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() {

internal/service/analytics_p513_test.go

@@ -237,6 +237,24 @@ func TestAnalyticsOutgoingMessagesCountLabelUsesAccountLabelName(t *testing.T) {
 	assert.Equal(t, int64(1), rows[0]["outgoing_messages_count"])
 }
 
+func TestAnalyticsFirstResponseTimeDistributionAllowsMissingRange(t *testing.T) {
+	db, svc, account, inbox, _, user, _ := setupAnalyticsP513Test(t)
+	old := time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC)
+	recent := time.Date(2026, 6, 9, 0, 0, 0, 0, time.UTC)
+	require.NoError(t, db.Create(&model.ReportingEvent{Base: model.Base{CreatedAt: old}, AccountID: account.ID, Name: model.MetricNameFirstResponse, Value: 120, InboxID: &inbox.ID, UserID: &user.ID}).Error)
+	require.NoError(t, db.Create(&model.ReportingEvent{Base: model.Base{CreatedAt: recent}, AccountID: account.ID, Name: model.MetricNameFirstResponse, Value: 90000, InboxID: &inbox.ID, UserID: &user.ID}).Error)
+
+	allDistribution, err := svc.GetFirstResponseTimeDistribution(context.Background(), account.ID, time.Time{}, time.Time{})
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), allDistribution.(map[string]map[string]int64)["web_widget"]["0-1h"])
+	assert.Equal(t, int64(1), allDistribution.(map[string]map[string]int64)["web_widget"]["24h+"])
+
+	rangedDistribution, err := svc.GetFirstResponseTimeDistribution(context.Background(), account.ID, recent.Add(-time.Hour), recent.Add(time.Hour))
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), rangedDistribution.(map[string]map[string]int64)["web_widget"]["0-1h"])
+	assert.Equal(t, int64(1), rangedDistribution.(map[string]map[string]int64)["web_widget"]["24h+"])
+}
+
 func TestAnalyticsTimeseriesAndRollupWorker(t *testing.T) {
 	db, svc, account, inbox, contact, user, _ := setupAnalyticsP513Test(t)
 	since := time.Date(2026, 6, 2, 0, 0, 0, 0, time.UTC)

internal/service/analytics_query_helpers.go

@@ -853,7 +853,11 @@ func (s *AnalyticsService) firstResponseTimeDistribution(ctx context.Context, ac
 		return nil, err
 	}
 	var events []model.ReportingEvent
-	if err := db.WithContext(ctx).Where("account_id = ? AND name = ? AND created_at >= ? AND created_at < ?", accountID, model.MetricNameFirstResponse, since, until).Find(&events).Error; err != nil {
+	eventQ := db.WithContext(ctx).Where("account_id = ? AND name = ?", accountID, model.MetricNameFirstResponse)
+	if !since.IsZero() && !until.IsZero() {
+		eventQ = eventQ.Where("created_at >= ? AND created_at < ?", since, until)
+	}
+	if err := eventQ.Find(&events).Error; err != nil {
 		return nil, err
 	}
 	inboxIDs := make([]uint, 0, len(events))