package eu.dnetlib.dhp.graph.sx;

import com.mongodb.DBObject;
import com.mongodb.MongoClient;
import com.mongodb.QueryBuilder;
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import eu.dnetlib.dhp.application.ArgumentApplicationParser;
import org.apache.commons.io.IOUtils;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.bson.Document;
import org.bson.conversions.Bson;
import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Consumer;
import java.util.stream.Collectors;

/**
 * This job is responsible to collect
 * data from mongoDatabase and store in a sequence File on HDFS
 *   Mongo database contains information of each MDSTore in two collections:
 *     -metadata
 *         That contains info like:
 *             ID, format, layout, interpretation
 *     -metadataManager:
 *         that contains info :
 *             ID, mongoCollectionName
 *     from the metadata collection we filter the ids with Format, layout, and Interpretation
 *     from the metadataManager we get the current MONGO collection name which contains metadata XML
 *     see function getCurrentId
 *
 *  This Job will be called different times in base at the triple we want import,
 *  and generates for each triple a sequence file of XML
 *
 */

public class ImportDataFromMongo {
    /**
     * It requires in input some parameters described on a file eu/dnetlib/dhp/graph/sx/import_from_mongo_parameters.json
     *
     *  - the name node
     *  - the paht where store HDFS File
     *  - the mongo host
     *  - the mongo port
     *  - the metadata format to import
     *  - the metadata layout to import
     *  - the metadata interpretation to import
     *  - the mongo database Name
     *
     *  This params are encoded into args
     *
     *

     *
     *
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        final ArgumentApplicationParser parser = new ArgumentApplicationParser(
                IOUtils.toString(
                        ImportDataFromMongo.class.getResourceAsStream(
                                "/eu/dnetlib/dhp/sx/graph/argumentparser/import_from_mongo_parameters.json")));
        parser.parseArgument(args);
        final int port = Integer.parseInt(parser.get("dbport"));
        final String host = parser.get("dbhost");

        final String format = parser.get("format");
        final String layout = parser.get("layout");
        final String interpretation = parser.get("interpretation");

        final String dbName = parser.get("dbName");
        final MongoClient client = new MongoClient(host, port);
        MongoDatabase database = client.getDatabase(dbName);

        MongoCollection<Document> metadata = database.getCollection("metadata");
        MongoCollection<Document> metadataManager = database.getCollection("metadataManager");
        final DBObject query = QueryBuilder.start("format").is(format).and("layout").is(layout).and("interpretation").is(interpretation).get();
        final List<String> ids = new ArrayList<>();
        metadata.find((Bson) query).forEach((Consumer<Document>) document -> ids.add(document.getString("mdId")));
        List<String> databaseId = ids.stream().map(it -> getCurrentId(it, metadataManager)).filter(Objects::nonNull).collect(Collectors.toList());


        final String hdfsuri = parser.get("namenode");
        // ====== Init HDFS File System Object
        Configuration conf = new Configuration();
        // Set FileSystem URI
        conf.set("fs.defaultFS", hdfsuri);
        // Because of Maven
        conf.set("fs.hdfs.impl", org.apache.hadoop.hdfs.DistributedFileSystem.class.getName());
        conf.set("fs.file.impl", org.apache.hadoop.fs.LocalFileSystem.class.getName());

        FileSystem.get(URI.create(hdfsuri), conf);
        Path hdfswritepath = new Path(parser.get("targetPath"));

        final AtomicInteger counter = new AtomicInteger(0);
        try (SequenceFile.Writer writer = SequenceFile.createWriter(conf,
                SequenceFile.Writer.file(hdfswritepath), SequenceFile.Writer.keyClass(IntWritable.class),
                SequenceFile.Writer.valueClass(Text.class))) {
            final IntWritable key = new IntWritable(counter.get());
            final Text value = new Text();
            databaseId.forEach(id -> {
                System.out.println("Reading :"+id);
                MongoCollection<Document> collection = database.getCollection(id);
                collection.find().forEach((Consumer<Document>) document ->
                        {
                            key.set(counter.getAndIncrement());
                            value.set(document.getString("body"));

                            if (counter.get() % 10000 == 0) {
                                System.out.println("Added "+counter.get());
                            }
                            try {
                                writer.append(key, value);
                            } catch (IOException e) {
                                throw new RuntimeException(e);
                            }
                        }
                );
            });
        }
    }

    /**
     * Return the name of mongo collection giving an MdStore ID
     * @param mdId The id of the MDStore
     * @param metadataManager The collection metadataManager on mongo which contains this information
     * @return
     */
    private static String getCurrentId(final String mdId, final MongoCollection<Document> metadataManager) {
        FindIterable<Document> result = metadataManager.find((Bson) QueryBuilder.start("mdId").is(mdId).get());
        final Document item = result.first();
        return item == null ? null : item.getString("currentId");
    }

}