val subjectIri = st.subj.stringValue
          val predicateIri = st.pred.stringValue
          val objectIri = st.obj.stringValue
          val currentStatementsForSubject: Seq[(IRI, String)] =
            statementMap.getOrElse(subjectIri, Vector.empty[(IRI, String)])
          statementMap += (subjectIri -> (currentStatementsForSubject :+ (predicateIri, objectIri)))
        }

        SparqlConstructResponse(statementMap.toMap)
      }

      parseTry match {
        case Success(parsed) => Success(parsed)
        case Failure(e) =>
          if (turtleStr.contains("##  Query cancelled due to timeout during execution")) {
            log.error(e, "Triplestore timed out while sending a response, after sending statuscode 200.")
            Failure(
              TriplestoreTimeoutException(
                "Triplestore timed out while sending a response, after sending statuscode 200.",
                e,
                log
              )
            )
          } else {
            log.error(
              e,
              s"Couldn't parse response from triplestore:$logDelimiter$turtleStr${logDelimiter}in response to SPARQL query:$logDelimiter$sparql"
            )
            Failure(TriplestoreResponseException("Couldn't parse Turtle from triplestore", e, log))
          }
      }
    }

    for {
      turtleStr <-
        getSparqlHttpResponse(sparqlConstructRequest.sparql, isUpdate = false, acceptMimeType = mimeTypeTextTurtle)

      response <- parseTurtleResponse(
        sparql = sparqlConstructRequest.sparql,
        turtleStr = turtleStr,
        rdfFormatUtil = rdfFormatUtil
      )
    } yield response
  }

  /**
   * Given a SPARQL CONSTRUCT query string, runs the query, saving the result in a file.
   *
   * @param sparql       the SPARQL CONSTRUCT query string.
   * @param graphIri     the named graph IRI to be used in the output file.
   * @param outputFile   the output file.
   * @param outputFormat the output file format.
   * @return a [[FileWrittenResponse]].
   */
  private def sparqlHttpConstructFile(
    sparql: String,
    graphIri: IRI,
    outputFile: Path,
    outputFormat: QuadFormat,
    featureFactoryConfig: FeatureFactoryConfig
  ): Try[FileWrittenResponse] = {
    val rdfFormatUtil: RdfFormatUtil = RdfFeatureFactory.getRdfFormatUtil(featureFactoryConfig)

    for {
      turtleStr <- getSparqlHttpResponse(sparql, isUpdate = false, acceptMimeType = mimeTypeTextTurtle)

      _ = rdfFormatUtil.turtleToQuadsFile(
        rdfSource = RdfStringSource(turtleStr),
        graphIri = graphIri,
        outputFile = outputFile,
        outputFormat = outputFormat
      )
    } yield FileWrittenResponse()
  }

  /**
   * Given a SPARQL CONSTRUCT query string, runs the query, returns the result as a [[SparqlExtendedConstructResponse]].
   *
   * @param sparqlExtendedConstructRequest the request message.
   * @return a [[SparqlExtendedConstructResponse]]
   */
  private def sparqlHttpExtendedConstruct(
    sparqlExtendedConstructRequest: SparqlExtendedConstructRequest
  ): Try[SparqlExtendedConstructResponse] = {
    // println(sparql)
    val rdfFormatUtil: RdfFormatUtil =
      RdfFeatureFactory.getRdfFormatUtil(sparqlExtendedConstructRequest.featureFactoryConfig)

    val parseTry = for {
      turtleStr <- getSparqlHttpResponse(
        sparqlExtendedConstructRequest.sparql,
        isUpdate = false,
        acceptMimeType = mimeTypeTextTurtle
      )

      response <- SparqlExtendedConstructResponse.parseTurtleResponse(
        turtleStr = turtleStr,
        rdfFormatUtil = rdfFormatUtil,
        log = log
      )
    } yield response

    parseTry match {
      case Success(parsed)                               => Success(parsed)
      case Failure(timeout: TriplestoreTimeoutException) => Failure(timeout)
      case Failure(e) =>
        Failure(
          TriplestoreResponseException(
            s"Couldn't parse Turtle from triplestore: ${sparqlExtendedConstructRequest}",
            e,
            log
          )
        )
    }
  }

