feat: implement chat persistence with MongoDB

- Add full chat persistence to database (conversations and messages)
- Implement MongoChatRepository with cursor-based pagination
- Add getConversations/getConversation endpoints in ChatController
- Save user and assistant messages in ChatService.processMessage()
- Track respondedAction (confirm/reject) on proposed event messages
- Load existing messages on chat screen mount
- Add addMessages() bulk action and chatMessageToMessageData() helper to ChatStore
- Add RespondedAction type and UpdateMessageDTO to shared types

CLAUDE.md

@@ -91,7 +91,7 @@ src/
 └── stores/                     # Zustand state management
     ├── index.ts                # Re-exports all stores
     ├── AuthStore.ts            # user, token, isAuthenticated, login(), logout(), setToken()
-    ├── ChatStore.ts            # messages[], addMessage(), updateMessage(), clearMessages()
+    ├── ChatStore.ts            # messages[], addMessage(), addMessages(), updateMessage(), clearMessages(), chatMessageToMessageData()
     └── EventsStore.ts          # events[], setEvents(), addEvent(), updateEvent(), deleteEvent()
 ```
 
@@ -172,7 +172,7 @@ src/
 │   ├── CalendarEvent.ts  # CalendarEvent, CreateEventDTO, UpdateEventDTO, ExpandedEvent
 │   ├── ChatMessage.ts    # ChatMessage, Conversation, SendMessageDTO, CreateMessageDTO,
 │   │                     # GetMessagesOptions, ChatResponse, ConversationSummary,
-│   │                     # ProposedEventChange, EventAction
+│   │                     # ProposedEventChange, EventAction, RespondedAction, UpdateMessageDTO
 │   └── Constants.ts      # DAYS, MONTHS, Day, Month, DAY_INDEX, DAY_INDEX_TO_DAY,
 │                         # DAY_TO_GERMAN, DAY_TO_GERMAN_SHORT, MONTH_TO_GERMAN
 └── utils/
@@ -184,12 +184,14 @@ src/
 - `User`: id, email, displayName, passwordHash?, createdAt?, updatedAt?
 - `CalendarEvent`: id, userId, title, description?, startTime, endTime, note?, isRecurring?, recurrenceRule?
 - `ExpandedEvent`: Extends CalendarEvent with occurrenceStart, occurrenceEnd (for recurring event instances)
-- `ChatMessage`: id, conversationId, sender ('user' | 'assistant'), content, proposedChange?
+- `ChatMessage`: id, conversationId, sender ('user' | 'assistant'), content, proposedChange?, respondedAction?
 - `ProposedEventChange`: action ('create' | 'update' | 'delete'), eventId?, event?, updates?
 - `Conversation`: id, userId, createdAt?, updatedAt? (messages loaded separately via lazy loading)
 - `CreateEventDTO`: Used for creating events AND for AI-proposed events
 - `GetMessagesOptions`: Cursor-based pagination with `before?: string` and `limit?: number`
 - `ConversationSummary`: id, lastMessage?, createdAt? (for conversation list)
+- `UpdateMessageDTO`: respondedAction? (for marking messages as confirmed/rejected)
+- `RespondedAction`: 'confirm' | 'reject' (tracks user response to proposed events)
 - `Day`: "Monday" | "Tuesday" | ... | "Sunday"
 - `Month`: "January" | "February" | ... | "December"
 
@@ -281,12 +283,14 @@ MONGODB_URI=mongodb://root:mongoose@localhost:27017/calchat?authSource=admin
   - `EventService`: Full CRUD with recurring event expansion via recurrenceExpander
   - `utils/eventFormatters`: getWeeksOverview(), getMonthOverview() with German localization
   - `utils/recurrenceExpander`: expandRecurringEvents() using rrule library for RRULE parsing
+  - `ChatController`: getConversations(), getConversation() with cursor-based pagination support
+  - `ChatService`: getConversations(), getConversation(), processMessage() now persists user/assistant messages to DB, confirmEvent()/rejectEvent() update respondedAction and persist response messages
+  - `MongoChatRepository`: Full CRUD implemented (getConversationsByUser, createConversation, getMessages with cursor pagination, createMessage, updateMessage)
