Metacat

/**

 *  '$RCSfile$'

 *  Copyright: 2000-2005 Regents of the University of California and the

 *             National Center for Ecological Analysis and Synthesis

 *

 *   '$Author: jones $'

 *     '$Date: 2005-12-07 10:59:03 -0800 (Wed, 07 Dec 2005) $'

 * '$Revision: 2819 $'

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

package edu.ucsb.nceas.metacat.lsid;

import java.io.BufferedReader;

import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.Reader;

import java.io.StringReader;

import java.util.Hashtable;

import java.util.ResourceBundle;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.stream.StreamResult;

import javax.xml.transform.stream.StreamSource;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import com.ibm.lsid.LSID;

import com.ibm.lsid.MalformedLSIDException;

import com.ibm.lsid.MetadataResponse;

import com.ibm.lsid.server.LSIDMetadataService;

import com.ibm.lsid.server.LSIDRequestContext;

import com.ibm.lsid.server.LSIDServerException;

import com.ibm.lsid.server.LSIDServiceConfig;

import edu.ucsb.nceas.metacat.client.Metacat;

import edu.ucsb.nceas.metacat.client.MetacatFactory;

import edu.ucsb.nceas.metacat.client.MetacatInaccessibleException;

public class LSIDAuthorityMetaData implements LSIDMetadataService

{

    private LSIDDataLookup lookup = null;

    private static Hashtable currentLSIDs = new Hashtable();

    private static Log logger = LogFactory

                    .getLog("edu.ucsb.nceas.metacat.lsid");

    public void initService(LSIDServiceConfig cf) throws LSIDServerException

    {

        logger.info("Starting LSIDAuthorityMetadata.");

        lookup = new LSIDDataLookup();

    }

    private static final String RDF_NS = "http://www.w3.org/1999/02/22-rdf-syntax-ns#";

    private static final String DC_NS = "http://purl.org/dc/elements/1.1/";

    private static final String I3CP_NS = "urn:lsid:i3c.org:predicates:";

    private static final String I3C_CONTENT = "urn:lsid:i3c.org:types:content";

    public MetadataResponse getMetadata(LSIDRequestContext req, String[] formats)

                    throws LSIDServerException

    {

        LSID lsid = req.getLsid();

        ByteArrayInputStream theMetadata = doMetadataRequest(lsid);

        return new MetadataResponse(theMetadata, null,

                                    MetadataResponse.RDF_FORMAT);

    }

    private ByteArrayInputStream doMetadataRequest(LSID lsid)

                    throws LSIDServerException

    {

        logger.debug("getting metadata for lsid " + lsid.getLsid());

        try {

            String styleSheetName = null;

            styleSheetName = "metacat.xslt";

            LSIDDataLookup myLookup = new LSIDDataLookup();

            InputStream content = myLookup.lsidData(lsid);

            InputStream content2 = myLookup.lsidData(lsid);

            if (!isEML(content2)) {

                content = getEML(lsid);

            }

            content2.close();

            setCurrentLSID(lsid);

            InputStream styleSheet = getClass()

                            .getResourceAsStream(styleSheetName);

            TransformerFactory factory = TransformerFactory.newInstance();

            Transformer transformer = factory

                            .newTransformer(new StreamSource(styleSheet));

            ByteArrayOutputStream out = new ByteArrayOutputStream();

            transformer.transform(new StreamSource(content),

                                  new StreamResult(out));

            content.close();

            clearState();

            return new ByteArrayInputStream(out.toByteArray());

        } catch (Exception e) {

            throw new LSIDServerException(e, "Error transforming XML for: "

                                             + lsid);

        }

    }

    private String getStringFromInputStream(InputStream input)

    {

        StringBuffer result = new StringBuffer();

        BufferedReader in = new BufferedReader(new InputStreamReader(input));

        String line;

        try {

            while ((line = in.readLine()) != null) {

                result.append(line);

            }

        } catch (IOException e) {

            logger.error("IOexception " + e);

        }

        return result.toString();

    }

    /**

     * figure out is this inputstream is an eml document or not

     * TODO: need a better way to figure out if this is an eml document 

     */

    private boolean isEML(InputStream input)

