ElasticsearchSearchClient.cs

using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace SemanticSearchImplementation
{
    /// <summary>
    /// Implements necessary functions to use Elasticsearch as a search engine.
    /// </summary>
    /// <inheritdoc cref="ISearchClient"/>
    public class ElasticsearchSearchClient : ISearchClient
    {
        // API
        private const string ALIASES = "_aliases";
        private const string SEARCH = "_search";
        private const string MAPPING = "_mapping";
        private const string BULK = "_bulk";

        private static readonly HttpClient client = new HttpClient();

        private readonly string baseUrl;

        private string _index;

        public ElasticsearchSearchClient(string server = "localhost", string port = "9200")
        {
            baseUrl = $"http://{server}:{port}/";
            client.DefaultRequestHeaders.Add("Accept", "application/json");
        }

        public void ChangeIndex(string index)
        {
            _index = index;
        }

        public async Task<IDictionary<string, string>> GetMappingAsync()
        {
            var response = await client.GetAsync(baseUrl + _index + "/" + MAPPING);
            JObject jObject = JObject.Parse(await response.Content.ReadAsStringAsync());
            var fieldMappings = (JObject)jObject[_index]["mappings"]["properties"];

            IDictionary<string, string> mapping = new Dictionary<string, string>();
            foreach (var prop in fieldMappings)
            {
                mapping.Add(prop.Key, (string) prop.Value["type"]);      
            }
            return mapping;
        }

        /// <summary>
        /// Queries the document ID for a metadata graph.
        /// </summary>
        /// <param name="graphName">ID of the metadata graph.</param>
        /// <returns>ID of the Elasticsearch document.</returns>
        private async Task<string> GetIdFromGraphNameAsync(string graphName)
        {
            var content = new JObject() {
                new JProperty("query", new JObject
                {
                    new JProperty("term", new JObject
                    {
                        new JProperty(ElasticsearchIndexMapper.LABEL_GRAPHNAME, new JObject
                        {
                            new JProperty("value", graphName)
                        })
                    })