feat: implement CalDAV discovery API and enhance calendar ID handling

app/api/caldav/discover/route.ts

@@ -0,0 +1,103 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { logger } from '@/lib/logger';
+import { getStalwartCredentials } from '@/lib/stalwart/credentials';
+
+interface DiscoveryAccountRequest {
+  key: string;
+  candidates: string[];
+}
+
+interface DiscoveryResult {
+  url: string | null;
+  resolvedAccount: string | null;
+}
+
+function buildPublicUrl(serverUrl: string, path: string): string {
+  return new URL(path, serverUrl).toString();
+}
+
+async function probeCalendarHome(serverUrl: string, authHeader: string, accountName: string): Promise<string | null> {
+  const targetUrl = buildPublicUrl(serverUrl, `/dav/cal/${encodeURIComponent(accountName)}`);
+  const response = await fetch(targetUrl, {
+    method: 'PROPFIND',
+    headers: {
+      Authorization: authHeader,
+      Depth: '0',
+      'Content-Type': 'application/xml; charset=utf-8',
+    },
+    body: `<?xml version="1.0" encoding="utf-8"?>
+<D:propfind xmlns:D="DAV:">
+  <D:prop>
+    <D:resourcetype/>
+    <D:displayname/>
+  </D:prop>
+</D:propfind>`,
+    redirect: 'manual',
+  });
+
+  if (response.status === 207) {
+    return targetUrl;
+  }
+
+  if (response.status >= 300 && response.status < 400) {
+    const location = response.headers.get('Location');
+    if (location) {
+      return new URL(location, targetUrl).toString();
+    }
+  }
+
+  return null;
+}
+
+export async function POST(request: NextRequest) {
+  try {
+    const creds = await getStalwartCredentials(request);
+    if (!creds) {
+      return NextResponse.json({ error: 'Not authenticated' }, { status: 401 });
+    }
+
+    const body = await request.json().catch(() => ({}));
+    const accounts = Array.isArray(body.accounts) ? body.accounts as DiscoveryAccountRequest[] : [];
+    const wellKnownUrl = buildPublicUrl(creds.serverUrl, '/.well-known/caldav');
+    const discovered: Record<string, DiscoveryResult> = {};
+
+    for (const account of accounts) {
+      if (!account?.key) continue;
+
+      const candidates = Array.from(new Set(
+        (account.candidates || [])
+          .map((candidate) => candidate?.trim())
+          .filter((candidate): candidate is string => Boolean(candidate))
+      ));
+
+      let url: string | null = null;
+      let resolvedAccount: string | null = null;
+
+      for (const candidate of candidates) {
+        try {
+          url = await probeCalendarHome(creds.serverUrl, creds.authHeader, candidate);
+          if (url) {
+            resolvedAccount = candidate;
+            break;
+          }
+        } catch (error) {
+          logger.warn('CalDAV discovery probe failed', {
+            accountKey: account.key,
+            candidate,
+            error: error instanceof Error ? error.message : 'Unknown',
+          });
+        }
+      }
+
+      discovered[account.key] = { url, resolvedAccount };
+    }
+
+    return NextResponse.json({
+      wellKnownUrl,
+      accounts: discovered,
+    });
+  } catch (error) {
+    logger.error('CalDAV discovery failed', { error: error instanceof Error ? error.message : 'Unknown' });
+    return NextResponse.json({ error: 'Internal server error' }, { status: 500 });
+  }
+}

components/calendar/calendar-agenda-view.tsx

@@ -6,7 +6,7 @@ import { format, parseISO, isToday, isTomorrow } from "date-fns";
 import { Calendar as CalendarIcon, MapPin, Users } from "lucide-react";
 import { cn } from "@/lib/utils";
 import { parseDuration, getEventColor } from "./event-card";
-import { getEventDayBounds } from "@/lib/calendar-utils";
+import { getEventDayBounds, getPrimaryCalendarId } from "@/lib/calendar-utils";
 import { getParticipantCount } from "@/lib/calendar-participants";
 import type { CalendarEvent, Calendar } from "@/lib/jmap/types";
 
