Erweitere Statusuebersicht um Zeit- und Mengengrenzen

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

docs/PLAYER-STATUS-HTTP.md

@@ -77,6 +77,13 @@ Zusätzlich zur Write-Route gibt es in dieser Stufe:
 `GET /api/v1/screens/status` liefert eine kleine Uebersicht aller bisher berichtenden Screens mit ihrem jeweils letzten bekannten Datensatz.
 Die Rueckgabe wird aktuell fuer Diagnosezwecke priorisiert sortiert: zuerst `offline`, dann `degraded`, dann `online`, innerhalb derselben Gruppe nach `screen_id`.
 
+Aktuell unterstuetzte Query-Parameter fuer die Uebersicht:
+
+- `server_connectivity=<value>` zum Filtern nach Reachability-Zustand
+- `stale=true|false` zum Filtern nach serverseitiger Veraltet-Einschaetzung
+- `updated_since=<RFC3339>` zum Filtern nach `received_at`
+- `limit=<positive integer>` zum Begrenzen der Anzahl zurueckgelieferter Screens
+
 `GET /api/v1/screens/{screenId}/status` liefert den zuletzt akzeptierten Status fuer einen einzelnen Screen zurueck.
 Wenn fuer den Screen noch kein Status vorliegt, liefert das Backend `404` mit dem gemeinsamen Fehlerumschlag.
 

server/backend/internal/httpapi/playerstatus.go

@@ -3,6 +3,7 @@ package httpapi
 import (
 	"net/http"
 	"sort"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -132,10 +133,23 @@ func handleListLatestPlayerStatuses(store playerStatusStore) http.HandlerFunc {
 		records := store.List()
 		wantConnectivity := strings.TrimSpace(r.URL.Query().Get("server_connectivity"))
 		wantStale := strings.TrimSpace(r.URL.Query().Get("stale"))
+		updatedSince, err := parseOptionalRFC3339(r.URL.Query().Get("updated_since"))
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "invalid_updated_since", "updated_since ist kein gueltiger RFC3339-Zeitstempel", nil)
+			return
+		}
+		limit, err := parseOptionalPositiveInt(r.URL.Query().Get("limit"))
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "invalid_limit", "limit muss eine positive Ganzzahl sein", nil)
+			return
+		}
 		filtered := make([]playerStatusRecord, 0, len(records))
 		for i := range records {
 			records[i].Stale = isStale(records[i], store.Now())
 			records[i].DerivedState = deriveState(records[i])
+			if updatedSince != nil && !isUpdatedSince(records[i], *updatedSince) {
+				continue
+			}
 			if wantConnectivity != "" && records[i].ServerConnectivity != wantConnectivity {
 				continue
 			}
@@ -160,6 +174,10 @@ func handleListLatestPlayerStatuses(store playerStatusStore) http.HandlerFunc {
 			return filtered[i].ScreenID < filtered[j].ScreenID
 		})
 
+		if limit > 0 && len(filtered) > limit {
+			filtered = filtered[:limit]
+		}
+
 		writeJSON(w, http.StatusOK, map[string]any{
 			"screens": filtered,
 		})
@@ -175,6 +193,32 @@ func validateOptionalRFC3339(value string) error {
 	return err
 }
 
+func parseOptionalRFC3339(value string) (*time.Time, error) {
+	if strings.TrimSpace(value) == "" {
+		return nil, nil
+	}
+
+	parsed, err := time.Parse(time.RFC3339, strings.TrimSpace(value))
+	if err != nil {
+		return nil, err
+	}
+
+	return &parsed, nil
+}
+
+func parseOptionalPositiveInt(value string) (int, error) {
+	if strings.TrimSpace(value) == "" {
+		return 0, nil
+	}
+
+	parsed, err := strconv.Atoi(strings.TrimSpace(value))
+	if err != nil || parsed <= 0 {
+		return 0, strconv.ErrSyntax
+	}
+
+	return parsed, nil
+}
+
 func isStale(record playerStatusRecord, now time.Time) bool {
 	if strings.TrimSpace(record.ReceivedAt) == "" {
 		return false
@@ -209,6 +253,19 @@ func deriveState(record playerStatusRecord) string {
 	return "online"
 }
 
