D-Net

package eu.dnetlib.dli.collector.plugin;

import com.google.gson.JsonArray;

import com.google.gson.JsonElement;

import com.google.gson.JsonObject;

import com.google.gson.JsonParser;

import eu.dnetlib.dli.resolver.model.DLIObjectProvenance;

import eu.dnetlib.dli.resolver.model.DLIObjectRelation;

import eu.dnetlib.dli.resolver.model.DLIResolvedObject;

import eu.dnetlib.pid.resolver.AbstractPIDResolver;

import eu.dnetlib.pid.resolver.model.ObjectType;

import eu.dnetlib.pid.resolver.model.PID;

import org.antlr.stringtemplate.NoIndentWriter;

import org.antlr.stringtemplate.StringTemplate;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import java.io.StringWriter;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

public class CrossRefIterator implements Iterator<String> {

    private static final Log log = LogFactory.getLog(CrossRefIterator.class);

    private int current = 0;

    private int total =0;

    private String nextCursor;

    private final  StringTemplate resolverSerializer;

    private List<JsonElement> buffer = new ArrayList<>();

    private String nextItem;

    public CrossRefIterator(final StringTemplate resolverSerializer) {

        this.resolverSerializer = resolverSerializer;

        nextItem = calculateNextItem();

    }

    @Override

    public boolean hasNext() {

        return nextItem != null;

    }

    @Override

    public String next() {

        final String tmp = nextItem;

        nextItem = calculateNextItem();

        current ++;

        return tmp;

    }

    private String calculateNextItem() {

        if (buffer.isEmpty())

        {

            if (!requestNextBuffer()) return null;

        }

        if (buffer.isEmpty()) return null;

        final JsonObject item = buffer.remove(0).getAsJsonObject();

        try {

            final DLIResolvedObject object = new DLIResolvedObject();

            final String id = item.get("Source").getAsJsonObject().get("Identifier").getAsJsonObject().get("ID").getAsString();

            final String id_type = item.get("Source").getAsJsonObject().get("Identifier").getAsJsonObject().get("IDScheme").getAsString();

            object.setPid(id);

            object.setPidType(id_type);

            final JsonElement licenseURL = item.get("LicenseURL");

            final String type = item.get("Source").getAsJsonObject().get("Type").getAsJsonObject().get("Name").isJsonNull()?"unknownw":item.get("Source").getAsJsonObject().get("Type").getAsJsonObject().get("Name").getAsString();

            object.setType(type.equals("literature") ? ObjectType.publication : ObjectType.dataset);

            final String relType = item.get("RelationshipType").getAsJsonObject().get("Name").getAsString();

            object.setDatasourceProvenance(Collections.singletonList(new DLIObjectProvenance().setDatasource("Crossref").setDatasourceId("dli_________::crossref")));

            DLIObjectRelation relation = new DLIObjectRelation();

            relation.setRelationSemantics(relType);

            final String t_id = item.get("Target").getAsJsonObject().get("Identifier").getAsJsonObject().get("ID").getAsString();

            final String t_id_type = item.get("Target").getAsJsonObject().get("Identifier").getAsJsonObject().get("IDScheme").getAsString();

            final String t_type = item.get("Target").getAsJsonObject().get("Type").getAsJsonObject().get("Name").isJsonNull()?"unknown":item.get("Target").getAsJsonObject().get("Type").getAsJsonObject().get("Name").getAsString();

            if (licenseURL!= null && !licenseURL.isJsonNull())

                relation.setLicense(licenseURL.getAsString());

            relation.setTargetPID(new PID(t_id, t_id_type));

            relation.setTargetType(t_type.equals("literature") ? ObjectType.publication : ObjectType.dataset);

            object.setRelations(Collections.singletonList(relation));

            relation.setCompletionStatus("incomplete");

            relation.setRelationProvenance(Collections.singletonList(new DLIObjectProvenance().setDatasource("Crossref").setDatasourceId("dli_________::crossref")));

            try {

                StringWriter writer = new StringWriter(16);

                NoIndentWriter out = new NoIndentWriter(writer);

                resolverSerializer.removeAttribute("object");

                resolverSerializer.setAttribute("object", object);

                resolverSerializer.write(out);

                String result = writer.toString();

                writer.close();

                return result;

            } catch (Throwable e) {

                throw new RuntimeException(e);

            }

        }catch (Throwable e) {

            System.out.println(item.toString());

            throw new RuntimeException(e);

        }

    }

    private boolean requestNextBuffer() {

        String templateUrlWithCursor = "https://api.eventdata.crossref.org/v1/events/scholix?mailto=sandro.labruzzo@isti.cnr.it&rows=1000&cursor=%s";

        String templateUrl = "https://api.eventdata.crossref.org/v1/events/scholix?mailto=sandro.labruzzo@isti.cnr.it&rows=1000";

        final String s = AbstractPIDResolver.requestURL(nextCursor == null ? templateUrl : String.format(templateUrlWithCursor, nextCursor), 30, 2);

        if (s!= null)

        {

            JsonElement jElement = new JsonParser().parse(s);

            if (jElement.getAsJsonObject().has("message"))

            {

                JsonObject message = jElement.getAsJsonObject().get("message").getAsJsonObject();

                if (message.has("next-cursor") && !message.get("next-cursor").isJsonNull())

                    nextCursor = message.get("next-cursor").getAsString();

                else

                    nextCursor = null;

                total = message.get("total-results").getAsInt();

                final JsonArray items = message.get("link-packages").getAsJsonArray();

                if (items== null || items.size() ==0) {

                    return requestNextBuffer();

                }

                items.forEach(buffer::add);

                return nextCursor!=null;

            }

        }

        return false;

    }

    public int getTotal() {

        return total;

    }

    public void setTotal(int total) {

        this.total = total;

    }

    public int getCurrent() {

        return current;

    }

    public void setCurrent(int current) {

        this.current = current;

    }

}