refactor: improve AI event handling and conflict display in chat

- AI fetches events on-demand via callbacks for better efficiency
- Add conflict detection with warning display when proposing overlapping events
- Improve event search and display in chat interface
- Load full chat history for display while limiting AI context

apps/server/src/services/ChatService.ts

@@ -9,8 +9,8 @@ import {
   CreateEventDTO,
   UpdateEventDTO,
   EventAction,
-  CreateMessageDTO,
   RecurringDeleteMode,
+  ConflictingEvent,
 } from "@calchat/shared";
 import { ChatRepository, EventRepository, AIProvider } from "./interfaces";
 import { EventService } from "./EventService";
@@ -570,7 +570,6 @@ export class ChatService {
       responseIndex++;
     } else {
       // Production mode: use real AI
-      const events = await this.eventRepo.findByUserId(userId);
       const history = await this.chatRepo.getMessages(conversationId, {
         limit: 20,
       });
@@ -578,8 +577,16 @@ export class ChatService {
       response = await this.aiProvider.processMessage(data.content, {
         userId,
         conversationHistory: history,
-        existingEvents: events,
         currentDate: new Date(),
+        fetchEventsInRange: async (start, end) => {
+          return this.eventService.getByDateRange(userId, start, end);
+        },
+        searchEvents: async (query) => {
+          return this.eventRepo.searchByTitle(userId, query);
+        },
+        fetchEventById: async (eventId) => {
+          return this.eventService.getById(eventId, userId);
+        },
       });
     }
 
@@ -713,6 +720,56 @@ export class ChatService {
     proposalId: string,
     event: CreateEventDTO,
   ): Promise<ChatMessage | null> {
-    return this.chatRepo.updateProposalEvent(messageId, proposalId, event);
+    // Get the message to find the conversation
+    const message = await this.chatRepo.getMessageById(messageId);
+    if (!message) {
+      return null;
+    }
+
+    // Get the conversation to find the userId
+    const conversation = await this.chatRepo.getConversationById(
+      message.conversationId,
+    );
+    if (!conversation) {
+      return null;
+    }
+    const userId = conversation.userId;
+
+    // Get event times
+    const eventStart = new Date(event.startTime);
+    const eventEnd = new Date(event.endTime);
+
+    // Get day range for conflict checking
+    const dayStart = new Date(eventStart);
+    dayStart.setHours(0, 0, 0, 0);
+    const dayEnd = new Date(dayStart);
+    dayEnd.setDate(dayStart.getDate() + 1);
+
+    // Fetch events for the day
+    const dayEvents = await this.eventService.getByDateRange(
+      userId,
+      dayStart,
+      dayEnd,
+    );
+
+    // Check for time overlaps (use occurrenceStart/End for expanded recurring events)
+    const conflicts: ConflictingEvent[] = dayEvents
+      .filter(
+        (e) =>
+          new Date(e.occurrenceStart) < eventEnd &&
+          new Date(e.occurrenceEnd) > eventStart,
+      )
+      .map((e) => ({
+        title: e.title,
+        startTime: new Date(e.occurrenceStart),
+        endTime: new Date(e.occurrenceEnd),
+      }));
+
+    return this.chatRepo.updateProposalEvent(
+      messageId,
+      proposalId,
+      event,
+      conflicts.length > 0 ? conflicts : undefined,
+    );
   }
 }

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

@@ -1,14 +1,21 @@
 import {
-  CalendarEvent,
   ChatMessage,
   ProposedEventChange,
+  ExpandedEvent,
+  CalendarEvent,
 } from "@calchat/shared";
 
 export interface AIContext {
   userId: string;
   conversationHistory: ChatMessage[];
-  existingEvents: CalendarEvent[];
   currentDate: Date;
+  // Callback to load events from a specific date range
+  // Returns ExpandedEvent[] with occurrenceStart/occurrenceEnd for recurring events
+  fetchEventsInRange: (startDate: Date, endDate: Date) => Promise<ExpandedEvent[]>;
+  // Callback to search events by title
+  searchEvents: (query: string) => Promise<CalendarEvent[]>;
+  // Callback to fetch a single event by ID
+  fetchEventById: (eventId: string) => Promise<CalendarEvent | null>;
 }
 
 export interface AIResponse {

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

@@ -5,11 +5,13 @@ import {
   CreateEventDTO,
   GetMessagesOptions,
   UpdateMessageDTO,
+  ConflictingEvent,
 } from "@calchat/shared";
 
 export interface ChatRepository {
   // Conversations
   getConversationsByUser(userId: string): Promise<Conversation[]>;
+  getConversationById(conversationId: string): Promise<Conversation | null>;
   createConversation(userId: string): Promise<Conversation>;
 
   // Messages (cursor-based pagination)
@@ -38,5 +40,8 @@ export interface ChatRepository {
     messageId: string,
     proposalId: string,
     event: CreateEventDTO,
+    conflictingEvents?: ConflictingEvent[],
   ): Promise<ChatMessage | null>;
+
+  getMessageById(messageId: string): Promise<ChatMessage | null>;
 }

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

@@ -8,6 +8,7 @@ export interface EventRepository {
     startDate: Date,
     endDate: Date,
   ): Promise<CalendarEvent[]>;
+  searchByTitle(userId: string, query: string): Promise<CalendarEvent[]>;
   create(userId: string, data: CreateEventDTO): Promise<CalendarEvent>;
   update(id: string, data: UpdateEventDTO): Promise<CalendarEvent | null>;
   delete(id: string): Promise<boolean>;