    {

        if (input == null) { return false; }

        int loop = 0;

        boolean itIsEML = false;

        String line = "";

        try {

            BufferedReader in = new BufferedReader(new InputStreamReader(input));

            while ((loop < 20) && (line != null) && (!itIsEML)) {

                line = in.readLine();

                line = line.toLowerCase();

                if (line.indexOf("eml:eml") != -1) {

                    itIsEML = true;

                }

                loop++;

            }

        } catch (IOException e) {

            logger.error("ioerror in LSIDAuthorityMetadata: " + e);

        }

        return itIsEML;

    }

    /**

     * this lsid points to a data object - get the metadata objects which refer

     * to this document

     */

    private InputStream getEML(LSID theLSID)

    {

        InputStream response = null;

        // need to find things with this object in any of the elements

        // using the metacat api

        // get back dataset/docid and dataset/title

        // create the query

        String theQuery = getMetaCatQuery(theLSID);

        // get the metacat record

        Reader metaCatResponse = getMetaCatResponse(theQuery);

        // parse the metadata to get the applicable rdf information

        response = parseMetaCatResponse(metaCatResponse, theLSID);

        return response;

    }

    /**

     * given an LSID return a metacat query which will return docs mentioning

     * this LSID

     */

    private String getMetaCatQuery(LSID lsid)

    {

        logger.debug("getting Metacat Query for: " + lsid.toString());

        String ns = lsid.getNamespace();

        String id = lsid.getObject();

        String ver = lsid.getRevision();

        String theName = ns + "." + id + "." + ver;

        String theQuery = null;

        theQuery = "<?xml version=\"1.0\"?>\n"

                   + "<pathquery version=\"1.2\">\n"

                   + "  <querytitle>"

                   + theName

                   + " search</querytitle>\n"

                   + "  <returnfield>dataset/docid</returnfield>\n"

                   + "  <returnfield>dataset/title</returnfield>\n"

                   + "  <querygroup operator=\"UNION\">\n"

                   + "    <queryterm searchmode=\"contains\" casesensitive=\"false\">\n"

                   + "      <value>" + theName + "</value>\n"

                   + "      <pathexpr>anyfield</pathexpr>\n"

                   + "    </queryterm>\n" + "  </querygroup>\n"

                   + "<pathquery>\n";

        return theQuery;

    }

    /**

     * given a query string, query MetaCat and return the response

     */

    private Reader getMetaCatResponse(String query)

    {

        logger.debug("Querying the metacat server.");

        // get the metacat server from the configuration file

        //

        ResourceBundle rb = ResourceBundle.getBundle("metacat-lsid");

        String url = rb.getString("metacatserver");

        Reader r = null;

        try {

            Metacat m = MetacatFactory.createMetacatConnection(url);

            r = m.query(new StringReader(query));

        } catch (MetacatInaccessibleException mie) {

            logger.error("Metacat Inaccessible:\n" + mie.getMessage());

        } catch (Exception e) {

            logger.error("General exception:\n" + e.getMessage());

        }

        return r;

    }

    /**

     * Given a reader which is a metacat response, parse it and return the

     * appropriate rdf

     */

    private InputStream parseMetaCatResponse(Reader reader, LSID theLSID)

    {

        InputStream response = null;

        logger.debug("Parsing the metacat response.");

        // if there's more than one document, then return rdf listing the

        // documents

        // otherwise get the document and return rdf based on it

        String contents = getStringFromReader(reader);

        if (numberDocuments(contents) < 1) {

            response = noMetaDataResponse(theLSID);

        } else if (numberDocuments(contents) > 1) {

            response = metaDataList(contents, theLSID);

        } else {

            response = getMetaData(contents, theLSID);

        }

        return response;

    }

    /**

     * There's no metadata for this document

     */

    private ByteArrayInputStream noMetaDataResponse(LSID theLSID)

    {

        ResourceBundle rb = ResourceBundle.getBundle("metacat-lsid");

        String metadataLabels = rb.getString("metadatalabels");

        String result = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"

                        + "<rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\" \n"

