refactor: stabilize calendar loading effects and menubar redirect

- Memoize calendar range strings and stabilize effect deps
- Guard updateDarkColor to avoid dispatch loops
- Add resilient cache-clear handling with refs
- Memoize calendar/temp ids to prevent rerenders
- Update event handler hooks with missing deps
- Add guards and dependency fixes across Calendar effects

__test__/components/Calendar.test.tsx

@@ -581,4 +581,188 @@ describe("calendar Availability search", () => {
     expect(startDate.getTime()).toBeLessThanOrEqual(viewStart.getTime());
     expect(endDate.getTime()).toBeGreaterThanOrEqual(viewEnd.getTime());
   });
+
+  describe("Batch loading and prefetching", () => {
+    beforeEach(() => {
+      jest.clearAllMocks();
+    });
+
+    it("loads active calendars in batches of 5", async () => {
+      const manyCalendars = Array.from({ length: 12 }, (_, i) => ({
+        [`user1/cal${i + 1}`]: {
+          name: `Calendar ${i + 1}`,
+          id: `user1/cal${i + 1}`,
+          color: { light: "#FF0000", dark: "#000" },
+          events: {},
+        },
+      })).reduce((acc, cal) => ({ ...acc, ...cal }), {});
+
+      const stateWithManyCalendars = {
+        ...preloadedState,
+        calendars: {
+          ...preloadedState.calendars,
+          list: manyCalendars,
+        },
+      };
+
+      const spy = jest
+        .spyOn(calendarThunks, "getCalendarDetailAsync")
+        .mockImplementation(() => ({
+          type: "getCalendarDetailAsync",
+          unwrap: () => Promise.resolve({}),
+        })) as any;
+
+      await act(async () => {
+        renderWithProviders(
+          <CalendarApp calendarRef={{ current: null }} />,
+          stateWithManyCalendars
+        );
+      });
+
+      await waitFor(
+        () => {
+          expect(spy).toHaveBeenCalled();
+        },
+        { timeout: 3000 }
+      );
+
+      const callCount = spy.mock.calls.length;
+      expect(callCount).toBeGreaterThan(0);
+      expect(callCount).toBeLessThanOrEqual(24);
+    });
+
+    it("prefetches hidden calendars only after active load completes", async () => {
+      const calendarsWithSelected = {
+        ...preloadedState,
+        calendars: {
+          ...preloadedState.calendars,
+          list: {
+            "user1/cal1": {
+              name: "Selected Calendar",
+              id: "user1/cal1",
+              color: { light: "#FF0000", dark: "#000" },
+              events: {},
+            },
+            "user1/cal2": {
+              name: "Hidden Calendar 1",
+              id: "user1/cal2",
+              color: { light: "#00FF00", dark: "#000" },
+              events: {},
+            },
+            "user1/cal3": {
+              name: "Hidden Calendar 2",
+              id: "user1/cal3",
+              color: { light: "#0000FF", dark: "#000" },
+              events: {},
+            },
+          },
+        },
+      };
+
+      const spy = jest
+        .spyOn(calendarThunks, "getCalendarDetailAsync")
+        .mockImplementation(() => ({
+          type: "getCalendarDetailAsync",
+          unwrap: () => Promise.resolve({}),
+        })) as any;
+
+      await act(async () => {
+        renderWithProviders(
+          <CalendarApp calendarRef={{ current: null }} />,
+          calendarsWithSelected
+        );
+      });
+
+      await waitFor(
+        () => {
+          expect(spy).toHaveBeenCalled();
+        },
+        { timeout: 3000 }
+      );
+
+      const selectedCalls = spy.mock.calls.filter(
+        (call) => call[0].calId === "user1/cal1"
+      );
+      const hiddenCalls = spy.mock.calls.filter(
+        (call) =>
+          call[0].calId === "user1/cal2" || call[0].calId === "user1/cal3"
+      );
+
+      expect(selectedCalls.length).toBeGreaterThan(0);
+    });
+
+    it("does not make duplicate API calls for same calendar and range", async () => {
+      const spy = jest
+        .spyOn(calendarThunks, "getCalendarDetailAsync")
+        .mockImplementation(() => ({
+          type: "getCalendarDetailAsync",
+          unwrap: () => Promise.resolve({}),
+        })) as any;
+
+      await act(async () => {
+        renderWithProviders(
+          <CalendarApp calendarRef={{ current: null }} />,
+          preloadedState
+        );
+      });
+
+      await waitFor(
+        () => {
+          expect(spy).toHaveBeenCalled();
+        },
+        { timeout: 3000 }
+      );
+
+      const callsForCal1 = spy.mock.calls.filter(
+        (call) => call[0].calId === "user1/cal1"
+      );
+
+      const uniqueRanges = new Set(
+        callsForCal1.map(
+          (call) => `${call[0].match.start}_${call[0].match.end}`
+        )
+      );
+
+      expect(uniqueRanges.size).toBeLessThanOrEqual(callsForCal1.length);
+    });
+
+    it("handles undefined calendars gracefully", async () => {
+      const stateWithUndefinedCalendars = {
+        ...preloadedState,
+        calendars: {
+          list: undefined as any,
+          templist: undefined as any,
+          pending: false,
+        },
+      };
+
+      await act(async () => {
+        renderWithProviders(
+          <CalendarApp calendarRef={{ current: null }} />,
+          stateWithUndefinedCalendars
+        );
+      });
+
+      expect(screen.getByText("calendar.personal")).toBeInTheDocument();
+    });
+
+    it("handles undefined tempcalendars gracefully", async () => {
+      const stateWithUndefinedTemp = {
+        ...preloadedState,
+        calendars: {
+          ...preloadedState.calendars,
+          templist: undefined as any,
+        },
+      };
+
+      await act(async () => {
+        renderWithProviders(
+          <CalendarApp calendarRef={{ current: null }} />,
+          stateWithUndefinedTemp
+        );
+      });
+
+      expect(screen.getByText("calendar.personal")).toBeInTheDocument();
+    });
+  });
 });

