proxy.ts

import { isMarkdownPreferred, rewritePath } from "fumadocs-core/negotiation"
import { type NextRequest, NextResponse } from "next/server"
import { docsContentRoute, docsRoute } from "@/lib/shared"

const { rewrite: rewriteDocs } = rewritePath(
  `${docsRoute}{/*path}`,
  `${docsContentRoute}{/*path}/content.md`,
)
const { rewrite: rewriteSuffix } = rewritePath(
  `${docsRoute}{/*path}.md`,
  `${docsContentRoute}{/*path}/content.md`,
)

export default function proxy(request: NextRequest) {
  const result = rewriteSuffix(request.nextUrl.pathname)
  if (result) {
    return NextResponse.rewrite(new URL(result, request.nextUrl))
  }

  if (isMarkdownPreferred(request)) {
    const result = rewriteDocs(request.nextUrl.pathname)

    if (result) {
      return NextResponse.rewrite(new URL(result, request.nextUrl), {
        // this URL has two representations, selected by `Accept`
        headers: { Vary: "Accept" },
      })
    }
  }

  return NextResponse.next()
}