// db.js —— 只做两件事：导出连接池；启动时建库/建表/插 admin
require('dotenv').config() //自动寻找.env文件，并把里面的键值对全部导入进来
const mysql = require('mysql2/promise')
const bcrypt = require('bcryptjs') //用来给密码做哈希加密

// ============ 1. 连接池 ============
// 业务代码里用 pool.query() / pool.execute()，会自动从池里取/还连接
const pool = mysql.createPool({
  host: process.env.DB_HOST,
  port: Number(process.env.DB_PORT) || 3306,
  user: process.env.DB_USER,
  password: process.env.DB_PASSWORD,
  database: process.env.DB_NAME,
  waitForConnections: true,   // 池里没连接时排队等
  connectionLimit: 10,        // 最多 10 个连接
  decimalNumbers: true,
})

// ============ 2. 启动时初始化 ============
// 思路：先用一个"无 database"的连接建库，再回到 pool 建表、插 admin
async function initDB() {
  const { DB_HOST, DB_PORT, DB_USER, DB_PASSWORD, DB_NAME } = process.env

  // 2.1 建库（如果不存在）
  const conn = await mysql.createConnection({
    host: DB_HOST,
    port: Number(DB_PORT) || 3306,
    user: DB_USER,
    password: DB_PASSWORD,
  })
  await conn.query(
    `CREATE DATABASE IF NOT EXISTS \`${DB_NAME}\` DEFAULT CHARACTER SET utf8mb4`
  )
  await conn.end()

  // 2.2 建表
  await pool.query(`
    CREATE TABLE IF NOT EXISTS users (
      id          INT PRIMARY KEY AUTO_INCREMENT,
      username    VARCHAR(50)  UNIQUE NOT NULL,
      password    VARCHAR(255) NOT NULL,
      nickname    VARCHAR(50)  DEFAULT '',
      avatar      VARCHAR(255) DEFAULT '',
      role        VARCHAR(20)  DEFAULT 'user',
      created_at  DATETIME     DEFAULT CURRENT_TIMESTAMP
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
  `)

  // 2.3 插 admin（仅当不存在时）
  const [rows] = await pool.query(
    'SELECT id FROM users WHERE username = ?',
    ['admin']
  )
  if (rows.length === 0) {
    const hash = await bcrypt.hash('123456', 10)
    await pool.query(
      'INSERT INTO users (username, password, nickname, role) VALUES (?, ?, ?, ?)',
      ['admin', hash, '超级管理员', 'admin']
    )
    console.log('[init] 已创建默认账号 admin / 123456')
  } else {
    console.log('[init] admin 已存在，跳过')
  }
}

module.exports = { pool, initDB }