__test__/features/Calendars/CalendarSlice.test.tsx

@@ -140,6 +140,203 @@ describe("CalendarSlice", () => {
       expect(state.list).toEqual({});
     });
 
+    it("getCalendarsListAsync loads user details in parallel for multiple owners", async () => {
+      const mockCalendars = [
+        {
+          _links: { self: { href: "/calendars/u1/cal1.json" } },
+          "dav:name": "Calendar 1",
+          "apple:color": "#FF0000",
+          acl: [],
+        },
+        {
+          _links: { self: { href: "/calendars/u2/cal2.json" } },
+          "dav:name": "Calendar 2",
+          "apple:color": "#00FF00",
+          acl: [],
+        },
+        {
+          _links: { self: { href: "/calendars/u3/cal3.json" } },
+          "dav:name": "Calendar 3",
+          "apple:color": "#0000FF",
+          acl: [],
+        },
+      ];
+
+      (userAPI.getOpenPaasUser as jest.Mock).mockResolvedValue({ id: "u1" });
+      (calAPI.getCalendars as jest.Mock).mockResolvedValue({
+        _embedded: { "dav:calendar": mockCalendars },
+      });
+
+      const getUserDetailsMock = userAPI.getUserDetails as jest.Mock;
+      getUserDetailsMock
+        .mockResolvedValueOnce({
+          firstname: "Alice",
+          lastname: "Smith",
+          emails: ["alice@example.com"],
+        })
+        .mockResolvedValueOnce({
+          firstname: "Bob",
+          lastname: "Jones",
+          emails: ["bob@example.com"],
+        })
+        .mockResolvedValueOnce({
+          firstname: "Charlie",
+          lastname: "Brown",
+          emails: ["charlie@example.com"],
+        });
+
+      const store = storeFactory();
+      await store.dispatch(getCalendarsListAsync() as any);
+
+      expect(getUserDetailsMock).toHaveBeenCalledTimes(3);
+      expect(getUserDetailsMock).toHaveBeenCalledWith("u1");
+      expect(getUserDetailsMock).toHaveBeenCalledWith("u2");
+      expect(getUserDetailsMock).toHaveBeenCalledWith("u3");
+
+      const state = store.getState().calendars;
+      expect(state.list["u1/cal1"].owner).toContain("Alice");
+      expect(state.list["u2/cal2"].owner).toContain("Bob");
+      expect(state.list["u3/cal3"].owner).toContain("Charlie");
+    });
+
+    it("getCalendarsListAsync deduplicates getUserDetails calls for same ownerId", async () => {
+      const mockCalendars = [
+        {
+          _links: { self: { href: "/calendars/u1/cal1.json" } },
+          "dav:name": "Calendar 1",
+          "apple:color": "#FF0000",
+          acl: [],
+        },
+        {
+          _links: { self: { href: "/calendars/u1/cal2.json" } },
+          "dav:name": "Calendar 2",
+          "apple:color": "#00FF00",
+          acl: [],
+        },
+        {
+          _links: { self: { href: "/calendars/u1/cal3.json" } },
+          "dav:name": "Calendar 3",
+          "apple:color": "#0000FF",
+          acl: [],
+        },
+      ];
+
+      (userAPI.getOpenPaasUser as jest.Mock).mockResolvedValue({ id: "u1" });
+      (calAPI.getCalendars as jest.Mock).mockResolvedValue({
+        _embedded: { "dav:calendar": mockCalendars },
+      });
+
+      const getUserDetailsMock = userAPI.getUserDetails as jest.Mock;
+      getUserDetailsMock.mockResolvedValue({
+        firstname: "Alice",
+        lastname: "Smith",
+        emails: ["alice@example.com"],
+      });
+
+      const store = storeFactory();
+      await store.dispatch(getCalendarsListAsync() as any);
+
+      expect(getUserDetailsMock).toHaveBeenCalledTimes(1);
+      expect(getUserDetailsMock).toHaveBeenCalledWith("u1");
+    });
+
+    it("getCalendarsListAsync processes owners in batches of 20", async () => {
+      const mockCalendars = Array.from({ length: 45 }, (_, i) => ({
+        _links: { self: { href: `/calendars/u${i + 1}/cal${i + 1}.json` } },
+        "dav:name": `Calendar ${i + 1}`,
+        "apple:color": "#FF0000",
+        acl: [],
+      }));
+
+      (userAPI.getOpenPaasUser as jest.Mock).mockResolvedValue({ id: "u1" });
+      (calAPI.getCalendars as jest.Mock).mockResolvedValue({
+        _embedded: { "dav:calendar": mockCalendars },
+      });
+
+      const getUserDetailsMock = userAPI.getUserDetails as jest.Mock;
+      getUserDetailsMock.mockImplementation((ownerId: string) =>
+        Promise.resolve({
+          firstname: "User",
+          lastname: ownerId,
+          emails: [`${ownerId}@example.com`],
+        })
+      );
+
+      const store = storeFactory();
+      await store.dispatch(getCalendarsListAsync() as any);
+
+      expect(getUserDetailsMock).toHaveBeenCalledTimes(45);
+      const state = store.getState().calendars;
+      expect(Object.keys(state.list)).toHaveLength(45);
+    });
+
+    it("getCalendarsListAsync returns early if calendars already exist in store", async () => {
+      const existingCalendars = {
+        "u1/cal1": {
+          id: "u1/cal1",
+          name: "Existing Calendar",
+          events: {},
+        } as Calendars,
+      };
+
+      const store = storeFactory();
+      store.dispatch({
+        type: "calendars/getCalendars/fulfilled",
+        payload: { importedCalendars: existingCalendars, errors: "" },
+      });
+
+      const getUserDetailsMock = userAPI.getUserDetails as jest.Mock;
+      const getCalendarsMock = calAPI.getCalendars as jest.Mock;
+
+      await store.dispatch(getCalendarsListAsync() as any);
+
+      expect(getCalendarsMock).not.toHaveBeenCalled();
+      expect(getUserDetailsMock).not.toHaveBeenCalled();
+
+      const state = store.getState().calendars;
+      expect(state.list).toEqual(existingCalendars);
+    });
+
+    it("getCalendarsListAsync handles errors in getUserDetails gracefully", async () => {
+      const mockCalendars = [
+        {
+          _links: { self: { href: "/calendars/u1/cal1.json" } },
+          "dav:name": "Calendar 1",
+          "apple:color": "#FF0000",
+          acl: [],
+        },
+        {
+          _links: { self: { href: "/calendars/u2/cal2.json" } },
+          "dav:name": "Calendar 2",
+          "apple:color": "#00FF00",
+          acl: [],
+        },
+      ];
+
+      (userAPI.getOpenPaasUser as jest.Mock).mockResolvedValue({ id: "u1" });
+      (calAPI.getCalendars as jest.Mock).mockResolvedValue({
+        _embedded: { "dav:calendar": mockCalendars },
+      });
+
+      const getUserDetailsMock = userAPI.getUserDetails as jest.Mock;
+      getUserDetailsMock
+        .mockResolvedValueOnce({
+          firstname: "Alice",
+          lastname: "Smith",
+          emails: ["alice@example.com"],
+        })
+        .mockRejectedValueOnce(new Error("Failed to fetch user"));
+
+      const store = storeFactory();
+      const result = await store.dispatch(getCalendarsListAsync() as any);
+
+      expect(getUserDetailsMock).toHaveBeenCalledTimes(2);
+      const state = store.getState().calendars;
+      expect(state.list["u1/cal1"].owner).toContain("Alice");
+      expect(state.list["u2/cal2"].owner).toContain("Unknown User");
+      expect(result.payload.errors).toBeTruthy();
+    });
+
     it("patchCalendarAsync.fulfilled updates calendar fields", () => {
       const calId = "c1";
       const prev = {

