package eu.dnetlib.dhp.sx.graph;

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;

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 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;

/**
 * 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
 * <p>
 * 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
	 * <p>
	 * - 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
	 * <p>
	 * 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");
	}
}