package eu.dnetlib.data.collector.plugins.projects.grist;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Iterator;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.PriorityBlockingQueue;

import eu.dnetlib.data.collector.rmi.CollectorServiceException;
import eu.dnetlib.data.collector.rmi.CollectorServiceRuntimeException;
import eu.dnetlib.enabling.resultset.SizedIterable;
import org.apache.commons.io.IOUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class GristProjectsIterable implements SizedIterable<String> {

	private static final Log log = LogFactory.getLog(GristProjectsIterable.class); // NOPMD by marko on 11/24/08 5:02 PM

	private String queryURL;
	private int total;
	private SAXReader reader;

	public GristProjectsIterable(String baseURL) throws CollectorServiceException {
		queryURL = baseURL;
		reader = new SAXReader();
		total = getTotalCount();
	}

	@Override
	public int getNumberOfElements() {
		return total;
	}

	private int getTotalCount() throws CollectorServiceException {
		try {
			URL pageUrl = new URL(queryURL);
			log.debug("Getting hit count from: " + pageUrl.toString());
			String resultPage = IOUtils.toString(pageUrl);
			Document doc = reader.read(IOUtils.toInputStream(resultPage));
			String hitCount = doc.selectSingleNode("/Response/HitCount").getText();
			return Integer.parseInt(hitCount);
		} catch (NumberFormatException e) {
			log.warn("Cannot set the total count from '/Response/HitCount'");
		} catch (DocumentException e) {
			throw new CollectorServiceException(e);
		} catch (MalformedURLException e) {
			throw new CollectorServiceException(e);
		} catch (IOException e) {
			throw new CollectorServiceException(e);
		}
		return -1;
	}

	@Override
	public Iterator<String> iterator() {
		return new Iterator<String>() {

			private Queue<String> projects = new PriorityBlockingQueue<String>();
			private boolean morePages = true;
			private int pageNumber = 0;
			private SAXReader reader = new SAXReader();
			//The following is for debug only
			private int nextCounter = 0;

			@Override
			public boolean hasNext() {
				try {
					fillProjectListIfNeeded();
				} catch (CollectorServiceException e) {
					throw new CollectorServiceRuntimeException(e);
				}
				return !projects.isEmpty();
			}

			@Override
			public String next() {
				nextCounter++;
				log.debug(String.format("Calling next %s times. projects queue has %s elements", nextCounter, projects.size()));
				try {
					fillProjectListIfNeeded();
					return projects.poll();
				} catch (CollectorServiceException e) {
					throw new CollectorServiceRuntimeException(e);
				}
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException();
			}

			private boolean fillProjectListIfNeeded() throws CollectorServiceException {
				if (morePages && projects.isEmpty()) {
					String resultPage = getNextPage();
					Document doc = null;
					try {
						doc = reader.read(IOUtils.toInputStream(resultPage));
						List<Element> records = doc.selectNodes("//RecordList/Record");
						if (records != null && !records.isEmpty()) {
							for (Element p : records) {

								projects.add(p.asXML());
							}
							return true;
						} else {
							log.info("No more projects to read at page nr. " + pageNumber);
							morePages = false;
							return false;
						}
					} catch (DocumentException e) {
						throw new CollectorServiceException(e);
					}
				} else return false;
			}

			private String getNextPage() {
				pageNumber++;
				try {
					URL pageUrl = new URL(queryURL + "&page=" + pageNumber);
					log.debug("Getting page at: " + pageUrl.toString());
					return IOUtils.toString(pageUrl);
				} catch (Exception e) {
					throw new CollectorServiceRuntimeException("Error on page " + pageNumber, e);
				}
			}
		};
	}

}