Merge pull request 'date-histogram-agg' (#3) from date-histogram-agg into master

Reviewed-on: #3

README.md

@@ -158,6 +158,7 @@ The following aggregations are currently supported:
 | `"string_stats"`        | `StringStats()`       |
 | `"top_hits"`            | `TopHits()`           |
 | `"terms"`               | `TermsAgg()`          |
+| `"date_histogram"`      | `DateHistogramAgg()`  |
 
 ### Supported Top Level Options
 

aggregations_test.go

@@ -62,7 +62,14 @@ func TestAggregations(t *testing.T) {
 			"a complex, multi-aggregation, nested",
 			Aggregate(
 				NestedAgg("categories", "categories").
-					Aggs(TermsAgg("type", "outdoors")),
+					Aggs(
+						TermsAgg("type", "outdoors").Aggs(
+							DateHistogramAgg("time", "timestamp").
+								Fixedinterval("3m").MinDocCount(0).Aggs(
+								Sum("sumPeople", "people"),
+							),
+						),
+					),
 				FilterAgg("filtered",
 					Term("type", "t-shirt")),
 			),
@@ -77,6 +84,22 @@ func TestAggregations(t *testing.T) {
 								"terms": map[string]interface{}{
 									"field": "outdoors",
 								},
+								"aggs": map[string]interface{}{
+									"time": map[string]interface{}{
+										"date_histogram": map[string]interface{}{
+											"field":          "timestamp",
+											"fixed_interval": "3m",
+											"min_doc_count":  0,
+										},
+										"aggs": map[string]interface{}{
+											"sumPeople": map[string]interface{}{
+												"sum": map[string]interface{}{
+													"field": "people",
+												},
+											},
+										},
+									},
+								},
 							},
 						},
 					},

aggs_bucket.go

@@ -110,3 +110,144 @@ func (agg *TermsAggregation) Map() map[string]interface{} {
 
 	return outerMap
 }
+
+//----------------------------------------------------------------------------//
+
+// DateHistogramAggregation represents an aggregation of type "date_histogram", as described in
+// https://www.elastic.co/guide/en/elasticsearch/reference/current/
+//      search-aggregations-bucket-datehistogram-aggregation.html
+type DateHistogramAggregation struct {
+	name             string
+	field            string
+	calendarInterval string
+	fixedInterval    string
+	format           string
+	offset           string
+	keyed            *bool
+	minDocCount      *uint64
+	missing          string
+	order            map[string]string
+
+	aggs []Aggregation
+}
+
+// DateHistogramAgg creates a new aggregation of type "date_histogram".
+func DateHistogramAgg(name, field string) *DateHistogramAggregation {
+	return &DateHistogramAggregation{
+		name:  name,
+		field: field,
+	}
+}
+
+// Name returns the name of the aggregation.
+func (agg *DateHistogramAggregation) Name() string {
+	return agg.name
+}
+
+// Aggs sets sub-aggregations for the aggregation.
+func (agg *DateHistogramAggregation) Aggs(aggs ...Aggregation) *DateHistogramAggregation {
+	agg.aggs = aggs
+	return agg
+}
+
+// CalendarInterval sets calendarInterval
+func (agg *DateHistogramAggregation) CalendarInterval(interval string) *DateHistogramAggregation {
+	agg.calendarInterval = interval
+	return agg
+}
+
+// Fixedinterval sets fixedInterval
+func (agg *DateHistogramAggregation) Fixedinterval(interval string) *DateHistogramAggregation {
+	agg.fixedInterval = interval
+	return agg
+}
+
+// Format sets format
+func (agg *DateHistogramAggregation) Format(format string) *DateHistogramAggregation {
+	agg.format = format
+	return agg
+}
+
+// Offset sets offset
+func (agg *DateHistogramAggregation) Offset(offset string) *DateHistogramAggregation {
+	agg.offset = offset
+	return agg
+}
+
+// Order sets the sort for terms agg
+func (agg *DateHistogramAggregation) Order(order map[string]string) *DateHistogramAggregation {
+	agg.order = order
+	return agg
+}
+
+// Keyed sets keyed is true or false
+func (agg *DateHistogramAggregation) Keyed(keyed bool) *DateHistogramAggregation {
+	agg.keyed = &keyed
+	return agg
+}
+
+// Missing sets missing value
+func (agg *DateHistogramAggregation) Missing(missing string) *DateHistogramAggregation {
+	agg.missing = missing
+	return agg
+}
+
+// MinDocCount sets min doc count
+func (agg *DateHistogramAggregation) MinDocCount(minDocCount uint64) *DateHistogramAggregation {
+	agg.minDocCount = &minDocCount
+	return agg
+}
+
+// Map returns a map representation of the aggregation, thus implementing the
+// Mappable interface.
+func (agg *DateHistogramAggregation) Map() map[string]interface{} {
+	innerMap := map[string]interface{}{
+		"field": agg.field,
+	}
+
+	if agg.calendarInterval != "" {
+		innerMap["calendar_interval"] = agg.calendarInterval
+	}
+
+	if agg.fixedInterval != "" {
+		innerMap["fixed_interval"] = agg.fixedInterval
+	}
+
+	if agg.format != "" {
+		innerMap["format"] = agg.format
+	}
+
+	if agg.offset != "" {
+		innerMap["offset"] = agg.offset
+	}
+
+	if agg.missing != "" {
+		innerMap["missing"] = agg.missing
+	}
+
+	if agg.minDocCount != nil {
+		innerMap["min_doc_count"] = agg.minDocCount
+	}
+
+	if agg.keyed != nil {
+		innerMap["keyed"] = *agg.keyed
+	}
+
+	if agg.order != nil {
+		innerMap["order"] = agg.order
+	}
+
+	outerMap := map[string]interface{}{
+		"date_histogram": innerMap,
+	}
+
+	if len(agg.aggs) > 0 {
+		subAggs := make(map[string]map[string]interface{})
+		for _, sub := range agg.aggs {
+			subAggs[sub.Name()] = sub.Map()
+		}
+		outerMap["aggs"] = subAggs
+	}
+
+	return outerMap
+}