@@ -113,8 +113,8 @@ export function CalendarAgendaView({
 
           <div className="divide-y divide-border">
             {group.events.map((ev) => {
-              const calId = Object.keys(ev.calendarIds)[0];
+              const calId = getPrimaryCalendarId(ev);
-              const calendar = calendarMap.get(calId);
+              const calendar = calId ? calendarMap.get(calId) : undefined;
               const color = getEventColor(ev, calendar);
               const start = parseISO(ev.start);
               const durMin = parseDuration(ev.duration);

components/calendar/calendar-day-view.tsx

@@ -6,7 +6,7 @@ import { format, isToday, parseISO } from "date-fns";
 import { cn } from "@/lib/utils";
 import { EventCard, parseDuration } from "./event-card";
 import { QuickEventInput } from "./quick-event-input";
-import { getEventDayBounds, layoutOverlappingEvents, formatSnapTime } from "@/lib/calendar-utils";
+import { formatSnapTime, getEventDayBounds, getPrimaryCalendarId, layoutOverlappingEvents } from "@/lib/calendar-utils";
 import type { CalendarEvent, Calendar } from "@/lib/jmap/types";
 import { useTimeGridInteractions } from "@/hooks/use-time-grid-interactions";
 
@@ -127,12 +127,12 @@ export function CalendarDayView({
           <div className="text-[10px] text-muted-foreground mb-1">{t("events.all_day")}</div>
           <div className="space-y-1">
             {allDayEvents.map((ev) => {
-              const calId = Object.keys(ev.calendarIds)[0];
+              const calId = getPrimaryCalendarId(ev);
               return (
                 <EventCard
                   key={ev.id}
                   event={ev}
-                  calendar={calendarMap.get(calId)}
+                  calendar={calId ? calendarMap.get(calId) : undefined}
                   variant="chip"
                   onClick={(rect) => onSelectEvent(ev, rect)}
                   onMouseEnter={(rect) => onHoverEvent?.(ev, rect)}
@@ -192,7 +192,7 @@ export function CalendarDayView({
               const top = (startMin / 60) * HOUR_HEIGHT;
               const baseHeight = Math.max(24, (durMin / 60) * HOUR_HEIGHT);
               const height = resizeVisual?.eventId === ev.id ? resizeVisual.heightPx : baseHeight;
-              const calId = Object.keys(ev.calendarIds)[0];
+              const calId = getPrimaryCalendarId(ev);
               const leftPct = (column / totalColumns) * 100;
               const widthPct = (1 / totalColumns) * 100;
 
@@ -205,7 +205,7 @@ export function CalendarDayView({
                 >
                   <EventCard
                     event={ev}
-                    calendar={calendarMap.get(calId)}
+                    calendar={calId ? calendarMap.get(calId) : undefined}
                     variant="block"
                     onClick={(rect) => onSelectEvent(ev, rect)}
                     onMouseEnter={(rect) => onHoverEvent?.(ev, rect)}

components/calendar/calendar-month-view.tsx

@@ -8,7 +8,7 @@ import {
 } from "date-fns";
 import { cn } from "@/lib/utils";
 import { EventCard } from "./event-card";
-import { buildWeekSegments, getEventDayBounds } from "@/lib/calendar-utils";
+import { buildWeekSegments, getEventDayBounds, getPrimaryCalendarId } from "@/lib/calendar-utils";
 import type { CalendarEvent, Calendar } from "@/lib/jmap/types";
 import { useAuthStore } from "@/stores/auth-store";
 import { useCalendarStore } from "@/stores/calendar-store";
@@ -197,8 +197,8 @@ export function CalendarMonthView({
                     dayEvents.length > 0 && (
                       <div className="flex items-center justify-center gap-0.5 flex-wrap">
                         {dayEvents.slice(0, 3).map((ev) => {
-                          const calId = Object.keys(ev.calendarIds)[0];
+                          const calId = getPrimaryCalendarId(ev);
-                          const cal = calendarMap.get(calId);
+                          const cal = calId ? calendarMap.get(calId) : undefined;
                           const evColor = ev.color || cal?.color || "#3b82f6";
                           return (
                             <span
@@ -222,7 +222,7 @@ export function CalendarMonthView({
             {!isMobile && segments.length > 0 && (
               <div className="absolute inset-x-0 pointer-events-none" style={{ top: 30 }}>
                 {segments.map((segment) => {
-                  const calId = Object.keys(segment.event.calendarIds)[0];
+                  const calId = getPrimaryCalendarId(segment.event);
                   return (
                     <div
                       key={`${segment.event.id}-${segment.startIndex}-${segment.row}`}
@@ -236,7 +236,7 @@ export function CalendarMonthView({
                     >
                       <EventCard
                         event={segment.event}
-                        calendar={calendarMap.get(calId)}
+                        calendar={calId ? calendarMap.get(calId) : undefined}
                         variant="span"
                         continuesBefore={segment.continuesBefore}
                         continuesAfter={segment.continuesAfter}

