import crypto from 'node:crypto'
import fs from 'node:fs'
import path from 'node:path'

export function safeImageExt(filename) {
  const ext = path.extname(String(filename || '')).toLowerCase()
  const allowed = new Set(['.png', '.jpg', '.jpeg', '.webp'])
  return allowed.has(ext) ? ext : null
}

export function uploadError(message, statusCode = 400) {
  const err = new Error(message)
  err.statusCode = statusCode
  return err
}

export async function persistMultipartImages(request, { maxFiles = 10 } = {}) {
  if (!request.isMultipart()) {
    throw uploadError('Ожидается multipart/form-data')
  }

  const uploadsDir = path.join(process.cwd(), 'uploads')
  await fs.promises.mkdir(uploadsDir, { recursive: true })

  const urls = []
  const parts = request.parts()
  for await (const part of parts) {
    if (part.type !== 'file') continue
    if (urls.length >= maxFiles) {
      throw uploadError(`Можно загрузить не более ${maxFiles} файл(ов)`)
    }
    const ext = safeImageExt(part.filename)
    if (!ext) {
      throw uploadError('Разрешены только файлы: png, jpg, jpeg, webp')
    }

    const fileName = `${crypto.randomUUID()}${ext}`
    const fullPath = path.join(uploadsDir, fileName)
    await fs.promises.writeFile(fullPath, await part.toBuffer())
    urls.push(`/uploads/${fileName}`)
  }

  return urls
}