implement frontend skeleton with tab navigation and service layer

- Add tab-based navigation (Chat, Calendar) using Expo-Router
- Create auth screens (login, register) as skeletons
- Add dynamic routes for event detail and note editing
- Implement service layer (ApiClient, AuthService, EventService, ChatService)
- Add Zustand stores (AuthStore, EventsStore) for state management
- Create EventCard and EventConfirmDialog components
- Update CLAUDE.md with new frontend architecture documentation
- Add Zustand and FlashList to technology stack

CLAUDE.md

@@ -39,6 +39,8 @@ npm run start -w @caldav/server        # Run compiled server (port 3000)
 | | Expo | Development platform |
 | | Expo-Router | File-based routing |
 | | NativeWind | Tailwind CSS for React Native |
+| | Zustand | State management |
+| | FlashList | High-performance lists |
 | Backend | Express.js | Web framework |
 | | MongoDB | Database |
 | | Mongoose | ODM |
@@ -57,13 +59,39 @@ packages/shared  - @caldav/shared - Shared TypeScript types and models
 
 ### Frontend Architecture (apps/client)
 
-**Screens** (`src/app/`): Login, Register, Calendar, Chat, Event Detail, Notes - file-based routing via Expo-Router
+```
+src/
+├── app/                        # Expo-Router file-based routing
+│   ├── _layout.tsx             # Root Stack layout
+│   ├── index.tsx               # Entry redirect
+│   ├── login.tsx               # Login screen
+│   ├── register.tsx            # Registration screen
+│   ├── (tabs)/                 # Tab navigation group
+│   │   ├── _layout.tsx         # Tab bar configuration
+│   │   ├── chat.tsx            # Chat screen (AI conversation)
+│   │   └── calendar.tsx        # Calendar overview
+│   ├── event/
+│   │   └── [id].tsx            # Event detail screen (dynamic route)
+│   └── note/
+│       └── [id].tsx            # Note editor for event (dynamic route)
+├── components/
+│   ├── BaseBackground.tsx      # Common screen wrapper
+│   ├── Header.tsx              # Header component
+│   ├── EventCard.tsx           # Event card for calendar display
+│   └── EventConfirmDialog.tsx  # AI-proposed event confirmation modal
+├── services/
+│   ├── index.ts                # Re-exports all services
+│   ├── ApiClient.ts            # HTTP client (get, post, put, delete)
+│   ├── AuthService.ts          # login(), register(), logout(), refresh()
+│   ├── EventService.ts         # getAll(), getById(), getByDateRange(), create(), update(), delete()
+│   └── ChatService.ts          # sendMessage(), confirmEvent(), rejectEvent(), getConversations(), getConversation()
+└── stores/                     # Zustand state management
+    ├── index.ts                # Re-exports all stores
+    ├── AuthStore.ts            # user, token, isAuthenticated, login(), logout(), setToken()
+    └── EventsStore.ts          # events[], setEvents(), addEvent(), updateEvent(), deleteEvent()
+```
 
-**Services**: API Client for HTTP requests, plus AuthService, EventService, ChatService for domain logic
-
-**Components**: Reusable UI (EventCard, ChatBubble, EventConfirmDialog, MonthSelector)
-
-**Stores**: AuthStore (user + token), EventsStore (calendar events)
+**Routing:** Tab-based navigation with Chat and Calendar as main screens. Auth screens (login, register) outside tabs. Dynamic routes for event detail and note editing.
 
 ### Backend Architecture (apps/server)
 
@@ -176,7 +204,14 @@ The repository pattern allows swapping databases:
 
 **Shared:** Types and DTOs defined and exported.
 
-**Frontend:** Calendar screen partially implemented, Chat screen exists but not connected to backend.
+**Frontend:** Skeleton complete with file-based routing structure:
+- Tab navigation (Chat, Calendar) implemented with basic UI
+- Calendar screen has month navigation and grid display (partially functional)
+- Chat screen has message list UI with FlashList (mock data only)
+- Auth screens (Login, Register), Event Detail, and Note screens exist as skeletons
+- Services (ApiClient, AuthService, EventService, ChatService) defined with `throw new Error('Not implemented')`
+- Zustand stores (AuthStore, EventsStore) defined with `throw new Error('Not implemented')`
+- Components (EventCard, EventConfirmDialog) exist as skeletons
 
