/*******************************************************************************
 * Copyright (C) 2017 ANSYS medini Technologies AG
 * 
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 * 
 * SPDX-License-Identifier: EPL-2.0
 * 
 * Contributors: 
 * 	ANSYS medini Technologies AG - initial API and implementation
 ******************************************************************************/
package org.eclipse.opencert.elastic;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Collections;
import java.util.Date;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.nio.client.DefaultAsyncUserTokenHandler;
import org.apache.http.nio.entity.NStringEntity;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.Response;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.index.query.QueryBuilder;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.index.query.QueryStringQueryBuilder;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.builder.SearchSourceBuilder;

import com.google.gson.Gson;
import com.google.gson.JsonObject;

/**
 * {@link DefaultAsyncUserTokenHandler} implementation of {@link ElasticClient}.
 * 
 * @author mauersberger
 */
public class ElasticClientImpl implements ElasticClient, AutoCloseable {

	// the "real" client
	private RestClient restClient;

	@SuppressWarnings("unused")
	private int lastStatus;

	/**
	 * Factory method to create a new {@link ElasticClient}.
	 * 
	 * @param host
	 *            server name or IP
	 * @param port
	 *            port
	 * @param scheme
	 *            "http" or "https"
	 * @return the new {@link ElasticClient} instance
	 */
	public static ElasticClient on(String host, int port, String scheme) {
		ElasticClientImpl client = new ElasticClientImpl();
		client.restClient = RestClient.builder(new HttpHost(host, port, scheme)).build();
		return client;
	}

	/*
	 * Intentionally private.
	 */
	private ElasticClientImpl() {
		// just to avoid instantiation, force using the factory API
	}

	@Override
	public ElasticClient store(ElasticDocument document) throws IOException {
		HttpEntity entity = new NStringEntity(document.source.toString(), ContentType.APPLICATION_JSON);
		Response response = this.restClient.performRequest("PUT", document.getEndPoint(), Collections.emptyMap(), entity); //$NON-NLS-1$
		lastStatus = response.getStatusLine().getStatusCode();
		return this;
	}

	@Override
	public ElasticClient storeAll(Iterator<ElasticDocument> documents) throws IOException {
		while (documents.hasNext()) {
			store (documents.next());
		}
		return this;
	}

	@Override
	public Set<ElasticDocument> search(String indexName, String queryString, Map<String, Object> filters)  throws Exception {
		RestHighLevelClient highLevel = new RestHighLevelClient(this.restClient);
		SearchRequest searchRequest = new SearchRequest(indexName);
		// see example at https://dzone.com/articles/java-high-level-rest-client-elasticsearch
		SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
		searchRequest.source(sourceBuilder);
		// find the best query builder depending on the arguments
		QueryBuilder queryBuilder = QueryBuilders.matchAllQuery();
		if (queryString != null) {
			queryString = queryString.replaceAll(".*", "*");
			QueryStringQueryBuilder stringQuery = QueryBuilders.queryStringQuery(queryString);
			stringQuery.allowLeadingWildcard(true);
			queryBuilder = stringQuery;
		}
		sourceBuilder.query(queryBuilder);
		
		SearchResponse response = highLevel.search(searchRequest);
		System.out.println(response);
		lastStatus = response.status().getStatus();
		
		Set<ElasticDocument> result = new HashSet<>();
		SearchHits hits = response.getHits();
		// Note: total hits might be much bigger 
		for (SearchHit hit : hits.getHits()) {
			// convert Hit to Json
			JsonObject json = new JsonObject();
			
			// put all source information back into JSON
			Map<String, Object> fields = hit.getSource();
			Set<String> keys = fields.keySet();
			for (String key : keys) {
				Object field = fields.get(key);
				json.addProperty(key, (String) field.toString()); 
			}
			
			ElasticDocument doc = new ElasticDocument(json, hit.getIndex(), hit.getType(), hit.getId());
			result.add(doc);
		}
		
		return result;
	}
	
	@Override
	public ElasticClient ping() throws Exception {
		Response response = this.restClient.performRequest("GET", "/"); //$NON-NLS-1$ //$NON-NLS-2$
		lastStatus = response.getStatusLine().getStatusCode();
		return this;
	}

	@Override
	public ElasticClient delete(String indexName) throws Exception {
		Response response = this.restClient.performRequest("DELETE", "/" + indexName, Collections.emptyMap()); //$NON-NLS-1$ //$NON-NLS-2$
		lastStatus = response.getStatusLine().getStatusCode();
		return this;
	}

	@Override
	public String version() throws IOException {
		Response response = this.restClient.performRequest("GET", "/"); //$NON-NLS-1$ //$NON-NLS-2$
		lastStatus = response.getStatusLine().getStatusCode();

		// we assume its a JSON response
		try (InputStream content = response.getEntity().getContent()) {
			InputStreamReader reader = new InputStreamReader(content, "UTF8"); //$NON-NLS-1$
			JsonObject json = new Gson().fromJson(reader, JsonObject.class);
			return json.get("version").getAsJsonObject().get("number").getAsString(); //$NON-NLS-1$//$NON-NLS-2$
		} catch (Exception exception) {
			throw new IOException("Unable to ping server"); //$NON-NLS-1$
		}
	}

	@Override
	public String indexStatus(String indexName) throws Exception {
		Response response = this.restClient.performRequest("GET", "/" + indexName); //$NON-NLS-1$ //$NON-NLS-2$
		lastStatus = response.getStatusLine().getStatusCode();

		// we assume its a JSON response
		try (InputStream content = response.getEntity().getContent()) {

			InputStreamReader reader = new InputStreamReader(content, "UTF8"); //$NON-NLS-1$
			JsonObject root = new Gson().fromJson(reader, JsonObject.class);
			JsonObject index = root.get(indexName).getAsJsonObject();
			JsonObject settings = index.get("settings").getAsJsonObject(); //$NON-NLS-1$
			JsonObject indexSettings = settings.get("index").getAsJsonObject(); //$NON-NLS-1$
			long date = indexSettings.get("creation_date").getAsLong(); //$NON-NLS-1$
			return "Created " + new Date(date).toString(); //$NON-NLS-1$ 
		} catch (Exception exception) {
			throw new IOException("Unable to ping index", exception); //$NON-NLS-1$
		}
	}

	@Override
	public void close() throws IOException {
		if (restClient != null) {
			restClient.close();
			restClient = null;
		}
	}
}