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/repositories/mongo/MongoChatRepository.ts

@@ -5,6 +5,7 @@ import {
   CreateEventDTO,
   GetMessagesOptions,
   UpdateMessageDTO,
+  ConflictingEvent,
 } from "@calchat/shared";
 import { ChatRepository } from "../../services/interfaces";
 import { Logged } from "../../logging";
@@ -25,12 +26,20 @@ export class MongoChatRepository implements ChatRepository {
     return conversation.toJSON() as unknown as Conversation;
   }
 
+  async getConversationById(
+    conversationId: string,
+  ): Promise<Conversation | null> {
+    const conversation = await ConversationModel.findById(conversationId);
+    return conversation
+      ? (conversation.toJSON() as unknown as Conversation)
+      : null;
+  }
+
   // Messages (cursor-based pagination)
   async getMessages(
     conversationId: string,
     options?: GetMessagesOptions,
   ): Promise<ChatMessage[]> {
-    const limit = options?.limit ?? 20;
     const query: Record<string, unknown> = { conversationId };
 
     // Cursor: load messages before this ID (for "load more" scrolling up)
@@ -39,9 +48,12 @@ export class MongoChatRepository implements ChatRepository {
     }
 
     // Fetch newest first, then reverse for chronological order
-    const docs = await ChatMessageModel.find(query)
-      .sort({ _id: -1 })
-      .limit(limit);
+    // Only apply limit if explicitly specified (no default - load all messages)
+    let queryBuilder = ChatMessageModel.find(query).sort({ _id: -1 });
+    if (options?.limit) {
+      queryBuilder = queryBuilder.limit(options.limit);
+    }
+    const docs = await queryBuilder;
 
     return docs.reverse().map((doc) => doc.toJSON() as unknown as ChatMessage);
   }
@@ -88,12 +100,28 @@ export class MongoChatRepository implements ChatRepository {
     messageId: string,
     proposalId: string,
     event: CreateEventDTO,
+    conflictingEvents?: ConflictingEvent[],
   ): Promise<ChatMessage | null> {
+    // Always set both fields - use empty array when no conflicts
+    // (MongoDB has issues combining $set and $unset on positional operator)
+    const setFields: Record<string, unknown> = {
+      "proposedChanges.$.event": event,
+      "proposedChanges.$.conflictingEvents":
+        conflictingEvents && conflictingEvents.length > 0
+          ? conflictingEvents
+          : [],
+    };
+
     const doc = await ChatMessageModel.findOneAndUpdate(
       { _id: messageId, "proposedChanges.id": proposalId },
-      { $set: { "proposedChanges.$.event": event } },
+      { $set: setFields },
       { new: true },
     );
     return doc ? (doc.toJSON() as unknown as ChatMessage) : null;
   }
+
+  async getMessageById(messageId: string): Promise<ChatMessage | null> {
+    const doc = await ChatMessageModel.findById(messageId);
+    return doc ? (doc.toJSON() as unknown as ChatMessage) : null;
+  }
 }

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

@@ -28,6 +28,14 @@ export class MongoEventRepository implements EventRepository {
     return events.map((e) => e.toJSON() as unknown as CalendarEvent);
   }
 
+  async searchByTitle(userId: string, query: string): Promise<CalendarEvent[]> {
+    const events = await EventModel.find({
+      userId,
+      title: { $regex: query, $options: "i" },
+    }).sort({ startTime: 1 });
+    return events.map((e) => e.toJSON() as unknown as CalendarEvent);
+  }
+
   async create(userId: string, data: CreateEventDTO): Promise<CalendarEvent> {
     const event = await EventModel.create({ userId, ...data });
     // NOTE: Casting required because Mongoose's toJSON() type doesn't reflect our virtual 'id' field

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

@@ -5,6 +5,7 @@ import {
   CreateEventDTO,
   UpdateEventDTO,
   ProposedEventChange,
+  ConflictingEvent,
 } from "@calchat/shared";
 import { IdVirtual } from "./types";
 
@@ -41,6 +42,15 @@ const UpdatesSchema = new Schema<UpdateEventDTO>(
   { _id: false },
 );
 
+const ConflictingEventSchema = new Schema<ConflictingEvent>(
+  {
+    title: { type: String, required: true },
+    startTime: { type: Date, required: true },
+    endTime: { type: Date, required: true },
+  },
+  { _id: false },
+);
+
 const ProposedChangeSchema = new Schema<ProposedEventChange>(
   {
     id: { type: String, required: true },
@@ -61,6 +71,7 @@ const ProposedChangeSchema = new Schema<ProposedEventChange>(
       enum: ["single", "future", "all"],
     },
     occurrenceDate: { type: String },
+    conflictingEvents: { type: [ConflictingEventSchema] },
   },
   { _id: false },
 );