 ## Documentation
 

apps/client/package.json

@@ -38,7 +38,8 @@
     "react-native-safe-area-context": "5.6.0",
     "react-native-screens": "~4.16.0",
     "react-native-web": "~0.21.0",
-    "react-native-worklets": "0.5.1"
+    "react-native-worklets": "0.5.1",
+    "zustand": "^5.0.9"
   },
   "devDependencies": {
     "@types/react": "~19.1.0",

apps/client/src/app/(tabs)/_layout.tsx

@@ -0,0 +1,29 @@
+import { Ionicons } from "@expo/vector-icons";
+import { Tabs } from "expo-router";
+import theme from "../../Themes";
+
+export default function TabLayout() {
+  return (
+    <Tabs screenOptions={{
+      headerShown: false,
+      tabBarActiveTintColor: theme.chatBot,
+      tabBarInactiveTintColor: theme.primeFg,
+      tabBarStyle: { backgroundColor: theme.primeBg },
+    }}>
+      <Tabs.Screen
+        name="chat"
+        options={{
+          title: 'Chat',
+          tabBarIcon: ({ color }) => <Ionicons size={28} name="chatbubble" color={color} />,
+        }}
+      />
+      <Tabs.Screen
+        name="calendar"
+        options={{
+          title: 'Calendar',
+          tabBarIcon: ({ color }) => <Ionicons size={28} name="calendar" color={color} />,
+        }}
+      />
+    </Tabs>
+  );
+}

apps/client/src/app/(tabs)/calendar.tsx

@@ -1,9 +1,9 @@
 import { Animated, Modal, Pressable, Text, View } from "react-native";
-import { DAYS, MONTHS, Month } from "../Constants";
-import Header from "../components/Header";
+import { DAYS, MONTHS, Month } from "../../Constants";
+import Header from "../../components/Header";
 import React, { useEffect, useMemo, useRef, useState } from "react";
-import currentTheme from "../Themes";
-import BaseBackground from "../components/BaseBackground";
+import currentTheme from "../../Themes";
+import BaseBackground from "../../components/BaseBackground";
 import { FlashList } from "@shopify/flash-list";
 
 // TODO: month selection dropdown menu

apps/client/src/app/(tabs)/chat.tsx

@@ -1,8 +1,8 @@
 import { View, Text, TextInput } from "react-native";
-import currentTheme from "../Themes";
+import currentTheme from "../../Themes";
 import { useState } from "react";
-import Header from "../components/Header";
-import BaseBackground from "../components/BaseBackground";
+import Header from "../../components/Header";
+import BaseBackground from "../../components/BaseBackground";
 import { FlashList } from "@shopify/flash-list";
 
 // TODO: better shadows for everything

apps/client/src/app/Hello_World.tsx

@@ -1,49 +0,0 @@
-import React, { useState } from 'react';
-import { Button, Text, View } from 'react-native';
-
-// const styles = StyleSheet.create({
-//   container: {
-//     alignItems: 'center',
-//   },
-//   text: {
-//     fontSize: 40
-//   }
-// })
-
-type HelloWorldProps = {
-  text: string;
-  aNumber: number;
-}
-
-const HelloWorld = (props: HelloWorldProps) => {
-  return (
-    <View className='flex-1 items-center justify-center'>
-      <Text>{props.text} : {props.aNumber}</Text>
-    </View>
-  )
-}
-
-const Counter = () => {
-  const [count, setCount] = useState<number>(0);
-
-  return (
-    <View>
-      <Button
-        onPress={() => setCount(count + 1)}
-        title={`You tabbed me ${count} times`}/>
-    </View>
-  )
-}
-
-const ManyHelloes = () => {
-  return (
-    <View>
-      <HelloWorld text="first number" aNumber={1}/>
-      <HelloWorld text="second number" aNumber={2}/>
-      <HelloWorld text="third number" aNumber={3}/>
-      <Counter/>
-    </View>
-  )
-}
-
-export default ManyHelloes;

apps/client/src/app/_layout.tsx

@@ -2,5 +2,13 @@ import { Stack } from "expo-router";
 import "../../global.css";
 