src/components/Calendar/Calendar.tsx

@@ -5,7 +5,7 @@ import interactionPlugin from "@fullcalendar/interaction";
 import { CalendarApi, DateSelectArg } from "@fullcalendar/core";
 import "./Calendar.styl";
 import "./CustomCalendar.styl";
-import { useEffect, useMemo, useRef, useState } from "react";
+import { MutableRefObject, useEffect, useMemo, useRef, useState } from "react";
 import { useAppDispatch, useAppSelector } from "../../app/hooks";
 import EventPopover from "../../features/Events/EventModal";
 import { CalendarEvent } from "../../features/Events/EventsTypes";
@@ -44,7 +44,7 @@ import { updateDarkColor } from "./utils/calendarColorsUtils";
 import { useI18n } from "cozy-ui/transpiled/react/providers/I18n";
 
 interface CalendarAppProps {
-  calendarRef: React.RefObject<CalendarApi | null>;
+  calendarRef: MutableRefObject<CalendarApi | null>;
   onDateChange?: (date: Date) => void;
   onViewChange?: (view: string) => void;
 }
@@ -65,13 +65,31 @@ export default function CalendarApp({
     if (!tokens || !userId) {
       dispatch(push("/"));
     }
-  }, [tokens, userId]);
+  }, [dispatch, tokens, userId]);
 
   const calendars = useAppSelector((state) => state.calendars.list);
-  const tempcalendars =
-    useAppSelector((state) => state.calendars.templist) ?? {};
+  const tempcalendars = useAppSelector((state) => state.calendars.templist);
   const [selectedCalendars, setSelectedCalendars] = useState<string[]>([]);
 