components/calendar/calendar-sidebar-panel.tsx

@@ -47,7 +47,7 @@ export function CalendarSidebarPanel({
     const shared = calendars.filter(c => c.isShared);
     const groups = new Map<string, { accountName: string; calendars: Calendar[] }>();
     for (const cal of shared) {
-      const key = cal.accountId!;
+      const key = cal.accountId || cal.accountName || cal.id;
       if (!groups.has(key)) {
         groups.set(key, { accountName: cal.accountName || key, calendars: [] });
       }

components/calendar/calendar-toolbar.tsx

@@ -183,7 +183,7 @@ export function CalendarToolbar({
                 const shared = calendars.filter(c => c.isShared);
                 const groups = new Map<string, { accountName: string; cals: typeof shared }>();
                 for (const c of shared) {
-                  const key = c.accountId!;
+                  const key = c.accountId || c.accountName || c.id;
                   if (!groups.has(key)) groups.set(key, { accountName: c.accountName || key, cals: [] });
                   groups.get(key)!.cals.push(c);
                 }

components/calendar/calendar-week-view.tsx

@@ -8,7 +8,7 @@ import {
 import { cn } from "@/lib/utils";
 import { EventCard, parseDuration } from "./event-card";
 import { QuickEventInput } from "./quick-event-input";
-import { buildWeekSegments, getEventDayBounds, layoutOverlappingEvents, formatSnapTime } from "@/lib/calendar-utils";
+import { buildWeekSegments, formatSnapTime, getEventDayBounds, getPrimaryCalendarId, layoutOverlappingEvents } from "@/lib/calendar-utils";
 import type { CalendarEvent, Calendar } from "@/lib/jmap/types";
 import { useTimeGridInteractions } from "@/hooks/use-time-grid-interactions";
 
@@ -162,7 +162,7 @@ export function CalendarWeekView({
 
             <div className="absolute inset-0 pointer-events-none">
               {allDaySegments.map((segment) => {
-                const calId = Object.keys(segment.event.calendarIds)[0];
+                const calId = getPrimaryCalendarId(segment.event);
                 return (
                   <div
                     key={`${segment.event.id}-${segment.startIndex}-${segment.row}`}
@@ -176,7 +176,7 @@ export function CalendarWeekView({
                   >
                     <EventCard
                       event={segment.event}
-                      calendar={calendarMap.get(calId)}
+                      calendar={calId ? calendarMap.get(calId) : undefined}
                       variant="span"
                       continuesBefore={segment.continuesBefore}
                       continuesAfter={segment.continuesAfter}
@@ -284,7 +284,7 @@ export function CalendarWeekView({
                     const top = (startMin / 60) * HOUR_HEIGHT;
                     const baseHeight = Math.max(20, (durMin / 60) * HOUR_HEIGHT);
                     const height = resizeVisual?.eventId === ev.id ? resizeVisual.heightPx : baseHeight;
-                    const calId = Object.keys(ev.calendarIds)[0];
+                    const calId = getPrimaryCalendarId(ev);
                     const leftPct = (column / totalColumns) * 100;
                     const widthPct = (1 / totalColumns) * 100;
 
@@ -297,7 +297,7 @@ export function CalendarWeekView({
                       >
                         <EventCard
                           event={ev}
-                          calendar={calendarMap.get(calId)}
+                          calendar={calId ? calendarMap.get(calId) : undefined}
                           variant="block"
                           onClick={(rect) => onSelectEvent(ev, rect)}
                           onMouseEnter={(rect) => onHoverEvent?.(ev, rect)}

components/calendar/event-modal.tsx

@@ -8,7 +8,7 @@ import { X, Trash2, Check, Users, CalendarDays, Copy, Pencil, Clock, MapPin, Vid
 import { format, parseISO, addHours, addDays } from "date-fns";
 import type { CalendarEvent, Calendar, CalendarParticipant } from "@/lib/jmap/types";
 import { parseDuration, getEventColor } from "./event-card";
-import { buildAllDayDuration, getEventDisplayEndDate } from "@/lib/calendar-utils";
+import { buildAllDayDuration, getEventDisplayEndDate, getPrimaryCalendarId } from "@/lib/calendar-utils";
 import { ParticipantInput } from "./participant-input";
 import {
   isOrganizer,
@@ -184,7 +184,7 @@ export function EventModal({
   const [endTime, setEndTime] = useState(formatTimeInput(getInitialEnd()));
   const [allDay, setAllDay] = useState(event?.showWithoutTime || false);
   const [calendarId, setCalendarId] = useState<string>(() => {
-    if (event?.calendarIds) return Object.keys(event.calendarIds)[0] || calendars[0]?.id || "";
+    if (event?.calendarIds) return getPrimaryCalendarId(event) || calendars[0]?.id || "";
     const defaultCal = calendars.find(c => c.isDefault);
     return defaultCal?.id || calendars[0]?.id || "";
   });