 export default function RootLayout() {
-  return <Stack screenOptions={{ headerShown: false }} />;
+  return (
+    <Stack screenOptions={{ headerShown: false }}>
+      <Stack.Screen name="(tabs)" />
+      <Stack.Screen name="login" />
+      <Stack.Screen name="register" />
+      <Stack.Screen name="event/[id]" />
+      <Stack.Screen name="note/[id]" />
+    </Stack>
+  );
 }

apps/client/src/app/event/[id].tsx

@@ -0,0 +1,44 @@
+import { View, Text, TextInput, Pressable } from 'react-native';
+import { useLocalSearchParams } from 'expo-router';
+import BaseBackground from '../../components/BaseBackground';
+
+const EventDetailScreen = () => {
+  const { id } = useLocalSearchParams<{ id: string }>();
+
+  // TODO: Fetch event by id using EventService.getById()
+  // TODO: Display event details (title, description, start/end time)
+  // TODO: Edit mode toggle
+  // TODO: Save changes -> EventService.update()
+  // TODO: Delete button -> EventService.delete()
+  // TODO: Link to NoteScreen for this event
+  // TODO: Loading and error states
+  throw new Error('Not implemented');
+
+  return (
+    <BaseBackground>
+      <View className="flex-1 p-4">
+        <Text className="text-2xl mb-4">Event Detail</Text>
+        <Text className="text-gray-500 mb-4">ID: {id}</Text>
+        <TextInput
+          placeholder="Title"
+          className="w-full border rounded p-2 mb-4"
+        />
+        <TextInput
+          placeholder="Description"
+          multiline
+          className="w-full border rounded p-2 mb-4 h-24"
+        />
+        <View className="flex-row gap-2">
+          <Pressable className="bg-blue-500 p-3 rounded flex-1">
+            <Text className="text-white text-center">Save</Text>
+          </Pressable>
+          <Pressable className="bg-red-500 p-3 rounded flex-1">
+            <Text className="text-white text-center">Delete</Text>
+          </Pressable>
+        </View>
+      </View>
+    </BaseBackground>
+  );
+};
+
+export default EventDetailScreen;

apps/client/src/app/index.tsx

@@ -1,10 +1,5 @@
-import React from "react";
-import Chat from "./Chat";
-import Calender from "./Calender";
+import { Redirect } from "expo-router";
 
 export default function Index() {
-  return (
-    // <Chat />
-    <Calender />
-  );
+  return <Redirect href="/(tabs)/chat" />;
 }

apps/client/src/app/login.tsx

@@ -0,0 +1,34 @@
+import { View, Text, TextInput, Pressable } from 'react-native';
+import BaseBackground from '../components/BaseBackground';
+
+const LoginScreen = () => {
+  // TODO: Email input field
+  // TODO: Password input field
+  // TODO: Login button -> AuthService.login()
+  // TODO: Link to RegisterScreen
+  // TODO: Error handling and display
+  // TODO: Navigate to Calendar on success
+  throw new Error('Not implemented');
+
+  return (
+    <BaseBackground>
+      <View className="flex-1 justify-center items-center p-4">
+        <Text className="text-2xl mb-8">Login</Text>
+        <TextInput
+          placeholder="Email"
+          className="w-full border rounded p-2 mb-4"
+        />
+        <TextInput
+          placeholder="Password"
+          secureTextEntry
+          className="w-full border rounded p-2 mb-4"
+        />
+        <Pressable className="bg-blue-500 p-3 rounded w-full">
+          <Text className="text-white text-center">Login</Text>
+        </Pressable>
+      </View>
+    </BaseBackground>
+  );
+};
+
+export default LoginScreen;