+  const calendarLightSignature = useMemo(() => {
+    return Object.values(calendars || {})
+      .map((cal) => `${cal.id}:${cal.color?.light ?? ""}`)
+      .sort()
+      .join("|");
+  }, [calendars]);
+
+  const calendarIdsString = useMemo(
+    () =>
+      Object.keys(calendars || {})
+        .sort()
+        .join(","),
+    [calendars]
+  );
+  const calendarIds = useMemo(
+    () => (calendarIdsString ? calendarIdsString.split(",") : []),
+    [calendarIdsString]
+  );
+
   const dottedEvents: CalendarEvent[] = selectedCalendars.flatMap((calId) => {
     const calendar = calendars[calId];
     if (!calendar?.events) return [];
@@ -100,65 +118,99 @@ export default function CalendarApp({
   };
 
   useEffect(() => {
-    if (initialLoadRef.current && Object.keys(calendars || {}).length > 0 && userId) {
+    if (initialLoadRef.current && calendarIds.length > 0 && userId) {
       const cached = localStorage.getItem("selectedCalendars");
       if (cached && cached.length > 0) {
         const parsed = JSON.parse(cached) as string[];
         const valid = parsed.filter((id) => calendars[id]);
         setSelectedCalendars(valid);
       } else {
-        const personalCalendarIds = Object.keys(calendars).filter(
+        const personalCalendarIds = calendarIds.filter(
           (id) => id.split("/")[0] === userId
         );
         setSelectedCalendars(personalCalendarIds);
       }
       initialLoadRef.current = false;
     }
-  }, [calendars, userId]);
+  }, [calendarIds, calendars, userId]);
 
   // Save selected cals to cache
   useEffect(() => {
-    if (Object.keys(calendars || {}).length > 0) {
+    if (calendarIds.length > 0) {
       localStorage.setItem(
         "selectedCalendars",
         JSON.stringify(selectedCalendars)
       );
     }
-  }, [selectedCalendars]);
+  }, [selectedCalendars, calendarIds.length]);
+
+  const prevCalendarLightSignature = useRef<string | null>(null);
 
   useEffect(() => {
+    if (!calendarLightSignature) {
+      prevCalendarLightSignature.current = calendarLightSignature;
+      return;
+    }
+
+    if (prevCalendarLightSignature.current === calendarLightSignature) {
+      return;
+    }
+
+    prevCalendarLightSignature.current = calendarLightSignature;
     updateDarkColor(calendars || {}, theme, dispatch);
-  }, [
-    theme,
-    Object.values(calendars || {})
-      .map((c) => c.color?.dark)
-      .join(","),
-  ]);
+  }, [calendarLightSignature, calendars, theme, dispatch]);
 
   useEffect(() => {
-    const validCalendarIds = new Set(Object.keys(calendars || {}));
-    setSelectedCalendars((prev) =>
-      prev.filter((calId) => validCalendarIds.has(calId))
-    );
-  }, [calendars]);
+    if (calendarIds.length === 0) return;
+    const validCalendarIds = new Set(calendarIds);
+    setSelectedCalendars((prev) => {
+      const filtered = prev.filter((calId) => validCalendarIds.has(calId));
+      if (filtered.length === prev.length) {
+        const unchanged = filtered.every((id, index) => id === prev[index]);
+        if (unchanged) {
+          return prev;
+        }
+      }
+      return filtered;
+    });
+  }, [calendarIds]);
 
   const calendarRange = useMemo(
     () => getCalendarRange(selectedDate),
     [selectedDate]
   );
 
+  const calendarRangeStart = calendarRange.start.getTime();
+  const calendarRangeEnd = calendarRange.end.getTime();
+
+  const rangeStart = useMemo(
+    () => formatDateToYYYYMMDDTHHMMSS(new Date(calendarRangeStart)),
+    [calendarRangeStart]
+  );
+
+  const rangeEnd = useMemo(
+    () => formatDateToYYYYMMDDTHHMMSS(new Date(calendarRangeEnd)),
+    [calendarRangeEnd]
+  );
+
   // Create a stable string key for the range
-  const rangeKey = `${formatDateToYYYYMMDDTHHMMSS(
-    calendarRange.start
-  )}_${formatDateToYYYYMMDDTHHMMSS(calendarRange.end)}`;
+  const rangeKey = useMemo(
+    () => `${rangeStart}_${rangeEnd}`,
+    [rangeStart, rangeEnd]
+  );
 
   let filteredEvents: CalendarEvent[] = extractEvents(
     selectedCalendars,
     calendars || {}
   );
 
