feat(reports): align first response distribution range

internal/handler/api/v1/analytics_handler.go

@@ -566,7 +566,7 @@ func (h *AnalyticsHandler) FirstResponseTimeDistribution(c *gin.Context) {
 	if !ok {
 		return
 	}
-	since, until, ok := parseDateRange(c)
+	since, until, ok := parseOptionalReportDateRange(c)
 	if !ok {
 		return
 	}
@@ -581,6 +581,25 @@ func (h *AnalyticsHandler) FirstResponseTimeDistribution(c *gin.Context) {
 	c.JSON(http.StatusOK, result)
 }
 
+func parseOptionalReportDateRange(c *gin.Context) (since, until time.Time, ok bool) {
+	sinceRaw := c.Query("since")
+	untilRaw := c.Query("until")
+	if sinceRaw == "" || untilRaw == "" {
+		return time.Time{}, time.Time{}, true
+	}
+	since, err := parseChatwootReportTime(sinceRaw)
+	if err != nil {
+		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid since date format")
+		return time.Time{}, time.Time{}, false
+	}
+	until, err = parseChatwootReportTime(untilRaw)
+	if err != nil {
+		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "invalid until date format")
+		return time.Time{}, time.Time{}, false
+	}
+	return since, until, true
+}
+
 // OutgoingMessagesCount returns outgoing message count metrics.
 // GET /api/v1/accounts/:account_id/reports/outgoing_messages_count
 // Reference: Chatwoot reports#outgoing_messages_count

internal/handler/api/v1/analytics_handler_test.go

@@ -74,6 +74,7 @@ func (s *AnalyticsHandlerTestSuite) SetupSuite() {
 	accounts.GET("/reports/conversation_traffic", s.handler.ConversationTraffic)
 	accounts.GET("/reports/conversations", s.handler.Conversations)
 	accounts.GET("/reports/conversations_summary", s.handler.ConversationsSummary)
+	accounts.GET("/reports/first_response_time_distribution", s.handler.FirstResponseTimeDistribution)
 	accounts.GET("/reports/inbox_label_matrix", s.handler.InboxLabelMatrix)
 	accounts.GET("/reports/outgoing_messages_count", s.handler.OutgoingMessagesCount)
 	s.router = r
@@ -514,6 +515,21 @@ func (s *AnalyticsHandlerTestSuite) TestOutgoingMessagesCount_InvalidGroupByRetu
 	s.Empty(w.Body.String())
 }
 
+func (s *AnalyticsHandlerTestSuite) TestFirstResponseTimeDistribution_AllowsMissingRange() {
+	inbox := model.Inbox{AccountID: s.accountID, Name: "Web", ChannelType: "web_widget", ChannelID: 1, Enabled: true}
+	s.Require().NoError(s.db.Create(&inbox).Error)
+	s.Require().NoError(s.db.Create(&model.ReportingEvent{AccountID: s.accountID, Name: model.MetricNameFirstResponse, Value: 4000, InboxID: &inbox.ID}).Error)
+
+	w := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/accounts/1/reports/first_response_time_distribution", nil)
+	s.router.ServeHTTP(w, req)
+
+	s.Equal(http.StatusOK, w.Code)
+	var payload map[string]map[string]int64
+	s.Require().NoError(json.Unmarshal(w.Body.Bytes(), &payload))
+	s.Equal(int64(1), payload["web_widget"]["1-4h"])
+}
+
 // ========== Nil service guard ==========
 
 func (s *AnalyticsHandlerTestSuite) TestNilService() {