backend/src/ai/memory.ts

import { ChatMessage } from "../types.js";
import { LRUCache } from "lru-cache";

export type SessionState = {
  messages: ChatMessage[];
  summary: string;
  lastAccess: number;
};

const sessions = new LRUCache<string, SessionState>({
  max: 5000,
  ttl: 1000 * 60 * 60 * 6
});

export const memoryStore = {
  get(sessionId: string): SessionState {
    const existing = sessions.get(sessionId);
    if (existing) {
      existing.lastAccess = Date.now();
      return existing;
    }
    const created: SessionState = {
      messages: [],
      summary: "",
      lastAccess: Date.now()
    };
    sessions.set(sessionId, created);
    return created;
  },
  set(sessionId: string, state: SessionState) {
    state.lastAccess = Date.now();
    sessions.set(sessionId, state);
  }
};