dnet-docker/dnet-app/libs/dnet-oai-common/src/main/java/eu/dnetlib/common/oai/OaiClient.java

package eu.dnetlib.common.oai;

import java.util.List;
import java.util.function.Function;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.math.NumberUtils;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.Node;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.util.UriComponentsBuilder;

import eu.dnetlib.domain.oai.OaiIdentifier;
import eu.dnetlib.domain.oai.OaiInfo;
import eu.dnetlib.domain.oai.OaiMetadataFormat;
import eu.dnetlib.domain.oai.OaiRecord;
import eu.dnetlib.domain.oai.OaiSet;

public class OaiClient {

	public OaiResponse<List<OaiSet>> listSets(final String baseUrl, final String resumptionToken) throws Exception {

		final OaiRequest req = StringUtils.isNotBlank(resumptionToken)
				? OaiRequest.newListSetsWithToken(baseUrl, resumptionToken)
				: OaiRequest.newListSets(baseUrl);

		final OaiResponse<List<OaiSet>> res = new OaiResponse<>();

		callOaiVerb(req, res, doc -> doc
				.selectNodes("//*[local-name()='ListSets']/*[local-name()='set']")
				.stream()
				.map(node -> (Element) node)
				.map(OaiSetImpl::new)
				.map(set -> (OaiSet) set)
				.toList());

		return res;
	}

	public OaiResponse<List<OaiMetadataFormat>> listMetadataFormats(final String baseUrl) throws Exception {
		final OaiRequest req = OaiRequest.newListMetadataFormats(baseUrl);
		final OaiResponse<List<OaiMetadataFormat>> res = new OaiResponse<>();

		callOaiVerb(req, res, doc -> doc
				.selectNodes("//*[local-name()='ListMetadataFormats']/*[local-name()='metadataFormat']")
				.stream()
				.map(node -> (Element) node)
				.map(OaiMetadataFormatImpl::new)
				.map(set -> (OaiMetadataFormat) set)
				.toList());

		return res;
	}

	public OaiResponse<List<OaiRecord<String, String>>> listRecords(final String baseUrl, final String mdPrefix, final String set, final String resumptionToken)
			throws Exception {
		final OaiRequest req = StringUtils.isNotBlank(resumptionToken)
				? OaiRequest.newListRecordsWithToken(baseUrl, resumptionToken)
				: OaiRequest.newListRecords(baseUrl, mdPrefix, set);

		final OaiResponse<List<OaiRecord<String, String>>> res = new OaiResponse<>();

		callOaiVerb(req, res, doc -> doc
				.selectNodes("//*[local-name()='ListRecords']/*[local-name()='record']")
				.stream()
				.map(node -> (Element) node)
				.map(OaiRecordImpl::new)
				.map(r -> (OaiRecord<String, String>) r)
				.toList());

		return res;

	}

	public OaiResponse<List<OaiIdentifier<String>>> listIdentifiers(final String baseUrl, final String mdPrefix, final String set, final String resumptionToken)
			throws Exception {
		final OaiRequest req = StringUtils.isNotBlank(resumptionToken)
				? OaiRequest.newListIdentifiersWithToken(baseUrl, resumptionToken)
				: OaiRequest.newListIdentifiers(baseUrl, mdPrefix, set);

		final OaiResponse<List<OaiIdentifier<String>>> res = new OaiResponse<>();

		callOaiVerb(req, res, doc -> doc
				.selectNodes("//*[local-name()='ListIdentifiers']/*[local-name()='header']")
				.stream()
				.map(node -> (Element) node)
				.map(OaiIdentifierImpl::new)
				.map(r -> (OaiIdentifier<String>) r)
				.toList());

		return res;
	}

	public OaiResponse<OaiRecord<String, String>> getRecord(final String baseUrl, final String mdPrefix, final String id) throws Exception {
		final OaiRequest req = OaiRequest.newGetRecord(baseUrl, mdPrefix, id);

		final OaiResponse<OaiRecord<String, String>> res = new OaiResponse<>();

		callOaiVerb(req, res, doc -> doc
				.selectNodes("//*[local-name()='GetRecord']/*[local-name()='record']")
				.stream()
				.map(node -> (Element) node)
				.map(OaiRecordImpl::new)
				.map(r -> (OaiRecord<String, String>) r)
				.findFirst()
				.orElseThrow());

		return res;
	}

	public OaiResponse<OaiInfo<String>> info(final String baseUrl) throws Exception {
		final OaiRequest req = OaiRequest.newIdentify(baseUrl);

		final OaiResponse<OaiInfo<String>> res = new OaiResponse<>();

		callOaiVerb(req, res, doc -> doc
				.selectNodes("//*[local-name()='Identify']")
				.stream()
				.map(node -> (Element) node)
				.map(OaiInfoImpl::new)
				.map(r -> (OaiInfo<String>) r)
				.findFirst()
				.orElseThrow());

		return res;
	}

	private <T> void callOaiVerb(final OaiRequest req, final OaiResponse<T> res, final Function<Document, T> processBody) {
		final long start = System.currentTimeMillis();

		try {
			res.setVerb(req.getVerb());

			final UriComponentsBuilder urlBuilder = UriComponentsBuilder.fromHttpUrl(req.getBaseUrl());
			req.toQueryParams().forEach((k, v) -> urlBuilder.queryParam(k, v));

			final String url = urlBuilder.encode().toUriString();
			res.setUrl(url);

			final ResponseEntity<String> httpResponse = new RestTemplate().getForEntity(url, String.class);

			res.setHttpCode(httpResponse.getStatusCode().value());

			if (httpResponse.getStatusCode().isError()) {
				res.setValid(false);
				res.setError("ERROR: " + httpResponse.getStatusCode().value());
			} else {
				final Document doc = DocumentHelper.parseText(httpResponse.getBody());
				final Node node = doc.selectSingleNode("//*[local-name() = 'resumptionToken']");

				if (node != null) {
					res.setSize(doc.selectNodes("//*[local-name()='" + req.getVerb() + "']/*[local-name() != 'resumptionToken']").size());
					res.setCursor(NumberUtils.toInt(node.valueOf("@cursor"), -1));
					res.setTotal(NumberUtils.toInt(node.valueOf("@completeListSize"), -1));
					res.setResumptionToken(node.getText());
				}
				res.setBody(processBody.apply(doc));
				res.setValid(true);
			}
		} catch (final Throwable e) {
			res.setValid(false);
			res.setError(e.getMessage());
		} finally {
			res.setTime(System.currentTimeMillis() - start);
		}

	}

}