Percentile ranks aggregation support

Closes #821

Author: gmarz

Diff for: src/Nest/DSL/Aggregations/AggregationDescriptor.cs

@@ -75,6 +75,9 @@ public interface IAggregationContainer
 		[JsonProperty("value_count")]
 		IValueCountAggregator ValueCount { get; set; }
 
+		[JsonProperty("percentile_ranks")]
+		IPercentileRanksAggregaor PercentileRanks { get; set; }
+
 		[JsonProperty("aggs")]
 		[JsonConverter(typeof(DictionaryKeysAreNotPropertyNamesJsonConverter))]
 		IDictionary<string, IAggregationContainer> Aggregations { get; set; }
@@ -98,6 +101,7 @@ public class AggregationContainer : IAggregationContainer
 		private IRangeAggregator _range;
 		private ITermsAggregator _terms;
 		private ISignificantTermsAggregator _significantTerms;
+		private IPercentileRanksAggregaor _percentileRanks;
 		public IAverageAggregator Average { get; set; }
 		public IValueCountAggregator ValueCount { get; set; }
 		public IMaxAggregator Max { get; set; }
@@ -195,6 +199,12 @@ public ISignificantTermsAggregator SignificantTerms
 			get { return _significantTerms; }
 			set { _significantTerms = value; }
 		}
+		
+		public IPercentileRanksAggregaor PercentileRanks
+		{
+			get { return _percentileRanks; }
+			set { _percentileRanks = value; }
+		}
 
 		private void LiftAggregations(IBucketAggregator bucket)
 		{
@@ -251,6 +261,8 @@ public class AggregationDescriptor<T> : IAggregationContainer
 		IValueCountAggregator IAggregationContainer.ValueCount { get; set; }
 
 		ISignificantTermsAggregator IAggregationContainer.SignificantTerms { get; set; }
+
+		IPercentileRanksAggregaor IAggregationContainer.PercentileRanks { get;set; }
 
 		ITermsAggregator IAggregationContainer.Terms { get; set; }
 
@@ -271,6 +283,12 @@ public AggregationDescriptor<T> Percentiles(string name,
 			return _SetInnerAggregation(name, selector, (a, d) => a.Percentiles = d);
 		}
 
+		public AggregationDescriptor<T> PercentileRanks(string name,
+			Func<PercentileRanksAggregationDescriptor<T>, PercentileRanksAggregationDescriptor<T>> selector)
+		{
+			return _SetInnerAggregation(name, selector, (a, d) => a.PercentileRanks = d);
+		}
+
 		public AggregationDescriptor<T> DateRange(string name,
 			Func<DateRangeAggregationDescriptor<T>, DateRangeAggregationDescriptor<T>> selector)
 		{

Diff for: src/Nest/DSL/Aggregations/PercentileRanksAggregationDescriptor.cs

@@ -0,0 +1,36 @@
+using Nest.Resolvers.Converters;
+using Newtonsoft.Json;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Nest
+{
+	[JsonObject(MemberSerialization = MemberSerialization.OptIn)]
+	[JsonConverter(typeof(ReadAsTypeConverter<CardinalityAggregator>))]
+	public interface IPercentileRanksAggregaor : IMetricAggregator
+	{
+		[JsonProperty("values")]
+		IEnumerable<double> Values { get; set; }
+	}
+
+	public class PercentileRanksAggregation : MetricAggregator, IPercentileRanksAggregaor
+	{
+		public IEnumerable<double> Values { get; set; }
+	}
+
+	public class PercentileRanksAggregationDescriptor<T> 
+		: MetricAggregationBaseDescriptor<PercentileRanksAggregationDescriptor<T>, T>, IPercentileRanksAggregaor
+		where T : class
+	{
+		IPercentileRanksAggregaor Self { get { return this; } }
+		IEnumerable<double> IPercentileRanksAggregaor.Values { get; set; }
+
+		public PercentileRanksAggregationDescriptor<T> Values(IEnumerable<double> values)
+		{
+			this.Self.Values = values;
+			return this;
+		}
+	}
+}

Diff for: src/Nest/Domain/Aggregations/AggregationsHelper.cs

@@ -69,6 +69,12 @@ public PercentilesMetric Percentiles(string key)
 		{
 			return this.TryGet<PercentilesMetric>(key);
 		}
+
+		public PercentilesMetric PercentilesRank(string key)
+		{
+			return this.TryGet<PercentilesMetric>(key);
+		}
+
 		public SingleBucket Global(string key)
 		{
 			return this.TryGet<SingleBucket>(key);

Diff for: src/Nest/Nest.csproj

@@ -207,6 +207,7 @@
     <Compile Include="Domain\Stats\PercolateStats.cs" />
     <Compile Include="Domain\Stats\PluginStats.cs" />
     <Compile Include="Domain\Stats\SegmentsStats.cs" />
+    <Compile Include="DSL\Aggregations\PercentileRanksAggregationDescriptor.cs" />
     <Compile Include="DSL\CatIndicesDescriptor.cs" />
     <Compile Include="DSL\CatShardsDescriptor.cs" />
     <Compile Include="DSL\CatThreadPoolDescriptor.cs" />

Diff for: src/Tests/Nest.Tests.Integration/Aggregations/MetricAggregationTests.cs

@@ -119,5 +119,23 @@ public void ValueCount()
 			termBucket.Should().NotBeNull();
 			termBucket.Value.Should().HaveValue();
 		}
+
+		[Test]
+		public void PercentilesRank()
+		{
+			var results = this.Client.Search<ElasticsearchProject>(s => s
+				.Size(0)
+				.Aggregations(a => a
+					.PercentileRanks("percentile_ranks_agg", pr => pr
+						.Field(p => p.LongValue)
+						.Values(new double [] { 15, 30 })
+					)
+				)
+			);
+			results.IsValid.Should().BeTrue();
+			var percentiles = results.Aggs.PercentilesRank("percentile_ranks_agg");
+			percentiles.Should().NotBeNull();
+			percentiles.Items.Count.Should().BeGreaterThan(0);
+		}
 	}
 }