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

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);
   }
 }