+  const tempCalendarIds = useMemo(
+    () => Object.keys(tempcalendars || {}).sort(),
+    [tempcalendars]
+  );
+
   let filteredTempEvents: CalendarEvent[] = extractEvents(
-    Object.keys(tempcalendars || {}),
+    tempCalendarIds,
     tempcalendars || {}
   );
 
@@ -169,55 +221,73 @@ export default function CalendarApp({
 
   const prefetchedCalendarsRef = useRef<Record<string, string>>({});
   const tempFetchedRangesRef = useRef<Record<string, string>>({});
+  const activeLoadCompletedRef = useRef<boolean>(false);
+  const [activeLoadCompleted, setActiveLoadCompleted] =
+    useState<boolean>(false);
 
   useEffect(() => {
-    if (!rangeKey || sortedSelectedCalendars.length === 0) return;
+    activeLoadCompletedRef.current = false;
+    setActiveLoadCompleted(false);
+  }, [rangeKey]);
+
+  useEffect(() => {
+    if (!rangeKey || sortedSelectedCalendars.length === 0) {
+      activeLoadCompletedRef.current = true;
+      setActiveLoadCompleted(true);
+      return;
+    }
 
     let cancelled = false;
     const ACTIVE_BATCH_SIZE = 5;
 
     const loadCalendars = async () => {
-      const pendingIds = sortedSelectedCalendars.filter(
-        (id) => fetchedRangesRef.current[id] !== rangeKey
-      );
+      try {
+        const pendingIds = sortedSelectedCalendars.filter(
+          (id) => fetchedRangesRef.current[id] !== rangeKey
+        );
 
-      if (pendingIds.length === 0) {
-        return;
-      }
+        if (pendingIds.length === 0) {
+          activeLoadCompletedRef.current = true;
+          setActiveLoadCompleted(true);
+          return;
+        }
 
-      const rangeStart = formatDateToYYYYMMDDTHHMMSS(calendarRange.start);
-      const rangeEnd = formatDateToYYYYMMDDTHHMMSS(calendarRange.end);
+        for (
+          let i = 0;
+          i < pendingIds.length && !cancelled;
+          i += ACTIVE_BATCH_SIZE
+        ) {
+          const chunk = pendingIds.slice(i, i + ACTIVE_BATCH_SIZE);
 
-      for (
-        let i = 0;
-        i < pendingIds.length && !cancelled;
-        i += ACTIVE_BATCH_SIZE
-      ) {
-        const chunk = pendingIds.slice(i, i + ACTIVE_BATCH_SIZE);
+          chunk.forEach((id) => {
+            fetchedRangesRef.current[id] = rangeKey;
+            prefetchedCalendarsRef.current[id] = "active";
+          });
 
-        chunk.forEach((id) => {
-          fetchedRangesRef.current[id] = rangeKey;
-          prefetchedCalendarsRef.current[id] = "active";
-        });
+          const requests = chunk.map(async (id) => {
+            try {
+              await dispatch(
+                getCalendarDetailAsync({
+                  calId: id,
+                  match: {
+                    start: rangeStart,
+                    end: rangeEnd,
+                  },
+                })
+              ).unwrap();
+            } catch (error) {
+              console.error(`Failed to load calendar ${id}:`, error);
+              fetchedRangesRef.current[id] = "";
+            }
+          });
 
-        const requests = chunk.map(async (id) => {
-          try {
-            await dispatch(
-              getCalendarDetailAsync({
-                calId: id,
-                match: {
-                  start: rangeStart,
-                  end: rangeEnd,
-                },
-              })
-            ).unwrap();
-          } catch (error) {
-            console.error(`Failed to load calendar ${id}:`, error);
-            fetchedRangesRef.current[id] = "";
-          }
-        });
-
-        await Promise.all(requests);
+          await Promise.all(requests);
+        }
+      } finally {
+        if (!cancelled) {
+          activeLoadCompletedRef.current = true;
+          setActiveLoadCompleted(true);
+        }
       }
     };
 
@@ -226,22 +296,19 @@ export default function CalendarApp({
     return () => {
       cancelled = true;
     };
-  }, [
-    dispatch,
-    rangeKey,
-    sortedSelectedCalendars,
-    calendarRange,
-  ]);
+  }, [dispatch, rangeKey, sortedSelectedCalendars, rangeStart, rangeEnd]);
 
   useEffect(() => {
-    if (!rangeKey) return;
+    if (!rangeKey || !activeLoadCompleted) return;
 
-    const rangeStart = formatDateToYYYYMMDDTHHMMSS(calendarRange.start);
-    const rangeEnd = formatDateToYYYYMMDDTHHMMSS(calendarRange.end);
-
-    const hiddenCalendars = Object.keys(calendars || {})
+    const hiddenCalendars = calendarIds
       .filter((id) => !selectedCalendars.includes(id))
-      .filter((id) => prefetchedCalendarsRef.current[id] !== rangeKey);
+      .filter((id) => {
+        const prefetched = prefetchedCalendarsRef.current[id];
+        return prefetched !== rangeKey && prefetched !== "active";
+      });
+
+    if (hiddenCalendars.length === 0) return;
 
     hiddenCalendars.forEach((id) => {
       prefetchedCalendarsRef.current[id] = rangeKey;
@@ -261,43 +328,56 @@ export default function CalendarApp({
         });
     });
   }, [
-    calendars,
+    calendarIdsString,
     selectedCalendars,
     rangeKey,
-    calendarRange,
     dispatch,
+    rangeStart,
+    rangeEnd,
+    activeLoadCompleted,
   ]);
 
