Deserialize relation on TotalHits (#3667)

This commit deserializes the relation and renames HitsTotal to TotalHits, line with Java source.

Author: russcam

src/Elasticsearch.Net/Utf8Json/Formatters/EnumFormatter.cs

@@ -158,7 +158,7 @@ internal class EnumFormatter<T> : IJsonFormatter<T>, IObjectPropertyNameFormatte
 
 		static EnumFormatter()
 		{
-			var names = new List<String>();
+			var names = new List<string>();
 			var values = new List<object>();
 
 			var type = typeof(T);

src/Nest/Aggregations/AggregateFormatter.cs

@@ -205,7 +205,7 @@ private IAggregate GetTopHitsAggregate(ref JsonReader reader, IJsonFormatterReso
 		{
 			var count = 0;
 			double? maxScore = null;
-			HitsTotal total = null;
+			TotalHits total = null;
 			List<LazyDocument> topHits = null;
 
 			while (reader.ReadIsInObject(ref count))
@@ -216,7 +216,7 @@ private IAggregate GetTopHitsAggregate(ref JsonReader reader, IJsonFormatterReso
 					switch (value)
 					{
 						case 0:
-							var hitsFormatter = formatterResolver.GetFormatter<HitsTotal>();
+							var hitsFormatter = formatterResolver.GetFormatter<TotalHits>();
 							total = hitsFormatter.Deserialize(ref reader, formatterResolver);
 							break;
 						case 1:

src/Nest/Aggregations/Metric/TopHits/TopHitsAggregate.cs

@@ -19,7 +19,7 @@ internal TopHitsAggregate(IList<LazyDocument> hits, IJsonFormatterResolver forma
 
 		public double? MaxScore { get; set; }
 
-		public HitsTotal Total { get; set; }
+		public TotalHits Total { get; set; }
 
 		private IEnumerable<Hit<TDocument>> ConvertHits<TDocument>()
 			where TDocument : class

src/Nest/Search/Search/Hits/HitsMetaData.cs

@@ -5,13 +5,13 @@ namespace Nest
 {
 	public class HitsMetadata<T> where T : class
 	{
-		[DataMember(Name ="hits")]
+		[DataMember(Name = "hits")]
 		public IReadOnlyCollection<IHit<T>> Hits { get; internal set; } = EmptyReadOnly<IHit<T>>.Collection;
 
-		[DataMember(Name ="max_score")]
+		[DataMember(Name = "max_score")]
 		public double? MaxScore { get; internal set; }
 
-		[DataMember(Name ="total")]
-		public HitsTotal Total { get; internal set; }
+		[DataMember(Name = "total")]
+		public TotalHits Total { get; internal set; }
 	}
 }

src/Nest/Search/Search/Hits/HitsTotal.cs

@@ -13,7 +13,7 @@ public class InnerHitsMetadata
 		public double? MaxScore { get; internal set; }
 
 		[DataMember(Name = "total")]
-		public HitsTotal Total { get; internal set; }
+		public TotalHits Total { get; internal set; }
 