components/settings/calendar-management-settings.tsx

@@ -153,6 +153,9 @@ export function CalendarManagementSettings() {
   const { client, serverUrl, username } = useAuthStore();
   const { calendars, updateCalendar, createCalendar, removeCalendar, clearCalendarEvents, fetchCalendars, icalSubscriptions, removeICalSubscription, refreshICalSubscription, isSubscriptionCalendar } = useCalendarStore();
 
+  const [discoveredCalDavUrls, setDiscoveredCalDavUrls] = useState<Record<string, string | null>>({});
+  const [wellKnownCalDavUrl, setWellKnownCalDavUrl] = useState<string | null>(null);
+
   const [isCreating, setIsCreating] = useState(false);
   const [editingId, setEditingId] = useState<string | null>(null);
   const [deletingId, setDeletingId] = useState<string | null>(null);
@@ -175,6 +178,60 @@ export function CalendarManagementSettings() {
     }
   }, [client, calendars.length, fetchCalendars]);
 
+  useEffect(() => {
+    if (!client || !serverUrl || !username) {
+      setDiscoveredCalDavUrls({});
+      setWellKnownCalDavUrl(null);
+      return;
+    }
+
+    const primaryKey = username;
+    const accounts = new Map<string, string[]>();
+    accounts.set(primaryKey, [username]);
+
+    for (const calendar of calendars) {
+      if (!calendar.isShared) continue;
+      const key = calendar.accountId || calendar.accountName || calendar.id;
+      const candidates = accounts.get(key) || [];
+      if (calendar.accountId) candidates.push(calendar.accountId);
+      if (calendar.accountName) candidates.push(calendar.accountName);
+      accounts.set(key, candidates);
+    }
+
+    const controller = new AbortController();
+
+    fetch('/api/caldav/discover', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        accounts: Array.from(accounts.entries()).map(([key, candidates]) => ({ key, candidates })),
+      }),
+      signal: controller.signal,
+    })
+      .then(async (response) => {
+        if (!response.ok) throw new Error(`CalDAV discovery failed: ${response.status}`);
+        return response.json() as Promise<{
+          wellKnownUrl?: string;
+          accounts?: Record<string, { url: string | null }>;
+        }>;
+      })
+      .then((payload) => {
+        setWellKnownCalDavUrl(payload.wellKnownUrl || null);
+        const next: Record<string, string | null> = {};
+        for (const [key, value] of Object.entries(payload.accounts || {})) {
+          next[key] = value?.url || null;
+        }
+        setDiscoveredCalDavUrls(next);
+      })
+      .catch(() => {
+        const fallbackWellKnown = new URL('/.well-known/caldav', serverUrl).toString();
+        setDiscoveredCalDavUrls({});
+        setWellKnownCalDavUrl(fallbackWellKnown);
+      });
+
+    return () => controller.abort();
+  }, [client, calendars, serverUrl, username]);
+
   const handleRefreshSubscription = async (subId: string) => {
     if (!client) return;
     setRefreshingSubId(subId);
@@ -295,8 +352,10 @@ export function CalendarManagementSettings() {
 
   const buildCalDavUrl = (calendarId: string) => {
     if (!serverUrl || !username) return null;
-    const base = serverUrl.replace(/\/$/, '');
+    const calendar = calendars.find((entry) => entry.id === calendarId);
-    return `${base}/dav/cal/${encodeURIComponent(username)}/${encodeURIComponent(calendarId)}/`;
+    if (!calendar) return null;
+    const accountKey = calendar.isShared ? (calendar.accountId || calendar.accountName || calendar.id) : username;
+    return discoveredCalDavUrls[accountKey] || wellKnownCalDavUrl;
   };
 
   const handleCopyUrl = async (url: string) => {

lib/calendar-utils.ts

@@ -142,3 +142,7 @@ export function formatSnapTime(minutes: number, timeFormat: "12h" | "24h"): stri
   }
   return `${String(h).padStart(2, "0")}:${String(m).padStart(2, "0")}`;
 }
+
+export function getPrimaryCalendarId(event: Pick<CalendarEvent, 'calendarIds'>): string | undefined {
+  return Object.keys(event.calendarIds || {})[0];
+}