apps/client/src/app/note/[id].tsx

@@ -0,0 +1,34 @@
+import { View, Text, TextInput, Pressable } from 'react-native';
+import { useLocalSearchParams } from 'expo-router';
+import BaseBackground from '../../components/BaseBackground';
+
+const NoteScreen = () => {
+  const { id } = useLocalSearchParams<{ id: string }>();
+
+  // TODO: Fetch event by id using EventService.getById()
+  // TODO: Display and edit the event's note field
+  // TODO: Auto-save or manual save button
+  // TODO: Save changes -> EventService.update({ note: ... })
+  // TODO: Loading and error states
+  throw new Error('Not implemented');
+
+  return (
+    <BaseBackground>
+      <View className="flex-1 p-4">
+        <Text className="text-2xl mb-4">Note</Text>
+        <Text className="text-gray-500 mb-4">Event ID: {id}</Text>
+        <TextInput
+          placeholder="Write your note here..."
+          multiline
+          className="w-full border rounded p-2 flex-1 mb-4"
+          textAlignVertical="top"
+        />
+        <Pressable className="bg-blue-500 p-3 rounded">
+          <Text className="text-white text-center">Save Note</Text>
+        </Pressable>
+      </View>
+    </BaseBackground>
+  );
+};
+
+export default NoteScreen;

apps/client/src/app/register.tsx

@@ -0,0 +1,45 @@
+import { View, Text, TextInput, Pressable } from 'react-native';
+import BaseBackground from '../components/BaseBackground';
+
+const RegisterScreen = () => {
+  // TODO: Email input field
+  // TODO: Display name input field
+  // TODO: Password input field
+  // TODO: Password confirmation field
+  // TODO: Register button -> AuthService.register()
+  // TODO: Link to LoginScreen
+  // TODO: Error handling and display
+  // TODO: Navigate to Calendar on success
+  throw new Error('Not implemented');
+
+  return (
+    <BaseBackground>
+      <View className="flex-1 justify-center items-center p-4">
+        <Text className="text-2xl mb-8">Register</Text>
+        <TextInput
+          placeholder="Email"
+          className="w-full border rounded p-2 mb-4"
+        />
+        <TextInput
+          placeholder="Display Name"
+          className="w-full border rounded p-2 mb-4"
+        />
+        <TextInput
+          placeholder="Password"
+          secureTextEntry
+          className="w-full border rounded p-2 mb-4"
+        />
+        <TextInput
+          placeholder="Confirm Password"
+          secureTextEntry
+          className="w-full border rounded p-2 mb-4"
+        />
+        <Pressable className="bg-blue-500 p-3 rounded w-full">
+          <Text className="text-white text-center">Register</Text>
+        </Pressable>
+      </View>
+    </BaseBackground>
+  );
+};
+
+export default RegisterScreen;

apps/client/src/components/EventCard.tsx

@@ -0,0 +1,24 @@
+import { View, Text, Pressable } from 'react-native';
+import { CalendarEvent } from '@caldav/shared';
+
+type EventCardProps = {
+  event: CalendarEvent;
+  onPress?: (event: CalendarEvent) => void;
+};
+
+const EventCard = ({ event: _event, onPress: _onPress }: EventCardProps) => {
+  // TODO: Display event title, time, and description preview
+  // TODO: Handle onPress to navigate to EventDetailScreen
+  // TODO: Style based on event type or time of day
+  throw new Error('Not implemented');
+
+  return (
+    <Pressable>
+      <View>
+        <Text>EventCard - Not Implemented</Text>
+      </View>
+    </Pressable>
+  );
+};
+
+export default EventCard;

apps/client/src/components/EventConfirmDialog.tsx

@@ -0,0 +1,36 @@
+import { View, Text, Modal, Pressable } from 'react-native';
+import { CreateEventDTO } from '@caldav/shared';
+
+type EventConfirmDialogProps = {
+  visible: boolean;
+  proposedEvent: CreateEventDTO | null;
+  onConfirm: () => void;
+  onReject: () => void;
+  onClose: () => void;
+};
+
+const EventConfirmDialog = ({
+  visible: _visible,
+  proposedEvent: _proposedEvent,
+  onConfirm: _onConfirm,
+  onReject: _onReject,
+  onClose: _onClose,
+}: EventConfirmDialogProps) => {
+  // TODO: Display proposed event details (title, time, description)
+  // TODO: Confirm button calls onConfirm and closes dialog
+  // TODO: Reject button calls onReject and closes dialog
+  // TODO: Close button or backdrop tap calls onClose
+  throw new Error('Not implemented');
+
+  return (
+    <Modal visible={false} transparent animationType="fade">
+      <View>
+        <Pressable>
+          <Text>EventConfirmDialog - Not Implemented</Text>
+        </Pressable>
+      </View>
+    </Modal>
+  );
+};
+
+export default EventConfirmDialog;

