/**
 * 외부 DB 연결 헬퍼
 * 플로우 데이터 이동 시 외부 DB 연결 관리
 * PostgreSQL, MySQL/MariaDB, MSSQL, Oracle 지원
 */

import { Pool as PgPool } from "pg";
import * as mysql from "mysql2/promise";
import db from "../database/db";
import { PasswordEncryption } from "../utils/passwordEncryption";
import {
  getConnectionTestQuery,
  getPlaceholder,
  getBeginTransactionQuery,
  getCommitQuery,
  getRollbackQuery,
} from "./dbQueryBuilder";

interface ExternalDbConnection {
  id: number;
  connectionName: string;
  dbType: string;
  host: string;
  port: number;
  database: string;
  username: string;
  password: string;
  isActive: boolean;
}

// 외부 DB 연결 풀 캐시 (타입별로 다른 풀 객체)
const connectionPools = new Map<number, any>();

/**
 * 외부 DB 연결 정보 조회
 */
async function getExternalConnection(
  connectionId: number
): Promise<ExternalDbConnection | null> {
  const query = `SELECT * FROM external_db_connections WHERE id = $1 AND is_active = 'Y'`;

  const result = await db.query(query, [connectionId]);

  if (result.length === 0) {
    return null;
  }

  const row = result[0];

  // 비밀번호 복호화 (암호화된 비밀번호는 password 컬럼에 저장됨)
  let decryptedPassword = "";
  try {
    decryptedPassword = PasswordEncryption.decrypt(row.password);
  } catch (error) {
    console.error(`비밀번호 복호화 실패 (ID: ${connectionId}):`, error);
    // 복호화 실패 시 원본 비밀번호 사용 (fallback)
    decryptedPassword = row.password;
  }

  return {
    id: row.id,
    connectionName: row.connection_name,
    dbType: row.db_type,
    host: row.host,
    port: row.port,
    database: row.database_name,
    username: row.username,
    password: decryptedPassword,
    isActive: row.is_active,
  };
}

/**
 * 외부 DB 연결 풀 생성 또는 재사용
 */
export async function getExternalPool(connectionId: number): Promise<any> {
  // 캐시된 연결 풀 확인
  if (connectionPools.has(connectionId)) {
    const poolInfo = connectionPools.get(connectionId)!;
    const connection = await getExternalConnection(connectionId);

    // 연결이 유효한지 확인
    try {
      const testQuery = getConnectionTestQuery(connection!.dbType);
      await executePoolQuery(poolInfo.pool, connection!.dbType, testQuery, []);
      return poolInfo;
    } catch (error) {
      console.warn(
        `캐시된 외부 DB 연결 풀 무효화 (ID: ${connectionId}), 재생성합니다.`
      );
      connectionPools.delete(connectionId);
      await closePool(poolInfo.pool, connection!.dbType);
    }
  }

  // 새로운 연결 풀 생성
  const connection = await getExternalConnection(connectionId);

  if (!connection) {
    throw new Error(
      `외부 DB 연결 정보를 찾을 수 없습니다 (ID: ${connectionId})`
    );
  }

  const dbType = connection.dbType.toLowerCase();
  let pool: any;

  try {
    switch (dbType) {
      case "postgresql":
        pool = await createPostgreSQLPool(connection);
        break;

      case "mysql":
      case "mariadb":
        pool = await createMySQLPool(connection);
        break;

      case "mssql":
        pool = await createMSSQLPool(connection);
        break;

      case "oracle":
        pool = await createOraclePool(connection);
        break;

      default:
        throw new Error(`지원하지 않는 DB 타입입니다: ${connection.dbType}`);
    }

    // 연결 테스트
    const testQuery = getConnectionTestQuery(dbType);
    await executePoolQuery(pool, dbType, testQuery, []);

    console.log(
      `✅ 외부 DB 연결 풀 생성 성공 (ID: ${connectionId}, ${connection.connectionName}, ${connection.dbType})`
    );