+  - `ChatRepository` interface: updateMessage() added for respondedAction tracking
 - **Stubbed (TODO):**
   - `AuthMiddleware.authenticate()`: Currently uses fake user for testing
   - `AuthController`: refresh(), logout()
   - `AuthService`: refreshToken()
-  - `ChatController`: getConversations(), getConversation()
-  - `MongoChatRepository`: Database persistence for chat
 - **Not started:**
   - `ClaudeAdapter` (AI integration - currently using test responses)
 
@@ -302,20 +306,22 @@ MONGODB_URI=mongodb://root:mongoose@localhost:27017/calchat?authSource=admin
   - Tap-to-open modal overlay showing EventCards for selected day
   - Supports events from adjacent months visible in grid
   - Uses `useFocusEffect` for automatic reload on tab focus
-- Chat screen functional with FlashList, message sending, and event confirm/reject
-  - Messages persisted via ChatStore (survives tab switches)
+- Chat screen fully functional with FlashList, message sending, and event confirm/reject
+  - Messages persisted to database via ChatService and loaded on mount
+  - Tracks conversationId for message continuity across sessions
+  - ChatStore with addMessages() for bulk loading, chatMessageToMessageData() helper
   - KeyboardAvoidingView for proper keyboard handling (iOS padding, Android height)
   - Auto-scroll to end on new messages and keyboard show
   - keyboardDismissMode="interactive" and keyboardShouldPersistTaps="handled"
 - `ApiClient`: get(), post(), put(), delete() implemented
 - `EventService`: getAll(), getById(), getByDateRange(), create(), update(), delete() - fully implemented
-- `ChatService`: sendMessage(), confirmEvent(convId, msgId, action, event?, eventId?, updates?), rejectEvent() - supports create/update/delete actions
+- `ChatService`: sendMessage(), confirmEvent(), rejectEvent(), getConversations(), getConversation() - fully implemented with cursor pagination
 - `EventCardBase`: Shared base component with event layout (header, date/time/recurring icons, description) - used by both EventCard and ProposedEventCard
 - `EventCard`: Uses EventCardBase + edit/delete buttons for calendar display
 - `ProposedEventCard`: Uses EventCardBase + confirm/reject buttons for chat proposals (supports create/update/delete actions)
 - `Themes.tsx`: Centralized color definitions including textPrimary, borderPrimary, eventIndicator, secondaryBg
 - `EventsStore`: Zustand store with setEvents(), addEvent(), updateEvent(), deleteEvent() - stores ExpandedEvent[]
-- `ChatStore`: Zustand store with addMessage(), updateMessage(), clearMessages() - persists messages across tab switches
+- `ChatStore`: Zustand store with addMessage(), addMessages(), updateMessage(), clearMessages() - loads from server on mount and persists across tab switches
 - Auth screens (Login, Register), Event Detail, and Note screens exist as skeletons
 - AuthStore defined with `throw new Error('Not implemented')`
 

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

@@ -1,18 +1,25 @@
-import { View, Text, TextInput, Pressable, KeyboardAvoidingView, Platform, Keyboard } from "react-native";
+import {
+  View,
+  Text,
+  TextInput,
+  Pressable,
+  KeyboardAvoidingView,
+  Platform,
+  Keyboard,
+} from "react-native";
 import currentTheme from "../../Themes";
-import { useState, useRef, useEffect } from "react";
+import React, { useState, useRef, useEffect } from "react";
 import Header from "../../components/Header";
 import BaseBackground from "../../components/BaseBackground";
 import { FlashList } from "@shopify/flash-list";
 import { ChatService } from "../../services";
-import { useChatStore, MessageData } from "../../stores";
+import { useChatStore, chatMessageToMessageData, MessageData } from "../../stores";
 import { ProposedEventChange } from "@caldav/shared";
