proxy.ts

import type { NextRequest } from "next/server";
import { NextResponse } from "next/server";

function value(raw: string): number {
  const input = raw.trim();
  if (input.length === 0) {
    return 1;
  }
  const parsed = Number(input);
  if (!Number.isFinite(parsed)) {
    return 0;
  }
  if (parsed < 0) {
    return 0;
  }
  if (parsed > 1) {
    return 1;
  }
  return parsed;
}

function weight(entry: string): number {
  const parts = entry.split(";");
  for (const item of parts.slice(1)) {
    const [key, raw] = item.split("=");
    if ((key ?? "").trim().toLowerCase() === "q") {
      return value(raw ?? "");
    }
  }
  return 1;
}

function markdown(accept: string): boolean {
  let md = 0;
  let html = 0;
  for (const item of accept.split(",")) {
    const type = (item.split(";", 1).at(0) ?? "").trim().toLowerCase();
    const score = weight(item);
    if (score <= 0) {
      continue;
    }
    if (type === "text/markdown" || type === "text/x-markdown") {
      md = Math.max(md, score);
    }
    if (type === "text/html") {
      html = Math.max(html, score);
    }
  }
  return md > 0 && md >= html;
}

function rawslug(path: string): string | null {
  if (path === "/docs.md") {
    return "index";
  }
  if (!path.startsWith("/docs/") || !path.endsWith(".md")) {
    return null;
  }
  const slug = path.slice("/docs/".length, -".md".length).replace(/\/+$/, "");
  return slug.length > 0 ? slug : "index";
}

function docslug(path: string): string | null {
  if (path === "/docs" || path === "/docs/") {
    return "index";
  }
  if (!path.startsWith("/docs/")) {
    return null;
  }
  const slug = path.slice("/docs/".length).replace(/\/+$/, "");
  return slug.length > 0 ? slug : "index";
}

export function proxy(request: NextRequest) {
  const { pathname } = request.nextUrl;
  const accept = request.headers.get("accept") || "";
  const raw = rawslug(pathname);

  if (raw) {
    return NextResponse.rewrite(new URL(`/api/raw/${raw}`, request.url));
  }

  const slug = docslug(pathname);
  if (slug && markdown(accept)) {
    return NextResponse.rewrite(new URL(`/api/raw/${slug}`, request.url));
  }

  return NextResponse.next();
}

export const config = {
  matcher: ["/docs", "/docs/:path*", "/docs.md"],
};