    // 캐시에 저장 (dbType 정보 포함)
    const poolInfo = { pool, dbType };
    connectionPools.set(connectionId, poolInfo);

    return poolInfo;
  } catch (error) {
    if (pool) {
      await closePool(pool, dbType);
    }
    throw new Error(
      `외부 DB 연결 실패 (${connection.connectionName}, ${connection.dbType}): ${error}`
    );
  }
}

/**
 * PostgreSQL 연결 풀 생성
 */
async function createPostgreSQLPool(
  connection: ExternalDbConnection
): Promise<PgPool> {
  return new PgPool({
    host: connection.host,
    port: connection.port,
    database: connection.database,
    user: connection.username,
    password: connection.password,
    max: 5,
    idleTimeoutMillis: 30000,
    connectionTimeoutMillis: 5000,
  });
}

/**
 * MySQL/MariaDB 연결 풀 생성
 */
async function createMySQLPool(
  connection: ExternalDbConnection
): Promise<mysql.Pool> {
  return mysql.createPool({
    host: connection.host,
    port: connection.port,
    database: connection.database,
    user: connection.username,
    password: connection.password,
    connectionLimit: 5,
    waitForConnections: true,
    queueLimit: 0,
  });
}

/**
 * MSSQL 연결 풀 생성
 */
async function createMSSQLPool(connection: ExternalDbConnection): Promise<any> {
  // mssql 패키지를 동적으로 import (설치되어 있는 경우만)
  try {
    const sql = require("mssql");
    const config = {
      user: connection.username,
      password: connection.password,
      server: connection.host,
      port: connection.port,
      database: connection.database,
      options: {
        encrypt: true,
        trustServerCertificate: true,
        enableArithAbort: true,
      },
      pool: {
        max: 5,
        min: 0,
        idleTimeoutMillis: 30000,
      },
    };

    const pool = await sql.connect(config);
    return pool;
  } catch (error) {
    throw new Error(
      `MSSQL 연결 실패: mssql 패키지가 설치되어 있는지 확인하세요. (${error})`
    );
  }
}

/**
 * Oracle 연결 풀 생성
 */
async function createOraclePool(
  connection: ExternalDbConnection
): Promise<any> {
  try {
    // oracledb를 동적으로 import
    const oracledb = require("oracledb");

    // Oracle 클라이언트 초기화 (최초 1회만)
    if (!oracledb.oracleClientVersion) {
      // Instant Client 경로 설정 (환경변수로 지정 가능)
      const instantClientPath = process.env.ORACLE_INSTANT_CLIENT_PATH;
      if (instantClientPath) {
        oracledb.initOracleClient({ libDir: instantClientPath });
      }
    }

    // 연결 문자열 생성
    const connectString = connection.database.includes("/")
      ? connection.database // 이미 전체 연결 문자열인 경우
      : `${connection.host}:${connection.port}/${connection.database}`;

    const pool = await oracledb.createPool({
      user: connection.username,
      password: connection.password,
      connectString: connectString,
      poolMin: 1,
      poolMax: 5,
      poolIncrement: 1,
      poolTimeout: 60, // 60초 후 유휴 연결 해제
      queueTimeout: 5000, // 연결 대기 타임아웃 5초
      enableStatistics: true,
    });

    return pool;
  } catch (error: any) {
    throw new Error(
      `Oracle 연결 실패: ${error.message}. oracledb 패키지와 Oracle Instant Client가 설치되어 있는지 확인하세요.`
    );
  }
}

/**
 * 풀에서 쿼리 실행 (DB 타입별 처리)
 */
async function executePoolQuery(
  pool: any,
  dbType: string,
  query: string,
  params: any[]
): Promise<any> {
  const normalizedType = dbType.toLowerCase();

  switch (normalizedType) {
    case "postgresql": {
      const result = await pool.query(query, params);
      return { rows: result.rows, rowCount: result.rowCount };
    }

    case "mysql":
    case "mariadb": {
      const [rows] = await pool.query(query, params);
      return {
        rows: Array.isArray(rows) ? rows : [rows],
        rowCount: rows.length,
      };
    }

