export const ALLOWED_EXTENSIONS = ['pdf','doc','docx','xls','xlsx','ppt','pptx','txt','md','csv']
export const ACCEPT = ALLOWED_EXTENSIONS.map(ext => `.${ext}`).join(',')
export const MAX_FILE_SIZE = 50 * 1024 * 1024

export function validateBackgroundFile(file) {
  if (!file || !file.name || file.size === 0) return '请选择非空文件'
  if (file.name.length > 255) return '文件名不能超过255个字符'
  const ext = file.name.includes('.') ? file.name.split('.').pop().toLowerCase() : ''
  if (!ALLOWED_EXTENSIONS.includes(ext)) return '文件类型不支持'
  if (file.size > MAX_FILE_SIZE) return '单个文件不能超过50MB'
  return ''
}

export function formatFileSize(bytes) {
  if (!bytes) return '0 B'
  if (bytes < 1024) return `${bytes} B`
  if (bytes < 1024 * 1024) return `${Number((bytes / 1024).toFixed(1))} KB`
  return `${Number((bytes / 1024 / 1024).toFixed(1))} MB`
}