import multer from 'multer'
import path from 'path'
import crypto from 'crypto'
import fs from 'fs'

const UPLOAD_DIR = process.env.UPLOAD_DIR || './uploads'

/** 创建指定子目录的 multer 配置 */
export function createUploadConfig(subDir: string, maxFileSize = 5 * 1024 * 1024) {
  const targetDir = path.resolve(UPLOAD_DIR, subDir)

  // 确保目录存在
  if (!fs.existsSync(targetDir)) {
    fs.mkdirSync(targetDir, { recursive: true })
  }

  const storage = multer.diskStorage({
    destination: (_req, _file, cb) => {
      // 运行时再次确认（可能被手动删除）
      if (!fs.existsSync(targetDir)) {
        fs.mkdirSync(targetDir, { recursive: true })
      }
      cb(null, targetDir)
    },
    filename: (_req, file, cb) => {
      const ext = path.extname(file.originalname).toLowerCase() || '.jpg'
      const prefix = subDir === 'avatars' ? '' : 'notif_'
      cb(null, `${prefix}${Date.now()}_${crypto.randomInt(1000, 9999)}${ext}`)
    }
  })

  return multer({
    storage,
    limits: { fileSize: maxFileSize },
    fileFilter: (_req, file, cb) => {
      const allowed = ['.jpg', '.jpeg', '.png', '.webp']
      const ext = path.extname(file.originalname).toLowerCase()
      if (allowed.includes(ext)) {
        cb(null, true)
      } else {
        cb(new Error('仅支持 JPEG、PNG、WebP 格式'))
      }
    }
  })
}