  /**
   * Performs a SPARQL update operation.
   *
   * @param sparqlUpdate the SPARQL update.
   * @return a [[SparqlUpdateResponse]].
   */
  private def sparqlHttpUpdate(sparqlUpdate: String): Try[SparqlUpdateResponse] =
    // println(logDelimiter + sparqlUpdate)
    for {
      // Send the request to the triplestore.
      _ <- getSparqlHttpResponse(sparqlUpdate, isUpdate = true)
    } yield SparqlUpdateResponse()

  /**
   * Performs a SPARQL ASK query.
   *
   * @param sparql the SPARQL ASK query.
   * @return a [[SparqlAskResponse]].
   */
  def sparqlHttpAsk(sparql: String): Try[SparqlAskResponse] =
    for {
      resultString <- getSparqlHttpResponse(sparql, isUpdate = false)
      _ = log.debug("sparqlHttpAsk - resultString: {}", resultString)

      result: Boolean = resultString.parseJson.asJsObject.getFields("boolean").head.convertTo[Boolean]
    } yield SparqlAskResponse(result)

  private def resetTripleStoreContent(
    rdfDataObjects: Seq[RdfDataObject],
    prependDefaults: Boolean = true
  ): Try[ResetRepositoryContentACK] = {
    log.debug("resetTripleStoreContent")
    val resetTriplestoreResult = for {

      // drop old content
      _ <- dropAllTriplestoreContent()

      // insert new content
      _ <- insertDataIntoTriplestore(rdfDataObjects, prependDefaults)

      // any errors throwing exceptions until now are already covered so we can ACK the request
      result = ResetRepositoryContentACK()
    } yield result

    resetTriplestoreResult
  }

  private def dropAllTriplestoreContent(): Try[DropAllRepositoryContentACK] = {

    log.debug("==>> Drop All Data Start")

    val dropAllSparqlString =
      """
                DROP ALL
            """

    val response: Try[DropAllRepositoryContentACK] = for {
      result: String <- getSparqlHttpResponse(dropAllSparqlString, isUpdate = true)
      _ = log.debug(s"==>> Drop All Data End, Result: $result")
    } yield DropAllRepositoryContentACK()

    response.recover { case t: Exception =>
      throw TriplestoreResponseException("Reset: Failed to execute DROP ALL", t, log)
    }
  }

  /**
   * Inserts the data referenced inside the `rdfDataObjects` by appending it to a default set of `rdfDataObjects`
   * based on the list defined in `application.conf` under the `app.triplestore.default-rdf-data` key.
   *
   * @param rdfDataObjects  a sequence of paths and graph names referencing data that needs to be inserted.
   * @param prependDefaults denotes if the rdfDataObjects list should be prepended with a default set. Default is `true`.
   * @return [[InsertTriplestoreContentACK]]
   */
  private def insertDataIntoTriplestore(
    rdfDataObjects: Seq[RdfDataObject],
    prependDefaults: Boolean = true
  ): Try[InsertTriplestoreContentACK] = {
    val httpContext: HttpClientContext = makeHttpContext

    try {
      log.debug("==>> Loading Data Start")

      val defaultRdfDataList = settings.tripleStoreConfig.getConfigList("default-rdf-data")
      val defaultRdfDataObjectList = defaultRdfDataList.asScala.map { config =>
        RdfDataObjectFactory(config)
      }

      val completeRdfDataObjectList = if (prependDefaults) {
        //prepend default data objects like those of knora-base, knora-admin, etc.
        defaultRdfDataObjectList ++ rdfDataObjects
      } else {
        rdfDataObjects
      }

      log.debug("insertDataIntoTriplestore - completeRdfDataObjectList: {}", completeRdfDataObjectList)

      // Iterate over the list of graphs and try inserting each one.
      for (elem <- completeRdfDataObjectList) {
        val graphName: String = elem.name

        if (graphName.toLowerCase == "default") {
          throw TriplestoreUnsupportedFeatureException("Requests to the default graph are not supported")
        }

        val uriBuilder: URIBuilder = new URIBuilder(dataInsertPath)
        uriBuilder.addParameter("graph", graphName) //Note: addParameter encodes the graphName URL

        val httpPost: HttpPost = new HttpPost(uriBuilder.build())