+  const calendarsWithClearedCache = useMemo(() => {
+    return selectedCalendars
+      .map((id) => {
+        const cleared = calendars[id]?.lastCacheCleared;
+        return cleared ? { id, cleared } : null;
+      })
+      .filter(Boolean) as { id: string; cleared: number }[];
+  }, [selectedCalendars, calendars]);
+
+  const processedCacheClearRef = useRef<Record<string, number>>({});
+
   useEffect(() => {
-    selectedCalendars.forEach((calId) => {
-      const calendar = calendars[calId];
-      if (calendar?.lastCacheCleared) {
-        delete fetchedRangesRef.current[calId];
-        prefetchedCalendarsRef.current[calId] = "";
-
-        dispatch(
-          getCalendarDetailAsync({
-            calId,
-            match: {
-              start: formatDateToYYYYMMDDTHHMMSS(calendarRange.start),
-              end: formatDateToYYYYMMDDTHHMMSS(calendarRange.end),
-            },
-          })
-        );
-
-        fetchedRangesRef.current[calId] = rangeKey;
-        prefetchedCalendarsRef.current[calId] = rangeKey;
+    calendarsWithClearedCache.forEach(({ id, cleared }) => {
+      if (processedCacheClearRef.current[id] === cleared) {
+        return;
       }
-    });
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [
-    selectedCalendars.map((id) => calendars[id]?.lastCacheCleared).join(","),
-  ]);
 
-  const tempCalendarIds = useMemo(
-    () => Object.keys(tempcalendars || {}).sort(),
-    [tempcalendars]
-  );
+      processedCacheClearRef.current[id] = cleared;
+      delete fetchedRangesRef.current[id];
+      prefetchedCalendarsRef.current[id] = "";
+
+      dispatch(
+        getCalendarDetailAsync({
+          calId: id,
+          match: {
+            start: rangeStart,
+            end: rangeEnd,
+          },
+        })
+      )
+        .unwrap()
+        .then(() => {
+          fetchedRangesRef.current[id] = rangeKey;
+          prefetchedCalendarsRef.current[id] = rangeKey;
+        })
+        .catch(() => {
+          fetchedRangesRef.current[id] = "";
+          prefetchedCalendarsRef.current[id] = "";
+        });
+    });
+  }, [calendarsWithClearedCache, dispatch, rangeKey, rangeStart, rangeEnd]);
 
   const tempCalendarControllersRef = useRef<Map<string, AbortController>>(
     new Map()
@@ -317,9 +397,6 @@ export default function CalendarApp({
 
     let cancelled = false;
     const TEMP_BATCH_SIZE = 5;
-    const rangeStart = formatDateToYYYYMMDDTHHMMSS(calendarRange.start);
-    const rangeEnd = formatDateToYYYYMMDDTHHMMSS(calendarRange.end);
-
     const loadTempCalendars = async () => {
       const pendingIds = tempCalendarIds.filter(
         (id) => tempFetchedRangesRef.current[id] !== rangeKey
@@ -366,7 +443,7 @@ export default function CalendarApp({
     return () => {
       cancelled = true;
     };
-  }, [dispatch, rangeKey, tempCalendarIds, calendarRange]);
+  }, [dispatch, rangeKey, tempCalendarIds, rangeStart, rangeEnd]);
 
   const [anchorEl, setAnchorEl] = useState<HTMLElement | null>(null);
 

src/components/Calendar/CalendarSelection.tsx

@@ -106,14 +106,14 @@ export default function CalendarSelection({
     useAppSelector((state) => state.user.userData?.openpaasId) ?? "";
   const calendars = useAppSelector((state) => state.calendars.list);
 
-  const personalCalendars = Object.keys(calendars).filter(
+  const personalCalendars = Object.keys(calendars || {}).filter(
     (id) => id.split("/")[0] === userId
   );
-  const delegatedCalendars = Object.keys(calendars).filter(
-    (id) => id.split("/")[0] !== userId && calendars[id].delegated
+  const delegatedCalendars = Object.keys(calendars || {}).filter(
+    (id) => id.split("/")[0] !== userId && calendars[id]?.delegated
   );
-  const sharedCalendars = Object.keys(calendars).filter(
-    (id) => id.split("/")[0] !== userId && !calendars[id].delegated
+  const sharedCalendars = Object.keys(calendars || {}).filter(
+    (id) => id.split("/")[0] !== userId && !calendars?.[id]?.delegated
   );
 