+func isUpdatedSince(record playerStatusRecord, threshold time.Time) bool {
+	if strings.TrimSpace(record.ReceivedAt) == "" {
+		return false
+	}
+
+	receivedAt, err := time.Parse(time.RFC3339, record.ReceivedAt)
+	if err != nil {
+		return false
+	}
+
+	return !receivedAt.Before(threshold)
+}
+
 func derivedStatePriority(state string) int {
 	switch state {
 	case "offline":

server/backend/internal/httpapi/playerstatus_test.go

@@ -511,3 +511,63 @@ func TestHandleListLatestPlayerStatusesFiltersByConnectivityAndStale(t *testing.
 		t.Fatalf("response.Screens[0].ScreenID = %q, want %q", got, want)
 	}
 }
+
+func TestHandleListLatestPlayerStatusesAppliesLimit(t *testing.T) {
+	store := newInMemoryPlayerStatusStore()
+	store.now = func() time.Time {
+		return time.Date(2026, 3, 22, 16, 10, 0, 0, time.UTC)
+	}
+	store.Save(playerStatusRecord{ScreenID: "screen-online", Timestamp: "2026-03-22T16:09:30Z", Status: "running", ServerConnectivity: "online", ReceivedAt: "2026-03-22T16:09:30Z", HeartbeatEverySeconds: 30})
+	store.Save(playerStatusRecord{ScreenID: "screen-offline", Timestamp: "2026-03-22T16:00:00Z", Status: "running", ServerConnectivity: "offline", ReceivedAt: "2026-03-22T16:00:00Z", HeartbeatEverySeconds: 30})
+	store.Save(playerStatusRecord{ScreenID: "screen-degraded", Timestamp: "2026-03-22T16:09:00Z", Status: "running", ServerConnectivity: "degraded", ReceivedAt: "2026-03-22T16:09:00Z", HeartbeatEverySeconds: 30})
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/screens/status?limit=2", nil)
+	w := httptest.NewRecorder()
+
+	handleListLatestPlayerStatuses(store)(w, req)
+
+	var response struct {
+		Screens []playerStatusRecord `json:"screens"`
+	}
+	if err := json.Unmarshal(w.Body.Bytes(), &response); err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if got, want := len(response.Screens), 2; got != want {
+		t.Fatalf("len(response.Screens) = %d, want %d", got, want)
+	}
+
+	if got, want := response.Screens[0].ScreenID, "screen-offline"; got != want {
+		t.Fatalf("response.Screens[0].ScreenID = %q, want %q", got, want)
+	}
+
+	if got, want := response.Screens[1].ScreenID, "screen-degraded"; got != want {
+		t.Fatalf("response.Screens[1].ScreenID = %q, want %q", got, want)
+	}
+}
+
+func TestHandleListLatestPlayerStatusesFiltersByUpdatedSince(t *testing.T) {
+	store := newInMemoryPlayerStatusStore()
+	store.Save(playerStatusRecord{ScreenID: "screen-old", Timestamp: "2026-03-22T16:00:00Z", Status: "running", ServerConnectivity: "online", ReceivedAt: "2026-03-22T16:00:00Z", HeartbeatEverySeconds: 30})
+	store.Save(playerStatusRecord{ScreenID: "screen-new", Timestamp: "2026-03-22T16:06:00Z", Status: "running", ServerConnectivity: "online", ReceivedAt: "2026-03-22T16:06:00Z", HeartbeatEverySeconds: 30})
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/screens/status?updated_since=2026-03-22T16:05:00Z", nil)
+	w := httptest.NewRecorder()
+
+	handleListLatestPlayerStatuses(store)(w, req)
+
+	var response struct {
+		Screens []playerStatusRecord `json:"screens"`
+	}
+	if err := json.Unmarshal(w.Body.Bytes(), &response); err != nil {
+		t.Fatalf("Unmarshal() error = %v", err)
+	}
+
+	if got, want := len(response.Screens), 1; got != want {
+		t.Fatalf("len(response.Screens) = %d, want %d", got, want)
+	}
+
+	if got, want := response.Screens[0].ScreenID, "screen-new"; got != want {
+		t.Fatalf("response.Screens[0].ScreenID = %q, want %q", got, want)
+	}
+}