        // Add the input file to the body of the request.
        // here we need to tweak the base directory path from "webapi"
        // to the parent folder where the files can be found
        val inputFile = Paths.get("..", elem.path)
        if (!Files.exists(inputFile)) {
          throw BadRequestException(s"File ${inputFile} does not exist")
        }

        val fileEntity = new FileEntity(inputFile.toFile, ContentType.create(mimeTypeTextTurtle, "UTF-8"))
        httpPost.setEntity(fileEntity)
        val makeResponse: CloseableHttpResponse => InsertGraphDataContentResponse = returnInsertGraphDataResponse(
          graphName
        )

        // Do the post request for the graph.
        doHttpRequest(
          client = longRequestClient,
          request = httpPost,
          context = httpContext,
          processResponse = makeResponse
        )

        log.debug(s"added: $graphName")
      }

      log.debug("==>> Loading Data End")

      // Return success if all graphs are inserted successfully.
      Success(InsertTriplestoreContentACK())
    } catch {
      case e: TriplestoreUnsupportedFeatureException => Failure(e)
      case e: Exception =>
        Failure(TriplestoreResponseException("Reset: Failed to execute insert into triplestore", e, log))
    }
  }

  /**
   * Checks connection to the triplestore.
   */
  private def checkTriplestore(): Try[CheckTriplestoreResponse] = checkFusekiTriplestore()

  /**
   * Checks the Fuseki triplestore if it is available and configured correctly. If the it is not
   * configured, tries to automatically configure (initialize) the required dataset.
   */
  private def checkFusekiTriplestore(afterAutoInit: Boolean = false): Try[CheckTriplestoreResponse] = {
    import org.knora.webapi.messages.store.triplestoremessages.FusekiJsonProtocol._

    try {
      log.debug("checkFusekiRepository entered")

      // Call an endpoint that returns all datasets.

      val context: HttpClientContext = makeHttpContext

      val httpGet = new HttpGet(checkRepositoryPath)
      httpGet.addHeader("Accept", mimeTypeApplicationJson)

      val responseStr: String = {
        var maybeResponse: Option[CloseableHttpResponse] = None

        val responseTry: Try[String] = Try {
          maybeResponse = Some(queryHttpClient.execute(targetHost, httpGet, context))
          EntityUtils.toString(maybeResponse.get.getEntity, StandardCharsets.UTF_8)
        }

        maybeResponse.foreach(_.close())
        responseTry.get
      }

      val nameShouldBe = settings.triplestoreDatabaseName
      val fusekiServer: FusekiServer = JsonParser(responseStr).convertTo[FusekiServer]
      val neededDataset: Option[FusekiDataset] =
        fusekiServer.datasets.find(dataset => dataset.dsName == s"/$nameShouldBe" && dataset.dsState)

      if (neededDataset.nonEmpty) {
        // everything looks good
        Success(
          CheckTriplestoreResponse(
            triplestoreStatus = TriplestoreStatus.ServiceAvailable,
            msg = "Triplestore is available."
          )
        )
      } else {
        // none of the available datasets meet our requirements
        log.info(s"None of the active datasets meet our requirement of name: $nameShouldBe")
        if (settings.triplestoreAutoInit) {
          // try to auto-init if we didn't tried it already
          if (afterAutoInit) {
            // we already tried to auto-init but it wasn't successful
            Success(
              CheckTriplestoreResponse(
                triplestoreStatus = TriplestoreStatus.NotInitialized,
                msg =
                  s"Sorry, we tried to auto-initialize and still none of the active datasets meet our requirement of name: $nameShouldBe"
              )
            )
          } else {
            // try to auto-init
            log.info("Triplestore auto-init is set. Trying to auto-initialize.")
            initJenaFusekiTriplestore()
          }
        } else {
          Success(
            CheckTriplestoreResponse(
              triplestoreStatus = TriplestoreStatus.NotInitialized,
              msg = s"None of the active datasets meet our requirement of name: $nameShouldBe"
            )
          )
        }
      }
    } catch {
      case e: Exception =>
        // println("checkRepository - exception", e)
        Success(
          CheckTriplestoreResponse(
            triplestoreStatus = TriplestoreStatus.ServiceUnavailable,
            msg = s"Triplestore not available: ${e.getMessage}"
          )
        )
    }
  }

