/**
 * NAC知识引擎 MongoDB连接模块
 *
 * 安全说明：MongoDB连接串通过 secrets.ts 模块读取，绝不硬编码
 */
import { MongoClient, Db, IndexDirection } from "mongodb";
import { getNacMongoUrl } from "./secrets";

let client: MongoClient | null = null;
let db: Db | null = null;

export async function getMongoDb(): Promise<Db | null> {
  if (db) return db;
  try {
    client = new MongoClient(getNacMongoUrl(), {
      serverSelectionTimeoutMS: 5000,
      connectTimeoutMS: 5000,
    });
    await client.connect();
    db = client.db("nac_knowledge_engine");
    console.log("[MongoDB] Connected to nac_knowledge_engine");
    return db;
  } catch (error) {
    // 只记录错误类型，不记录连接串（含密码）
    console.error("[MongoDB] Connection failed:", (error as Error).message);
    return null;
  }
}

export async function closeMongoDb() {
  if (client) {
    await client.close();
    client = null;
    db = null;
  }
}

// 集合名称常量
export const COLLECTIONS = {
  COMPLIANCE_RULES: "compliance_rules",
  CRAWLERS: "crawlers",
  CRAWLER_LOGS: "crawler_logs",
  APPROVAL_CASES: "approval_cases",
  TAG_RULES: "tag_rules",
  PROTOCOL_REGISTRY: "protocol_registry",
  AUDIT_LOGS: "audit_logs",
  KNOWLEDGE_STATS: "knowledge_stats",
  // AI智能体对话历史
  AGENT_CONVERSATIONS: "agent_conversations",
  AGENT_MESSAGES: "agent_messages",
  // v15: 规则版本历史
  RULE_VERSIONS: "compliance_rule_versions",
};

/**
 * 初始化MongoDB索引（首次连接时调用）
 * - agent_conversations: userId + updatedAt 索引（按用户查询最近会话）
 * - agent_messages: conversationId + createdAt 索引（按会话查询消息）
 * - compliance_rules: 全文检索索引（RAG检索增强）
 */
export async function ensureIndexes(database: Db): Promise<void> {
  try {
    // 对话会话索引
    await database.collection(COLLECTIONS.AGENT_CONVERSATIONS).createIndex(
      { userId: 1, updatedAt: -1 },
      { background: true }
    );
    // 对话消息索引
    await database.collection(COLLECTIONS.AGENT_MESSAGES).createIndex(
      { conversationId: 1, createdAt: 1 },
      { background: true }
    );
    // 知识库全文检索索引（RAG）
    await database.collection(COLLECTIONS.COMPLIANCE_RULES).createIndex(
      { ruleName: "text", description: "text", content: "text" },
      { background: true, default_language: "none" } // none = 支持中文分词
    );
    console.log("[MongoDB] Indexes ensured");
  } catch (e) {
    // 索引已存在时忽略错误
    console.warn("[MongoDB] Index creation warning:", (e as Error).message);
  }
}