 import { ProposedEventCard } from "../../components/ProposedEventCard";
 
 // TODO: better shadows for everything
 // (maybe with extra library because of differences between android and ios)
 // TODO: max width for messages
-// TODO: create new messages
 
 type BubbleSide = "left" | "right";
 
@@ -30,14 +37,43 @@ type ChatInputProps = {
 };
 
 const Chat = () => {
-  const { messages, addMessage, updateMessage } = useChatStore();
-  const listRef = useRef<FlashList<MessageData>>(null);
+  const { messages, addMessage, addMessages, updateMessage } = useChatStore();
+  const listRef =
+    useRef<React.ComponentRef<typeof FlashList<MessageData>>>(null);
+  const [currentConversationId, setCurrentConversationId] = useState<
+    string | undefined
+  >();
 
   useEffect(() => {
-    const keyboardDidShow = Keyboard.addListener("keyboardDidShow", scrollToEnd);
+    const keyboardDidShow = Keyboard.addListener(
+      "keyboardDidShow",
+      scrollToEnd,
+    );
     return () => keyboardDidShow.remove();
   }, []);
 
+  // Load existing messages from database on mount
+  useEffect(() => {
+    const fetchMessages = async () => {
+      try {
+        const conversationSummaries = await ChatService.getConversations();
+        if (conversationSummaries.length > 0) {
+          const conversationId = conversationSummaries[0].id;
+          setCurrentConversationId(conversationId);
+
+          const serverMessages =
+            await ChatService.getConversation(conversationId);
+          const clientMessages = serverMessages.map(chatMessageToMessageData);
+          addMessages(clientMessages);
+          scrollToEnd();
+        }
+      } catch (error) {
+        console.error("Failed to load messages:", error);
+      }
+    };
+    fetchMessages();
+  }, []);
+
   const scrollToEnd = () => {
     setTimeout(() => {
       listRef.current?.scrollToEnd({ animated: true });
@@ -87,13 +123,22 @@ const Chat = () => {
       id: Date.now().toString(),
       side: "right",
       content: text,
+      conversationId: currentConversationId,
     };
     addMessage(userMessage);
     scrollToEnd();
 
     try {
-      // Fetch server response
-      const response = await ChatService.sendMessage({ content: text });
+      // Fetch server response (include conversationId for existing conversations)
+      const response = await ChatService.sendMessage({
+        content: text,
+        conversationId: currentConversationId,
+      });
+
+      // Track conversation ID for subsequent messages
+      if (!currentConversationId) {
+        setCurrentConversationId(response.conversationId);
+      }
 
       // Show bot response
       const botMessage: MessageData = {

apps/client/src/services/ChatService.ts

@@ -47,13 +47,20 @@ export const ChatService = {
   },
 
   getConversations: async (): Promise<ConversationSummary[]> => {
-    throw new Error("Not implemented");
+    return ApiClient.get<ConversationSummary[]>("/chat/conversations");
   },
 
   getConversation: async (
-    _id: string,
-    _options?: GetMessagesOptions,
+    id: string,
+    options?: GetMessagesOptions,
   ): Promise<ChatMessage[]> => {
-    throw new Error("Not implemented");
+    const params = new URLSearchParams();
+    if (options?.before) params.append("before", options.before);
+    if (options?.limit) params.append("limit", options.limit.toString());
+
+    const queryString = params.toString();
+    const url = `/chat/conversations/${id}${queryString ? `?${queryString}` : ""}`;
+
+    return ApiClient.get<ChatMessage[]>(url);
   },
 };

apps/client/src/stores/ChatStore.ts

@@ -1,5 +1,5 @@
 import { create } from "zustand";
-import { ProposedEventChange } from "@caldav/shared";
+import { ChatMessage, ProposedEventChange } from "@caldav/shared";
 