  /**
   * Initialize the Jena Fuseki triplestore. Currently only works for
   * 'knora-test' and 'knora-test-unit' repository names. To be used, the
   * API needs to be started with 'KNORA_WEBAPI_TRIPLESTORE_AUTOINIT' set
   * to 'true' (settings.triplestoreAutoInit). This is set to `true` for tests
   * (`test/resources/test.conf`).Usage is only recommended for automated
   * testing and not for production use.
   */
  private def initJenaFusekiTriplestore(): Try[CheckTriplestoreResponse] = {

    // TODO: Needs https://github.com/scalameta/metals/issues/3623 to be resolved
    // val configFileName = s"webapi/scripts/fuseki-repository-config.ttl.template"
    val configFileName = s"fuseki-repository-config.ttl.template"

    val triplestoreConfig: String =
      try {
        // take config from the classpath and write to triplestore
        FileUtil.readTextResource(configFileName).replace("@REPOSITORY@", settings.triplestoreDatabaseName)
      } catch {
        case _: NotFoundException =>
          log.error(s"Cannot initialize repository. Config $configFileName not found.")
          ""
      }

    val httpContext: HttpClientContext = makeHttpContext
    val httpPost: HttpPost = new HttpPost("/$/datasets")
    val stringEntity = new StringEntity(triplestoreConfig, ContentType.create(mimeTypeTextTurtle))
    httpPost.setEntity(stringEntity)

    doHttpRequest(
      client = updateHttpClient,
      request = httpPost,
      context = httpContext,
      processResponse = returnUploadResponse
    )

    // do the check again
    checkFusekiTriplestore(true)
  }

  /**
   * Makes a triplestore URI for downloading a named graph.
   *
   * @param graphIri the IRI of the named graph.
   * @return a triplestore-specific URI for downloading the named graph.
   */
  private def makeNamedGraphDownloadUri(graphIri: IRI): URI = {
    val uriBuilder: URIBuilder = new URIBuilder(graphPath)
    uriBuilder.setParameter("graph", s"$graphIri")
    uriBuilder.build()
  }

  /**
   * Requests the contents of a named graph, saving the response in a file.
   *
   * @param graphIri             the IRI of the named graph.
   * @param outputFile           the file to be written.
   * @param outputFormat         the output file format.
   * @param featureFactoryConfig the feature factory configuration.
   * @return a string containing the contents of the graph in N-Quads format.
   */
  private def sparqlHttpGraphFile(
    graphIri: IRI,
    outputFile: Path,
    outputFormat: QuadFormat,
    featureFactoryConfig: FeatureFactoryConfig
  ): Try[FileWrittenResponse] = {
    val httpContext: HttpClientContext = makeHttpContext
    val httpGet = new HttpGet(makeNamedGraphDownloadUri(graphIri))
    httpGet.addHeader("Accept", mimeTypeTextTurtle)

    val makeResponse: CloseableHttpResponse => FileWrittenResponse = writeResponseFile(
      outputFile = outputFile,
      featureFactoryConfig = featureFactoryConfig,
      maybeGraphIriAndFormat = Some(GraphIriAndFormat(graphIri = graphIri, quadFormat = outputFormat))
    )

    doHttpRequest(
      client = queryHttpClient,
      request = httpGet,
      context = httpContext,
      processResponse = makeResponse
    )
  }

  /**
   * Requests the contents of a named graph, returning the response as Turtle.
   *
   * @param graphIri the IRI of the named graph.
   * @return a string containing the contents of the graph in Turtle format.
   */
  private def sparqlHttpGraphData(graphIri: IRI): Try[NamedGraphDataResponse] = {
    val httpContext: HttpClientContext = makeHttpContext
    val httpGet = new HttpGet(makeNamedGraphDownloadUri(graphIri))
    httpGet.addHeader("Accept", mimeTypeTextTurtle)
    val makeResponse: CloseableHttpResponse => NamedGraphDataResponse = returnGraphDataAsTurtle(graphIri)

    doHttpRequest(
      client = queryHttpClient,
      request = httpGet,
      context = httpContext,
      processResponse = makeResponse
    )
  }