    case "mssql": {
      const request = pool.request();
      // MSSQL은 명명된 파라미터 사용
      params.forEach((param, index) => {
        request.input(`p${index + 1}`, param);
      });
      const result = await request.query(query);
      return { rows: result.recordset, rowCount: result.rowCount };
    }

    case "oracle": {
      const oracledb = require("oracledb");
      const connection = await pool.getConnection();
      try {
        // Oracle은 :1, :2 형식의 바인드 변수 사용
        const result = await connection.execute(query, params, {
          autoCommit: false, // 트랜잭션 관리를 위해 false
          outFormat: oracledb.OUT_FORMAT_OBJECT, // 객체 형식으로 반환
        });
        return { rows: result.rows || [], rowCount: result.rowCount || 0 };
      } finally {
        await connection.close();
      }
    }

    default:
      throw new Error(`지원하지 않는 DB 타입: ${dbType}`);
  }
}

/**
 * 연결 풀 종료 (DB 타입별 처리)
 */
async function closePool(pool: any, dbType: string): Promise<void> {
  const normalizedType = dbType.toLowerCase();

  try {
    switch (normalizedType) {
      case "postgresql":
      case "mysql":
      case "mariadb":
        await pool.end();
        break;

      case "mssql":
      case "oracle":
        await pool.close();
        break;
    }
  } catch (error) {
    console.error(`풀 종료 오류 (${dbType}):`, error);
  }
}

/**
 * 외부 DB 쿼리 실행
 */
export async function executeExternalQuery(
  connectionId: number,
  query: string,
  params: any[] = []
): Promise<any> {
  const poolInfo = await getExternalPool(connectionId);
  return await executePoolQuery(poolInfo.pool, poolInfo.dbType, query, params);
}

/**
 * 외부 DB 트랜잭션 실행
 */
export async function executeExternalTransaction(
  connectionId: number,
  callback: (client: any, dbType: string) => Promise<any>
): Promise<any> {
  const poolInfo = await getExternalPool(connectionId);
  const { pool, dbType } = poolInfo;
  const normalizedType = dbType.toLowerCase();

  let client: any;

  try {
    switch (normalizedType) {
      case "postgresql": {
        client = await pool.connect();
        await client.query(getBeginTransactionQuery(dbType));
        const result = await callback(client, dbType);
        await client.query(getCommitQuery(dbType));
        return result;
      }

      case "mysql":
      case "mariadb": {
        client = await pool.getConnection();
        await client.beginTransaction();
        const result = await callback(client, dbType);
        await client.commit();
        return result;
      }

      case "mssql": {
        const transaction = new pool.constructor.Transaction(pool);
        await transaction.begin();
        client = transaction;
        const result = await callback(client, dbType);
        await transaction.commit();
        return result;
      }

      case "oracle": {
        client = await pool.getConnection();
        // Oracle은 명시적 BEGIN 없이 트랜잭션 시작
        const result = await callback(client, dbType);
        // 명시적 커밋
        await client.commit();
        return result;
      }

      default:
        throw new Error(`지원하지 않는 DB 타입: ${dbType}`);
    }
  } catch (error) {
    console.error(`외부 DB 트랜잭션 오류 (ID: ${connectionId}):`, error);

    // 롤백 시도
    if (client) {
      try {
        switch (normalizedType) {
          case "postgresql":
            await client.query(getRollbackQuery(dbType));
            break;

          case "mysql":
          case "mariadb":
            await client.rollback();
            break;

          case "mssql":
          case "oracle":
            await client.rollback();
            break;
        }
      } catch (rollbackError) {
        console.error("트랜잭션 롤백 오류:", rollbackError);
      }
    }

    throw error;
  } finally {
    // 연결 해제
    if (client) {
      try {
        switch (normalizedType) {
          case "postgresql":
            client.release();
            break;

          case "mysql":
          case "mariadb":
            client.release();
            break;

          case "oracle":
            await client.close();
            break;

          case "mssql":
            // MSSQL Transaction 객체는 자동으로 정리됨
            break;
        }
      } catch (releaseError) {
        console.error("클라이언트 해제 오류:", releaseError);
      }
    }
  }
}