 type BubbleSide = "left" | "right";
 
@@ -14,6 +14,7 @@ export type MessageData = {
 
 interface ChatState {
   messages: MessageData[];
+  addMessages: (messages: MessageData[]) => void;
   addMessage: (message: MessageData) => void;
   updateMessage: (id: string, updates: Partial<MessageData>) => void;
   clearMessages: () => void;
@@ -21,6 +22,9 @@ interface ChatState {
 
 export const useChatStore = create<ChatState>((set) => ({
   messages: [],
+  addMessages(messages) {
+    set((state) => ({messages: [...state.messages, ...messages]}))
+  },
   addMessage: (message: MessageData) => {
     set((state) => ({ messages: [...state.messages, message] }));
   },
@@ -35,3 +39,15 @@ export const useChatStore = create<ChatState>((set) => ({
     set({ messages: [] });
   },
 }));
+
+// Helper to convert server ChatMessage to client MessageData
+export function chatMessageToMessageData(msg: ChatMessage): MessageData {
+  return {
+    id: msg.id,
+    side: msg.sender === "assistant" ? "left" : "right",
+    content: msg.content,
+    proposedChange: msg.proposedChange,
+    respondedAction: msg.respondedAction,
+    conversationId: msg.conversationId,
+  };
+}

apps/client/src/stores/index.ts

@@ -1,3 +1,3 @@
 export { useAuthStore } from "./AuthStore";
-export { useChatStore, type MessageData } from "./ChatStore";
+export { useChatStore, chatMessageToMessageData, type MessageData } from "./ChatStore";
 export { useEventsStore } from "./EventsStore";

apps/server/src/controllers/ChatController.ts

@@ -4,6 +4,7 @@ import {
   CreateEventDTO,
   UpdateEventDTO,
   EventAction,
+  GetMessagesOptions,
 } from "@caldav/shared";
 import { ChatService } from "../services";
 import { AuthenticatedRequest } from "../middleware";
@@ -66,13 +67,43 @@ export class ChatController {
     req: AuthenticatedRequest,
     res: Response,
   ): Promise<void> {
-    throw new Error("Not implemented");
+    try {
+      const userId = req.user!.userId;
+      const conversations = await this.chatService.getConversations(userId);
+      res.json(conversations);
+    } catch (error) {
+      res.status(500).json({ error: "Failed to get conversations" });
+    }
   }
 
   async getConversation(
     req: AuthenticatedRequest,
     res: Response,
   ): Promise<void> {
-    throw new Error("Not implemented");
+    try {
+      const userId = req.user!.userId;
+      const { id } = req.params;
+      const { before, limit } = req.query as {
+        before?: string;
+        limit?: string;
+      };
+
+      const options: GetMessagesOptions = {};
+      if (before) options.before = before;
+      if (limit) options.limit = parseInt(limit, 10);
+
+      const messages = await this.chatService.getConversation(
+        userId,
+        id,
+        options,
+      );
+      res.json(messages);
+    } catch (error) {
+      if ((error as Error).message === "Conversation not found") {
+        res.status(404).json({ error: "Conversation not found" });
+      } else {
+        res.status(500).json({ error: "Failed to get conversation" });
+      }
+    }
   }
 }

apps/server/src/repositories/mongo/MongoChatRepository.ts

@@ -3,6 +3,7 @@ import {
   Conversation,
   CreateMessageDTO,
   GetMessagesOptions,
+  UpdateMessageDTO,
 } from "@caldav/shared";
 import { ChatRepository } from "../../services/interfaces";
 import { ChatMessageModel, ConversationModel } from "./models";
@@ -10,11 +11,15 @@ import { ChatMessageModel, ConversationModel } from "./models";
 export class MongoChatRepository implements ChatRepository {
   // Conversations
   async getConversationsByUser(userId: string): Promise<Conversation[]> {
-    throw new Error("Not implemented");
+    const conversations = await ConversationModel.find({ userId });
+    return conversations.map((c) => c.toJSON() as unknown as Conversation);
