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OAI-PMH service provider implementation. Use it as a harvesting client to read remote repositories.

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/*
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */

package io.gdcc.xoai.serviceprovider.parsers;

import static io.gdcc.xoai.model.oaipmh.Error.Code.NO_RECORDS_MATCH;
import static io.gdcc.xoai.xmlio.matchers.QNameMatchers.localPart;
import static io.gdcc.xoai.xmlio.matchers.XmlEventMatchers.aStartElement;
import static io.gdcc.xoai.xmlio.matchers.XmlEventMatchers.elementName;
import static io.gdcc.xoai.xmlio.matchers.XmlEventMatchers.theEndOfDocument;
import static org.hamcrest.CoreMatchers.allOf;
import static org.hamcrest.CoreMatchers.equalTo;

import io.gdcc.xoai.model.oaipmh.results.record.Header;
import io.gdcc.xoai.serviceprovider.exceptions.InvalidOAIResponse;
import io.gdcc.xoai.xmlio.XmlReader;
import io.gdcc.xoai.xmlio.exceptions.XmlReaderException;
import javax.xml.stream.events.XMLEvent;
import org.hamcrest.Matcher;

public class ListIdentifiersParser {
    private final XmlReader reader;
    private boolean awaitingNextInvocation = false;

    public ListIdentifiersParser(XmlReader reader) {
        this.reader = reader;
    }

    public boolean hasNext() throws XmlReaderException {
        if (!awaitingNextInvocation)
            reader.next(headerElement(), errorElement(), resumptionToken(), theEndOfDocument());
        awaitingNextInvocation = true;
        if (reader.current(errorElement())) {
            String code = reader.getAttributeValue(localPart(equalTo("code")));
            if (equalTo(NO_RECORDS_MATCH.id()).matches(code)) return false;
            else throw new InvalidOAIResponse("OAI responded with code: " + code);
        }
        return reader.current(headerElement());
    }

    private Matcher resumptionToken() {
        return allOf(aStartElement(), elementName(localPart(equalTo("resumptionToken"))));
    }

    public Header next() throws XmlReaderException {
        if (!hasNext()) throw new XmlReaderException("No more identifiers available");
        awaitingNextInvocation = false;
        return new HeaderParser().parse(reader);
    }

    private Matcher errorElement() {
        return elementName(localPart(equalTo("error")));
    }

    private Matcher headerElement() {
        return allOf(aStartElement(), elementName(localPart(equalTo("header"))));
    }
}