import { NextRequest, NextResponse } from 'next/server'

const API_BASE = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000'

async function handler(request: NextRequest): Promise<NextResponse> {
  const url = new URL(request.url)
  const targetPath = url.pathname.replace('/api/proxy', '')
  const targetUrl = `${API_BASE}${targetPath}${url.search}`

  const headers = new Headers(request.headers)
  // Remove Next.js internal headers that would confuse the upstream server.
  // Keep (or relay) x-forwarded-for so the backend's rate limiter can
  // identify individual clients — without it, all users share the Next.js
  // server IP and a single rate-limit bucket.
  headers.delete('host')
  headers.delete('x-forwarded-host')
  headers.delete('x-forwarded-proto')

  // Relay real client IP. Prefer the header Vercel/CDN already set; fall
  // back to x-real-ip; ultimately unknown if neither is present (e.g. local
  // dev through a raw Node server).
  const clientIp =
    request.headers.get('x-forwarded-for') ??
    request.headers.get('x-real-ip') ??
    'unknown'
  headers.set('x-forwarded-for', clientIp)

  const body =
    request.method !== 'GET' && request.method !== 'HEAD'
      ? await request.arrayBuffer()
      : undefined

  try {
    const upstream = await fetch(targetUrl, {
      method: request.method,
      headers,
      body,
    })

    const responseHeaders = new Headers(upstream.headers)
    responseHeaders.delete('transfer-encoding')

    const responseBody = await upstream.arrayBuffer()

    return new NextResponse(responseBody, {
      status: upstream.status,
      statusText: upstream.statusText,
      headers: responseHeaders,
    })
  } catch (err) {
    return NextResponse.json(
      { error: 'Upstream request failed', detail: String(err) },
      { status: 502 },
    )
  }
}

export const GET = handler
export const POST = handler
export const PUT = handler
export const PATCH = handler
export const DELETE = handler
export const HEAD = handler
export const OPTIONS = handler