feat: add SessionManager for multi-frontend session handling

src/session/manager.ts

@@ -0,0 +1,85 @@
+import type { Message } from '../models/types.js';
+import type { SessionStore } from './store.js';
+
+export interface Session {
+  id: string;
+  addMessage(message: Message): void;
+  getHistory(): Message[];
+  clear(): void;
+}
+
+export class ManagedSession implements Session {
+  constructor(
+    public readonly id: string,
+    private store: SessionStore,
+    private history: Message[] = []
+  ) {}
+
+  addMessage(message: Message): void {
+    this.history.push(message);
+    this.store.addMessage(this.id, message);
+  }
+
+  getHistory(): Message[] {
+    return [...this.history];
+  }
+
+  clear(): void {
+    this.history = [];
+    this.store.clearSession(this.id);
+  }
+
+  setHistory(messages: Message[]): void {
+    this.history = [...messages];
+  }
+}
+
+export class SessionManager {
+  private sessions: Map<string, ManagedSession> = new Map();
+
+  constructor(private store: SessionStore) {}
+
+  private makeSessionId(frontend: string, userId: string): string {
+    return `${frontend}:${userId}`;
+  }
+
+  getSession(frontend: string, userId: string): ManagedSession {
+    const id = this.makeSessionId(frontend, userId);
+
+    let session = this.sessions.get(id);
+    if (!session) {
+      const history = this.store.getMessages(id);
+      session = new ManagedSession(id, this.store, history);
+      this.sessions.set(id, session);
+    }
+
+    return session;
+  }
+
+  transferSession(
+    fromFrontend: string,
+    fromUserId: string,
+    toFrontend: string,
+    toUserId: string
+  ): void {
+    const fromSession = this.getSession(fromFrontend, fromUserId);
+    const toSession = this.getSession(toFrontend, toUserId);
+
+    const history = fromSession.getHistory();
+
+    // Clear target and copy history
+    toSession.clear();
+    for (const message of history) {
+      toSession.addMessage(message);
+    }
+  }
+
+  listSessions(): string[] {
+    return Array.from(this.sessions.keys());
+  }
+
+  closeSession(frontend: string, userId: string): void {
+    const id = this.makeSessionId(frontend, userId);
+    this.sessions.delete(id);
+  }
+}