  /**
   * Submits a SPARQL request to the triplestore and returns the response as a string.
   *
   * @param sparql         the SPARQL request to be submitted.
   * @param isUpdate       `true` if this is an update request.
   * @param acceptMimeType the MIME type to be provided in the HTTP Accept header.
   * @param simulateTimeout if `true`, simulate a read timeout.
   * @return the triplestore's response.
   */
  private def getSparqlHttpResponse(
    sparql: String,
    isUpdate: Boolean,
    acceptMimeType: String = mimeTypeApplicationSparqlResultsJson,
    simulateTimeout: Boolean = false
  ): Try[String] = {

    val httpContext: HttpClientContext = makeHttpContext

    val (httpClient: CloseableHttpClient, httpPost: HttpPost) = if (isUpdate) {
      // Send updates as application/sparql-update (as per SPARQL 1.1 Protocol §3.2.2, "UPDATE using POST directly").
      val requestEntity = new StringEntity(sparql, ContentType.create(mimeTypeApplicationSparqlUpdate, "UTF-8"))
      val updateHttpPost = new HttpPost(sparqlUpdatePath)
      updateHttpPost.setEntity(requestEntity)
      (updateHttpClient, updateHttpPost)
    } else {
      // Send queries as application/x-www-form-urlencoded (as per SPARQL 1.1 Protocol §2.1.2,
      // "query via POST with URL-encoded parameters"), so we can include the "infer" parameter when using GraphDB.
      val formParams = new util.ArrayList[NameValuePair]()
      formParams.add(new BasicNameValuePair("query", sparql))
      val requestEntity: UrlEncodedFormEntity = new UrlEncodedFormEntity(formParams, Consts.UTF_8)
      val queryHttpPost: HttpPost = new HttpPost(queryPath)
      queryHttpPost.setEntity(requestEntity)
      queryHttpPost.addHeader("Accept", acceptMimeType)
      (queryHttpClient, queryHttpPost)
    }

    doHttpRequest(
      client = httpClient,
      request = httpPost,
      context = httpContext,
      processResponse = returnResponseAsString,
      simulateTimeout = simulateTimeout
    )
  }

  /**
   * Dumps the whole repository in N-Quads format, saving the response in a file.
   *
   * @param outputFile           the output file.
   * @param featureFactoryConfig the feature factory configuration.
   * @return a string containing the contents of the graph in N-Quads format.
   */
  private def downloadRepository(
    outputFile: Path,
    featureFactoryConfig: FeatureFactoryConfig
  ): Try[FileWrittenResponse] = {
    val httpContext: HttpClientContext = makeHttpContext

    val uriBuilder: URIBuilder = new URIBuilder(repositoryDownloadPath)

    val httpGet = new HttpGet(uriBuilder.build())
    httpGet.addHeader("Accept", mimeTypeApplicationNQuads)
    val queryTimeoutMillis = settings.triplestoreQueryTimeout.toMillis.toInt * 10

    val queryRequestConfig = RequestConfig
      .custom()
      .setConnectTimeout(queryTimeoutMillis)
      .setConnectionRequestTimeout(queryTimeoutMillis)
      .setSocketTimeout(queryTimeoutMillis)
      .build

    val queryHttpClient: CloseableHttpClient = HttpClients.custom
      .setDefaultCredentialsProvider(credsProvider)
      .setDefaultRequestConfig(queryRequestConfig)
      .build

    val makeResponse: CloseableHttpResponse => FileWrittenResponse = writeResponseFile(
      outputFile = outputFile,
      featureFactoryConfig = featureFactoryConfig
    )

    doHttpRequest(
      client = queryHttpClient,
      request = httpGet,
      context = httpContext,
      processResponse = makeResponse
    )

  }

  /**
   * Uploads repository content from an N-Quads file.
   *
   * @param inputFile an N-Quads file containing the content to be uploaded to the repository.
   */
  private def uploadRepository(inputFile: Path): Try[RepositoryUploadedResponse] = {
    val httpContext: HttpClientContext = makeHttpContext
    val httpPost: HttpPost = new HttpPost(repositoryUploadPath)
    val fileEntity = new FileEntity(inputFile.toFile, ContentType.create(mimeTypeApplicationNQuads, "UTF-8"))
    httpPost.setEntity(fileEntity)

    doHttpRequest(
      client = longRequestClient,
      request = httpPost,
      context = httpContext,
      processResponse = returnUploadResponse
    )
  }

