Added validation on client_received_end_timestamp

api_helper.go

diff --git a/api_helper.go b/api_helper.go
index 45e99f0..ee65631 100644
--- a/api_helper.go
+++ b/api_helper.go
@@ -101,11 +101,11 @@
 
 /*
 Does basic validation on each analytics message
-1. client_received_start_timestamp should exist
-2. if client_received_end_timestamp exists then it should be > client_received_start_timestamp
+1. client_received_start_timestamp, client_received_end_timestamp should exist
+2. client_received_end_timestamp should be > client_received_start_timestamp and not 0
 */
 func validate(recordMap map[string]interface{}) (bool, errResponse) {
-	elems := []string{"client_received_start_timestamp"}
+	elems := []string{"client_received_start_timestamp", "client_received_end_timestamp"}
 	for _, elem := range elems {
 		if recordMap[elem] == nil {
 			return false, errResponse{
@@ -117,7 +117,12 @@
 	crst, exists1 := recordMap["client_received_start_timestamp"]
 	cret, exists2 := recordMap["client_received_end_timestamp"]
 	if exists1 && exists2 {
-		if crst.(json.Number) > cret.(json.Number) {
+		if crst.(json.Number) == json.Number("0") || cret.(json.Number) == json.Number("0") {
+			return false, errResponse{
+				ErrorCode: "BAD_DATA",
+				Reason: "client_received_start_timestamp or " +
+					"> client_received_end_timestamp cannot be 0"}
+		} else if crst.(json.Number) > cret.(json.Number) {
 			return false, errResponse{
 				ErrorCode: "BAD_DATA",
 				Reason: "client_received_start_timestamp " +

api_helper_test.go

diff --git a/api_helper_test.go b/api_helper_test.go
index 7b83679..4304769 100644
--- a/api_helper_test.go
+++ b/api_helper_test.go
@@ -36,8 +36,23 @@
 
 			Expect(valid).To(BeFalse())
 			Expect(e.ErrorCode).To(Equal("BAD_DATA"))
-			Expect(e.Reason).To(Equal("client_received_start_timestamp > client_received_end_timestamp"))
+			Expect(e.Reason).To(Equal("client_received_start_timestamp " +
+				"> client_received_end_timestamp"))
 
+			By("payload with clst = 0")
+			record = []byte(`{
+						"response_status_code": 200,
+						"client_id":"testapikey",
+						"client_received_start_timestamp": 0,
+						"client_received_end_timestamp": 1486406248260
+					}`)
+			raw = getRaw(record)
+			valid, e = validate(raw)
+
+			Expect(valid).To(BeFalse())
+			Expect(e.ErrorCode).To(Equal("BAD_DATA"))
+			Expect(e.Reason).To(Equal("client_received_start_timestamp or " +
+				"> client_received_end_timestamp cannot be 0"))
 		})
 	})
 	Context("valid record", func() {