apps/client/src/services/ApiClient.ts

@@ -0,0 +1,51 @@
+const API_BASE_URL =
+  process.env.EXPO_PUBLIC_API_URL || "http://localhost:3000/api";
+
+type HttpMethod = "GET" | "POST" | "PUT" | "DELETE";
+
+interface RequestOptions {
+  headers?: Record<string, string>;
+  body?: unknown;
+}
+
+async function request<T>(
+  _method: HttpMethod,
+  _endpoint: string,
+  _options?: RequestOptions,
+): Promise<T> {
+  throw new Error("Not implemented");
+}
+
+export const ApiClient = {
+  get: async <T>(
+    endpoint: string,
+    options?: Omit<RequestOptions, "body">,
+  ): Promise<T> => {
+    return request<T>("GET", endpoint, options);
+  },
+
+  post: async <T>(
+    endpoint: string,
+    body?: unknown,
+    options?: RequestOptions,
+  ): Promise<T> => {
+    return request<T>("POST", endpoint, { ...options, body });
+  },
+
+  put: async <T>(
+    endpoint: string,
+    body?: unknown,
+    options?: RequestOptions,
+  ): Promise<T> => {
+    return request<T>("PUT", endpoint, { ...options, body });
+  },
+
+  delete: async <T>(
+    endpoint: string,
+    options?: Omit<RequestOptions, "body">,
+  ): Promise<T> => {
+    return request<T>("DELETE", endpoint, options);
+  },
+};
+
+export { API_BASE_URL };

apps/client/src/services/AuthService.ts

@@ -0,0 +1,19 @@
+import { LoginDTO, CreateUserDTO, AuthResponse } from '@caldav/shared';
+
+export const AuthService = {
+  login: async (_credentials: LoginDTO): Promise<AuthResponse> => {
+    throw new Error('Not implemented');
+  },
+
+  register: async (_data: CreateUserDTO): Promise<AuthResponse> => {
+    throw new Error('Not implemented');
+  },
+
+  logout: async (): Promise<void> => {
+    throw new Error('Not implemented');
+  },
+
+  refresh: async (): Promise<AuthResponse> => {
+    throw new Error('Not implemented');
+  },
+};

apps/client/src/services/ChatService.ts

@@ -0,0 +1,39 @@
+import {
+  SendMessageDTO,
+  ChatResponse,
+  ChatMessage,
+  ConversationSummary,
+  GetMessagesOptions,
+  CalendarEvent,
+} from '@caldav/shared';
+
+export const ChatService = {
+  sendMessage: async (_data: SendMessageDTO): Promise<ChatResponse> => {
+    throw new Error('Not implemented');
+  },
+
+  confirmEvent: async (
+    _conversationId: string,
+    _messageId: string
+  ): Promise<CalendarEvent> => {
+    throw new Error('Not implemented');
+  },
+
+  rejectEvent: async (
+    _conversationId: string,
+    _messageId: string
+  ): Promise<void> => {
+    throw new Error('Not implemented');
+  },
+
+  getConversations: async (): Promise<ConversationSummary[]> => {
+    throw new Error('Not implemented');
+  },
+
+  getConversation: async (
+    _id: string,
+    _options?: GetMessagesOptions
+  ): Promise<ChatMessage[]> => {
+    throw new Error('Not implemented');
+  },
+};

apps/client/src/services/EventService.ts

@@ -0,0 +1,27 @@
+import { CalendarEvent, CreateEventDTO, UpdateEventDTO } from '@caldav/shared';
+
+export const EventService = {
+  getAll: async (): Promise<CalendarEvent[]> => {
+    throw new Error('Not implemented');
+  },
+
+  getById: async (_id: string): Promise<CalendarEvent> => {
+    throw new Error('Not implemented');
+  },
+
+  getByDateRange: async (_start: Date, _end: Date): Promise<CalendarEvent[]> => {
+    throw new Error('Not implemented');
+  },
+
+  create: async (_data: CreateEventDTO): Promise<CalendarEvent> => {
+    throw new Error('Not implemented');
+  },
+
+  update: async (_id: string, _data: UpdateEventDTO): Promise<CalendarEvent> => {
+    throw new Error('Not implemented');
+  },
+
+  delete: async (_id: string): Promise<void> => {
+    throw new Error('Not implemented');
+  },
+};

