/**
 * 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 org.dspace.discovery;

import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.io.Charsets;
import org.apache.commons.lang3.StringUtils;
import org.apache.log4j.Logger;
import org.apache.solr.common.util.ContentStreamBase;
import org.dspace.authorize.AuthorizeException;
import org.dspace.content.Bitstream;
import org.dspace.content.BitstreamFormat;
import org.dspace.content.Bundle;
import org.dspace.content.Item;
import org.dspace.content.factory.ContentServiceFactory;
import org.dspace.content.service.BitstreamService;
import org.dspace.core.Context;

import javax.annotation.Nullable;
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.sql.SQLException;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import static org.dspace.core.Utils.emptyIfNull;

/**
 * Construct a <code>ContentStream</code> from a <code>File</code>
 */
public class FullTextContentStreams extends ContentStreamBase
{
    private static final Logger log = Logger.getLogger(FullTextContentStreams.class);

    public static final String FULLTEXT_BUNDLE = "TEXT";

    protected final Context context;
    protected List<FullTextBitstream> fullTextStreams;
    protected BitstreamService bitstreamService;

    public FullTextContentStreams(Context context, Item parentItem) throws SQLException {
        this.context = context;
        init(parentItem);
    }

    protected void init(Item parentItem) {
        fullTextStreams = new LinkedList<>();

        if(parentItem != null) {
            sourceInfo = parentItem.getHandle();

            //extracted full text is always extracted as plain text
            contentType = "text/plain";

            buildFullTextList(parentItem);
        }
    }

    private void buildFullTextList(Item parentItem) {
        // now get full text of any bitstreams in the TEXT bundle
        // trundle through the bundles
        List<Bundle> myBundles = parentItem.getBundles();

        for (Bundle myBundle : emptyIfNull(myBundles)) {
            if (StringUtils.equals(FULLTEXT_BUNDLE, myBundle.getName())) {
                // a-ha! grab the text out of the bitstreams
                List<Bitstream> bitstreams = myBundle.getBitstreams();

                for (Bitstream fulltextBitstream : emptyIfNull(bitstreams)) {
                    fullTextStreams.add(new FullTextBitstream(sourceInfo, fulltextBitstream));

                    log.debug("Added BitStream: "
                            + fulltextBitstream.getStoreNumber() + " "
                            + fulltextBitstream.getSequenceID() + " "
                            + fulltextBitstream.getName());
                }
            }
        }
    }

    @Override
    public String getName() {
        return StringUtils.join(Iterables.transform(fullTextStreams, new Function<FullTextBitstream, String>() {
            @Nullable
            @Override
            public String apply(@Nullable FullTextBitstream input) {
                return input == null ? "" : input.getFileName();
            }
        }), ";");
    }

    @Override
    public Long getSize() {
        long result = 0;

        if(CollectionUtils.isNotEmpty(fullTextStreams)) {
            Iterable<Long> individualSizes = Iterables.transform(fullTextStreams, new Function<FullTextBitstream, Long>() {
                @Nullable
                @Override
                public Long apply(@Nullable FullTextBitstream input) {
                    return input == null ? 0L : input.getSize();
                }
            });

            for (Long size : individualSizes) {
                result += size;
            }
        }

        return result;
    }

    @Override
    public Reader getReader() throws IOException {
        return super.getReader();
    }

    @Override
    public InputStream getStream() throws IOException {
        try {
            return new SequenceInputStream(new FullTextEnumeration(fullTextStreams.iterator()));
        } catch (Exception e) {
            log.error("Unable to add full text bitstreams to SOLR for item " + sourceInfo + ": " + e.getMessage(), e);
            return new ByteArrayInputStream((e.getClass() + ": " + e.getMessage()).getBytes(StandardCharsets.UTF_8));
        }
    }

    public boolean isEmpty() {
        return CollectionUtils.isEmpty(fullTextStreams);
    }

    private BitstreamService getBitstreamService() {
        if(bitstreamService == null) {
            bitstreamService = ContentServiceFactory.getInstance().getBitstreamService();
        }
        return bitstreamService;
    }

    private class FullTextBitstream {
        private String itemHandle;
        private Bitstream bitstream;

        public FullTextBitstream(final String parentHandle, final Bitstream file) {
            this.itemHandle = parentHandle;
            this.bitstream = file;
        }

        public String getContentType(final Context context) throws SQLException {
            BitstreamFormat format = bitstream.getFormat(context);
            return format == null ? null : StringUtils.trimToEmpty(format.getMIMEType());
        }

        public String getFileName() {
            return StringUtils.trimToEmpty(bitstream.getName());
        }

        public long getSize() {
            return bitstream.getSize();
        }

        public InputStream getInputStream() throws SQLException, IOException, AuthorizeException {
            return getBitstreamService().retrieve(context, bitstream);
        }

        public String getItemHandle() {
            return itemHandle;
        }
    }

    private class FullTextEnumeration implements Enumeration<InputStream> {

        private final Iterator<FullTextBitstream> fulltextIterator;

        public FullTextEnumeration(final Iterator<FullTextBitstream> fulltextStreams) {
            this.fulltextIterator = fulltextStreams;
        }

        public boolean hasMoreElements() {
            return fulltextIterator.hasNext();
        }

        public InputStream nextElement() {
            InputStream inputStream = null;
            FullTextBitstream bitstream = null;

            try {
                bitstream = fulltextIterator.next();
                inputStream = bitstream.getInputStream();
            } catch (Exception e) {
                log.warn("Unable to add full text bitstream " + (bitstream == null ? "NULL" :
                        bitstream.getFileName() + " for item " + bitstream.getItemHandle())
                        + " to SOLR:" + e.getMessage(), e);

                inputStream = new ByteArrayInputStream((e.getClass() + ": " + e.getMessage()).getBytes(StandardCharsets.UTF_8));
            }

            return inputStream == null ? null : new SequenceInputStream(
                    new ByteArrayInputStream("\n".getBytes(Charsets.UTF_8)), inputStream);
        }
    }

}