                        + "	xmlns:dc=\"http://purl.org/dc/elements/1.1/\" \n"

                        + "	xmlns:pred=\"urn:lsid:i3c.org:predicates:\" xmlns=\"urn:lsid:"

                        + metadataLabels

                        + ":predicates:\"> \n"

                        + "<rdf:Description rdf:about=\""

                        + theLSID.getLsid()

                        + "\"> \n"

                        + "	<pred:title xmlns:pred=\"http://purl.org/dc/elements/1.1/\">There is no metadata for this LSID.</pred:title>\n"

                        + "</rdf:Description>\n" + "</rdf:RDF>\n";

        return new ByteArrayInputStream(result.getBytes());

    }

    /**

     * There's more than one metdata document

     */

    private ByteArrayInputStream metaDataList(String contents, LSID theLSID)

    {

        ResourceBundle rb = ResourceBundle.getBundle("metacat");

        String metadataLabels = rb.getString("metadatalabels");

        String result = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"

                        + "<rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\" \n"

                        + "	xmlns:dc=\"http://purl.org/dc/elements/1.1/\" \n"

                        + "	xmlns:pred=\"urn:lsid:i3c.org:predicates:\" xmlns=\"urn:lsid:"

                        + metadataLabels

                        + ":predicates:\"> \n"

                        + "<rdf:Description rdf:about=\""

                        + theLSID.getLsid()

                        + "\"> \n"

                        + "	<pred:title xmlns:pred=\"http://purl.org/dc/elements/1.1/\">There is more than one metadata document for this LSID - which confuses me right now.  Try again soon and I'll be less confused.</pred:title>\n"

                        + "</rdf:Description>\n" + "</rdf:RDF>\n";

        return new ByteArrayInputStream(result.getBytes());

    }

    /**

     * There's just one metadata document

     */

    private ByteArrayInputStream getMetaData(String contents, LSID theLSID)

    {

        String paramString = "<param name=\"dataset/title\">";

        ByteArrayInputStream result = null;

        if (contents.indexOf(paramString) == -1) {

            return noMetaDataResponse(theLSID);

        } else {

            String parts[] = contents.split(paramString);

            String parts2[] = parts[1].split("</param>");

            try {

                LSID newLSID = new LSID(parts2[0]);

                result = doMetadataRequest(newLSID);

            } catch (MalformedLSIDException e) {

                logger.error("problem generating LSID: " + e);

                e.printStackTrace();

            } catch (LSIDServerException e) {

                logger.error("problem generating LSID: " + e);

                e.printStackTrace();

            }

        }

        return result;

    }

    /**

     * Find out how many contents are in this metacat response I'm just using

     * string stuff for this - sort of lame, but does the trick more cool would

     * be to use xml stuff

     */

    private int numberDocuments(String contents)

    {

        String[] docSplit = contents.split("<document>");

        return (docSplit.length - 1);

    }

    /**

     * Given a reader, return a string

     */

    private String getStringFromReader(Reader reader)

    {

        StringBuffer response = new StringBuffer();

        try {

            BufferedReader bufReader = new BufferedReader(reader);

            String line = null;

            while ((line = bufReader.readLine()) != null) {

                response.append(line);

            }

            bufReader.close();

        } catch (IOException e) {

            logger.error("error getting string from reader " + e);

        }

        return response.toString();

    }

    /**

     * set the LSID for the current thread

     */

    static void setCurrentLSID(LSID lsid)

    {

        currentLSIDs.put(Thread.currentThread(), lsid);

    }

    static void clearState()

    {

        currentLSIDs.remove(Thread.currentThread());

    }

    /**

     * get the current LSID for the given thread, for use in XSLT so return a

     * string

     */

    public static String getLSID(

                         org.apache.xalan.extensions.XSLProcessorContext foo,

                         org.apache.xalan.templates.ElemExtensionCall bar)

                    throws MalformedLSIDException

    {

        return ((LSID) currentLSIDs.get(Thread.currentThread())).toString();

    }

    public static String getLSID() throws MalformedLSIDException

    {

        return ((LSID) currentLSIDs.get(Thread.currentThread())).toString();

    }

}