apps/client/src/services/index.ts

@@ -0,0 +1,4 @@
+export { ApiClient, API_BASE_URL } from './ApiClient';
+export { AuthService } from './AuthService';
+export { EventService } from './EventService';
+export { ChatService } from './ChatService';

apps/client/src/stores/AuthStore.ts

@@ -0,0 +1,26 @@
+import { create } from 'zustand';
+import { User } from '@caldav/shared';
+
+interface AuthState {
+  user: User | null;
+  token: string | null;
+  isAuthenticated: boolean;
+  login: (user: User, token: string) => void;
+  logout: () => void;
+  setToken: (token: string) => void;
+}
+
+export const useAuthStore = create<AuthState>((set) => ({
+  user: null,
+  token: null,
+  isAuthenticated: false,
+  login: (_user: User, _token: string) => {
+    throw new Error('Not implemented');
+  },
+  logout: () => {
+    throw new Error('Not implemented');
+  },
+  setToken: (_token: string) => {
+    throw new Error('Not implemented');
+  },
+}));

apps/client/src/stores/EventsStore.ts

@@ -0,0 +1,26 @@
+import { create } from 'zustand';
+import { CalendarEvent } from '@caldav/shared';
+
+interface EventsState {
+  events: CalendarEvent[];
+  setEvents: (events: CalendarEvent[]) => void;
+  addEvent: (event: CalendarEvent) => void;
+  updateEvent: (id: string, event: Partial<CalendarEvent>) => void;
+  deleteEvent: (id: string) => void;
+}
+
+export const useEventsStore = create<EventsState>((set) => ({
+  events: [],
+  setEvents: (_events: CalendarEvent[]) => {
+    throw new Error('Not implemented');
+  },
+  addEvent: (_event: CalendarEvent) => {
+    throw new Error('Not implemented');
+  },
+  updateEvent: (_id: string, _event: Partial<CalendarEvent>) => {
+    throw new Error('Not implemented');
+  },
+  deleteEvent: (_id: string) => {
+    throw new Error('Not implemented');
+  },
+}));

apps/client/src/stores/index.ts

@@ -0,0 +1,2 @@
+export { useAuthStore } from './AuthStore';
+export { useEventsStore } from './EventsStore';

apps/client/tsconfig.json

@@ -2,12 +2,14 @@
   "extends": "../../tsconfig.json",
   "compilerOptions": {
     "target": "ES2020",
-    "module": "CommonJS",
+    "module": "ESNext",
     "outDir": "dist",
     "strict": true,
     "esModuleInterop": true,
     "forceConsistentCasingInFileNames": true,
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "jsx": "react-native",
+    "moduleResolution": "bundler"
   },
   "include": [
     "**/*.ts",

package-lock.json

@@ -47,7 +47,8 @@
         "react-native-safe-area-context": "5.6.0",
         "react-native-screens": "~4.16.0",
         "react-native-web": "~0.21.0",
-        "react-native-worklets": "0.5.1"
+        "react-native-worklets": "0.5.1",
+        "zustand": "^5.0.9"
       },
       "devDependencies": {
         "@types/react": "~19.1.0",
@@ -15412,6 +15413,35 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/zustand": {
+      "version": "5.0.9",
+      "resolved": "https://registry.npmjs.org/zustand/-/zustand-5.0.9.tgz",
+      "integrity": "sha512-ALBtUj0AfjJt3uNRQoL1tL2tMvj6Gp/6e39dnfT6uzpelGru8v1tPOGBzayOWbPJvujM8JojDk3E1LxeFisBNg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=12.20.0"
+      },
+      "peerDependencies": {
+        "@types/react": ">=18.0.0",
+        "immer": ">=9.0.6",
+        "react": ">=18.0.0",
+        "use-sync-external-store": ">=1.2.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        },
+        "immer": {
+          "optional": true
+        },
+        "react": {
+          "optional": true
+        },
+        "use-sync-external-store": {
+          "optional": true
+        }
+      }
+    },
     "packages/shared": {
       "name": "@caldav/shared",
       "version": "1.0.0"