package eu.dnetlib.download.plugin;

import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import com.google.gson.Gson;
import eu.dnetlib.data.download.rmi.AbstractDownloadPlugin;
import eu.dnetlib.data.download.rmi.DownloadItem;
import eu.dnetlib.data.download.rmi.DownloadPlugin;
import eu.dnetlib.data.download.rmi.DownloadPluginException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

public class FollowPDFLinkPlugins extends AbstractDownloadPlugin implements DownloadPlugin {

    /**
     * The Constant log.
     */
    private static final Log log = LogFactory.getLog(FollowPDFLinkPlugins.class);

    private final static int maxNumberJump = 10;

    /**
     * Extract url.
     *
     * @param url the url
     * @return the string
     */
    @Override
    public String extractURL(final String url) throws DownloadPluginException {
        try {
            URL startURL = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) startURL.openConnection();

	        conn.setConnectTimeout(AbstractDownloadPlugin.DEFAULT_TIMEOUT);

            conn.setInstanceFollowRedirects(true);  // you still need to handle redirect manully.
            HttpURLConnection.setFollowRedirects(true);
            String location = url;

            int numJump =1;

            int responseCode = conn.getResponseCode();

            while ((responseCode >= 300) && (responseCode < 400) &&  (numJump++ < maxNumberJump)) {
                location = conn.getHeaderFields().get("Location").get(0);
                conn.disconnect();
                startURL = new URL(location);
                conn = (HttpURLConnection) startURL.openConnection();
                conn.setConnectTimeout(AbstractDownloadPlugin.DEFAULT_TIMEOUT);
                conn.setInstanceFollowRedirects(true);  // you still need to handle redirect manully.
                HttpURLConnection.setFollowRedirects(true);
                responseCode = conn.getResponseCode();
            }
            conn.disconnect();
            if (!((responseCode >= 200) && (responseCode < 300)))
                return null;
            Document doc = Jsoup.connect(location).get();
            Elements links = doc.select("a[href$=.pdf]");

            for (Element link : links) {
                String linkValue = link.attr("abs:href");
                if (regularExpression != null) {
                    for (String regex : regularExpression) {
                        if (linkValue.matches(regex))
                            return linkValue;
                    }
                } else
                    return linkValue;
            }
            return null;
        } catch (Throwable e) {
	        throw new DownloadPluginException("Error on extract URL", e);
        }

    }

    @Override
    public Iterable<DownloadItem> retrieveUrls(final Iterable<DownloadItem> urls) {
        return Iterables.transform(urls, new Function<DownloadItem, DownloadItem>() {

            @Override
            public DownloadItem apply(final DownloadItem input) {
                return retrieveUrl(input);
            }
        });
    }

    /*
     * (non-Javadoc)
     *
     * @see eu.dnetlib.data.download.rmi.DownloadPlugin#getPluginName()
     */
    @Override
    public String getPluginName() {
        return "FollowPDFLinkPlugins";
    }

    /*
     * (non-Javadoc)
     *
     * @see eu.dnetlib.data.download.rmi.DownloadPlugin#retrieveUrl(eu.dnetlib.data.download.rmi.DownloadItem)
     */
    @Override
    public DownloadItem retrieveUrl(final DownloadItem input) {
        if (checkOpenAccess(input) == null) return null;
        String url = input.getOriginalUrl();

        if ((url == null) || (url.trim().length() == 0)) return input;
        @SuppressWarnings("unchecked")
        List<String> urls = new Gson().fromJson(url, ArrayList.class);
        if ((urls == null) || (urls.size() == 0)) return input;
        if (checkUrlsNotNull(input, urls))
            return input;
        input.setOriginalUrl(null);
        input.setUrl(null);
        return input;
    }

    @Override
    public void setBasePath(final String basePath) {
        // TODO Auto-generated method stub

    }

}