import type { IncomingMessage, ServerResponse } from 'node:http'

/** 读取 Node HTTP 请求体（供 dev API 中间件转为 Fetch Request） */
export async function readIncomingBody(req: IncomingMessage): Promise<Buffer> {
  const chunks: Buffer[] = []
  for await (const chunk of req) {
    chunks.push(typeof chunk === 'string' ? Buffer.from(chunk) : chunk)
  }
  return Buffer.concat(chunks)
}

/** 将 Node IncomingMessage 转为 Web Fetch Request（含 POST/PUT body 与 headers） */
export async function toFetchRequest(req: IncomingMessage, path: string): Promise<Request> {
  const host = req.headers.host ?? '127.0.0.1'
  const method = req.method ?? 'GET'
  const headers = new Headers()

  for (const [key, value] of Object.entries(req.headers)) {
    if (value == null) continue
    if (Array.isArray(value)) {
      for (const v of value) headers.append(key, v)
    } else {
      headers.set(key, value)
    }
  }

  const hasBody = method !== 'GET' && method !== 'HEAD'
  const rawBody = hasBody ? await readIncomingBody(req) : Buffer.alloc(0)

  return new Request(`http://${host}${path}`, {
    method,
    headers,
    body:
      hasBody && rawBody.length > 0 ? new Uint8Array(rawBody) : undefined,
  })
}

/** 将 Fetch Response 写回 Node ServerResponse */
export async function writeFetchResponse(
  res: ServerResponse,
  response: Response
): Promise<void> {
  res.statusCode = response.status
  response.headers.forEach((value, key) => {
    if (key === 'transfer-encoding') return
    res.setHeader(key, value)
  })
  const body = Buffer.from(await response.arrayBuffer())
  res.end(body)
}