Add Esql.QueryAsObjectsAsync high level API (#8214) (#8223)

Co-authored-by: Florian Bernd <git@flobernd.de>

src/Elastic.Clients.Elasticsearch.Shared/Client/ElasticsearchClient.Esql.cs

@@ -0,0 +1,96 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information.
+
+#if !ELASTICSEARCH_SERVERLESS
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using System.Threading.Tasks;
+using System.Threading;
+
+#if ELASTICSEARCH_SERVERLESS
+namespace Elastic.Clients.Elasticsearch.Esql.Serverless;
+#else
+
+namespace Elastic.Clients.Elasticsearch.Esql;
+#endif
+
+public partial class EsqlNamespacedClient
+{
+	public virtual async Task<IEnumerable<TDocument>> QueryAsObjectsAsync<TDocument>(
+		Action<EsqlQueryRequestDescriptor<TDocument>> configureRequest,
+		CancellationToken cancellationToken = default)
+	{
+		if (configureRequest is null)
+			throw new ArgumentNullException(nameof(configureRequest));
+
+		var response = await QueryAsync<TDocument>(Configure, cancellationToken).ConfigureAwait(false);
+
+		return EsqlToObject<TDocument>(Client, response);
+
+		void Configure(EsqlQueryRequestDescriptor<TDocument> descriptor)
+		{
+			configureRequest(descriptor);
+			descriptor.Format("JSON");
+			descriptor.Columnar(false);
+		}
+	}
+
+	private static IEnumerable<T> EsqlToObject<T>(ElasticsearchClient client, EsqlQueryResponse response)
+	{
+		// TODO: Improve performance
+
+		using var doc = JsonSerializer.Deserialize<JsonDocument>(response.Data) ?? throw new JsonException();
+
+		if (!doc.RootElement.TryGetProperty("columns"u8, out var columns) || (columns.ValueKind is not JsonValueKind.Array))
+			throw new JsonException("");
+
+		if (!doc.RootElement.TryGetProperty("values"u8, out var values) || (values.ValueKind is not JsonValueKind.Array))
+			yield break;
+
+		var names = columns.EnumerateArray()
+			.Select(x =>
+			{
+				if (!x.TryGetProperty("name"u8, out var prop))
+				{
+					throw new JsonException();
+				}
+
+				var result = prop.GetString() ?? throw new JsonException();
+
+				return result;
+			})
+			.ToArray();
+
+		var obj = new JsonObject();
+		using var ms = new MemoryStream();
+		using var writer = new Utf8JsonWriter(ms);
+
+		foreach (var document in values.EnumerateArray())
+		{
+			obj.Clear();
+			ms.SetLength(0);
+			writer.Reset();
+
+			var properties = names.Zip(document.EnumerateArray(),
+				(key, value) => new KeyValuePair<string, JsonNode?>(key, JsonValue.Create(value)));
+			foreach (var property in properties)
+				obj.Add(property);
+
+			obj.WriteTo(writer);
+			writer.Flush();
+			ms.Position = 0;
+
+			var result = client.SourceSerializer.Deserialize<T>(ms) ?? throw new JsonException("");
+
+			yield return result;
+		}
+	}
+}
+
+#endif

src/Elastic.Clients.Elasticsearch.Shared/Client/NamespacedClientProxy.cs

@@ -24,14 +24,14 @@ public abstract class NamespacedClientProxy
 	private const string InvalidOperation = "The client has not been initialised for proper usage as may have been partially mocked. Ensure you are using a " +
 		"new instance of ElasticsearchClient to perform requests over a network to Elasticsearch.";
 
-	private readonly ElasticsearchClient _client;
+	protected ElasticsearchClient Client { get; }
 
 	/// <summary>
 	/// Initializes a new instance for mocking.
 	/// </summary>
 	protected NamespacedClientProxy() { }
 
-	internal NamespacedClientProxy(ElasticsearchClient client) => _client = client;
+	internal NamespacedClientProxy(ElasticsearchClient client) => Client = client;
 
 	internal TResponse DoRequest<TRequest, TResponse, TRequestParameters>(TRequest request)
 		where TRequest : Request<TRequestParameters>
@@ -46,10 +46,10 @@ internal TResponse DoRequest<TRequest, TResponse, TRequestParameters>(
 		where TResponse : ElasticsearchResponse, new()
 		where TRequestParameters : RequestParameters, new()
 	{
-		if (_client is null)
+		if (Client is null)
 			ThrowHelper.ThrowInvalidOperationException(InvalidOperation);
 
-		return _client.DoRequest<TRequest, TResponse, TRequestParameters>(request, forceConfiguration);
+		return Client.DoRequest<TRequest, TResponse, TRequestParameters>(request, forceConfiguration);
 	}
 
 	internal Task<TResponse> DoRequestAsync<TRequest, TResponse, TRequestParameters>(
@@ -68,9 +68,9 @@ internal Task<TResponse> DoRequestAsync<TRequest, TResponse, TRequestParameters>
 		where TResponse : ElasticsearchResponse, new()
 		where TRequestParameters : RequestParameters, new()
 	{
-		if (_client is null)
+		if (Client is null)
 			ThrowHelper.ThrowInvalidOperationException(InvalidOperation);
 
-		return _client.DoRequestAsync<TRequest, TResponse, TRequestParameters>(request, forceConfiguration, cancellationToken);
+		return Client.DoRequestAsync<TRequest, TResponse, TRequestParameters>(request, forceConfiguration, cancellationToken);
 	}
 }