   }
 
   async createConversation(userId: string): Promise<Conversation> {
-    throw new Error("Not implemented");
+    const conversation = await ConversationModel.create({
+      userId,
+    });
+    return conversation.toJSON() as unknown as Conversation;
   }
 
   // Messages (cursor-based pagination)
@@ -22,13 +27,44 @@ export class MongoChatRepository implements ChatRepository {
     conversationId: string,
     options?: GetMessagesOptions,
   ): Promise<ChatMessage[]> {
-    throw new Error("Not implemented");
+    const limit = options?.limit ?? 20;
+    const query: Record<string, unknown> = { conversationId };
+
+    // Cursor: load messages before this ID (for "load more" scrolling up)
+    if (options?.before) {
+      query._id = { $lt: options.before };
+    }
+
+    // Fetch newest first, then reverse for chronological order
+    const docs = await ChatMessageModel.find(query)
+      .sort({ _id: -1 })
+      .limit(limit);
+
+    return docs.reverse().map((doc) => doc.toJSON() as unknown as ChatMessage);
   }
 
   async createMessage(
     conversationId: string,
     message: CreateMessageDTO,
   ): Promise<ChatMessage> {
-    throw new Error("Not implemented");
+    const repoMessage = await ChatMessageModel.create({
+      conversationId: conversationId,
+      sender: message.sender,
+      content: message.content,
+      proposedChange: message.proposedChange,
+    });
+    return repoMessage.toJSON() as unknown as ChatMessage;
+  }
+
+  async updateMessage(
+    messageId: string,
+    updates: UpdateMessageDTO,
+  ): Promise<ChatMessage | null> {
+    const doc = await ChatMessageModel.findByIdAndUpdate(
+      messageId,
+      { $set: updates },
+      { new: true },
+    );
+    return doc ? (doc.toJSON() as unknown as ChatMessage) : null;
   }
 }

apps/server/src/repositories/mongo/models/ChatModel.ts

@@ -80,6 +80,10 @@ const ChatMessageSchema = new Schema<
     proposedChange: {
       type: ProposedChangeSchema,
     },
+    respondedAction: {
+      type: String,
+      enum: ["confirm", "reject"],
+    },
   },
   {
     timestamps: true,

apps/server/src/services/ChatService.ts

@@ -9,6 +9,7 @@ import {
   CreateEventDTO,
   UpdateEventDTO,
   EventAction,
+  CreateMessageDTO,
 } from "@caldav/shared";
 import { ChatRepository, EventRepository, AIProvider } from "./interfaces";
 import { getWeeksOverview, getMonthOverview } from "../utils/eventFormatters";
@@ -252,6 +253,18 @@ export class ChatService {
     userId: string,
     data: SendMessageDTO,
   ): Promise<ChatResponse> {
+    let conversationId = data.conversationId;
+    if (!conversationId) {
+      const conversation = await this.chatRepo.createConversation(userId);
+      conversationId = conversation.id;
+    }
+
+    // Save user message
+    await this.chatRepo.createMessage(conversationId, {
+      sender: "user",
+      content: data.content,
+    });
+
     const response = await getTestResponse(
       responseIndex,
       this.eventRepo,
@@ -259,15 +272,14 @@ export class ChatService {
     );
     responseIndex++;
 
-    const message: ChatMessage = {
-      id: Date.now().toString(),
-      conversationId: data.conversationId || "temp-conv-id",
+    // Save and then return assistant response
+    const answerMessage = await this.chatRepo.createMessage(conversationId, {
       sender: "assistant",
       content: response.content,
       proposedChange: response.proposedChange,
-    };
+    });
 
-    return { message, conversationId: message.conversationId };
+    return { message: answerMessage, conversationId: conversationId };
   }
 
   async confirmEvent(
@@ -279,6 +291,10 @@ export class ChatService {
     eventId?: string,
     updates?: UpdateEventDTO,
   ): Promise<ChatResponse> {
+    // Update original message with respondedAction