  /**
   * Puts a data graph into the repository.
   *
   * @param graphContent a data graph in Turtle format to be inserted into the repository.
   * @param graphName    the name of the graph.
   */
  private def insertDataGraphRequest(graphContent: String, graphName: String): Try[InsertGraphDataContentResponse] = {
    val httpContext: HttpClientContext = makeHttpContext
    val uriBuilder: URIBuilder = new URIBuilder(dataInsertPath)
    uriBuilder.addParameter("graph", graphName)
    val httpPut: HttpPut = new HttpPut(uriBuilder.build())
    val requestEntity = new StringEntity(graphContent, ContentType.create(mimeTypeTextTurtle, "UTF-8"))
    httpPut.setEntity(requestEntity)
    val makeResponse: CloseableHttpResponse => InsertGraphDataContentResponse = returnInsertGraphDataResponse(graphName)

    doHttpRequest(
      client = updateHttpClient,
      request = httpPut,
      context = httpContext,
      processResponse = makeResponse
    )
  }

  /**
   * Formulate HTTP context.
   *
   * @return httpContext with credentials and authorization
   */
  private def makeHttpContext: HttpClientContext = {
    val authCache: AuthCache = new BasicAuthCache
    val basicAuth: BasicScheme = new BasicScheme
    authCache.put(targetHost, basicAuth)

    val httpContext: HttpClientContext = HttpClientContext.create
    httpContext.setCredentialsProvider(credsProvider)
    httpContext.setAuthCache(authCache)
    httpContext
  }

  /**
   * Makes an HTTP connection to the triplestore, and delegates processing of the response
   * to a function.
   *
   * @param client          the HTTP client to be used for the request.
   * @param request         the request to be sent.
   * @param context         the request context to be used.
   * @param processResponse a function that processes the HTTP response.
   * @param simulateTimeout if `true`, simulate a read timeout.
   * @tparam T the return type of `processResponse`.
   * @return the return value of `processResponse`.
   */
  private def doHttpRequest[T](
    client: CloseableHttpClient,
    request: HttpRequest,
    context: HttpClientContext,
    processResponse: CloseableHttpResponse => T,
    simulateTimeout: Boolean = false
  ): Try[T] = {
    // Make an Option wrapper for the response, so we can close it if we get one,
    // even if an error occurs.
    var maybeResponse: Option[CloseableHttpResponse] = None

    val triplestoreResponseTry = Try {
      if (simulateTimeout) {
        throw new java.net.SocketTimeoutException("Simulated read timeout")
      }

      val start = System.currentTimeMillis()
      val response = client.execute(targetHost, request, context)
      maybeResponse = Some(response)
      val statusCode: Int = response.getStatusLine.getStatusCode

      if (statusCode == 404) {
        throw NotFoundException("The requested data was not found")
      } else {
        val statusCategory: Int = statusCode / 100

        if (statusCategory != 2) {
          Option(response.getEntity)
            .map(responseEntity => EntityUtils.toString(responseEntity, StandardCharsets.UTF_8)) match {
            case Some(responseEntityStr) =>
              val msg = s"Triplestore responded with HTTP code $statusCode: $responseEntityStr"
              log.error(msg)
              if (statusCode == 503 && responseEntityStr.contains("Query timed out"))
                throw TriplestoreTimeoutException(msg)
              else throw TriplestoreResponseException(msg)

            case None =>
              log.error(s"Triplestore responded with HTTP code $statusCode")
              throw TriplestoreResponseException(s"Triplestore responded with HTTP code $statusCode")
          }
        }
      }

      val took = System.currentTimeMillis() - start
      metricsLogger.info(s"[$statusCode] Triplestore query took: ${took}ms")
      processResponse(response)
    }

    maybeResponse.foreach(_.close)

    // TODO: Can we make Fuseki abandon the query if it takes too long?