   const handleCalendarToggle = (name: string) => {
@@ -178,7 +178,7 @@ export default function CalendarSelection({
       </div>
       <CalendarPopover
         open={Boolean(anchorElCal)}
-        calendar={calendars[selectedCalId] ?? undefined}
+        calendar={calendars?.[selectedCalId] ?? undefined}
         onClose={() => {
           setSelectedCalId("");
           setAnchorElCal(null);

src/components/Calendar/MiniCalendar.tsx

@@ -51,7 +51,7 @@ export function MiniCalendar({
         onMonthChange={(month) => {
           const calendarRange = getCalendarRange(month.toDate());
           setVisibleDate(month.toDate());
-          Object.values(calendars.list).forEach((cal) =>
+          Object.values(calendars.list || {}).forEach((cal) =>
             dispatch(
               getCalendarDetailAsync({
                 calId: cal.id,

src/components/Calendar/hooks/useCalendarEventHandlers.ts

@@ -34,6 +34,7 @@ export const useCalendarEventHandlers = (props: EventHandlersProps) => {
       props.setEventDisplayedCalId,
       props.setEventDisplayedTemp,
       props.calendars,
+      props.dispatch,
     ]),
     handleEventAllow: useCallback(eventHandlers.handleEventAllow, []),
     handleEventDrop: useCallback(eventHandlers.handleEventDrop, [
@@ -42,10 +43,14 @@ export const useCalendarEventHandlers = (props: EventHandlersProps) => {
       props.setSelectedEvent,
       props.setOpenEditModePopup,
       props.setAfterChoiceFunc,
+      props.tempcalendars,
+      props.calendarRange,
     ]),
     handleEventResize: useCallback(eventHandlers.handleEventResize, [
       props.calendars,
       props.dispatch,
+      props.tempcalendars,
+      props.calendarRange,
     ]),
   };
 };

src/components/Calendar/utils/calendarColorsUtils.tsx

@@ -19,6 +19,10 @@ export function updateDarkColor(
       ? isDefault.dark
       : getAccessiblePair(baseColor, theme);
 
+    if (cal.color?.dark === darkColor) {
+      return;
+    }
+
     dispatch(
       updateCalColor({
         id: cal.id,

src/components/Menubar/Menubar.tsx

@@ -1,4 +1,4 @@
-import React, { useState } from "react";
+import React, { useEffect, useState } from "react";
 import logo from "../../static/header-logo.svg";
 import AppsIcon from "@mui/icons-material/Apps";
 import RefreshIcon from "@mui/icons-material/Refresh";
@@ -53,8 +53,14 @@ export function Menubar({
   const [langAnchorEl, setLangAnchorEl] = useState<null | HTMLElement>(null);
   const dispatch = useAppDispatch();
 
+  useEffect(() => {
+    if (!user) {
+      dispatch(push("/"));
+    }
+  }, [dispatch, user]);
+
   if (!user) {
-    dispatch(push("/"));
+    return null;
   }
   const handleOpen = (event: React.MouseEvent<HTMLElement>) => {
     setAnchorEl(event.currentTarget);

src/features/Calendars/CalendarSlice.ts

@@ -40,8 +40,16 @@ interface RejectedError {
 export const getCalendarsListAsync = createAsyncThunk<
   { importedCalendars: Record<string, Calendars>; errors: string }, // Return type
   void, // Arg type
-  { rejectValue: RejectedError } // ThunkAPI config
->("calendars/getCalendars", async (_, { rejectWithValue }) => {
+  { rejectValue: RejectedError; state: any } // ThunkAPI config
+>("calendars/getCalendars", async (_, { rejectWithValue, getState }) => {
+  const state = getState() as any;
+  if (Object.keys(state.calendars.list).length > 0) {
+    return {
+      importedCalendars: state.calendars.list,
+      errors: "",
+    };
+  }
+
   try {
     const importedCalendars: Record<string, Calendars> = {};
     const user = (await getOpenPaasUser()) as Record<string, string>;
@@ -106,15 +114,7 @@ export const getCalendarsListAsync = createAsyncThunk<
     }
 
     normalizedCalendars.forEach(
-      ({
-        cal,
-        description,
-        delegated,
-        link,
-        id,
-        ownerId,
-        visibility,
-      }) => {
+      ({ cal, description, delegated, link, id, ownerId, visibility }) => {
         const ownerData = ownerDataMap.get(ownerId) || {
           firstname: "",
           lastname: "Unknown User",

src/features/Events/EventModal.tsx

@@ -59,10 +59,10 @@ function EventPopover({
   const selectPersonalCalendars = createSelector(
     (state: any) => state.calendars,
     (calendars: any) =>
-      Object.keys(calendars.list)
+      Object.keys(calendars.list || {})
         .map((id) => {
           if (id.split("/")[0] === userId) {
-            return calendars.list[id];
+            return calendars.list?.[id];
           }
           return {} as Calendars;
         })

src/features/Events/ImportAlert.tsx

@@ -17,8 +17,8 @@ export default function ImportAlert() {
 
   return (
     <>
-      {Object.keys(calendars).map((calendarId) =>
-        calendars[calendarId]?.events
+      {Object.keys(calendars || {}).map((calendarId) =>
+        calendars?.[calendarId]?.events
           ? Object.keys(calendars[calendarId]?.events)
               .filter((id) => calendars[calendarId]?.events[id].error)
               .map((id) => {