+    await this.chatRepo.updateMessage(messageId, { respondedAction: "confirm" });
+
+    // Perform the actual event operation
     let content: string;
 
     if (action === "create" && event) {
@@ -298,12 +314,12 @@ export class ChatService {
       content = "Ungültige Aktion.";
     }
 
-    const message: ChatMessage = {
-      id: Date.now().toString(),
-      conversationId,
+    // Save response message to DB
+    const message = await this.chatRepo.createMessage(conversationId, {
       sender: "assistant",
       content,
-    };
+    });
+
     return { message, conversationId };
   }
 
@@ -312,17 +328,34 @@ export class ChatService {
     conversationId: string,
     messageId: string,
   ): Promise<ChatResponse> {
-    const message: ChatMessage = {
-      id: Date.now().toString(),
-      conversationId,
+    // Update original message with respondedAction
+    await this.chatRepo.updateMessage(messageId, { respondedAction: "reject" });
+
+    // Save response message to DB
+    const message = await this.chatRepo.createMessage(conversationId, {
       sender: "assistant",
       content: "Der Vorschlag wurde abgelehnt.",
-    };
+    });
+
     return { message, conversationId };
   }
 
   async getConversations(userId: string): Promise<ConversationSummary[]> {
-    throw new Error("Not implemented");
+    const conversations = await this.chatRepo.getConversationsByUser(userId);
+
+    // For each conversation, get the last message
+    const summaries: ConversationSummary[] = await Promise.all(
+      conversations.map(async (conv) => {
+        const messages = await this.chatRepo.getMessages(conv.id, { limit: 1 });
+        return {
+          id: conv.id,
+          lastMessage: messages[0],
+          createdAt: conv.createdAt,
+        };
+      }),
+    );
+
+    return summaries;
   }
 
   async getConversation(
@@ -330,6 +363,14 @@ export class ChatService {
     conversationId: string,
     options?: GetMessagesOptions,
   ): Promise<ChatMessage[]> {
-    throw new Error("Not implemented");
+    // Verify conversation belongs to user
+    const conversations = await this.chatRepo.getConversationsByUser(userId);
+    const conversation = conversations.find((c) => c.id === conversationId);
+
+    if (!conversation) {
+      throw new Error("Conversation not found");
+    }
+
+    return this.chatRepo.getMessages(conversationId, options);
   }
 }

apps/server/src/services/interfaces/ChatRepository.ts

@@ -3,6 +3,7 @@ import {
   Conversation,
   CreateMessageDTO,
   GetMessagesOptions,
+  UpdateMessageDTO,
 } from "@caldav/shared";
 
 export interface ChatRepository {
@@ -15,8 +16,14 @@ export interface ChatRepository {
     conversationId: string,
     options?: GetMessagesOptions,
   ): Promise<ChatMessage[]>;
+
   createMessage(
     conversationId: string,
     message: CreateMessageDTO,
   ): Promise<ChatMessage>;
+
+  updateMessage(
+    messageId: string,
+    updates: UpdateMessageDTO,
+  ): Promise<ChatMessage | null>;
 }

packages/shared/src/models/ChatMessage.ts

@@ -4,6 +4,8 @@ export type MessageSender = "user" | "assistant";
 
 export type EventAction = "create" | "update" | "delete";
 
+export type RespondedAction = "confirm" | "reject";
+
 export interface ProposedEventChange {
   action: EventAction;
   eventId?: string; // Required for update/delete
@@ -17,6 +19,7 @@ export interface ChatMessage {
   sender: MessageSender;
   content: string;
   proposedChange?: ProposedEventChange;
+  respondedAction?: RespondedAction;
   createdAt?: Date;
 }
 
@@ -43,6 +46,10 @@ export interface GetMessagesOptions {
   limit?: number; // Default: 20
 }
 
+export interface UpdateMessageDTO {
+  respondedAction?: RespondedAction;
+}
+
 export interface ChatResponse {
   message: ChatMessage;
   conversationId: string;