    triplestoreResponseTry.recover {
      case tre: TriplestoreResponseException => throw tre

      case socketTimeoutException: java.net.SocketTimeoutException =>
        val message =
          "The triplestore took too long to process a request. This can happen because the triplestore needed too much time to search through the data that is currently in the triplestore. Query optimisation may help."
        log.error(socketTimeoutException, message)
        throw TriplestoreTimeoutException(message = message, e = socketTimeoutException, log = log)

      case timeout: TriplestoreTimeoutException => throw timeout

      case notFound: NotFoundException => throw notFound

      case e: Exception =>
        val message = "Failed to connect to triplestore"
        log.error(e, message)
        throw TriplestoreConnectionException(message = message, e = e, log = log)
    }
  }

  def returnResponseAsString(response: CloseableHttpResponse): String =
    Option(response.getEntity) match {
      case None => ""

      case Some(responseEntity) =>
        EntityUtils.toString(responseEntity, StandardCharsets.UTF_8)
    }

  def returnGraphDataAsTurtle(graphIri: IRI)(response: CloseableHttpResponse): NamedGraphDataResponse =
    Option(response.getEntity) match {
      case None =>
        log.error(s"Triplestore returned no content for graph $graphIri")
        throw TriplestoreResponseException(s"Triplestore returned no content for graph $graphIri")

      case Some(responseEntity: HttpEntity) =>
        NamedGraphDataResponse(
          turtle = EntityUtils.toString(responseEntity, StandardCharsets.UTF_8)
        )
    }

  def returnUploadResponse: CloseableHttpResponse => RepositoryUploadedResponse = { _ =>
    RepositoryUploadedResponse()
  }

  def returnInsertGraphDataResponse(
    graphName: String
  )(response: CloseableHttpResponse): InsertGraphDataContentResponse =
    Option(response.getEntity) match {
      case None =>
        log.error(s"$graphName could not be inserted into Triplestore.")
        throw TriplestoreResponseException(s"$graphName could not be inserted into Triplestore.")

      case Some(_) =>
        InsertGraphDataContentResponse()
    }

  /**
   * Represents a named graph IRI and the file format that the graph should be written in.
   *
   * @param graphIri   the named graph IRI.
   * @param quadFormat the file format.
   */
  case class GraphIriAndFormat(graphIri: IRI, quadFormat: QuadFormat)

  /**
   * Writes an HTTP response to a file.
   *
   * @param outputFile             the output file.
   * @param featureFactoryConfig   the feature factory configuration.
   * @param maybeGraphIriAndFormat a graph IRI and quad format for the output file. If defined, the response
   *                               is parsed as Turtle and converted to the output format, with the graph IRI
   *                               added to each statement. Otherwise, the response is written as-is to the
   *                               output file.
   * @param response               the response to be read.
   * @return a [[FileWrittenResponse]].
   */
  def writeResponseFile(
    outputFile: Path,
    featureFactoryConfig: FeatureFactoryConfig,
    maybeGraphIriAndFormat: Option[GraphIriAndFormat] = None
  )(response: CloseableHttpResponse): FileWrittenResponse =
    Option(response.getEntity) match {
      case Some(responseEntity: HttpEntity) =>
        // Are we converting the response to a quad format?
        maybeGraphIriAndFormat match {
          case Some(GraphIriAndFormat(graphIri, quadFormat)) =>
            // Yes. Stream the HTTP entity to a temporary Turtle file.
            val turtleFile = Paths.get(outputFile.toString + ".ttl")
            Files.copy(responseEntity.getContent, turtleFile, StandardCopyOption.REPLACE_EXISTING)

            // Convert the Turtle to the output format.

            val rdfFormatUtil: RdfFormatUtil = RdfFeatureFactory.getRdfFormatUtil(featureFactoryConfig)

            val processFileTry: Try[Unit] = Try {
              rdfFormatUtil.turtleToQuadsFile(
                rdfSource = RdfInputStreamSource(new BufferedInputStream(Files.newInputStream(turtleFile))),
                graphIri = graphIri,
                outputFile = outputFile,
                outputFormat = quadFormat
              )
            }

            Files.delete(turtleFile)

            processFileTry match {
              case Success(_)  => ()
              case Failure(ex) => throw ex
            }

          case None =>
            // No. Stream the HTTP entity directly to the output file.
            Files.copy(responseEntity.getContent, outputFile)
        }

        FileWrittenResponse()

      case None =>
        maybeGraphIriAndFormat match {
          case Some(GraphIriAndFormat(graphIri, _)) =>
            log.error(s"Triplestore returned no content for graph $graphIri")
            throw TriplestoreResponseException(s"Triplestore returned no content for graph $graphIri")

          case None =>
            log.error(s"Triplestore returned no content for repository dump")
            throw TriplestoreResponseException(s"Triplestore returned no content for for repository dump")
        }
    }
}