import type { NextRequest } from "next/server"
import { backendInternalUrl } from "@/lib/backend-internal-url"

type ProxyBackendRequestOptions = {
  method?: string
  forwardRequestBody?: boolean
}

export async function proxyBackendRequest(
  request: NextRequest,
  backendPath: string,
  options: ProxyBackendRequestOptions = {},
): Promise<Response> {
  const method = options.method ?? request.method
  const headers = new Headers()
  for (const [key, value] of request.headers.entries()) {
    const lower = key.toLowerCase()
    if (lower === "host" || lower === "connection") continue
    headers.set(key, value)
  }

  const fetchInit: RequestInit & { duplex?: "half" } = {
    method,
    headers,
    cache: "no-store",
  }

  const forwardRequestBody = options.forwardRequestBody ?? !["GET", "HEAD"].includes(method)
  if (forwardRequestBody && request.body) {
    fetchInit.body = request.body
    fetchInit.duplex = "half"
  }

  try {
    const upstream = await fetch(`${backendInternalUrl()}${backendPath}`, fetchInit)
    const responseHeaders = new Headers()
    const contentType = upstream.headers.get("Content-Type")
    const contentDisposition = upstream.headers.get("Content-Disposition")
    if (contentType) responseHeaders.set("Content-Type", contentType)
    if (contentDisposition) responseHeaders.set("Content-Disposition", contentDisposition)

    return new Response(upstream.body, {
      status: upstream.status,
      headers: responseHeaders,
    })
  } catch (error) {
    const message = error instanceof Error ? error.message : "Не удалось связаться с бекендом"
    return Response.json({ error: message }, { status: 502 })
  }
}