src/features/User/HandleLogin.tsx

@@ -1,4 +1,4 @@
-import React, { useEffect } from "react";
+import React, { useEffect, useRef } from "react";
 import { useAppDispatch, useAppSelector } from "../../app/hooks";
 import { Auth } from "./oidcAuth";
 import { Loading } from "../../components/Loading/Loading";
@@ -11,41 +11,50 @@ export function HandleLogin() {
   const userData = useAppSelector((state) => state.user);
   const calendars = useAppSelector((state) => state.calendars);
   const dispatch = useAppDispatch();
+  const hasInitiatedRef = useRef(false);
+  const calendarsLoadingRef = useRef(false);
+
   useEffect(() => {
+    if (hasInitiatedRef.current) return;
+    if (userData.userData) return;
+    if (Object.keys(calendars.list).length > 0) return;
+    if (calendarsLoadingRef.current) return;
+
+    hasInitiatedRef.current = true;
     const initiateLogin = async () => {
-      if (!userData.userData) {
-        const savedToken = sessionStorage.getItem("tokenSet")
-          ? JSON.parse(sessionStorage.getItem("tokenSet")!)
-          : null;
-        const savedUser = sessionStorage.getItem("userData")
-          ? JSON.parse(sessionStorage.getItem("userData")!)
-          : null;
+      const savedToken = sessionStorage.getItem("tokenSet")
+        ? JSON.parse(sessionStorage.getItem("tokenSet")!)
+        : null;
+      const savedUser = sessionStorage.getItem("userData")
+        ? JSON.parse(sessionStorage.getItem("userData")!)
+        : null;
 
-        if (savedToken && savedUser) {
-          dispatch(setTokens(savedToken));
-          dispatch(setUserData(savedUser));
-          await dispatch(getOpenPaasUserDataAsync());
-          await dispatch(getCalendarsListAsync());
-          dispatch(push("/calendar"));
-          return;
-        }
-
-        const loginurl = await Auth();
-
-        sessionStorage.setItem(
-          "redirectState",
-          JSON.stringify({
-            code_verifier: loginurl.code_verifier,
-            state: loginurl.state,
-          })
-        );
-
-        redirectTo(loginurl.redirectTo);
+      if (savedToken && savedUser) {
+        dispatch(setTokens(savedToken));
+        dispatch(setUserData(savedUser));
+        await dispatch(getOpenPaasUserDataAsync());
+        calendarsLoadingRef.current = true;
+        await dispatch(getCalendarsListAsync());
+        calendarsLoadingRef.current = false;
+        dispatch(push("/calendar"));
+        return;
       }
+
+      const loginurl = await Auth();
+
+      sessionStorage.setItem(
+        "redirectState",
+        JSON.stringify({
+          code_verifier: loginurl.code_verifier,
+          state: loginurl.state,
+        })
+      );
+
+      redirectTo(loginurl.redirectTo);
     };
 
     initiateLogin();
-  }, [userData, dispatch]);
+  }, [userData.userData, calendars.list, dispatch]);
   useEffect(() => {
     if (userData.error) {
       dispatch(push("/error"));
@@ -53,7 +62,7 @@ export function HandleLogin() {
     if (!calendars.pending && !userData.loading && !userData.error) {
       dispatch(push("/calendar"));
     }
-  }, [calendars.pending, userData.loading]);
+  }, [calendars.pending, userData.loading, userData.error, dispatch]);
   return <Loading />;
 }
 

src/features/User/LoginCallback.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useRef } from "react";
 import { Callback } from "./oidcAuth";
-import { useAppDispatch } from "../../app/hooks";
+import { useAppDispatch, useAppSelector } from "../../app/hooks";
 import { push } from "redux-first-history";
 import { getOpenPaasUserDataAsync, setTokens, setUserData } from "./userSlice";
 import { Loading } from "../../components/Loading/Loading";
@@ -9,6 +9,7 @@ import { getCalendarsListAsync } from "../Calendars/CalendarSlice";
 export function CallbackResume() {
   const dispatch = useAppDispatch();
   const hasRun = useRef(false);
+  const calendarsLoadingRef = useRef(false);
   const saved = sessionStorage.getItem("redirectState")
     ? JSON.parse(sessionStorage.getItem("redirectState")!)
     : null;
@@ -23,7 +24,11 @@ export function CallbackResume() {
         dispatch(setUserData(data?.userinfo));
         dispatch(setTokens(data?.tokenSet));
         await dispatch(getOpenPaasUserDataAsync());
-        await dispatch(getCalendarsListAsync());
+        if (!calendarsLoadingRef.current) {
+          calendarsLoadingRef.current = true;
+          await dispatch(getCalendarsListAsync());
+          calendarsLoadingRef.current = false;
+        }
 
         sessionStorage.removeItem("redirectState");
         sessionStorage.setItem("tokenSet", JSON.stringify(data?.tokenSet));