 		public IEnumerable<T> Documents<T>() where T : class
 		{

src/Nest/Search/Search/Hits/InnerHitsMetaData.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Runtime.Serialization;
+using Elasticsearch.Net;
+
+namespace Nest
+{
+	/// <summary>
+	/// Description of the total number of hits of a query. The total hit count
+	/// can't generally be computed accurately without visiting all matches, which
+	/// is costly for queries that match lots of documents. Given that it is often
+	/// enough to have a lower bounds of the number of hits, such as
+	/// "there are more than 1000 hits", Elasticsearch has options to stop counting as soon
+	/// as a threshold has been reached in order to improve query times.
+	/// </summary>
+	[JsonFormatter(typeof(TotalHitsFormatter))]
+	public class TotalHits
+	{
+		/// <summary>Whether <see cref="Value"/> is the exact hit count, in which case <see cref="Relation"/> is
+		/// <see cref="TotalHitsRelation.EqualTo"/>, or a lower bound of the total hit count, in which case
+		/// <see cref="Relation"/> is <see cref="TotalHitsRelation.GreaterThanOrEqualTo"/>
+		/// </summary>
+		[DataMember(Name = "relation")]
+		public TotalHitsRelation? Relation { get; internal set; }
+
+		/// <summary>The value of the total hit count. Must be interpreted in the context of <see cref="Relation"/></summary>
+		[DataMember(Name = "value")]
+		public long Value { get; internal set; }
+	}
+
+	/// <summary>How the <see cref="TotalHits.Value"/> should be interpreted</summary>
+	[StringEnum]
+	public enum TotalHitsRelation
+	{
+		/// <summary>The total hit count is equal to <see cref="TotalHits.Value"/></summary>
+		[EnumMember(Value = "eq")]
+		EqualTo,
+
+		/// <summary>The total hit count is greater than or equal to <see cref="TotalHits.Value"/></summary>
+		[EnumMember(Value = "gte")]
+		GreaterThanOrEqualTo,
+	}
+
+	internal class TotalHitsFormatter : IJsonFormatter<TotalHits>
+	{
+		private static readonly byte[] ValueField = JsonWriter.GetEncodedPropertyNameWithoutQuotation("value");
+		private static readonly byte[] RelationField = JsonWriter.GetEncodedPropertyNameWithoutQuotation("relation");
+		private static readonly EnumFormatter<TotalHitsRelation> RelationFormatter = new EnumFormatter<TotalHitsRelation>(true);
+
+		public TotalHits Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver)
+		{
+			switch (reader.GetCurrentJsonToken())
+			{
+				case JsonToken.BeginObject:
+					var count = 0;
+					long value = -1;
+					TotalHitsRelation? relation = null;
+					while (reader.ReadIsInObject(ref count))
+					{
+						var propertyName = reader.ReadPropertyNameSegmentRaw();
+						if (propertyName.EqualsBytes(ValueField))
+							value = reader.ReadInt64();
+						else if (propertyName.EqualsBytes(RelationField))
+							relation = RelationFormatter.Deserialize(ref reader, formatterResolver);
+						else
+							reader.ReadNextBlock();
+					}
+
+					return new TotalHits { Value = value, Relation = relation };
+				case JsonToken.Number:
+					return new TotalHits { Value = reader.ReadInt64() };
+				default:
+					reader.ReadNextBlock();
+					return null;
+			}
+		}
+
+		public void Serialize(ref JsonWriter writer, TotalHits value, IJsonFormatterResolver formatterResolver)
+		{
+			if (value == null)
+			{
+				writer.WriteNull();
+				return;
+			}
+
+			if (value.Relation.HasValue)
+			{
+				writer.WriteBeginObject();
+				writer.WritePropertyName("value");
+				writer.WriteInt64(value.Value);
+				writer.WriteValueSeparator();
+				writer.WritePropertyName("relation");
+				RelationFormatter.Serialize(ref writer, value.Relation.Value, formatterResolver);
+				writer.WriteEndObject();
+			}
+			else
+				writer.WriteInt64(value.Value);
+		}
+	}
+}

src/Nest/Search/Search/Hits/TotalHits.cs

@@ -186,6 +186,6 @@ public class SearchResponse<T> : ResponseBase, ISearchResponse<T> where T : clas
 
 		/// <inheritdoc />
 		[IgnoreDataMember]
-		public long Total => HitsMetadata?.Total.Value ?? 0;
+		public long Total => HitsMetadata?.Total.Value ?? -1;
 	}
 }

src/Nest/Search/Search/SearchResponse.cs

@@ -16,8 +16,6 @@
 
 namespace Tests.Search.MultiSearch
 {
-	[SkipVersion(">5.0.0-alpha1", "format of percolate query changed.")]
-	[BlockedByIssue("https://github.com/elastic/elasticsearch/pull/39987")]
 	public class MultiSearchApiTests
 		: ApiIntegrationTestBase<ReadOnlyCluster, IMultiSearchResponse, IMultiSearchRequest, MultiSearchDescriptor, MultiSearchRequest>
 	{

src/Tests/Tests/Search/MultiSearch/MultiSearchApiTests.cs

@@ -96,7 +96,10 @@ protected override LazyResponses ClientUsage() => Calls(
 
 		protected override void ExpectResponse(ISearchResponse<Project> response)
 		{
-			response.Hits.Count().Should().BeGreaterThan(0);
+			response.Total.Should().BeGreaterThan(0);
+			response.Hits.Count.Should().BeGreaterThan(0);
+			response.HitsMetadata.Total.Value.Should().Be(response.Total);
+			response.HitsMetadata.Total.Relation.Should().Be(TotalHitsRelation.EqualTo);
 			response.Hits.First().Should().NotBeNull();
 			response.Hits.First().Source.Should().NotBeNull();
 			response.Aggregations.Count.Should().BeGreaterThan(0);